By on September 12, 2012

In the last article, we explored what influences a suspension to ‘feel sporty’ vs. actually deliver better performance. A great car rewards us with a sublime driving experience while many (most?) let us down in a various ways. As part of that article, I dove into fairly technical terms without much introduction, so I’m taking a step back to do an overview and define a few terms. Then, I’ll get into the real meat of Suspension Truth and why we’re on The Truth About Cars – more seat-of-the-pants impressions tied to juicy technical details and real-world test data like shock dyno graphs, 3-axis accelerometer results – even raw shock velocity measurements from our Aim EVO system! From here we’ll be able to give metrics for different vehicles and see what we like and what we’d like to improve.

A number of you asked in the last article’s comments “is it possible to improve upon something so-so?” with the complementary question of “why does model X feel really good?” The same design factors are at work in both cases, differing only in how they’re managed. With a holistic approach, I’d like to convey my view of how those factors work. First, as independent parts and second, how they relate to the whole vehicle’s to create a ride or handling experience and your subjective experience of that.

Like any system with many variables, there are many interactions at play, but at least in my empirically minded way, a few are more dominant than others and also depend upon the road environment (like smoother vs. rougher). For simplicity’s sake, I’d like to use this breakdown of the behaviors we care about: a) grip and stability going around turns,  b) comfort driving in a straight line and c) responsiveness to direction changes.

So what are the most important factors in how a car feels and responds? Some factors influence both straight line and cornering, which isn’t always intuitive. Dampers really do matter in cornering, because we all know (sing it with me now) ‘there’s no such thing as s smooth road’. The video is referenced in the previous article. Here’s my list of vital factors in a suspension design plus the impact on ride and/or handling:

 

  • Total body roll or roll stiffness index, generally determined by overall roll stiffness normalized to the vehicle weight. The stiffness comes from springs and sway bars (though bump stops often contribute as well) divided by the vehicle’s weight which is what I call the “roll stiffness index”. You can directly measure the roll angle – a head-on photograph is wonderful for this. The roll stiffness index requires more calculations. Lots of body roll means less tire contact patch and less grip.
  • The amount and build-up of shock damping force, especially at low-speed – the region where the shock changes direction, from extension to compression and back again – is what controls all driver-induced inputs (steering, brake, gas) and also small chassis movements. There can be a subtle quality of ease or dis-ease depending upon this hidden effect, which we talked about in the last article. It’s certainly possible to get good body control without undue harshness if the damper forces vary smoothly instead of having sudden changes in slope.
  • A suspension geometry (MacPherson strut, double-wishbone, etc.) that provides a consistent tire contact patch, bushings and suspension members that behave predictably so the driver can be confident extracting the available grip without nervous handling.
  • Bump stop interactions during cornering – this is the least understood, most often ignored and most important of all the factors, both in my opinion and experience. At the extremes of handling or ride is where the extremes of bump stop behavior comes into play. Most people think they’re not hitting them because modern bump stops feel very supple most of the time. Because of this, a behavior like terminal understeer (‘the car won’t turn and I’ve cranked the wheel all the way over!’) will almost always be due to the bump stop tuning. Because this part of the suspension is both hidden (under dust boots) and non-intuitive (how does it respond to a load?) it’s usually overly simplified, ignored, literally removed or cut in half, making matters even more. Plus, how the front and rear bump stops interact relative to each other greatly influences the steady-state cornering response. Simply attending to bump stop interactions and keeping in mind the suspension design can give one insights that turn a vehicle from pushy to playful!
  • Chassis settling time in response to vertical disturbances – this comes via choice of ride frequencies with attention to ‘Flat Ride’, how the shock builds force in the velocity range associated with the time period of the chassis movement, bump stop length/stiffness to help manage big impacts, suspension bushing density and whether any micro-cellular urethane (MCU) has been incorporated into the design of the shock mounts or other areas of the chassis to help reduce NVH (noise-vibration-harshness) by absorbing high-frequency vibrations.
  • Center of gravity height, which we have only a little control over via lowering or perhaps lightening. Generally, the more passenger- and cargo-oriented the vehicle, the heavier and taller it’ll be, the more weight transfer will occurs and the less grip available, not to mention horror-inducing body roll from usually low roll stiffness! But a tall, heavy vehicle can still behave reasonably well if the other factors are managed, or adjusted. As the expression goes, you can’t make a pig into a race car, but you can make a very fast pig.
  • Chassis stiffness – having gone to a nearly full cage and hardtop on my ’95 convertible Miata convertible (‘Senna’), I was amazed at how much less of the road I felt. The suspension and tires communicated nuances so much better! On a convertible or other flexi-frame vehicle, shoring up the chassis rigidity helps in numerous ways. The higher resonant frequency means less ‘noise’ couples from the road through the chassis and into you.
  • Seats – this was mentioned in the comments and is a great point I’m going to ‘borrow’! A bench seat won’t give us much confidence compared to a bucket, or a proper race seat. Being confident and not having to brace yourself all the time is really a good recipe for feeling more connected to the car. Conversely, a race seat with no cushioning is simply going to feel abusive.

I’ve thrown a lot of primary and sub-factors out, giving much to discuss in comments and additional blog posts. In that spirit, perhaps you can mention (even repeating yourself from the previous article is fine) a specific vehicle you have in mind and how you feel about it in regards to these primary factors:

 

  1. Total body roll or overall chassis stiffness and center of gravity
  2. Responsiveness to steering
  3. Ride quality and chassis response on small, medium and big bumps
  4. Chassis stiffness
  5. Seats, confidence in cornering or support for long-distance driving

I will reply to your comments with my relevant experience or observations, forming a thread as I see already happens. Your feedback will help me learn more about the spectrum of vehicle’s you’re using, have owned, and are interested in buying or learning about.

Before the next article, I’ll record a video with my vision of how steady-state cornering operates combining many of the factors above. First, taking springs and sways together to create a certain dynamic balance – I use the term ‘front roll couple’ or ‘FRC’ which I calculate as the percent of roll stiffness across the front axle vs. the total vehicle roll stiffness. Then I’ll add the effect of bump stops, then throw in camber front vs. rear, and finally the impact of shock damping on the whole mess – for both smooth and rough roads! Building up step by step, I think this video (or two or three) will be fun and insightful! I’ve certainly wanted to create them for some time. Plus it’s necessary as I’ve been attempting to wave my hands around as I type, hence why this article took longer to write (and re-write and re-write…).

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36 Comments on “Suspension Truth # 3:What Makes A Car “Fun To Drive”? Factors In Suspension Dynamics...”


  • avatar
    Volt 230

    I lost my sports car virginity last weekend at age 59, when I got a chnce to drive my son’s FR-S over the same familiar roads I travel daily in my 98 Corolla, when I got back to the tired, old Toyota, I actually felt a sloppy, bouncy, poor road-holding econobox that I had never noticed in 14 yrs of daily driving.

  • avatar
    let_that_pony_gallop

    As an owner of a 2012 mustang im gonna have to say that I feel that the car does decently well in all the categories you mentioned except for one. The body roll is terrible for a sporty type car. That combined with the high center of gravity can be really bad for driver confidence. I think the car would benifit greatly from a drop of about 1″ to get that center of gravity lower, in turn lowering the body roll.

  • avatar
    danio3834

    I’m really interested in how you recommend tuning bump stop interaction with the suspension to improve overall performance.

    You’re right, it is a area of the suspension that I’ve never paid much attention to other than assuming it’s only purpose was fixed and to ultimately limit jounce.

    For example we run a 1995 Dodge Stratus as a competition road course car. They have a very good starting point for a suspension, especially in comparison to the ever popular amateur racer the Neon.

    I forget the actual measurements as it was a while ago that it was set up, but we lowered the car 1-2 inches with approximately 2 inches of suspension travel at ride height front and rear.

    The upper control arm mounts are now adjustable and IIRC we have them now set around -2 degees camber. Toe is set slightly out at all four corners.

    The car behaves very well on the track with more oversteer evident on turn in than understeer. My only complaints of understeer come after having to brake in a corner harder than expected then attempting to drive out. With the weight shifted to the front of the car in that way, it is takes some effort to get the power back in the direction it needs to be.

    Since in that situation there is most definitely bump stop interaction taking place, I wonder if changing the way the bump stops interact with the strut in that situation could improve the dynamics of the car.

    In a typical turn if you get to brake exactly as you want and make a nice smooth exit, this isn’t an issue at all, it’s in those situations where you need to come in a little tighter and brake harder where it feels especially slow to claw out of the corner.

    Any suggestions?

  • avatar
    ciddyguy

    When I first heard about the Fiat 500 back in, oh, 2009 (the European one), I immediately dialed into the sport trim, with its firmer suspension (and for what it had as part of that trim too, standard)

    But I’ve also never liked an overly cushy ride, and having driven cars like the 83 Honda Civic 1500DX hatchback with its MUCH better handling than anything I’d had previously, I’d since then preferred a bit firmer suspension overall than a softer one.

    When I test drove the Fiat 500 over a year ago, I test drove a sport version as that was what I’d have bought, if my budget had let me and I loved how despite its very short wheelbase, that the car didn’t pitch, nor yaw like it would have and with rough roads, the Fiat smoothed out the sharp peaks/valleys to where the movements, while there, weren’t harsh, nor jostling, they were subtle, and rather supple, but had a firm ride overall, and thus I felt it would be a very liveable car for daily driving.

    The car I ended up with instead, again, thanks to my budget was a used ’03 Mazda Protege5, thanks to my old truck dying before I wanted it to, so had no choice in the matter has a firm, but compliant suspension. I don’t mind feeling what it has to communicate in terms of what its doing while going down the road, and it has a communicative steering wheel too, and that alone allows it to be a fun car, though a tad too buttoned down IME.

    I am not young anymore (late 40′s) and don’t want a rock, hard suspension as found in many lowered cars where the car undulates along with the wheels as if they ARE riding all the time on their bump stops and have NO suspension at all, but I do like the suspension to be communicative with little body roll, but is very liveable too, and the Mazda P5 provides that, as would the Fiat if I had been able to purchase one.

    That said, I have discovered that after driving the Mazda, my Mom’s 04 Dodge Stratus, while it has a semi firm-ish ride, it’s not as elegantly done as it crashes over rough road surfaces, and is noisy at highway speeds, and just feels piggish, had vague, wide turn in and such, a definite letdown. However, when I had the truck (92 Ford Ranger), I didn’t detect much of a difference between the two, the Mazda provided the contrast, I’ll take my P5, thankyouverymuch.

  • avatar
    carve

    Question: why not design a car with a roll axis lined up with the vertical center of gravity…or even slightly above. Couldn’t such a car have a supple suspension and still corner dead flat…or even be made to lean into the corners?

    • 0 avatar
      cdotson

      I actually met a guy who worked for a company who did just this. The vehicle (SUV or truck) was barrell-rolled the first time out for high-speed testing. They said the confidence it inspired was God-like and the vehicle would just corner flat right up until the speed at which centripetal acceleration exceeded gravity’s ability to keep all four wheels on the ground.

      They surmised that progressive body roll was a necessary sensory input to determine the ultimate limits of grip. But definitely, moving in this direction from where most production vehicles start is the ultimate goal.

    • 0 avatar
      Brian P

      This implies having an excessively high geometric roll center. It’s an inherent side effect of having an excessively high roll center, that the tire contact patch moves sideways when the suspension moves up and down in response to a bump, leading to an unsettling sideways “kick” when going over bumps. Does this sound like the criticism leveled to, for example, the Mustang’s solid-axle rear suspension (which has a higher geometric roll center than most IRS designs have)?

      Having a very high roll center with an independent suspension design also inherently leads to a phenomenon called “jacking”. The sideways force on the contact patch creates an upward force at the suspension attachment points. And with that, I bring you the 1960 Chevrolet Corvair, with its swing-axle rear suspension.

      No free lunch. Modern vehicle suspension designs have moved beyond having excessively high geometric roll centers for good reason.

  • avatar
    cdotson

    Interesting to see you bring up roll stiffness. Would you agree that the location of the instant roll center determined by suspension construction can affect the roll stiffness independently of the springs and anti-roll bars? Years ago I started reading about the force-constructed roll center and it seemed a byproduct of that was that altering the kinematics of the suspension to move the instant center caused a calculable change in roll stiffness for the same spring rate and track width.

    I’ve driven two trucks, a 1988 Dodge Ramcharger 2wd and a 2002 Dodge Ram 2wd. I thought it interesting that the 88 has a negative-SLA front (the spindle is shorter than the distance between the UCA and LCA bushings). It rolled like a pig, and its lack of anti-roll bars never helped. It also would always wear the corners of the tires very round and frequently would cause wear to raised lettering on the sidewall. The 2002 has a more typical SLA front end with an exceptionally tall upright placing the UBJ beside the inner sidewall. The increase in the newer truck’s height means it still rolls, but overall cornering confidence is WAY better and I can drive it much faster around interchanges with less total roll (the big anti-roll bar helps). Both trucks are safe-understeer biased.

    Another vehicle I’ve worked on is an off-highway 4wd UTV that had parallel, equal-length dual wishbone front end. This front essentially allowed wallowish body roll with essentially no weight transfer. Combined with a rigid dual-swingarm rear axle it would snap oversteer due to a rear-biased roll stiffness. My take on parallel/equal arms was that the roll center moved laterally great distances with mild body roll, but also that it would move below grade causing cascading roll and an ever-decreasing roll stiffness based on what I learned in undergraduate vehicle dynamics. The guy who designed it disagreed, but aside from being an amateur GrandAm race engineer his only experience was having taken the same course I did (at the same school) 10 years earlier. I’d be interested in your thoughts.

    Steering responsiveness is definitely affected by suspension design and tuning but without including steering-specific design items like rack vs. worm, Ackermann, bump-steer/roll-steer, dynamic ratio etc it’s somewhat incomplete.

    • 0 avatar
      Pagani Baguette

      cdotson wrote: “Would you agree that the location of the instant roll center determined by suspension construction can affect the roll stiffness independently of the springs and anti-roll bars?”

      Hi,

      The very short answer is yes. (Someone may argue that the stiffness per se’ is only controlled by the springs and bars, not the roll centers, but what I am saying is that the roll centers position(s) affect how much a car wants to roll, so in reality it is a factor in controlling stiffness/resistance to roll). And this is exactly why in many street cars when you lover the car, it tends to roll more than what it was at stock height. Because in many cases lowering the car by say 1″, makes it so the roll center is lowered by say 2″ or more, while the center of gravity remains virtually unchanged. So now you have longer “lever” between the CG (center of gravity) and RC (roll center). But in general when lowering with off the shelf aftermarket parts, the car sits so firmly on the bumpstops, the perception is that the car rolls less and handles better. but such result is not because the owner improved the geometry….

      This actually is very interesting and very long topic, which perhaps deserves an entire chapter. A LOT of how a car handles and behaves comes from how these invisible points and axes (Center of Gravity, Instant Roll Center, Roll Axis, etc.) interacts and how they are position in relation to each other. People tune with springs, shocks and sway bars because those are the easy (and relatively cheap) things we can buy and mess with, but the true giant leap in improving cornering power and handling is made by optimizing the geometry of the suspension and carefully positioning (and then managing) the CG and RC where needed for the task.

      This whole conversation would be much more interesting and easy to understand if we could post pictures, graphs and animations. I wonder if anyone got a reply to our requests about posting pictures in the comments section.

      Cheers.

      PB

  • avatar
    lzaffuto

    We just bought a 2008 Infiniti EX35. I wanted a G35 Coupe and my wife wanted something more practical so this was the compromise. I don’t like sedans but I do like hatchbacks. I’m thinking about buying some H&R lowering springs for it hoping to make it ride a little more like the coupe/sedan. It seems like they raised the ride height more than necessary to be able to market it as a CUV instead of the G35 hatchback it essentially is. My impressions:

    1. Some body roll, caused by the higher ride height I presume and probably amplified by the high seating position.

    2. Decent responsiveness, could be better.

    3. Ride quality is overall very good. Small and medium bumps are absorbed really well to the point where it just communicates what the surface you’re driving on is but doesn’t punish you or rattle you. One weird thing is that it does “crash” over big bumps like speed bumps similar to a car with a much harsher and firmer suspension like my MR2.

    4. Hard for me to judge chassis stiffness, but seems really good for a large hatchback with a giant door and cargo area in the rear.

    5. Seats don’t have much bolstering for cornering, have really big, fat cushions on the bottom, and sit very high in respect to the actual ride height of the car (making you feel like the car is taller than it actually is). Extremely comfortable though, and definitely more for cruising than cornering.

    The sport springs reduce ride height by 1.3 inches front and 1.2 inches rear. I’m hoping installing them will give better results on 1 and 2 without hurting 3 so much that I get aches and pains after a long ride.

  • avatar
    Pagani Baguette

    cdotson wrote: “Would you agree that the location of the instant roll center determined by suspension construction can affect the roll stiffness independently of the springs and anti-roll bars?”

    Hi,

    The very short answer is yes. (Someone may argue that the stiffness per se is only controlled by the springs and bars, not the roll centers, but what I am saying is that the roll centers position(s) affect how much a car wants to roll, so in reality it is a factor in controlling stiffness/resistance to roll). And this is exactly why in many street cars when you lover the car, it tends to roll more than what it was at stock height. Because in many cases lowering the car by say 1″, makes it so the roll center is lowered by say 2″ or more, while the center of gravity remains virtually unchanged. So now you have longer “lever” between the CG (center of gravity) and RC (roll center). But in general when lowering with off the shelf aftermarket parts, the car sits so firmly on the bump stops, the perception is that the car rolls less and handles better. but such result is not because the owner improved the geometry….

    This actually is very interesting and very long topic, which perhaps deserves an entire chapter. A LOT of how a car handles and behaves comes from how these invisible points and axes (Center of Gravity, Instant Roll Center, Roll Axis, etc.) interacts and how they are position in relation to each other. People tune with springs, shocks and sway bars because those are the easy (and relatively cheap) things we can buy and mess with, but the true giant leap in improving cornering power and handling is made by optimizing the geometry of the suspension and carefully positioning (and then managing) the CG and RC where needed for the task.

    This whole conversation would be much more interesting and easy to understand if we could post pictures, graphs and animations. I wonder if anyone got a reply to our requests about posting pictures in the comments section.

    Cheers.

    PB

  • avatar
    Pagani Baguette

    Something went wrong and could not post the rather long reply. but it looks like now it is working, so I am going to use this post space, edit it and write a short form of that (sorry, not much time today)…

    cdotson wrote: “Would you agree that the location of the instant roll center determined by suspension construction can affect the roll stiffness independently of the springs and anti-roll bars?”…

    The short answer is that location of the roll center(s) affects how much the car wants to roll. So, yes, it affects how much the springs, bars, etc have to work as to fight roll. The very simple explanation is that the distance between the CG (center of gravity) and the RC (roll center) is one of the big factors in how much the car will want to roll. As a chassis designer/suspension designer you may not be able to control too much where the CG is, but you can definitely affect where the RC is through suspension geometry.

    This is one of the reasons lowering a production car may not result in improving roll. Because if you lower the car, and therefore lower the CG say 1″, you are also altering the suspension geometry in a way that it moved the RC say 2″ or more further AWAY from the CG, which then results in a much higher tendency to roll, which then you have to compensate with much stiffer springs and the whole thing goes down the hill very fast. People usually lower the car and that makes it sit very permanently on the bump stops, so by killing suspension travel you kill roll, and so they think that the lowering of the car cured roll, but in reality they just killed the suspension…

    This is a very interesting and long conversation, it deserves an entire chapter alone. I hope we can get a way of posting pictures and animations, so to make this a lot easier to explore.

    Cheers.

    pb.

  • avatar
    eliandi

    My car:
    2007 MINI Cooper S, mainly daily driver but has see the track and auto-x
    Stock suspension except: stiffer rear ARB, front camber plates (-1.2deg), and non-runflat summer performance tires

    1.Total body roll or overall chassis stiffness and center of gravity

    Body roll is minimal. Good chassis stiffness. Relatively low CG, though I’ve thought about lowering but not made the move because of the impact to overall ride.

    2.Responsiveness to steering

    Very quick at turn-in, especially if off-throttle. On-throttle it will push, lift throttle will bring it back to neutral. This performance was what I was looking for by adding stiffer rear ARB and camber plates. The camber plates also helped even front tire wear.

    3.Ride quality and chassis response on small, medium and big bumps

    Small bumps are pretty well controlled. Medium bumps are ok but can be jittery, and large bumpes will rattle the teeth. Car has 50k miles…I’ve been wondering if I need to replace the shocks.

    4.Chassis stiffness

    As a coupe, it seems very good.

    5.Seats, confidence in cornering or support for long-distance driving

    Seats are the stock sport leatherette MINI seats. They have ok lateral support, but the leatherette helps you stick. The seats are ok for long trips.

    So my questions for you:
    Will lowering it with some spring would kill the ride? There are MINI springs that advertise a bit of lowering with no overall increase in ride harshness.
    Will new shocks could help the overall ride? If so, what specific type?

  • avatar
    What-the-_

    Thanks Shaikh, these articles are truly eye opening
    2011 WRX, mid 40′s – I know, sounds odd, but the car fit my criteria of usability and sportiness, comfort (it’s actually pretty comfortable), and performance summer and winter in Canada-for the most part. When I first drove around a cloverleaf, it definitely rolls, and initially really tended to understeer,moreso than our 2010 forester, and there seems to be an odd underdamped bouncyness at moderate cornering loads that I am guessing is the suspension going off and on to the bump stops (higher load-goes away). I’m certain the performance is higher than the forester, but the confidence just wasn’t there.

    Chassis is reasonably stiff, but underbracing will be happening. It has a lot of doors and a hatch afterall
    Bumps are all over the place…small is ok, some tire frapp, medium is ok unless hit as a parrallel edge, then kind of makes a sizable thump through the car, large can be bangy, unless it’s kind of a g-out bump, then its, well, whoopty a bit
    steering is acceptable…but only because I haven’t driven anything since my manual rack and pinion car in the mid 70′s that had any steering feel.
    After reading several forums, rear antiroll bar was my first and so far only modification. It has greatly improved the car in my opinion..still comfortable, but more…confidence inspiring, however that bounciness can still occur, like there is a bunch of negative travel being used up. Like most people, I would like to go further, but don’t want to wreck the nature of the car. I have been considering the slightest of lowering springs and perhaps a little more front and rear antiroll. But the alternate direction is firmer bushings and perhaps the available anti lift kit…which I think (maybe) I’ve wrapped my head around, and some alignment for more camber. So far no makers have offered struts for these, just coilovers which might be too much for me, so not sure what I can do for damping.
    Having followed these articles I realize the many ways my car could be buggered up and am looking for a direction that will keep it comfortable, but with improved feel and performance in handling, summer and winter.

    Thanks for taking the time to inform

  • avatar

    So, going by the photo: Boobs? -Boobs make a car more fun to drive?

  • avatar
    HiFlite999

    I like where you are going with this!

    The stock RX-8 suspension is a lesson in excellent chassis dynamics when cornering, without a punishing ride. I’ve been slowly making changes, with, I think, decent results. Adding a 6-pt GTSPEC strut brace and matching underbrace seems to have moved the roll center forward so that the roll/bump response seems to be even Front to Rear, vs the stock rear bias. (Don’t know if I’m using the right terms.) Dropping the ride height by ~20 mm and increasing the spring rate by about 25% was a plus too. The biggest gain though was in adding D-Spec shocks which allow a wide range of compression and rebound adjustability (though not independently). Superslab = soft, curves/track = firm. I could go with a stiffer spring set, but don’t want the greater drop that comes with the available ones. I looked at full coilovers, but all I could find about tripled the spring rates over stock! Is there a reason for this huge hole in spring rates between spring/shock setups and coilovers? (On the RX8, the only obvious mechanical difference between the two is the coilovers offer adjustable ride height and pre-load.)

    • 0 avatar
      Georgewilliamherbert

      My daily driver is a very early 2004 RX-8 I’ve had for about 2 years now. I have as of yet not modified anything in the suspension. My wife drives another (later 2004) RX-8; mine has solid roof and fabric interior, she has the slightly heavier leather interior and moonroof. Both are automatics (mine due to intermittent permanent knee problems, hers because she’s 4’11″ and arthritic). They’re at 55,000 and about 50,000 miles respectively (and both on engine #2).

      My car is usually driven with a 10 lb “class” fire extinguisher in the trunk along with tire inflator kit and spare quart of oil, and for daily driving with a 20 lb laptop case. I’m big (6’4.5″ and 240 lbs).

      1. Total body roll or overall chassis stiffness and center of gravity

      Perception is that roll is very low and controllable. A lot like much more expensive sports cars I’ve driven. Chassis stiffness and center of gravity seem good.

      2. Responsiveness to steering

      Excellent. Good feedback, very light inputs, my only problem is that it is responsive enough that if I get lazy and loosen my grip a lot, the stiffness of my hands and wrists and the response of the steering when I go over bumps cause an exaggerated directional wiggle from the bump. If I just tighten / stiffen up it’s fine. More of a daily driving issue than when I’m intentionally pushing it somewhere, because if I know I’m pushing it I just stiffen up my grip and arms and it goes away.

      At the extreme edge, with traction control on I get very symmetrical breakout F/R if I go past limits, with it off it’s slightly understeery but very smooth. Compares well with higher end sports cars I’ve driven. It’s for road use, not set up for a track racer, so I avoid extreme edge most of the time, though I have felt it out under controlled conditions (and a couple of avoidance incidents).

      3. Ride quality and chassis response on small, medium and big bumps

      Small – smooth, no problem.
      Medium – feels fairly jarring. Ride is highly annoying on, for example, San Mateo Bridge eastbound in the #2 lane. #1 and 3 lanes are fine.
      Big – Slightly worse than medium, but doesn’t bottom out as badly as my previous (late 90s) Mustang. I hurt my back on one particular freeway bridge (#2 lane 880 NB in Fremont between North Fremont Blvd and Alvarado Blvd) in the Mustang some years ago. I avoid that lane like the plague now, but the couple of times I hit it in the RX-8 it wasn’t painful.

      Oddly, my wife’s car is noticably less jarring on the mid-range bumpy road. I don’t know if that’s slightly differing chassis setup over the 2004 model year or if the extra weight of the leather and moonroof makes a difference. It’s remotely possible a prior owner did something to the suspension on mine, but the dealers have indicated it looks stock.

      4. Chassis stiffness

      Fine. Could be better but not a noticeable problem even when pushing it.

      5. Seats, confidence in cornering or support for long-distance driving

      Good but not great; these are the factory seats. For cornering, I could use a touch more side support (I am 6’4.5″ and around 240 lbs). I notice when I’m really pushing it that the seats’s support aren’t all I would like, but it takes a lot of driving effort. For long distance driving, ok but not great. My left foot in the gap between the rest and the brake (where a clutch would be) puts my outer left thigh up against the seat where it starts to turn up, sort of an uncomfortable rest position. For an hour no big deal, for six hours starts to get annoying.

      • 0 avatar
        HiFlite999

        A pretty good summary! The sunroof/leather car, aka GT model is heavier than the unoptioned car but about ~100 lbs. A good portion of that difference is the seats, particularly, the drivers seat which is ~30-40 lbs heavier than cloth. The cloth seats too are better at holding you in place. Seating position is comfortable, but there’s not a lot of room to move around. That being said, the difference in ride comfort between the two cars I’d guess to be mostly a difference in the condition of the OEM shocks. New/upgraded shocks will make a big difference. Because of the rather ideal suspension geometry, the eight works it’s shocks harder than most cars, so they will wear faster. For taller drivers, I advise removing the dead pedal on the left (it’s held in with only 2 nuts), which gives semi-infinite leg room and would let you change up the seating position on long trips.

        Many owners consider the body roll to be a bit too much, but stiffer bars will degrade ride and possibly performance on rough roads. The traction control (which can be fully switched off), I find to be excellent, only nagging when needed. On dry good pavement, I can do full 4-wheel drifts with no interference unless one end or the other starts to come around. I never ever shut it off in the wet; if it gets loose, she goes very fast.

        Steering response is among the worlds best, at the cost of being very unforgiving of distracted driving.

        Rotor on!

  • avatar
    calhounje

    I have a 2012 Honda Fit Base model because it was cheap and it fits my 3 kids and giant dog unbelievably well for it’s size. It’s pretty fun to drive but the under-steer is just ridiculous.
    1. Body rolls a lot but not unpleasant to my mind
    2. Steering is quite good
    3. The ride is excellent except over large bumps at highway speeds when it really whacks you.
    4. The chassis stiffness is excellent IMHO
    5. The seats are just fine

    I’m a strong proponent that it’s more fun to drive a slow car fast than a fast car slowly. I think the Fit has a lot of potential to be more fun to drive on my daily commute and regular trips into NYC. I don’t care about ultimate grip because I’d rather drift a bit around an exit ramp on cheap tires at 30 mph than zip around on rails at 45mph. The problem with this car is the understeer. I have found only one aftermarket rear sway bar so I guess I should start there…?

    • 0 avatar
      eliandi

      Here is what HPD does to take a Fit b-spec racing. Might give you ideas on where to start. No mention of a rear sway bar, but they do coil-overs, camber bolts, and springs.

      “Now, Honda has announced their line of “manufacturer-approved suspension components.” For $2,800 you’ll get coil-over shocks, camber bolts, braided stainless brake lines, an air filter, front and rear race springs, a cat-back exhaust, front brake pads and an A/C delete belt. The kits will be available on 2/1/2012 through HPD.”

    • 0 avatar
      Brian P

      3 is likely due to the suspension hitting travel limits (bump stops). Soft springing is the likely cause. Stiffening up the spring rates would help with 1, also. The damping rates would have to change to match. Therefore, the above approach in the previous post makes sense.

    • 0 avatar
      nikita

      I also drive a Fit Base (2010). Honda greatly increased chassis stiffness over the 1st gen, and it shows. The car is very composed even going over big bumps and hitting the stops. I agree that the firm seats are good. Since the Sport model comes with a small rear sway bar for the twist beam suspension, I am considering the Progress rear sway bar. The car does respond to adjustments in tire pressures, so you might play with that to see what you like. I did change the tires from 175/65-15 Dunlop SP-31 to 195/60-15 Yokohama Avid Envigor and am happy that I did.

  • avatar
    Power6

    Still loving this series! Its great to see the game moved on from “lowering springs” and I would like to see your take on the aftermarket business and the perceived wants they satisfy just like the OEMs and the “sporty feeling” sport suspensions.

    I think the Subaru community and the rally car revolution in general in the US has done at least as much as the Miata to move the game on from punishment=handling. The all surface long travel strut suspension of the WRX has always favored mild roll stiffness and good damping over slamming, when it comes to handling.

    It seems the ultimate in suspension for the handling enthusiast, is the “boutique” approach: A specific vendor deep into a particular make/chassis, using quality parts and customized specs. This like Racecomp engineering for Subarus, their springs wound by Eibach and struts built by Bilstein but valved to their specs using their body of knowledge. I imagine this is where Fat Cat fits? The standard Eibach off the shelf spring by comparison, is just a soft “lowering spring” designed to look good and not blow the stock struts.

    I was amazed at what sort of suspension the RCE guys and Bilstein put together when handling/comfort was the primary goal and mass market appeal and safety and all the other big company concerns go away. Lots of compression damping and firm linear springs, little reliance on bump stops. Not a very typical ride and it took many of us some adjustment, but the results are quite astounding compared to a stock, sorta-firmly sprung but weakly damped WRX.

    The other side of this is the standardized Chinese made “30-way” damper body threaded into coilovers for every fitment imaginable. I consider this the “suspension for looks” category, BC Racing is the king of this. There are a lot of people using the BC and other low end product for track days and TT though so they have some street cred deserved or not.

  • avatar
    Brian P

    My own vehicle is a 2006 Mk5 VW Jetta with the base suspension (TDI). From stock, the only things I didn’t like were somewhat too much body roll, and a considerable bias towards understeer. I installed a 23mm rear antiroll bar in place of the stock 18mm bar and did nothing else. I’m happy with this.

    The bar had two holes in each end into which each end-link could be attached. I have it on the outer “soft” position at each end. I tried it on the “hard” position just to see what would happen … too much. This made the car twitchy and prone to oversteer. On “soft” it feels about right.

    Many criticisms have been leveled towards electric power steering systems in general, but the VW system seems quite good. I prefer (insist upon, would perhaps be better words) somewhat firm steering. I like the trend towards driver adjustability in this regard. Hyundai appears to have started this; apparently the Golf 7 will take it to another level.

    • 0 avatar
      Pagani Baguette

      Brian, did you try outer hole on one side and inner hole on the other side? It gives quite great “medium” feel (if “soft” is about right, but something is still missing)…

      • 0 avatar
        Brian P

        I know about that trick but I never tried it. The balance seems just about right with this bar on “soft” so upon finding this, I left well enough alone.

        I should mention one other niggle about the suspension on this model. If one tries to take a corner hard and there are sharp dips such as cracks or expansion joints in the pavement, the rear end feels like it steps sideways on each one, even well below what the actual traction limit ought to be. Other VW Mk5 owners have said the same thing, so it isn’t just me. The rear antiroll bar didn’t affect this. I suspect that there is too much high-speed rebound damping in the rear shocks. Front seems OK. It doesn’t bother me enough to consider replacing the shocks.

        This model uses multi-link IRS, not the twist-beam axle that VW historically used.

    • 0 avatar
      Pagani Baguette

      Funny, you can’t reply to the reply to your own reply to the original comment….

      Brian, the “medium” setting may help you Go Faster :-)

      If you believe the issue is your high speed rebound, the trouble is that you will never find off the shelf aftermarket damper with less rebound (low or high speed) than what the OEM damper comes with.

  • avatar
    kablamo

    Car: 2001 Honda Prelude 70k (non-SH, unmodified)

    1. Body Roll/Center of Gravity: significant body roll, borderline excessive. CoG feels low but not *that* low

    2. Responsiveness to Steering: very responsive; tire pressure too low (35psi) seems to reduce responsiveness.

    3. Ride Quality & Chassis Response: Ride quality good, comfortable on most quality of roads without floatiness. Chassis feels best when driven at 7 or 8 tenths.

    4. Chassis stiffness: Good overall, feels like it could be matched with a slightly stiffer suspension.

    5. Seats: adequate support, nothing more. Keep you in place, barely.

    Loving this series, really makes you think!

  • avatar
    Tummy

    So a car equipped with Mercedes Active Body Control, or GM/Audi/Ferrari Magnetic Ride Control, which has nearly no body roll and can be adjusted for different conditions is the most fun?

  • avatar
    daiheadjai

    2002 Celica GT (5-spd), 251,000km

    1) Total body roll or overall chassis stiffness and center of gravity: Low-moderate body roll as the car is fairly low, and lightweight. Not sure how to gauge chassis stiffness (no complaints thus far), but it IS a hatchback.

    2) Responsiveness to steering: Excellent – not overly-boosted or numb, but not too jittery either. Does understeer somewhat, but I chalk this up to poor 195/60R15 tires/wheels combo, which howl in protest in harder turns taken at moderate pace.

    3) Ride quality and chassis response on small, medium and big bumps:
    Good levels of comfort over uneven surfaces and bumps(especially since I come from a high CoG, marshmallow-suspension Yaris); while it may be a bit more firm, I personally feel better in this car because of much reduced feelings of “floating” on the suspension.

    4) Chassis stiffness: Not sure how to gauge, but it hasn’t felt like an issue.

    5) Seats, confidence in cornering or support for long-distance driving: Very comfortable, with grippy fabric and good bolstering. Not sure how it would hold up under very long distances (have driven maximum of about 2-3hrs in a sitting, without discomfort).

  • avatar
    redav

    I’m interested in content about the trend to oversized wheels: the effect of adding more mass to the wheel & removing tire compliance. Shorter sidewalls obviously give a harsher straight-line ride, but I’ve read before that if they become too stiff, the tire loses contact patch area with the road and can actually reduce cornering grip.

    • 0 avatar
      Brian P

      It’s true. There is a balance between grip and feedback to the driver that has to be found. And high unsprung weight is never good, and that extra weight is rotating weight, which is doubly not good.

      On smooth surfaces, unsprung weight and sidewall compliance don’t matter so much, but as soon as things get bumpy, they matter a lot.

  • avatar

    Shaikh, on a slightly off-topic note here, have you tried your hand or considered tuning long travel desert trucks? i’m as much an off-road fan as i am a pavement fan and while shock technology in the off-road world has expanded far beyond what is out their for pavement use, what with bypass shocks, air bumpstops and the like, the actual tuning knowledge is quite low outside of the major manufacturers(king, fox, bilstien, etc.) who seem hold their cards close to their chest. suspension tuning in the off-road world basically involves spending a day or two out in the desert and just changing spring rates and shim stacks in ‘trial-&-error’ fashion without any real science. the off-road world could certainly use a more objective, scientific approach to suspension tuning.
    i’m absolutely obsessed with tech, so i’m loving these articles! keep it up, this is good stuff!!!

  • avatar
    Charlie84

    Great articles, Shaikh. You and my favorite poster on VWVortex, TechEd, should get together to compare notes. I think one could safely say that he’s designed/tuned a few suspensions in his day.

    You previously mentioned having done some work with BMWs. Will Fat Cat Motorsports ever offer anything for the E36 chassis? I love my E36 M3, but the OEM shocks/dampers wear out notoriously quickly and the aftermarket has a very poor offering of shocks, unless one is willing to go to a full coil-over (overkill, for my application). Basically, our options are limited to the Koni Sports or Bilstein Sports. The Billie Sports are notorious within the E36 community for having ridiculously over-stiff compression damping (or at least, that’s how people have interpreted it via subjective observation). They ride terribly and probably do not deliver an overall handling improvement –on the contrary, they probably make matters worse on real-world roads. Unfortunately, I (stupidly) purchased these shocks for my M3! I’d love to have them re-valved. Would would Fat Cat recommend?


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