Thank you for all the info. When I test for the wheels, I didn't rub. So I didn't roll the fenders. So if I followed this I would be fine?

front toe: zerofront camber: -.5 to -1 degreescaster: Personally, I wouldn't worry about this too much. Some people insist on max caster (heavier steering), but I actually prefer minimal caster (lighter steering, but IMO better *feel*).Rear toe: 0.1 to 0.3 degrees total (0.05 to 0.15 degrees per side) Too much of this is the #1 reason for ill-handling S2000's that wear out rear tires in no time! I like ~0.1 to 0.2 total, anything over 0.4 degrees total is IMO excessive.rear camber: -1 to -1.5 degrees.

 

That's a fairly broad spectrum of alignment settings. Factory camber is not bad, it is just the rear toe.

I would ask for front toe 0.00 with even caster and -0.5 camber
rear -1.5 camber with 1/8 inch toe for 1/4 total. This is half of factory toe. (AP1)

Caster is strut lean so it is not a rear adjustment since it directly affects wheel turn only.



Here is the thing that is hard to find in an alignment tech. Make them get your camber even on each side. You don't want -1.0 on the left rear and -1.5 on the right. Even if you have to run more than what we've said is good if toe is good it won't matter much. Be sure to get a print out and post it.

I brought up rubbing because with minimal camber your rear could rub on strut compression. My car was bad about this on bumpy interstate bridges that had harsh endings. It's actually ruined my rear quarters, not too bad but I notice.

 

I think you mean 1/8" total, 1/16" per side.
1/4" is WAY more than "half the factory toe". If I recall correctly, "factory" spec is 0.32 to 0.64 degrees total (from "a bit much but not too bad" to way excessive)

1/4" total is:
sin[sup]-1[/sup](0.25"/25") = 0.57 degrees total
Closer to the max end of the factory AP1 range, and way too much. Running this much will give undesirable handling characteristics and halve rear tire life.

You want more like 0.20 degrees total, which is:
25" sin(0.2) = 0.087" total

If your shop does toe in inches, ask for 1/16" to 1/8" *total* (1/32" to 1/16" per side). That's 0.14 to 0.29 degrees total. My preference would be for the lower end of that range.

 

Just remember Caster does more than steering feel.

Caster adds Camber to the outside wheel and reduces Camber on the inside wheel during a turn (which is exactly what you want).

 

You are right Dan. Good catch.


TMartin, you are right but the OP has said he doesn't track his car. Which your point still matters and it is valid I was just implying no matter where is it that it will not wear tires.

 

This effect is smaller than most realize. For autoX, where speeds are low and steering angles big, the effect will be bigger.

Consider a car cornering at 1g with 9 degrees of steering angle at the road wheels. That's about 120 degrees at the steering wheel (AP1), a fair amount of steering input. Assuming 6 degrees slip angle at the tires, it works out to a 51' radius corner at 27.5mph.

That's a pretty tight/low-speed corner, which will emphasize the difference in camber due to caster.

If caster is 6.5degrees, the change in camber due to caster is going to be: sin(6.5deg) * 9 deg = 1.019 degrees (amount of decreased camber on the inside wheel, increased camber on the outside wheel)

If caster is one whole degree less, 5.5degrees, change in camber is: sin(5.5deg) * 9deg = 0.863deg

The difference in camber gained/lost due to caster is 0.16 degrees. Not negligible, but not a huge amount. And this is for a very tight/low-speed corner. At higher speeds, the difference will be reduced.

In general, I think that caster can be overrated, and there have been cases where race cars had so much that the driver's couldn't feel the subtle effects of changing slip angle over the increased mechanical effort required to hold a given steering angle. IIRC, the "too much" level was on the order of 6.5 degrees.

Also worth noting that increased caster increases the difference in high- and low-speed balance. More caster => relatively more high speed understeer/low speed oversteer. If the driver is happy with the high- and low-speed balance, I wouldn't add caster.

Like most things in car setup, MORE is not always BETTER.

And for big heavy production cars (as opposed to forumula cars), I think that caster is more of a feel thing. Personally, I tend to like lower caster than most for reduced effort and increased signal/noise on steering feel.

 

So i got my alignment today, what do you guys think?
I wrote down all the info i learned from this thread and showed them the specs that i would like them to stay in. The only thing i wasnt too happy about was the rear camber. Would 2.2 affect tire wear much?

 

I like the "before" settings better than the "after"...

Typical "all green" alignment, but you were better off IMO with closer to 1deg camber up front and .12in (.275deg) total rear toe.
With .21in (.48deg) toe, you can expect much greater rear tire wear rate, and less linear handling characteristics (more twitchy over bumps).

sigh...

 

Aw so I should most likely go back and get it adjusted again? Is it a lot more tire wear than before?

 

Which is the BEFORE and which is the AFTER?

The TOP alignment is better.