robrob

Speaking of AP1 dynamic toe, a few years ago I was talking to JFO about TT points and I told him I was considering removing my rear bump steer kit to gain a point. He looked at me like I was crazy. He owned 2 AP1 race cars and one had a bump steer kit and the other didn't. He confirmed to me that it made a big difference and suggested I look elsewhere for points reduction. I was recently setting my rear toe using laser projection on the opposite hub and confirmed I had almost 0 toe change from loaded suspension to full droop. I'm using the Megan Racing bump steer kit set with the larger spacer closest to the joint and I run about 1 inch lower than stock.

Also keep in mind that a tire doesn't simply drag across the pavement from toe-in. The rubber contact patch stretches and r-compound tires are pretty happy with some pretty extreme slip angles so the tire wear rate between 0.1" total toe-in (0.11 degree at each tire) and 0.25" (0.29 degree) probably isn't as extreme as you would think.

oinojo

Good to know, however in STR we can't use a Rear Bump Steer Kit. Good point about the rear slip angle and its relation to rear toe. Some street tires have more "give" than others so rear toe-in would definitely be a fine tune setting for different setups/tires. For instance I went from 3/16" Toe-in to 5/16" Toe-in and found small gain. My current 5/16" is way too much for my Bridgestone RE-11A's and has created a push in the car that I am struggling with. I plan to back it back down to 3/16" and see how it does. The Bridgestone definitely tolerates more slip angle compared to the Dunlop.

ZDan

No, I do observe the ap1 toe wankness, but if you read my posts more closely you'll see that what I've been talking about isn't strictly related to that. I kinda went out of my way to include this in my posts. What i'm talking about is superimposed on top of the dynamic toe issue (which is not desirable but is totally drive-aroundable, at least with modest levels of rear toe). There's info in these forums showing 1/8" toal toe-in for 1" bump dating back to before I started tracking the car in 2007, it's not like that was only discovered last year!

Experiencing a very twitchy tail driving down the straight in the rain at Mont Tremblant had nothing to do with AP1 toe change with bump. And experiencing a huge push at turn in and all the way around the long right-hander at the backside of the track in the low-grip conditions didn't result in nearly enough body roll for the outside rear toeing in to be the root of it. That was with the hosed setup with 1 degree total toe-in. While 1 degree is a lot, and more than I've heard anyone recommend, it isn't terribly far from the oft-cited 1/4" total (max spec AP1).

Under similar conditions with MINIMAL toe (0.2 degrees total), my car is utterly stable in the pouring rain, while also turning-in with typical AP1 eagerness and remaining tossably neutral in turns. On the same tires (StarSpecs).

Of course. But in situations where one rear has greater grip due to surface conditions, more toe can still cause twitchiness even without any suspension travel.

Yup, that's my observation of the stock AP1 vs. my other cars as well. I've observed other "too-much-rear-toe" driveability issues with my much more track-oriented 240Z, as well, though.


In my experience, my cars have performed more consistently and better over a much wider range of track and traction conditions running minimal rear toe (~0.1 - 0.3 degrees total) and have had serous variation in handling characteristics for different conditions on track and street with a lot of rear toe (~0.65 degrees total and up).

In terms of outright lap times in ideal conditions, I wouldn't put much between minimal toe and maximal toe. But for consistency over a number of laps and over different conditions, I've never had issues at the tiny end, and pretty much always had issues at the big end.

ZDan

R-comps will also develop greater lateral grip at small slip angles, so that if one tire goes over a low-traction surface, the lateral push at the rear of the car will be greater vs. street tires. And also, grippier tires will be working that much harder against each other down the straights vs. street tires.

Running 0.64 degrees total rear toe (just over .25") resulted in life of my first set of R-comps being less than half the tire life (better than 1/3, though!) I got out of the same tires with 0.15 degrees total. But that was subjected to a fair amount of street usage driving to/from events... I wouldn't expect that radical a difference for track-only usage, but I would expect a significant difference.

More static toe-in means that the inside rear is contributing less in cornering, and the outside rear will have to run at a greater slip angle. I don't see any reason why this should be better for overall performance.

I tried it based on supposedly getting "better stability" to mitigate AP1 quirkiness and the effects of much less tire stagger, but that turned out to be a misconception on my part on both points.

robrob

AP1 (2000 - 2003) Rear Toe-In Specs: In Inches: Total Toe-In is 0.25 inch +/- .08 inch or the range of 0.17 - 0.33 inch

mLeach

If you want to settle down the rear of an AP1, make it low, and run lots of rebound on a high quality digressive shock that doesn't complain over bumps. It will slow down the rate of toe change, which is what makes it skiddish. The shock will keep things calm, letting you take advantage of the suspension design.

josh7owens

I like the effects of more rebound in the rear on my ap1. I ran .29 degrees on each side on the ap1 and seemed to like it better then when it was less. On the ap2 I'm debating backing it off to maybe .1 each side. hmmm

ZDan

Duly corrected. Not sure where I had gotten it from, but for some reason had thought it was .48 degrees +/-.16 (~3/16" +/-1/16") way back when I first tracked the S, and had toe set to 0.64 degrees total thinking that was max spec. Then after excessive tire wear, I'd intended to have it set to min spec which I thought was 0.32 degrees, but the shop misunderstood and gave me 0.15 degrees total. Which worked out fine despite my trepidation.

Anyway, .32 - .64 degrees was stuck in my head as spec, wrongly.

IntegraR0064

Well I went ahead and upped rear toe from 3/16" to 1/4" and it is much better, seems to have fixed the issues I was having. At least for my setup...your mileage may vary.

PedalFaster

Sorry if this has been asked and answered already (I skimmed every page in this thread but could have missed it): how much camber can you get at a moderate ride height (say 13" hub center to fender) *without* a camber kit?

I'm thinking about doing a low budget STR build, and am wondering how much I'd be giving up if I skipped a kit.

Thanks!

Edit: I can get between -1.8 and -2.0 degrees at stock ride height, depending on the rack and the day.