Was talking with a guy at college who races various homebuilders and told how mine was gonna be setup. He asked me about how the rear wheel toe-in was set and said without it the car would be un-driveable.

I said I didn't know but thinking about it does such a thing even exist? If you're using a Live Axle how can it exist? If you're using IRS then presumably it can be built into the wishbone/upright.

Was he in fact insane and meant either camber or castor?

Dubiously,

James

Not entirely insane...

If I remember correctly (and I'm sure people will tell me if I'm wrong) a RWD back axle should have a degree or so of toe out to cater for the bending forces when the tyres are driven forward.

This is the same as the front wheels of a FWD car.

This toe-out is built into a fixed axle and, presumably, must be set by the builder in an independent setup.

David

[Edited on 13/2/03 by David Jenkins]

[Edited on 13/2/03 by David Jenkins]

Yep, as a rule of thumb, the driven wheels (front or rear wheel drive) usually have some degree of toe out, for the reason David says, with non-driven having toe-in. This is basically to compensate for flex in rubber suspension nushes etc. But there are quite a few examples out there that dont follow the rules, either due to the way the suspension is designed, or the fact that the bushes or joints used are not going to flex in the first place. For something like a Locost, the reverse is likely to be more beneficial, i.e. toe in on the rear and toe out on the front. Trouble is, the ideal settings depend on lots of other stuff.....
If you are using a live axle then you are pretty much tied to the original setting of the donor axle. As for being undrivable, I think there are a few builders out there who would be inclined to disagree.....

HTH Stu.

Toe in on the rear is a good thing it helps keep the car stable at speed but to much and it can promote understeer and premature wear on your tyres, we run a little toe in on our race car, i know of some people using as much as 12 degrees total, i intend to run around 1degree toe in on the rear and probably 0.5 (or less) toe out on the front.
wether or not this will suit you, i dunno, but should make for a quick reacting car.
but this is just my opinion, i am suire you will get a few people saying i am wrong.

It is probably not relevant to locosts, but I have come to locosts after a long line of X19's (a truly great car apart from the 14' x 5' rectangle of rust shale left on the road where you have parked!, I go really fed up with welding the damn things up at least every month, yes really every month!!)

The rear ends of these run between 5 and 9mm of toe in and if you play with the settings (I did cos I had all the gear at work to accuratly set any parameters), anythig less than 2mm of toe in will make the car have severe snap oversteer (I suppose the rear wheels as they approach toe out would be pointing in the opposite direction of the corner, and therefore already trying to oversteer). If you set 7mm toe in, the oversteer if fairly neutral, but if you floor it mid corner whilst it is drifting, the oversteer comes in very controlably so you can balance it on the throttle with very minor steering imputs.

I had a quick flick through the data manuals, the only cars I could find with toe out are the early Lancia Integrale and the Nissan Praire 4x4 (never knew there was one!)

I originally had no toe in at the rear of my race car and had dreadful power on oversteer. Have toed it in a bit now and it is a lot better.