The Truth About Cars » geometry http://www.thetruthaboutcars.com The Truth About Cars is dedicated to providing candid, unbiased automobile reviews and the latest in auto industry news. Thu, 30 Apr 2015 19:00:07 +0000 en-US hourly 1 http://wordpress.org/?v=4.0.1 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 editors@ttac.com editors@ttac.com (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 » geometry http://www.thetruthaboutcars.com/wp-content/themes/ttac-theme/images/logo.gif http://www.thetruthaboutcars.com Piston Slap: A Primer on Wheel Offset and Backspacing http://www.thetruthaboutcars.com/2015/01/piston-slap-primer-wheel-offset-backspacing/ http://www.thetruthaboutcars.com/2015/01/piston-slap-primer-wheel-offset-backspacing/#comments Mon, 19 Jan 2015 13:26:07 +0000 http://www.thetruthaboutcars.com/?p=984898   Long-time TTAC Commentator 86er writes: Hi Sajeev, Could Piston Slap furnish me with a be-all/end-all explanation about wheel offsets? The more I try to read up on it on the web, the more confused I get. I’m pretty clear that RWD (at least traditionally) went with the low-offset while the FWD revolution made high […]

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Yum. (photo courtesy: www.crownvic.net)

 

Long-time TTAC Commentator 86er writes:

Hi Sajeev,

Could Piston Slap furnish me with a be-all/end-all explanation about wheel offsets? The more I try to read up on it on the web, the more confused I get. I’m pretty clear that RWD (at least traditionally) went with the low-offset while the FWD revolution made high positive offsets the industry standard, at least in passenger cars.

A few years back, I had purchased a set of winter tires on rims for my trusty ol’ 92 Vic and later after research found out that the rims were medium-offset that went on a 4×4 Ranger of similar years. I’ve heard that putting on a different-offset wheel can hurt steering/suspension parts like ball joints, but I’ve never seen it in black-and-white, so to speak.

Sajeev answers:

Let’s cover the basics of both wheel offset and backspacing: offset is the location of the mounting hub in relation to the center of the wheel’s barrel.  This mounting hub goes to flat surface where car’s suspension holds the wheel (i.e. the hub on the spindle).

http://www.fastcar.co.uk/

Image Courtesy: www.fastcar.co.uk

 

A positive offset pushes the wheel’s hub away from center, closer to the outside of the car. Negative offset is the opposite: sucking the wheel’s hub closer to the inside of the car. Zero offset means it’s smack dab in the center.

I question if the traditional FWD/RWD offset difference still holds water.  While FWD wheels often have a more positive offset than their RWD counterparts, all (most?) modern vehicles have flat faced wheels (for aerodynamics and countless suspension needs?) stemming from a more positive offset wheel. Need proof? Look at your own platform: peep the redesigned front clip and the mandated wheel redesign of the 2003+ Crown Vic.

CrownVicFrontSusp05_06_edited

(photo courtesy: http://www.ridetech.com)

Oh wait, the Crown Vic barely changed at all from 1979 to 2011.  It was such an antiquated pile: must remember to toe the autojourno line, never speak of Panther Love! But I digress…

In theory you should keep a close-to-factory offset to optimize steering geometry and wheel bearing health.  In practice, it might not matter: especially for a set of winter tires. You probably can’t drive aggressive/fast enough to care.  Probably…

There’s also the matter of torque steer on FWD machines, mostly for those with unequal length half-shafts. But most modern vehicles use equal length shafts?  (Have at that, B&B!)

You also need to consider backspacing. This ensures the width and offset of wheel you chose will clear your body or suspension, especially on cars with strut suspensions.  Instead of my usual ramble, I think this video really nails it.

Click here to view the embedded video.

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.

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Vellum Venom Vignette: It’s Hip to be…Hexagon??? http://www.thetruthaboutcars.com/2012/10/vellum-venom-vignette-its-hip-to-be-hexagon/ http://www.thetruthaboutcars.com/2012/10/vellum-venom-vignette-its-hip-to-be-hexagon/#comments Thu, 18 Oct 2012 18:33:53 +0000 http://www.thetruthaboutcars.com/?p=464147 My first semester’s Automotive Design class (an elective, taught on a Saturday no less) at CCS was taught by a cool, laid back dude.  But he’d get unhinged when his students drew static looking wheels: his beef was four spoke wheels. They are impossible to make “cool”, unless you own a Scion xBox or a […]

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My first semester’s Automotive Design class (an elective, taught on a Saturday no less) at CCS was taught by a cool, laid back dude.  But he’d get unhinged when his students drew static looking wheels: his beef was four spoke wheels. They are impossible to make “cool”, unless you own a Scion xBox or a Nissan Cube.  But can you have a cool wheel that’s not your average spoke-y affair?  Welcome to the Hexagon wheel.

 

Even this unit from the Fox Body Lincolns (1986 Continental and Mark VII) has a charm that verges on ludicrous. The dominance of the hexagonal hub cap is much like the Nissan truck above, but with cleaner lines (i.e. more expensive like an Apple) and a shiny finish.  Note how both the Lincoln and the Nissan utilize negative area on half of the Hexagon’s planes to add depth to the package. And the symmetry in the Lincoln’s positive/negative space around the hub cap makes the design more appealing the more you stare at it.  Possibly.

While the Nissan has 6 lug nuts and functional cooling passages, the Lincoln’s 5-lug affair is well…very Salt Flat Racer worthy. Point is, both designs work. Especially if you’re in the mood for some Harold Faltermeyer. Or some convulsion-inducing Dubstep.

 

Or not. Peep this vintage Packard wheel with a strong hexagonal form. Packards regularly sported the red hexagon, and I suspect that 6-lug wheels had something to do with it. Perhaps this was the genesis of it all. Did you think TTAC could make a correlation between a Nissan truck and a Packard today?

Well, there it is.  You’re welcome.

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