Track width

#1

I have a fairly serious oversteer issue that I can’t quite seem to fully get a handle on. I’m running an ST swaybar set to its softest setting, 0 toe, and about 1 psi higher starting pressure in the rear than in the front. Correct starting pressure for the RR’s still seems like black magic to me. Anyway, I finally got around to unearthing the race tires from the u-store that passes for a cockpit and measuring the rear track width. I’m at about 164.25 so 37.5 mm to go give or take. Are we talking about a miracle cure for oversteer, a definite change in handling characteristics, or a slight improvement? I’ll probably invest in spacers either way but just want to set expectations.

#2

What is yor rear toe? Even slight toe out will cause crazy oversteer. 15 or 20 mm spacers to the front will help slightly but I suspect the culprit is bad alignment or corner balance.

#3

Yep, to quote Chuck Baader, “Rear toe out will scare god”.

I don’t agree with Richard on spacers up front. I found that 5mm rear spacers tamed the oversteer on my car. And this was a case of where the corner and fore/aft balance was good and alignment/setup was good.

#4

Actually, "rear toe OUT will scare superman!!

Go with 1/16" to 1/8’ toe IN. Usually needs to be done at a very competent shop WITH YOU IN THE CAR.

If still loose, start adding rear wheel spacers…I like 10mm.

That should make the car push, so stiffen the rear bar to compensate.

#5

Oops. Toe was set at a competent shop, but not with me in the car. And it hasn’t been corner balanced yet. If, as Ranger asserts, toe doesn’t vary measurably with deflection, why does it matter if I’m in the car?

#6

You want the car setup exactly how it will be on the track. That means with you in the car and some amount of gas, corner weighted, and tires to the correct starting pressure.

Re corner weight: LF and RR should be as equal as possible to RF and LR. You can use spring rubbers to adjust corner weights. NOTE: the car must be adjusted with the sway bars disconnected. Then reconnect with no preload.

#7

How recently was the toe checked? I check (and often find the need to adjust) before every race weekend.

Lack of driver weight will have negligible effects on toe, but very important in camber and bar adjustment.

#8

You’re running 1 psi higher in the rear now and having oversteer issues. Before spending on spacers try playing with pressures a bit, either the same f/r or bump up the fronts slightly. FWIW, I use 2 psi higher in front.

#9

This afternoon, although to be honest I have a hard time getting repeatability closer than 1/16. I have the serrated IE adjusters and so far have not seen any change in camber or toe. Sounds like the general advice is get everything else so you trust it and then worry about spacers.

#10

Don’t worry about cold pressures on your tires, instead focus exclusively on hot pressures. Cold pressures are the primary variable you play with to get to your goal…your desired hot pressures. Focus on the objective. Then play around with how to achieve that objective.

Make sure nothing funny is going on. Binding sway bars or a weak shock will hose up handling, a diff that is too “tight” will cause understeer, tired bushings and loose fasteners will make for erratic handling, etc. Make sure everything is healthy, then carefully change one suspension setting at a time.