Alignment, caster question. How important is this?

[MrWizzard]

So I got my car aligned as usually when changing out it's shoes. They say the Caster is out of spec.

Front left.

Should be 5.8 to 6.3, it's 5.7 and the dealer says they can't get it to correct. The dealer says maybe something is bent. Their fix it idea is that they will just start replacing parts.

The dealer said maybe a body shop has more tools to deal with this. Body shops say the dealer is more equipped to deal with this as they would start just replacing parts until it is fixed.

Before I just start replacing suspension parts does anyone here have any constructive advice? Is the caster being out of spec by that little anything really to worry about? It’s a 01 S2000, not sure if that helps.

Thanks

THANKS FOR ALL THE INSIGHT YOU GUYS ANSWERED MY QUESTIONS!

While going through my records I remembered that someone in my parking lot backed into that tire and rim enough to damage it a while back, body shop said it was fixed but I think I see otherwise now.

 

[jlee]

http://robrobinette.com/S2000Alignment.htm

I wouldn't worry about it.

 

[Zenmervolt]

On a street-driven car, caster is not a huge concern. On many modern cars with strut-type suspension, it's not even really adjustable at all.

On a track, caster will affect dynamic camber (more caster means more camber is added/removed as the wheel turns with the steering) in ways that can change how the car feels at the limit, but on the street you're just not hitting that level where it matters.

ZV

 

[Wingznut]

A car can pull to the side with the more negative caster. Often, techs will set up a little less caster on the left side, to compensate for the crown of the road.

So, unless your car pulls to the left, your caster being just out of spec (.1°) is completely insignificant.

On a somewhat related note, but not to your specific situation... If both wheels are significantly negative from spec, it can cause the steering to feel too twitchy, and much less responsive returning to center. Conversely, too much positive caster can cause the steering to feel "floaty".

 

[bruceb]

I would not be too worried about being out of spec so little. How were the old tires ? Any unusual wear on them ? And did you ever hit a curb or large pothole ? If you did, then maybe something did get bent. A lot depends on tire wear and how the car feels in it's handling. If it seems like it should or was when new, do not worry about it. As you can see from the images below, caster means how far the wheel is forward or back in the wheel well. Camber sets the vertical tilt and will affect tire wear more.

Good explanations here:

http://www.ozebiz.com.au/racetech/theory/align.html

 

[JCH13]

OP: as long as the caster is nearly the same value on both sides of the car, and you're not looking to be competitive in racing, it's probably fine. If, however, this is a symptom of a damaged component, you'll want to fix that.

My guess, given the age of your car, is that many of the suspension components are due for replacement for optimum performance. My first guess is that your suspension bushings are shot, assuming they've never been replaced. I would assume that the shop made sure that all of your ball-joints were okay. After that, I'd take a straight-edge to various suspension parts and make sure they're not tweaked.

A car can pull to the side with the more negative caster. Often, techs will set up a little less caster on the left side, to compensate for the crown of the road.

So, unless your car pulls to the left, your caster being just out of spec (.1°) is completely insignificant.

On a somewhat related note, but not to your specific situation... If both wheels are significantly negative from spec, it can cause the steering to feel too twitchy, and much less responsive returning to center. Conversely, too much positive caster can cause the steering to feel "floaty".

I think you're confusing caster with camber, and maybe even toe.

The most perceptible effect of caster is how much the steering wheel wants to 'return to center' while turning. Having near zero caster could make the steering feel vauge, and having high caster makes the steering feel solid and 'sporty.'

I've heard of alignment techs adding a tiny bit of toe to compensate for road crown.

I would not be too worried about being out of spec so little. How were the old tires ? Any unusual wear on them ? And did you ever hit a curb or large pothole ? If you did, then maybe something did get bent. A lot depends on tire wear and how the car feels in it's handling. If it seems like it should or was when new, do not worry about it. As you can see from the images below, caster means how far the wheel is forward or back in the wheel well. Camber sets the vertical tilt and will affect tire wear more.

http://4wheelonline.com/images/caster.gif[IMG]

[IMG]http://4wheelonline.com/images/camber.gif[IMG]

Good explanations here:

[url]http://www.ozebiz.com.au/racetech/theory/align.html[/url][/QUOTE]

This is not correct. Caster is the angle between the steering axis and an imaginary 'true vertical' line, as is clearly illustrated in your diagram.

 

[thomsbrain]

I was going to say an S2000 deserves to have its suspension components be to spec, but since you think your S2000 has "shoes," I'm going to guess you will never notice the difference.

The knuckle is usually the first piece to bend on the S2000 suspension, and one of the most difficult for body shops to notice damage in. My bet is you need a new knuckle.

 

[Ferzerp]

but since you think your S2000 has "shoes,"

Sometimes people call getting new tires getting new shoes :gasp:. Oh no, the sky is falling!

 

[RLGL]

Sometimes people call getting new tires getting new shoes :gasp:. Oh no, the sky is falling!

Shoes.. what the ....? I thought they were Huggies

 

[Wingznut]

I think you're confusing caster with camber, and maybe even toe.

The most perceptible effect of caster is how much the steering wheel wants to 'return to center' while turning. Having near zero caster could make the steering feel vauge, and having high caster makes the steering feel solid and 'sporty.'

I've heard of alignment techs adding a tiny bit of toe to compensate for road crown.

Nah, I'm not confused at all. My background story is one of being an auto technician for a dozen years, in my previous career. I've done more alignments than I can count.

True that a car may pull toward the wheel with more positive camber, but caster will have a much more dramatic effect, if the two wheels aren't equal, toward the negative wheel. It is common to work in a -.5° caster on the left wheel to compensate for the road.

Toe will have absolutely zero impact on pull. Perhaps the perception, since toe can make the steering wheel crooked, but that's it. Think of it this way... Say you have 0" on the right, and +1" on the left. When you let go of the steering wheel, they will equalize, so you will essentially have +.5" on each side. However, your steering wheel will now be turned to the right.

 

[silicon]

So I got my car aligned as usually when changing out it's shoes. They say the Caster is out of spec.

Front left.

Should be 5.8 to 6.3, it's 5.7 and the dealer says they can't get it to correct. The dealer says maybe something is bent. Their fix it idea is that they will just start replacing parts.

The dealer said maybe a body shop has more tools to deal with this. Body shops say the dealer is more equipped to deal with this as they would start just replacing parts until it is fixed.

Before I just start replacing suspension parts does anyone here have any constructive advice? Is the caster being out of spec by that little anything really to worry about? It’s a 01 S2000, not sure if that helps.

Thanks

THANKS FOR ALL THE INSIGHT YOU GUYS ANSWERED MY QUESTIONS!

While going through my records I remembered that someone in my parking lot backed into that tire and rim enough to damage it a while back, body shop said it was fixed but I think I see otherwise now.

just as an aside your dealer who represents the car company should have a mechanic on staff knowledgeable enough to diagnose a bent suspension component. And if not then he/she should find someone.

 

[silicon]

I would not be too worried about being out of spec so little. How were the old tires ? Any unusual wear on them ? And did you ever hit a curb or large pothole ? If you did, then maybe something did get bent. A lot depends on tire wear and how the car feels in it's handling. If it seems like it should or was when new, do not worry about it. As you can see from the images below, caster means how far the wheel is forward or back in the wheel well. Camber sets the vertical tilt and will affect tire wear more.

Good explanations here:

http://www.ozebiz.com.au/racetech/theory/align.html

That explanation sums it up very clearly.

 

[DigDog]

ifyou alignement is evil, you can cast Cause Wonds instead of the corresponding Cure Wounds version; if you are Neutral, you oooh ok i see what you mean.

 

[JCH13]

Nah, I'm not confused at all. My background story is one of being an auto technician for a dozen years, in my previous career. I've done more alignments than I can count.

True that a car may pull toward the wheel with more positive camber, but caster will have a much more dramatic effect, if the two wheels aren't equal, toward the negative wheel. It is common to work in a -.5° caster on the left wheel to compensate for the road.

Toe will have absolutely zero impact on pull. Perhaps the perception, since toe can make the steering wheel crooked, but that's it. Think of it this way... Say you have 0" on the right, and +1" on the left. When you let go of the steering wheel, they will equalize, so you will essentially have +.5" on each side. However, your steering wheel will now be turned to the right.

Can you please explain how caster differences side-to-side helps to cancel out the road crown?

 

[tracerbullet]

Do you know if the strut or upper mount were replaced after the accident? They may be tweaked just enough to kick things out of spec. The whole strut tower could be off too though which isn't an easy fix. Either way it's just throwing parts at it, not great.

Also FWIW it's barely out of spec, and given that machines and people running them aren't always perfect it may actually be technically within spec. If you can't tell there's an issue then... there may not be one.

ifyou alignement is evil, you can cast Cause Wonds instead of the corresponding Cure Wounds version; if you are Neutral, you oooh ok i see what you mean.

Took me a minute. Good one.

 

[Wingznut]

Can you please explain how caster differences side-to-side helps to cancel out the road crown?

Steering forces will push the car towards the less positive caster. This is the same force that causes the wheels to straighten naturally. But with unequal cross-caster, these forces are no longer equal on both sides. On a crowned road, this will help pull away from the slope of the road.

If I'm not explaining it well, a search will probably do a better job. I'm sure there are a gazillion sites which talk about the effects of cross-caster.

 

[JCH13]

Steering forces will push the car towards the less positive caster. This is the same force that causes the wheels to straighten naturally. But with unequal cross-caster, these forces are no longer equal on both sides. On a crowned road, this will help pull away from the slope of the road.

If I'm not explaining it well, a search will probably do a better job. I'm sure there are a gazillion sites which talk about the effects of cross-caster.

That makes sense. Thanks.

 

[thomsbrain]

Do you know if the strut or upper mount were replaced after the accident? They may be tweaked just enough to kick things out of spec. The whole strut tower could be off too though which isn't an easy fix. Either way it's just throwing parts at it, not great.

Also FWIW it's barely out of spec, and given that machines and people running them aren't always perfect it may actually be technically within spec. If you can't tell there's an issue then... there may not be one.



Took me a minute. Good one.

S2000 doesn't use struts. The coilover has no effect on alignment. However, it does raise a good point that the upper A-arm attachment points are a known weak spot and can bend in a collision (or even under racing conditions with R-comps).

 

[tracerbullet]

S2000 doesn't use struts. The coilover has no effect on alignment.

Ahh, yeah, I see that now looking it up. Bad assumption on my part. Sweet setup!

Glad it at least gave an idea.