So I'm curious, who has played with rear toe? What effect exactly does putting more rear toe in have? I've been running 3/16" total (0.25 degrees per side) rear toe in on my 06. This year I've gone to a much higher rear roll stiffness (including rear bar whereas last year I had none) and while I love the car it seems to be less rock solid in the face of disturbances on course. In other words it's much more likely to be going turning just fine and then hit a bump and I'll have to countersteer to get the rear back in check.

I've always just dialed in a little rear toe to make sure it never toes out and then leaving it, never playing with it much. But this seems like a time that it could be useful, right?

What other effects will it have? What happens if you have too much rear toe?

Or should I change something else instead?

Any input would be helpful.

 

AP2 Rear Toe Specs:

 

I'm also highly interested in this question. I found out last year that I had 0.5" total rear toe for a year or so on my AP1. It was dropped back to 0.25", but not until I had a frustrating season... I'm debating going lower as my car is quite unfriendly over bumps.

 

So when you dropped from 1/2" to 1/4" this unpredictableness got better? Did you change other things at the same time?

I hear people talking about purposefully running 1/2" or 1" rear toe in order to calm the rear but that seems like it would just screw everything up to me.

 

Can you clarify frustrating season, and the differences you experienced between 0.5" and 0.25"?

 

I'm running 1/4" toe in the rear, Miata sway.

I don't have issues with the car's rear becoming lively due to bumps.

Just had an event this past sunday at a bumpy lot, was able to keep moderate throttle in second gear on the bumpiest section of the lot which included a turn around.

 

guys the toe will make no difference with bumps. you are unsettling the car. the stiffnes of the car and the shocks is what will unsettle the rear over bumps. the toe will only affect cornering as a constant not bumps

 

I've messed with rear toe a fair amount on the S and on the 240Z, both intentionally and unintentially. Short version: I've come to the conclusion that too much rear toe absolutely sucks, bad, for everything: tire life, straight-line stability, turn-in, everything turns to shite.

When I started tracking the AP1 (totally stock), I had rear toe set to the max AP1 spec, or about 0.64 degrees total (~1/4" total). My first track event at Watkins Glen (2 days, ~1.5hrs track time), I found the car to have somewhat nonlinear handling characteristics relative to my much more tossable 240Z. The AP1 had this initial oversteer LURCH on corner entry before settling down. Weird... Time trial went OK.

Towards the end of my second event on the tires (VictoRAcers), sharing the car at Mosport, the back end of the car started to get REALLY loose. Time trial laps were a total disaster. Rears were corded by the end of the 2nd day, after the equivalent of ~5 track hours in increments of ~15 minute sessions. I was used to getting something like 3x that out of Hoosiers on the 240Z! The front tires lasted several more events, btw...

After that, I knew I had to dial back on the rear toe in order to get decent life out of track tires, so I asked the shop for the minimum spec AP1 camber, or ~0.30 degrees (~1/8") total. Instead they gave me 0.15 degrees *total*. I was worried that the car was going to be all over the place due to the quite low toe-in, but actually found the car to handle a LOT more linearly and tire life more than doubled. Yay!

Fast forward a couple of years, and at Mont Tremblant in the wet the car was again *all over the place* going through minor puddles on the straightaway and in the braking zones, veering left and right constantly. Until I went to turn in, when the car just PUSHED like a pig. I tried the half-worn StarSpecs in place of the track tires, same issue. Then on the drive home in a torrential downpour, again on half-worn Star Specs, I had to slow to ~55mph and was still white-knuckling it while others were going 60+ without issue. The rear Dunlops were worn out pretty quickly after that, and I got a set of Sport Maxx TTs. The rears only lasted 3k miles! That was too big a clue to ignore, sure enough the alignment must have slipped because rear toe-in had crept up to ~1degree total! I had them reef in the bolts a bit harder the next time...

240Z: I had developed it into a TOTALLY sweet-handling and tossable street/track car. HUGELY fun. Then after a suspension mod (offset poly isolators allowing more front negative camber), the car just PUSHED like mad at the next event at my home track. Totally unfun to drive, obvious that something was up. Sure enough, the shop hadn't set the rear toe where I asked them to, it was up around .67 degrees total. Set back to ~0.2degrees total, and handling bliss was regained.

Anyway, these are my anecdotal results from playing with rear toe, on purpose and not on purpose. For me, a bit too much rear toe has sucked way way WAY more than having it set at the small end. I would sooner run zero rear toe than anything over about 0.4 degrees total again.

 

It will affect the car over bumps, particularly an AP1 with soft suspension settings (more suspension movement, more toe change with bump). When I was inadvertently running 1 degree rear toe-in (interestingly enough, that is the *middle* of the UK rear toe range, which is almost certainly erroneous!), The back end of the car would absolutely move around going over bumps, in a straight line, on the street! Excessive rear toe will also act to unsettle the car over surfaces where one side of the car is on a higher-traction surface than the other side.

This is particularly true with tires that give a lot of lateral grip at lowish slip angles.

Too much toe wastes rear grip, pitting the tires against each other. The left rear pushes the back of car slightly to the right, right rear pushes the back of car to the left, only under ideal conditions do they cancel. When road irregularities are encountered that temporarily give one of the rear tires either greater load or greater traction vs. the other, the back end of the car *will* get pushed to one side for a moment. Not confidence-inspiring, not fun...

 

Great input so far, thanks zdan and sacha and others. The toe will definitely affect bumps, particularly on an AP1 where the toe goes all over the place with suspension deflection. For example zero toe and the suspension moves far on one side due to a big bump and suddenly you have toe out on one side and thus rear wheel steering. But my suspicion was either too much or too little will make it worse and the input so far backs that up. Not sure if I should try lowering it or raising it...this has been what I've been running forever. Sounds like lowering it might be a good idea especially on an AP2 with its very stagnant toe curve.

I want to clarify that my car is very good...we're not talking about a huge problem here. I can power through bumps. I just feel like maybe it's not ideal and am trying to optimize as much as possible and toe is one thing I haven't played with much on rear wheel drive cars so I was curious about others' experiences.