Chris S

I had the car aligned using some of the helpful tips here (thanks everyone!), and moved the endlinks on the front swaybar to one postion tighter (from 3rd from the end to 4th from the end). Took it to the track today, and it was much more confidence-inspiring despite rear tires being near EOL. FWIW, here are the specs I ended up w/:

robrob

Quote:

ZDan said:

Holy S*^t, you're right ZDan. I wasn't accounting for the measurement at the back side of the tire. If you want to set 0.4 inches of toe-in you actually have 0.1 inch of displacement at the front of the left tire, 0.1 inch displacement at the rear of the left tire, and 0.1 inch at each end of the right tire for a total of 0.4 inches total toe-in.

Honda's bulletin really is crazy wrong on its Workshop Manual rear toe-in number. Like you said, 1 degree of total toe-in is insane--0.44 inch. Even the UK Spec of 40 minutes, 0.29 inch total toe-in is high.

I apologize for the nasty tone.

But my car is set to 0.25 inch rear total toe-in, that hasn't changed.

captain_pants

Thank you all for the informative debate. I'd been trying to find where/how to measure 0.25" of toe-in as my local alignment shop's machine/technicians are incapable of setting toe in inches. (likely a user problem, not a machine problem, but they'll at least TRY to get the specs I want as opposed to any other shop I've tried) They could only do degrees, so I set out to find where on the tire/wheel that a spec in inches is measured. I found arguments for measuring at the wheel edge, at some theoretical tire diameter, and at the actual tire diameter. All seemed completely confident that they were right. I took a shot at using the rim diameter based the advice of a Hunter technician that I happened to run into in a commercial truck shop. Seems he was likely wrong.

To tie this all together, I've had a foul-handling car for some time. It's very twitchy and loose on turn-in. Obviously I have way too much toe-in using the measurement at the wheel edge. Damn! Unfortunately I did this new alignment at the same time I put in my Penskes, so I was pretty sure that my handling issues were due to the shocks... I'll have to try 0.2 degrees per side.

ZDan

1deg spec'd in that manual is totally out to lunch.

Thanks! Same here


That's .57deg total, I do think that's still very high. Personally, my approach would be to knock that WAY down and make other adjustments if necessary for balance. I just hate the idea of having both rear tires scrubbing all the way down every straight (drag + tire wear)! And again, in my experience with a stock-suspended AP1, anything over ~.4-.5deg starts to suck really bad for handling characteristics. I ran 0.64 when I started tracking it, and got spooky/weird handling and insane rear tire wear rates.

A more stiffly-suspended car will not exhibit AP1 evils as much as a stock one does (stock = greater suspension motion = greater toe change).
And different drivers with different cars will have different optimal settings.
But still you might consider dropping it a bit with no other changes and see how you like it...

ZDan

IMO degrees is a much better unit to use. No confusion at all, the angle is the angle, period. Doesn't have to be referenced to another dimension like you have to do with inches or millimeters.

The usual method measures at the tire tread. Of course it makes a pretty big difference if you're measuring at 16" (rim) vs. 25" (tire)! Again, degrees don't care about any of that...

.25" total toe at 16.5" (dunno if you're on 16s or 17s, so splitting the difference...) is ~.45deg per side, ~.90deg total, YIKES!

Actually, when I was inadvertently running that much (1.05deg total), I *did* get initial oversteer, but then the car didn't want to make the apex and pushed through to track-out! It was like the rear toe was enough to give a big head-start on getting to excessive slip angle (sliding). At that point I didn't know I had issues with the alignment...

Yeah, knocking it down from that level to something reasonable (I still say 0.2 - 0.3 total, but 0.4deg total should be fine as well) will make a HUGE difference in handling.