Annie Sam 3 wheeling

The Ultimate Guide to Suspension and Handling Part I: Wheels and Tires

by Mike Kojima


Horsepower is sexy and chicks dig it, at least a lot of meatheads think that way. Making horsepower is relatively easy. A lot of competent people know how to make power, lots of it. Until drifting became the rage in this country, handling and cornering prowess was for geeks, the road racing elite and autocrossers. Handling was for dweebs that raced around cones in parking lots, or loners prowling canyon roads at night, not for cool people in the scene.

How to tune a car's suspension was an unknown art in the world of mainstream performance, simply because most people didn’t care about handling. Most people emulated the world of road racing by making their cars low. Low was cool, low was handling.


Dog II


Now that drifting, Time Attack, racetrack hotlapping and autocross are becoming popular, suspension tuning and handling are becoming important items for discussion, experimentation and debate. Building handling into a car is not necessarily any more complicated than building power; it’s just that the subject is somewhat more esoteric and definitive information is not as widely available.


Tyler McQuarrie Team Falken

Finding straight-line horsepower gurus for hire to help you is relatively easy, but finding an expert to make your car corner well is a tough deal, fraught with mystery and intrigue. The solution? Make yourself the guru. If your automotive interests are greater than the one-dimensional urge to blast straight down the 1320, brag about dyno sheets on internet forums or install neon and strobe lights to your interior and undercarriage, let’s get to work. There are 4 basic steps to achieving a well handling car and in this first part of our extensive series we'll discuss the first--wheels and tires.

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Tuesday, January 05, 2010 3:31 AM
I'll add that the wheel stiffness in the lateral direction is a point of interest. Making a wheel light is great, but doing so at the expense of lateral stiffness seems to raise lap times.
Mike Kojima
Mike Kojimalink
Tuesday, January 05, 2010 4:21 AM
I have never had a wheel flexing problem. Have you?
Tuesday, January 05, 2010 8:02 AM
this is exactly what I'm looking at now...
Big J
Big Jlink
Tuesday, January 05, 2010 8:52 AM
This is a lot of the reason the lightweight Wilwood brakes and rim combo we use on the track car works so well. They free up some power also. Inverted shocks/struts move the shock body from the unsprung side of things to the sprung side also. You get really nitpicky and you can add lightweight lugnuts to the mix and run less grease in the CV joints.
Tuesday, January 05, 2010 10:59 AM
No Mike I haven't, but that's because I run Panasports. ;)

There was a memorable test a Japanese magazine did where they took a well known racing wheel (17" and 11 lbs. I believe) and told the company to shave 2 lbs. off the wheel by redesigning it. (Or the company gave them two different wheels and told the magazine to "test" them to prove a point? I forget the details.)
The company insisted the lighter wheel would not perform as well because of the inevitable loss of stiffness. The test was done on a 350Z, and the driver lapped with the regular wheels and then the lighter wheels. While the driver could feel the difference in acceleration immediately between the two wheels he reported the lighter wheel feeling a little less planted and at the end of the day the stiffer wheel came out faster.

(They also reported on some new tire bead retaining compound applied inside the wheel rim that was basically like sandpaper and kept the tire from rotating much around the wheel as the laps piled up which kept them balanced better? Just trying to describe the article better in case someone can find it. I tried but came up empty.)

It makes complete sense to me. You don't want the wheel to flex in cornering so the tire and the rest of the suspension can do its job. Not much else to say really.

I know it's over simplifying the matter, but I tend to stay away from wheels with spoke designs that don't intrinsically help combat lateral flex. Sure, they give you the brake clearance everyone is after, but at what cost Mike? At what cost?

(Can you tell I'm just tired of typing and getting a little loopy?)
Tuesday, January 05, 2010 11:42 AM
This sounds like an interesting article Ben, do you remember at least which publication did this?

I'd disagree with this magazine that this was a fair test tho. Mostly because "shaveing 2 lbs" off a wheel will obviously, lower its strength to some extent, then increases the wheel deflections, then inevitably increasing compliance in you suspension system. But IMO the increase in compliance will be relatively insignificant in raising lap times as long as all the other variables were pretty close in each test. Theres plenty of other factors that could of resulted in slower lap times if these tests weren't thought out properly. So i don't agree with that conclusion and test. But i'd really be interested in reading about the details of this.

But anyways i think theres bigger battles to be fought in suspension tunning than to be worring about compliance from a wheel.
Mike Kojima
Mike Kojimalink
Tuesday, January 05, 2010 2:50 PM
If you take two lbs off of the wheel/tire, you will have to readjust the dampers on a real race car. I found that you have to readjust if you change the offset 10mm as well.

Perhaps the change for the negative is due to misadjusted dampers.
Tuesday, January 05, 2010 3:08 PM
Surprised not see Motgei Traklites on your list of light wheels. 15's clear Wilwoods with room to spare with an 11" rotor, and they have great lateral stiffness at just under 10 lbs per wheel in a 15x7. I've used mine on the street and track for 2+ years since Dave C put them on the car, they have been fantastic. I don't drive all that smooth of roads off the track, either. 205/50/15's and either Nitto NT01's or the Kuhmo XS's for tires. My only bitch with the Kuhmos is as they wear down after many heat cycles on the track, their wet traction drops significantly. I'll only be using my Nittos on dry days and saving the new set of XS's for getting to/from and rain tires. If I didn't have the Traklites, I'd have TE37's, much like the NISMO Ray's 5 spokers I run on my G Coupe. 275 tires are the sh*t on that car in the rear paired with 245 fronts.
Tuesday, January 05, 2010 3:10 PM
Mike, I can see of course changing the dampers, 2 lbs is a lot. But why the offset change? Running less offset? Or more? Look forward to reading more of this series, thanks.
Tuesday, January 05, 2010 3:11 PM
...and why does my Avatar look like a green triangle who picked a deathmatch fight with the wrong polygon? ;)
Tuesday, January 05, 2010 3:23 PM
Last question, really - Mike, why is Annie's car getting so much lift in that photo? Mine did that before I bumped up the springs (with a new set of dampers too) from 350R/250R to 450/350R - the front was too soft when pushed harder - and dialed back the rear Progress Sway from max stiff to soft or med. Front is also on softest or med depending and the car stays much flatter to the track at speed, doesn't tripod much at all. I'd go higher but this is still a street/track car, not a race car. But 450 was a good direction to go:
Pre-spring change May: http://www.cartct.com/results/05-08-09/05080989.jpg
Post-change same place Aug: http://www.cartct.com/results/08-28-09/082809333.jpg

yo vanilla
yo vanillalink
Tuesday, January 05, 2010 3:30 PM
Hey my Enkei's made the pic list :D . Glad to see this series, Mike's suspension bits were my favorite series from SCC. One concern though - some jokers who make a magazine in FL recently tested the theory of wider tires = better using an RX8. Granted both sets were wider than stock, but they found the narrower of the two to be faster on their auto-x course by a decent margin (although the wider gave the feel of more traction during the run).

I'd like to see more testing on this idea. I've had a few discussions with other local Subaru chaps who wouldn't consider that there may be a point of getting too wide.
Tuesday, January 05, 2010 4:21 PM
The R35 , an 18 inch wheel will clear the 380 mm brakes. You were there that day we tried those Nismo wheels on an R35 at Steves shop.
Mike Kojima
Mike Kojimalink
Tuesday, January 05, 2010 4:42 PM
But Mizuno says the clearance is needed for cooling.
Tuesday, January 05, 2010 4:44 PM
It takes more than clearance with no ducting, trying to stop a 480 hp, 4000lb car.

Doesn't matter if they are 380 mm with 6 pot vented pistons.

Mike Kojima
Mike Kojimalink
Tuesday, January 05, 2010 4:52 PM
If you change pads and rotors on the R35 it can stop pretty well. We are going to do an article on this in the near future.
Tuesday, January 05, 2010 5:15 PM
I am working on some R35 Brake info for my site. The available aftermarket parts. . Factory brakes are factory brakes. Everything is some kind of compromise. They don't stop bad stock, but they don't do it repeatably. Its that 4000 lbs of weight.
Mike Kojima
Mike Kojimalink
Tuesday, January 05, 2010 6:13 PM
1.7 g's decelleration. Holds up lap after lap.
Mike Kojima
Mike Kojimalink
Tuesday, January 05, 2010 6:24 PM
We had Motgei Track lites on Project Scion and they bent like butter the first time out. Plus they are no longer made although some places still have them in stock. When we swtiched to Enkei's RPO-1's no problem.

Changing the offset changes the suspension motion ratio and you can really feel it as it adds to the moment on the shocks. You would be amazed how different it can feel.

Annie used to take a way inside line at Buttonwillow running CW in the bus stop so she could take it flat. She would jump her car entirely over the FIA curbs on the inside of the last turn. This picture is right when she was landing. We have some of her up on two wheels with about a foot of air but its from the wrong side.

Buttonwillow shaved down the FIA curbs to attract motorcycle racing so now you can't get air like this anymore.
Wednesday, January 06, 2010 5:08 AM
I can't believe you had that kind of luck with Traklites, unless they were 17's or maybe even 16's. The only other pair I've seen toasted simply lacked enough tire to protect the rim, 16's with very low profile on a Honda, maybe +2 sized. Summit still lists 15's as in stock. Maybe the design just does not scale well w/o more tire sidewall (205/50/15).

I've driven these wheels 3000 miles XC in 2007, through construction and every bad stretch of hwy, 13k additional miles of East Coast hwys and backroads (not good pavement), 2000 miles to the SR20 Conv and back in March down I-95 (crap, esp in NJ), 2 seasons of autox, bumping off berms and a few off-line excursions (spins) over berms, one into the infield. That's a tough wheel - I'd buy another set of for my car in a minute. Still smooth as can be on the banking at 120+ at Pocono PA.

Plus recall Dave C had them, who knows what terrors they saw before I got them? ;)

IDK if the Enkei RPO-1 clears my front brakes in a 15", have to check into that.

So I inherited a set of Kosei K1's with my second car - 38 mm vs. 35 mm (Traklites). Enough difference to worry about?

Thanks for the info, look forward to the next installment!
Mike Kojima
Mike Kojimalink
Wednesday, January 06, 2010 7:07 AM
They were 16" With a more inboard offset, it won't be too bad, its outboard what makes things feel weird.
Dan Barnes
Dan Barneslink
Saturday, January 09, 2010 6:10 AM
A tire mounted on a rim at the wide end of the recommended range won't just be more responsive, it will actually make more grip. However, for street use, the sidewall will have less vertical compliance and ride a little bit stiffer. Or, depending on damper tuning, it may let the shocks do a better job of controlling things and actually ride better.

The article referenced by those guys in Florida was actually written by Woody Rogers of The Tire Rack, who shared a B-Stock RX-8 with another guy. The testing was done at the Rack's track. They were squeezing wider tires on B Stock-legal 8-in wide wheels, up to 285s, at least one of which wouldn't tolerate being mounted on a rim that narrow and still had a wrinkled sidewall, even when aired up. The guy who won five consecutive B-Stock national championships in an RX-8 uses 245s. When wheel width is limited by the rules, a little more rubber can help. A lot more may not be better than a little more.

245s will work better on 8.5, 9 or even 9.5-in wide wheels than they will on 8s, but you may not want to stretch them onto 10s. "If" you can't afford or borrow multiple sets of wheels to test, a safe bet is to pick a wheel at the maximum recommended width for the tires you're running, or maybe 0.5-in narrower than that. Don't take the "measuring size" in the middle of the range as any kind of ideal, it's just the size they picked for measuring section width, etc.
Mike Kojima
Mike Kojimalink
Saturday, January 09, 2010 8:41 AM
You are completely wrong. A stretched tire will have better transient response. It might be less camber sensitive but will probably have less braking and accelerative grip. The last three depend on the tire construction heavily and cannot be generalized. If the tires are stretched too far, the grip will fall off.

Improved transients are a big reason why stretching is popular in SP and Mod classes in autocross and in drifting. It can make the car very crisp in offsets and stuff sometimes at a loss of overall mechanical grip.

In a general article it is not wise to give specific advice like this due to the variables better different tires and cars, we just simply stated that a wider rim than the recommended middle of the road width will work better and caution not to over do it.

For instance on my personal EVO, I run a 245/35-18 on a 9.5 inch wide wheel so it is mildly stretched. The Cyber EVO runs this size tire on a 10.5" wide rim with apparent good results.
Mike Kojima
Mike Kojimalink
Saturday, January 09, 2010 8:46 AM
Dan Barnes found the original article on wheel stiffness.


Since dynamic links don't work in the comment section you have to cut and paste this into your browser.
Mike Kojima
Mike Kojimalink
Saturday, January 09, 2010 3:43 PM
Discovered how to get rid of the ghey avatars here.


Go here and register. By bye lame avatars!
Kit W
Kit Wlink
Saturday, January 09, 2010 6:56 PM

I have not found either of the following to be streetable race tires:
Michelin Pilot Sport Cup
Kumho Victoracer V700

I would put both in the 3rd category, I put about 3000 miles on a set of MPSCs and they got hard as rocks and I scared the CRAP out of CL Knight's husband in my e36 M3 with them since I couldn't keep the damn car pointed straight. The V700s are REALLY nasty as picking up punctures on the street and quickly heat cycle themselves to death
Mike Kojima
Mike Kojimalink
Saturday, January 09, 2010 10:40 PM
I sorta think that PSC's can be driven a long time, they would probably last 20k miles on the street. That doesn't mean they will be any good as race tires but they are not that good to begin with, as they are in my opinion weird tires. Don't wear, take a long time to come up to temp, then go away real fast and poor at heat cycling.

I agree with you that the V700's are close to 3. I was debating where to put them. I didn't think they were sticky enough for 3.
Monday, January 18, 2010 8:36 AM
Hi Mike

Some questions on offsets if you dont mind.

I recently got hold of some RE30 for my car (08 Audi S3, same platform as the mkv golf gti/r32) from a seller, and he "vouched" that they would fit my car. Apparently, that is not really the case, as the offset of the wheels are ET35, and the stock car is running on ET50.

So now, I'm 15mm too far out each side, what options do I have?

1) someone offered to skim/shave the wheel by a few mm, is that even safe? If yes, what sort of concerns that need to be addressed?

2) increase camber a little to tuck the wheel in further?

3) use 215-40-18 instead of 225 tyres to stretch it slightly? I'll reset the computer to correct the speedo.

4) ???

Will call the seller to exchange wheels to the right ones tomorrow, but if that doesnt work, I need a solution :(

Also, is the claim of running less positive offset will kill wheel bearings sooner true? Can the increase of a few mm of moment arm be that disastrous? Surely the lateral forces encountered while making a simple turn or carrying heavy loads are much larger than what the increase moment would do?
Mike Kojima
Mike Kojimalink
Monday, January 18, 2010 8:56 AM
I would really try to exchange the wheels for the correct offset, you were misrepresented in the sale so they are responsible. If not I would roll the fenders then run negative camber considering that I you go more than 1.7 or so negative you are gonna start to really hurt tire wear in a daily driving situation.

You can probably get away with negative 2 in the front with zero toe. I run 2.5 degrees negative in my EVO and my Z32 but they not daily drivers (I drive a turck most of the time). I used to run 2.5 degrees on my daily driven AE86 and RX7 without too much bad stuff happening.

Rolling fenders in a nice car is somwhat tricky. In my opinion the paint will crack no matter what tricks you do like heating, etc. So I control where it will crack by sanding to thin and area where the fold will be. After rolling I prime the fender lip and paint it with bedliner spray.
Miles (San Antonio)
Miles (San Antonio)link
Monday, January 18, 2010 12:49 PM
Yet another good article. I love my Gram Lights and can't see myself ever selling them. I noticed an immediate difference when running them with a good Nitto street tire the first time. 4 tire changes later....I still love the rims. I would be hard pressed to get anything other than the F series.
Thursday, January 20, 2011 2:28 PM
It is always awesome to read an article like this and find tidbits of information that aren't just slightly new but 100% new to you. And to think, when I was 17 I thought I knew everything. Learning is fun. Cause knowledge is power!
EB Turbo
EB Turbolink
Friday, March 25, 2011 1:30 PM
Mike, about your comment on wheel weight and offset making damper changes is correct. I believe your illustration on scrub radius is a bit misleading. You just so happened to draw the tire centerline right at the hub face which can be a bit misleading. The description of tire/wheel centerline is correct. But thinking it is the same thing as the hub centerline is not.

Changing the wheel weight and/or offset effect the damper in similar but their own ways. Changing any type of unsprung weight has the same effect as let's say a light weight flywheel has to an engine. When you change to a lighter wheel there is less mass/inertia working against the damper. this might force you to change your shock settings as piston velocity has changed. Making your damper work in a slightly different range then before.

By changing the wheel offset you are also your changing scrub radius. Doing so adds dynamics to your motion ratio. The more scrub you have the more your wheel has leverage against your damper. The less scrub the less leverage. I'm sure you know these things I just wanted to voice them to clear up any misconceptions the readers might have.
Tuesday, July 19, 2011 3:35 PM
Hi Mike! I’m sorry to revive an old post but I’m going from the ground up starting with this article. I have a list of questions that I hope they would be easy to answer as for I don’t want to monopolize on your free time. 1) I have the stock 19” RAYS (370Z Sport package) and I would like to continue with 19” but you stated the 18” is the usual practical maximum wheel diameter for larger cars, which I consider my car as a larger car. Should I consider going down to 18” to increase handling optimization? I feel that this shouldn’t be necessary since the design and engineering of the car took this into consideration for handling optimization but I rather not assume. 2) Outside of using other references like tirerack.com or whoever, do you have a general rule for increasing rim size and reducing sidewall height conversion for any car application? I know you gave a FWD example and the math made sense but, again, I rather not assume (I’m not going to apply this to my car but still curious). 3) I’ve received mixed advices that I should track my car stock before making any suspension modification so I understand the limits of my car and vice versa. What is your take on this? 4) I went from stock 275/35R19 to 185 rear and stock 245/40R19 front so I’m curious, will you write on the recommendations and limitations of staggered wheels? If you have already, sincerely apologize. As I had mentioned, I’m learning about suspension and handling from the beginning starting with this article. Thank you very much for taking the time and your generosity in sharing your knowledge!
Thursday, July 21, 2011 2:24 AM
Very nice article! However, don't suspension arms' weight count half in terms of unsprung mass?
Monday, July 25, 2011 12:50 PM
Hello Mr Mike! I come from speedhunters and i must say is the TECH side i was looking for. It's nice to see you getting in this specific details. Very nice article, but still i've got some questions. I've got a 180sx(s13) carrying 225/50R16 on 16x7.5" aluminium rims, Bilstein B6 dampers, Tein springs(don't remember the spring rate), and polyurathane bushings all around. The chassis sits on what i think 0-2cm higher than normal. Here in Cyprus because of various road upgrading the tarmac is very bumpy. Yes the tire wall explodes out like a drag racer wheels but i still haven't feel insecure about grip. The tires are not the softer/gripper ones but i haven't yet a problem with grip. About response yes it's true that is less, but after installing front and rear strut bars reducing the chassis flex response has improved significantly. Though you may sacrifice response you gain more grip by going wider, right? Still i've got s13's understeer;p
In addition i would like to see an article explaining tire profile sizing and how it affects handling(like GT500/GT1 cars), and how WHEELBASE and TRACK radio affects a chassis natural handling...like s15/rx-7 have neutral handling because of this...Cheers:))
Mike Kojima
Mike Kojimalink
Monday, July 25, 2011 1:05 PM
Lower profile means faster transient response.
Saturday, October 26, 2013 12:38 PM
Hello Mike, congrats for your willingness to write about the subject. I'm quite interested in kinematics and dynamics.

I'd like to clear something up in page 2 of this article when you mention that sticking the widest tyre you can fit in the wheel well is the best option to gain in cornering force.

I guess your affirmation is based on the assumption that people are reading the entire article series and have the intention of also carrying out mods to suspension to control a wider tyre, right?

I often see boyracers (bear in mind I live in the UK) with stock suspensions in their hatches but wide tyres and I wonder what is the point!

If a suspension of a production car is designed for a range of tyre sizes, such as 165 to 185, there is no point fitting a much wider tyre than that without any other mod since, during roll, chances are your suspension is either not stiff enough to control the contact patch or your camber gain is low.

What is your view on that?


Mike Kojima
Mike Kojimalink
Saturday, October 26, 2013 7:20 PM
I agree with you.
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