Unfortunately it was 5 months and a few parts difference between the changes, so I can't honestly say for sure. I also had shocks that made the car hyper-twitchy as well during this time. Didn't figure that out until I switched to STR and got Guy Ankeny to revalve them after a 1/2-season with STR springs.

Have you ever raced with almost-dead Hoosiers in the rear and ok ones in the front? It's not so bad that you immediately know that the tires are bad, but you spend a lot of time and effort trying to fix minor mistakes. That's what that whole season felt like. I'm bummed I didn't figure it out, but the shocks didn't help.

Sorry, I don't have any good scientific A-B testing.

 

One more interesting note on my toe experiences:
During the time I had truly absurd toe (1deg total, 0.55/0.45), I did a time trial day on street tires (StarSpec fronts, Dunlop Sport Maxx TT rears) at Watkins Glen. Just about every time I entered turn 1 (pretty high-speed downhill right hander), trail-braking, the back end would get out a bit. Car was driveable and I actually did an OK time trial, but at that particular turn it just wanted to enter sideways, to the extent that the corner-worker reported my dirt-tracking it into one pretty consistently Of course "more rear toe" is often prescribed to PREVENT turn-in oversteer!
Particularly strange given that that car suffered unbelievable, practically undriveable understeer at turn-in in the wet at Mont Tremblant with the same hosed setup.

That was with ~1000miles on the rears. After that, they ground away to nothing by 3000 street miles on them, with the one short track day (2 practice sessions, Time Trial).

I replaced those street rears with Hankook RS-3s and fixed the rear toe, taking it down to 0.2 degrees total from 1 degree. Did one wet/cold track day at Mosport with 1/2-worn StarSpec fronts and new RS-3 rears, same conditions that had given unbelievable understeer with the rear toe problem, totally driveable and enjoyable even in adverse conditions with the radically reduced rear toe-in! In the rain, the main shortcoming I found with the setup and the RS-3s was that exiting the very tight/slow "Moss Corner", I would lose rear grip, but more *longitudinal* than *lateral* grip. I.e., it was more an issue of losing drive than of the car going sideways.

FWIW, now at 18k miles on those rear RS-3s, with 2 to 3/32 left to the indicators. Taking a 1100 mile trip with them this week. Should get 20k miles out of them.

Anyway, for *me*, minimizing rear toe has *always* worked, and running big rear toe has *always* given me problems.

 

Thanks for writing that up but I'm pretty sure what you're describing is 100% the tires. If you told me you ran those tires in those conditions with perfectly normal rear toe I would expect exactly what happened. You ran in the dry, and the star specs have an order of magnitude more dry grip than those sport maxx's, so you had way less rear grip, so you were dirt tracking it. Then you were running in the wet, which the star specs aren't that great but the sport maxx's as far as I know are really good, and suddenly the car's shortcoming was front grip instead of rear. Then you changed to RS3's and they're actually very similar tires to the star specs, so you no longer had imbalanced tires so it felt good.

Of course the tire wear is all because of the toe, for sure.

 

Believe me, I've tried all manner of weird tire combinations and I KNOW what is down to the tire and what is down to other considerations in my S and my Z!

More grip, but not an order of magnitude more. Steady state cornering was neutral, not oversteery. It was a corner-entry phenomenon at Turn 1. I think that in the higher-grip conditions I was unloading the rears more, and the outside rear's initial *slip angle* (with the excessive toe-in) was so much closer to sliding, that it just wanted to let go. Getting off the brakes and into cornering, the outside rear loaded up and got some grip.

The first time when I had an issue with front grip in the wet was the event previous to Watkins Glen at Mont Tremblant. That was on StarSpec/StarSpec, R-comp/R-comp, and at one point even StarSpecs/R-comps! I was trying anything and everything to get the car to behave, tires did NOT matter, it was the setup (excessive rear toe) giving me a very LOOSE condition in a straight line and unbelievable PUSH at turn-in.
Then I went to StarSpecs/SportMaxx TTs for WGI in the dry.
Then next event was in the cold/wet at Mosport, the Sport Maxx TTs were long gone, I was on StarSpec fronts and RS-3 rears. And fixed rear toe-in! *THAT* was the difference.

Yup! Along with all the other issues which were also due to rear toe.

 

Good to know, thanks that makes sense. So that definitely says having that much is unlikely to be good. I wonder if maybe a more reasonable amount of rear toe might have helped though? Seems most are running 1/4" or so at least for STR autocross.

 

.29 degrees per side (1/4" total) crew checking in

 

You are running that much rear toe and ur car is that tail happy?
I'm at 0.1 per side, but I have significantly softer springs than you guys.

 

I blame it on springs to stiff for site, tire pressures being even (normally run 2lbs higher in front, very gravely site, fresh tires (first event), and my mistaken shock setting change for the guy that drove the car before me.

We'll see how this weekend goes!

 

I tried that amount when I was first tracking the S. Handling behavior was a bit weird, not an issue once adapted to, but tire wear was outrageous.

Regarding toe and over/understeer, at my first track day in the S, running 1/4" total, the car was pretty neutral except for characteristic AP1 initial oversteer lurch on turn-in. In fact on my first lap in the car, first lap on new tires, I lifted a tiny bit entering the left at top of the esses at the Glen and the back end *really* tried to step out, much more so than the more track-oriented Z would have.
Running the same 1/4" setup at next event in Mosport, the rears wore out at less than half the expected mileage, I was caught out with worn-out rears, which gave MASSIVE oversteer issues.
Going from 1/4" to 1/16" total rear toe, the car still had this AP1 behavior of exaggerating throttle-lift oversteer, but not as much.
I had expected a lot more to oversteer everywhere, but I didn't find overall handling balance to be that different between 1/4" total and 1/16" total. With less toe I did find that the handling to be more linear.

The only time I got serious understeer with too much rear toe (inadvertently running 1 degree, approaching 1/2" total) was in the wet at Mont Tremblant. MASSIVE turn-in and steady-state PUSH, but with the tail dancing all over the place down the straights! Same fuxored alignment at Watkins Glen in the dry and the car was gleefully oversteering into Turn 1 controllably and consistently, but overall balance was not a problem.

So, in my experience in my stock AP1, overall handling balance in the dry hasn't been tremendously affected over a *very* wide range of rear toe settings. Lower settings gave more "normal" handling characteristics independent of conditions, while high toe settings gave quirky handling characteristics in the dry and barely-driveable understeer in the wet. And of course 3x to 6x greater tire wear rate!

 

ZDan,
My observation would be that your rear toe experience is not completely relevant to this discussion because your car has a stock setup. You are mostly describing the highly dynamic toe curve of the AP1. The AP1 and AP2 dynamic toe curves were measured and posted in this thread last year. Viewing the AP1 curve helps see what you are describing in some of your description. See this post (AP1 Toe Curve) and this post for AP2 Toe Curve. Basically AP2 toe curve does not change dynamically.

The difference from stock to a typical STR setup is significant. IMO driving a stock setup vs STR is an apples and oranges comparison. One reason is the amount of suspension travel for stock is multiple inches compared to some STR setups which may be under two inches total for compression and rebound. Other differences that might play here are roll rate. STR cars typically have heavier springs, a heavy front sway bar, and top quality monotube racing shocks.

I do not get any of the lively rear bump steer in my AP1 STR car on the street over nasty bumps like I used to with the stock setup. The amount of bump steer is significantly less due to the lower amount of suspension travel.

The time it takes a typical STR car to take a set on corner entry is also significantly less than a stock car. My perception with an STR setup is that it's almost instantaneous as compared to a stock car that seems like an eternity for the suspension to transition especially in back to back left right turns like in a slalom or off set gates. With all that suspension travel dynamic toe in an AP1 plays a much bigger role in the behavior of the car. For STR the dynamic toe is virtually static in comparison.

This is just my opinion based on based on setting up an AP1 for STR over the last three years or so. I have also driven a few stock S2000s at local autocross events over this time frame for that comparison.

I would agree that too much rear toe is not a good thing. A lot of suspension settings are detrimental at some point of extreme setting.