wow. insane. i love diagnoses like these. fun little mysteries. they really challenge the thinking of a good wrench. hope its all sorted

fun fun.

 

Yeah, I'd get a new hub too, that might be what killed the new bearing. Hub is ~100 online. +10 for circlip. +20 for dust shield if you end up cutting it off.

 

Excessive rear toe absolutely will make the car more of a handful over bumps. Any road irregularities will result in rear-steering as one rear is loaded more heavily than the other, then unloaded again. This goes DOUBLE for the AP1, as the rear that gets more heavily loaded *also* toes in MORE. Better to have the rears closer to parallel.

Over the past four years dealing with different tire stagger and rear toe on my stock AP1, I've come to the following conclusions which go directly against 95% of what you'll read in these forums:

1. Rear toe does NOT make the AP1 more stable, quite the contrary! Excessive rear toe is WAY WAY WAY worse than running *minimal* rear toe. Running a lot of rear toe has in my experience made the handling very nonlinear and darty in a straight line (particularly evil in the wet), while KILLING turn-in responsiveness. LOSE/LOSE. Try 0.2deg *total*.

2. The effect of tire section width and/or tread width stagger on handling balance is not a big a deal. AT ALL. I've run from .5" to 1.5" stagger, and the fundamental nature of the handling balance of the car was largely unaffected (only time I spun it was on 205/245).

Long/short, when I first tracked the S, I tried to compensate for reduced tire stagger vs. stock by running more rear toe-in (max spec .64deg total). First track events I noted very nonlinear handling and really wicked tire wear (I was traveling to/from events on R-comps, btw). Despite being 5sec slower than the Z. When I decided I *had* to reduce rear toe in the interests of preserving the rear tires, I did so with much trepidation, as the car seemed spooky and twitchy already, surely running less rear toe would make it much WORSE, right? WRONG! The car became MUCH MUCH more linear-handling and predictable (despite the alignment shop giving me .15deg *TOTAL* instead of the asked-for .15deg per side/.30deg total!), *and* rear tire wear became much more reasonable.

The car is an evil bitch with too much rear toe.

PM me and I can give details if yer interested.

I recommend ~.1-.3deg total rear toe.

 

Toe in is given in inches. The stock AP1 calls for .4 inch total toe in. If you're having your guys set degrees that may be why you're getting anomalous results.

I've run from .1 to .4 total toe in in the rear (3.5 deg neg camber front, 3.0 rear, 7 caster, KW-V3s, BSK, Comptech adj front bar) and I had immediate over steer on high speed conner entry with less than .3". I would turn in and immediately have to put in a correction to get the car to take a set in the corner.

:BSFlag:

I've had the exact opposite experience. Keep in mind that toe in isn't static. The compliance in your bushings will toe the wheels out under trail braking so an older car will handle toe differently than a new one with fresh bushings. Of course how aggressively you use the traction circle and trail brake makes a big impact on your toe in needs.

 

Dan, why weren't you at NHMS 1? Some of this info would have been helpful! Paddy and I were debating changing the rear toe at the event. Would have been great to have another AP1 owner to chime in. Paddy wanted to put in more toe until we measured it and had me convinced not to reduce it. The car felt a lot more manageable at the other tracks we went to last year. We'll probably reduce the rear toe and put in new diff fluid. Hopefully that sorts it out.

 

Can anyone explain this >_<

 

Degrees are more appropriate units. You KNOW what your toe-in is if you have it in degrees. In inches, it depends. Is that at the outside diameter of the tire? If so, do you know exactly what your tire diameter is?

Toe-in is the ANGLE. Measuring it in inches isn't the best way, not enough information.

.4 *inches* of toe-in is roughly sin-1(.4"/25") = .92deg, or . 46deg per side. That is a RIDICULOUS amount of toe in. That is NOT the "stock" spec for the AP1. Last time I checked, the stock spec was .32 - .64deg total. Which is IMO entirely too much.

.4 *DEGREES* total toe-in would be within the stock spec range (but still way too much toe IMO), .4 *INCHES* (.92deg!) isn't. Where did you get that?


.1 to .4 inches, I guess? So, .23-.92deg. Again, .92deg is way way WAY too much toe.
The AP1 does tend to give initial oversteer if you crank in the steering too hard at turn-in. More subtle initial inputs required.

In my experience, too much toe makes the car much more darty/twitchy in a straight line, while giving more understeer when I *want* the car to turn.

The AP1's rear toe change with bump (an inexcusable mistake in an otherwise brilliant suspension design) makes the car quite a handful, and increased rear toe makes it worse. You have stiffer springs/damping, which will mask this effect (less travel/less toe change). On stock springs/dampers, with that much toe (I inadvertently had 1.05deg total toe once) the car is well nigh undriveable.

Are you *sure* you're running .4 inches rear toe? There's no way on earth that's anywhere near optimal.

 

I just looked up the alignment specs from the 2000 - 03 Service Manual and I was wrong. It calls for total toe in of 1/4 inch +- 1/16 inch. I'll double check my settings but I'm pretty sure it's set at .2 each side for .4 total.

 

I used to run 0.10 total toe when the car was understeery and now I went to 0.20 total I say go low.. anywhere between 0.10-0.30 total
I think stock for an Ap1 is somewhere between 0.35-40 total..

What Zdan says is interesting - My old uk car was a normal tailhappy S2000 before I had the "UK alignment" done on it.. I think this alignment has too much rear toe-in.
How the car handled after that was: Enterring or in a turn the rear would not slide it would grip and cause the front to understeer..
Then if you realy pushed the rear would "snap" break-away sharply adn the front was sliding too so it was kinda dangerous.
The upside was it took quite a lot to get to that limit and probly a bit safer to understeer on the road I think thats why they did that

 

I have similar experience with toe. It only helps to a certain point and then causes the rear to break away quickly vs more gradually/manageably.

For anyone talking about toe please refer to the measurement type. For those that need to convert here is a nice chart.