The Truth About Cars » shaikh ahmad The Truth About Cars is dedicated to providing candid, unbiased automobile reviews and the latest in auto industry news. Wed, 23 Apr 2014 14:09:20 +0000 en-US hourly 1 The Truth About Cars is dedicated to providing candid, unbiased automobile reviews and the latest in auto industry news. The Truth About Cars no The Truth About Cars (The Truth About Cars) 2006-2009 The Truth About Cars The Truth About Cars is dedicated to providing candid, unbiased automobile reviews and the latest in auto industry news. The Truth About Cars » shaikh ahmad Suspension Truth # 3.5: The Danger of Paying Top Dollar for Big Name Shocks Wed, 26 Sep 2012 14:16:55 +0000

Apologies for the delay in getting the next article to ‘press,’ a few matters including a misbehaving back were needing my attention! Too much sitting, not enough exercise!

Now that most of the national championship races are over, people are starting to bench race on what setup to get for next year, what’s ‘best’, etc. I was responding to one thread on and felt a slightly modified version would be appropriate for TTAC. I’d like to hear from people who have tested/tried different racing setups and what it was like to get, install, test, adjust and fine-tune those setups for the maximum result. I’ll have another article soon where we get back to the high-speed jacking down and display accelerometer data to support evidence of that behavior.

Buying expensive shocks or a ‘big name’ doesn’t guarantee they’re really tuned right, that the adjusters give you maximum grip, or that you’ll be able to integrate them seamlessly into your suspension without lots of head-scratching or potentially frustrating revisions to fix what’s wrong with the shocks.

Most people want to fall in love with whatever they buy – “it’s the best!” It’s natural (and probably a good thing when it comes to relationships!). But neither money nor love buy championships; intelligent choices (or bad choices leading later to better ones), measurement, testing and making effective changes in response to measured results does. Consider it the same as a lab experiment; following the scientific method is the only way to get worthwhile results.

Any number of the vendors that are considered ‘top shelf’ could give someone faster times. But why? and is that setup really ‘the best’? How can you tell if a suspension is really dialed in for maximum performance? That’s nearly impossible to answer. However, data acquisition doesn’t lie, nor do lap times. Combine the two and you have a powerful approach. If you’re able to create a theoretical model of your setup that relates to real-world test results, now you’re really cooking!

Knowing what to measure and then change is where the art and science of suspension tuning merge. I’m definitely still learning, but I’ve been paying attention to shocks from Stock class to XPrepared, street, backroads and track as well. Lessons learned in some areas factor in to others. I took National-level racer Bill Schenker’s advice when I met him for the first time at the Atwater, CA SCCA Solo National Tour in 2007. He slaughtered the very competitive C Street Prepared field. Incredulous, I asked him what made him so fast – ‘suspension!’ So I listened! Studied, tested, built, revised, paid attention to what I saw over the years. Stayed open-minded.

Maximum grip is one vital factor in getting exceptional results. Another factor is the car’s ‘feel’, how it communicates available grip to the driver. Driver ability and preference are the magical third and fourth parameters. From my calculations, actual shock dyno testing, and real-world shock potentiometer/accelerometer/lap time DAQ, I’ve been continually refining my understanding of how these interact.

Some setups will deliver more grip than feel. Others are more about feel than ultimate grip. I can tell what’s being emphasized by looking at dynos and how a car behaves on course . Without interviewing a driver before building shocks, how will the shock builder KNOW what kind of driver they’re working with? Does that builder actually know what creates grip vs. simply gives feel? That’s a subtle but important difference.

I’ve found that a builder usually ASSUMES everyone will want what makes that builder fast, or whatever philosophy that company espouses, or worse, what makes someone ‘feel’ fast. Something stiff and sporty – yay!  But there are enough sophisticated options and top-level results showing that ‘feel’ itself isn’t enough.

Does each driver at Nationals (or any race event) have the best setup? Maybe, maybe not. It usually depends upon how long they’ve been improving it. Many racers will readily admit they’re not master suspension tuners. Some can do both, or work with people who can assist in development.

So what kind of tuning will REALLY make you fastest? It’s a very important and oft-overlooked question at least in the amateur racing world. You hear it all the time in the realm of F1 though with driver preference. It’s a fairly big assumption that the shock builder really knows where grip comes from (definitely not intuitive) and that any adjusters present are able to get the maximum effective range for different surfaces or driving preferences.

Some people are faster with very stiff/tight setups, others like smoother/flow-y suspensions. An excessive preference for too stiff will cripple the ultimate grip. You can drive at 100% but if the setup is delivering 95% grip you’ll lose to a 98% driver with a 98% setup.

Low, mid and high speed damping all matter for autocross. Lincoln, NE, new home of the SCCA Solo National Championships, has seams between concrete slabs that induce high shock velocities (easily well over 10 in/sec) especially when taken at 50+ mph. Driver inputs are in the low-speed region. I’ve taken data at Lincoln last year (2011) in George Hudetz’s STX Mazda RX-8. It was about 95% dialed IMO and we were both in trophy position not having done more than a few practice runs in Lincoln. The first day, in searing heat and 90% humidity, I was in 8th (IIRC) out of 43 drivers. It was so easy to trust the car (yes, the RX-8 is an amazing platform!). With a clean run that first day (3 cheap/dumb cones) I would have been in 4th, only 0.6 out of first! Day 2, I slipped two spots to 10th by driving conservatively. I still took home my first trophy at Solo Nats and his car felt like a championship-winning machine! George’s FCM-tuned Street Touring Xtreme responded well, had so much grip (1.3g+ in sweepers) and we both knew we could drive it harder. I was better in sweepers, George faster through slaloms. The data helped show how much potential the car really had and it would have been enough to win the class.

I was glad that the data I’d taken at Packwood and elsewhere helped illustrate the value of our approach, plus further improvements we could make. Even though the data was on an RX-8, it helped me understand tuning as applied to a FWD coupe, RWD sedan, etc. Interconnectedness is a beautiful thing!

To anyone that really want to get a ‘dialed-in’ setup, simply having an adjuster won’t ensure you hit the sweet spot at every shock velocity range. Also, having seen some Penskes delivered without bump stops to a local autocrosser who was also told ‘you don’t need them’ and having a shock subsequently break, I really had to scratch my head at that glaring oversight.

There ARE subtle areas like bump stop tuning that play into a car’s poise and ability to be consistently taken to the limit and beyond (‘there and back again’). (I know certain National champions are making use of these and not just in Stock classes!).

I’ve talked a lot of  people out of buying more expensive adjustable options from us when it was pretty clear a well-tuned non-adjustable would do, at least until they really knew what they wanted. Most were extremely competitive right out of the box. I’ve also seen people with single and doubles make good use of the adjusters we’ve designed. They have an extremely wide ranges of forces and are concentrated in the 0-3 in/sec range, just where you want it for driver inputs/feel). We’ve made numerous design iterations on these high-end adjustable options, again tied to user feedback and test results. Suspension is one key part, interacting with our customers and being available for fine-tuning is another.

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Suspension Truth #2: Sport Suspensions – The Illusion of Performance Fri, 07 Sep 2012 17:26:11 +0000

Edit: Now with updated graph

So, what the heck does a manufacturer mean when they offer a ‘Sport Suspension’ and is it something you actually want? While I haven’t examined every version available, themes have carried through various makes/models, so what follows are safe generalizations. I even throw in a dyno chart!

OEMs give us lots of specs to get us warm and fuzzy about a car but the majority don’t affect your everyday, commuting-to-work driving experience. How they decide to set up a suspension does. They assume an average commute-only driver just wants a comfortable car. The enthusiast will opt for an (expected) upgrade via the sport version (with infinite colorful names). And if they happen to have a hard-core race version, that is another level all-together. What might feel fun on a 5 minute test drive (and help sell the sporty version) could get annoying (or literally painful) with ownership. Even more so with a disgruntled passenger (“I told you not to get this car!”). I believe (just as I’m writing this) that car makers know they have very little time to close a sale, like a first impression. If they can’t get your attention to begin with, they won’t capture it with pretty brochures or slick commercial spots. Your test drive experience is what will likely sell a particular package.

Fast forward to your first few months with this car; if you commute, most of the time you’re pointed straight and you really don’t want to be jostled all over the place. As I like to say (and have made a video using suspension potentiometer data to prove), there’s no such thing as a smooth road. The dampers and suspension are always working.

Click here to view the embedded video.

Even if most of one’s commute is a mountain road with 99 turns in 4 blissful miles, one still has to cross intersections, deal with potholes and other mundane events. Having a car that doesn’t beat you up is important, even if you’ve cultivated an immunity to the effects of poor damping. Why poison yourself to begin with?

In many sport suspensions, what you get is ‘the Illusion of Performance(IoP).’ I’d trademark it but would rather focus on the Perfect Ride! That IoP  gives your body the sensation of activity – remember that we only sense acceleration, not velocity – but a damper with sharp edges on its force profile will cause time-varying load on the tires. The effect is being jerked around, a change in acceleration over time, like being on a rollercoaster.

An ideal suspension needs to soften the edges of the road, so the tires maintain contact and you get a human body-friendly ride (via muted vertical accelerations) plus solid lateral grip (minimal change in contact patch load during cornering). If the suspension designer felt its buyers would associate roughness with speed (which younger drivers – myself included – usually do), then it’ll emphasize creating jerk via more low-speed damping). For a more sophisticated audience or more expensive car, the low and mid speed will change more smoothly (still not necessarily optimal, esp. due to less compression than the chassis could use) they will typically add more high-speed rebound while keeping high-speed bump lower.

For this article I’ll make reference to 2 suspension options available on the 99-05 Mazda Miata, with a third introduced for 04-05 years. Standard was a twin-tube damper made by Showa, then a ‘Hard S’ package which used a Bilstein monotube and ostensibly stiffer and/or lower springs. From 04-05, the Mazdaspeed Miata came with its own package that had a 1mm larger front bar, 3mm larger rear, and stiffer/slightly shorter. The dampers had been tuned even more aggressively than the Hard S but were otherwise dimensionally identical.

The graph at the top of the page shows the various rear dampers only, but the fronts follow the same trend. A few observations: notice how the standard suspension has a much more smoothly varying shape, a more constant slope from 0 to +/- 2 in/sec (negative = bump, positive = rebound in this graph and all the ones we’ll share). The slope determines how much jerk the tires and you experience. The Hard S is 50% stronger in compression @ 1 in/sec and the MSM another ~15% on top. The difference in rebound and ratio of bump to rebound is what determines the degree of jacking down. At 1 in/sec, where small, repeated movements (like any rippled road surface) will affect the dynamic ride height, the ratio is a little less than 1:1  R:B for Showa, then 1.5:1 for Hard S and about 2:1 for MSM. The ‘sportier’ suspension specialize in more immediate steering feedback, yes (turning the wheel results in movements up to ~3 in/sec at the damper in the Miata’s case). But that degrades ride quality and road holding as well. Notice that the mid and high-speed damping isn’t very much different. In fact, the Showa has a strong slope for both bump and rebound, so it would tend to resist bottoming out better than the ‘sportier’ OE, Bilstein-based suspensions! One could also argue that the Bilsteins will blow-off better, which is true but I don’t find the amount of damping to be objectionable and in fact one could almost do a rally setup which was the inverse of the OE curves and have a wicked fast, comfortable car. Yes, I’ve done this! Yes, we’ve built this for customers. How stupid fast do you want to go?

I want to make it very clear that 99% of all complaints of poor ride have to do with jacking down via excess rebound damping, potentially combined with frequent engagement of the front bump stops which gets worse due to excess rebound/jacking down.

Click here to view the embedded video.

Jacking down can be an automakers best friend for numerous reasons. First, you get an additional ‘jerk’ when the bump stop acts as a supplemental spring. Two, the front end will get stiffer as the bump stop engages, increasing weight transfer across that axle and inducing more understeer. So even if you chuck the car into a turn (a novice driver won’t be trail-braking), it won’t want to turn. At least, not as eagerly as you’d like. Jacking down exerts a self-corrective effect on the driver. You are going slower in turns, you’re actually driving 50 though it feels you’re doing 80 (‘wow, what a sporty ride!’). And if you have bigger sway bars, then that jacking effect causes a coupled (cross-axle) time-varying load on both tires! Holy understeer, Batman!

I don’t fault them for doing this. Putting a very capable car in the hands of an inexperienced driver could be a bad thing. But they don’t tell you that this IoP is what they’re up to and that lack of fine print has bothered me since I learned these Truths. Pricier vehicles get better suspensions though it seems there’s always room to remove a bit of understeer, to have a bit more grip and sure-footedness, a bit more confidence.  This isn’t including active suspension … although we did tune a Nissan GT-R last year using the OE Adaptronic Bilsteins. Results were very good and we could retain the Soft/Sport mode settings. It was a 2009 GT-R and the damping was definitely more biased to jacking the front down.

In the next article I’ll illustrate a few setups that have strong high-speed rebound and what effects you’d notice with that.  This will include accelerometer traces showing the strong downward (negative) accelerations which are very hard on one’s body. I’ll also continue discussing the effects of bump stops on ride and handling.

HOMEWORK! For fun, check how close your front dampers (strut or shock) are to sitting on the bump stops. Report back in the comments section! I know for certain the Mini Cooper rests on the front bump stops, the Mitsubishi Evo and Subaru WRX essentially do the same.

Shaikh Jalal Ahmad is the owner of Fat Cat Motorsports


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Suspension Truth #1: Planes, Trains and Automobiles – The Psychology of Suspension Tuning Fri, 24 Aug 2012 16:11:53 +0000

Our newest segment, “Suspension Truth”, comes to us courtesy of Shaikh J Ahmad.  An engineer by training, Shaikh is the owner of Fat Cat Motorsports, and a self-styled “Suspension Wizard”. Shaikh creates custom suspension components for a variety of cars, including the Mazda Miata and RX-8, the Nissan 350Z, Mini Cooper and Honda S2000. Back when I had my 1997 Miata, I ordered a set of coilovers from Shaikh, based on his reputation for creating suspension setups with a previously unheard of balance between ride and handling. The Fat Cat coilovers are one of the few products I’ve ever bought that were able to live up to the hype. Over the next few weeks, Shaikh will delve into the science of suspensions, and provide his own analysis of a number of production cars.

What’s your least memorable train ride? Simple question, right? If you’re reading this, I’m going to assume all of them. Unless a screenwriter threw you into an adventure film without your consent, it’s what we’d expect. This brings to mind a popular driving metaphor – ‘handles like it’s on rails.’ That’s our ideal in suspension tuning, to be glued to the ground and also as comfortable as possible. Easy when you’ve controlled every degree of freedom as with a train track and groomed earth beneath.

But what about your least memorable plane flight? Again, I’d hope most of them. How about the most memorable one – turbulence anyone?  Whether chop, CAT, or simply bumpy air, turbulence can be annoying, as in delayed beverage service, or utterly terrifying. The unpredictable, jerky movements of an airplane caught in Mother Nature’s fury sharply draws your attention to the immediate environment. You aren’t relaxed anymore, thinking about the miles of air between you and the ground. You have to trust in your pilot, crew and the plane itself to handle the situation, working in harmony to return you safely back to Earth.

In between these extremes is the spectrum of what an automobile suspension can offer.  As a driving enthusiast and amateur racer in my 20s, I only wanted suspensions that made my car handle better and go faster. Comfort was secondary and in fact I believed (as many do) that to be fast you must be uncomfortable. Ah, brainwashing by race companies and the follies of youth! Having trusted marketing hype from both automakers and aftermarket companies, I’ve come to see patterns in the past 15 years of my pursuit of Suspension Perfection. Ultimate speed and ultimate comfort. How are they linked, if at all? Can I make my trip to the race car unmemorably smooth and also have razor-sharp handling for a backroad jaunt, autocross run, track session or hill climb? What about safety, responsiveness and predictability?

Any automaker has to fulfill the task of keeping a vehicle on the road. They can do it in a bare-bones fashion, like a budget economy car that doesn’t inspire much confidence but gets you from point A to B. At the very high end, we have the Holy Grail: a buttery-smooth ride with incredible handling. Normally you pay superlative prices (Aston Martin, Ferrari, etc) for this achievement, but I’ve found that cost has very little to do with making an exceptional suspension. You need to understand the designer’s mandate, see if that matches your needs, then choose components (or a vehicle itself) that deliver. But we don’t get handled a personality test results for a Honda Civic, Toyota Camry or Porsche 911 Carrera. We have some bias based on past experience, what we’ve read, felt or been led to believe. But what really goes on in that murky black magic area of suspension design? By starting with an examination of the psychology behind a vehicle, why it exists, we can understand certain design choices then make targeted improvements to a production-based road car to the point it feels truly amazing.

Please note, this kind of suspension harmony matters whether one get groceries or chases championships. It’s been a fascinating process of discovering the truth of how grip produces both great ride and handling both. For a street-driven passenger car, how the suspension deals with the road, mile after mile, creates a somatic experience that can promote either ease or dis-ease. I’d rather see a driver smiling and relaxed after a trip than stressed and hurting. A relaxed (not numb), in-control driver is a safer driver and a happier human being. There’s also a very important somatic experience to the race car driver, who needs to have hyper-confidence in their machine’s responsiveness to dance it on the edge of adhesion.

One video in particular was very illuminating to me. It was of a journalist who had a chance to drive a few laps in a Formula 1 car. Once the lengthy process of preparing him for the experience was complete (simplified as it was in his not-very-physically-fit case), he took his laps, whooping the whole way through. Once he stopped the other reporters asked a seemingly rhetorical question ‘you just drove a Formula car! Wasn’t it really harsh?’ to which our lucky journalist gives a surprising answer: “No, in fact it was quite smooth once you were up to speed!”

Is it that really all that surprising to hear this truth? To give a driver confidence and ultimate speed, the proper suspension has to keep the tires in contact with the road. What’s good for the rather-soft tires (imagine driving around on a partially cooked egg) is good for the very soft driver.  Going stiffer than is necessary robs grip and induces more discomfort. The just-stiff-enough setup will reward the aggressive, competitive or racing driver in many ways.

We’ll continue our explorations next time with a topic that is even more subtle – what does it mean to have a “Sport Suspension” and do you really want one?

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