TunerN00b

There have definately been threads that discuss caster, and I have read all of them (I think), but there's still something I don't understand that I hope someone with more knowledge can clarify.

Why don't all FWD race Hondas run as much caster as possible?

To begin with, what does caster do? From everything that I have read, here and elsewhere, caster has its pros and cons. Please, correct this where its incorrect, but this is my understanding.

Caster:
- Provides dynamic camber, based on steering input, negative to the outside tire, positive to the inside. Sounds good so far.
- Transfers weight from the outside front and inside rear to the inside front and outside rear. Well, don't we run large rear swaybars and high rear spring rates to help transfer from rear inside to rear outside anyway? Those of us without a LSD have traction issues with the inside front on corner exit, so wouldn't moving more weight outside to inside help? We run smaller (or no) front swaybars, and (realtively) lower front spring rates because we don't want to transfer the weight inside to outside in the front.
- Provides additional turning resistance. I don't see this as good or bad.
- Provides better high speed stability. I do not understand how caster effects this, so if anyone wants to chime in here I'd appreciate it.
- Changes dynamic toe. Again, is this for better or worse?

Well, thats about the extent of my knowledge. I think the more I learn, the more confused I become.

RR98ITR

It's possible that mucho caster is overrated.

We turn the wheel as we turn in, the rear end starts to come around, we put the throttle down and straighten the wheel - ideally for most of the corner there'd be no caster induced camber.

And as to that weight transfer stuff you said... It sounds good till you realize that it isn't true.


Scott, who wishes knowledge was as clarifying as we wish it was...and yet it always seems that with just a little bit more knowledge...

LudemanDan

I believe high caster breaks axles somehow. Not sure I can explain it though.

The reason it creates more steering resistance is because the place where the steering axis hits the ground is farther away from the actual tire rotating point, so turning the tire moves the front of your car farther in the opposite direction. Correct me if I'm wrong. That's the way head angle works on bikes anyway, and I think caster is the same thing.

There is a really good article in Sport Compact Car about this from back in the day:
http://www.sportcompactcarweb....echno

Dan

Jaker

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RR98ITR &raquo;</TD></TR><TR><TD CLASS="quote">And as to that weight transfer stuff you said... It sounds good till you realize that it isn't true.
</TD></TR></TABLE>

I'm not sure I agree 100% with this statement. When a high caster"ed" (sick) car goes into a corner, and you turn the steering wheel, since the "kingpin" is tipped back at the top, the geometry causes the wheel on the inside of the turn to actually rise in relation to the chassis, and the one on the outside of the turn to consequently drop. We just had a suspension workshop hosted by our club last Sunday, and the instructor had built a model to demonstrate some of the ins and outs of changes in geometry/alignment, and you could see quite clearly what happens to the wheel as the steering turns.

RR98ITR

What you see on the scales is a bit different from what's happening on the track where at the key moment in the sequence many of us are driving 3 wheeled vehicles....but you are entitled to a few percent.

Scott, who saw lots of caster on RTR and Tri-Point cars in 2005... and surely they think they know something...or at the very least they think something...how bout this: there's no apparent dynamic Negative associated with running 6-7 degrees...

johng

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by LudemanDan &raquo;</TD></TR><TR><TD CLASS="quote">I believe high caster breaks axles somehow. Not sure I can explain it though.</TD></TR></TABLE>

Apparently, only on your generation Prelude. Corey had this issue a while ago, but I really haven't heard much else.

Johnny Mac

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RR98ITR &raquo;</TD></TR><TR><TD CLASS="quote">What you see on the scales is a bit different from what's happening on the track where at the key moment in the sequence many of us are driving 3 wheeled vehicles....but you are entitled to a few percent.

Scott, who saw lots of caster on RTR and Tri-Point cars in 2005... and surely they think they know something...or at the very least they think something...how bout this: there's no apparent dynamic Negative associated with running 6-7 degrees...</TD></TR></TABLE>

A large amount of caster is necessary when you have strut type suspension systems. This is because dynamic camber gain is minimal under bump/rebound changes in suspension geometry. However, with caster you get that dynamic camber back as a function of steering angle. Unfortunately, there are no free lunches and lots of caster is no exception. The steering effort is multiplied significantly with increased caster.

On non-strut systems, you can use more caster if, for some reason, you wanted to run less static camber or your camber gain curve was not agressive enough.

LudemanDan

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Johnny Mac &raquo;</TD></TR><TR><TD CLASS="quote">
On non-strut systems, you can use more caster if, for some reason, you wanted to run less static camber or your camber gain curve was not agressive enough. </TD></TR></TABLE>
"Some reason" seems pretty obvious: you drive your car as transportation and you don't want to wear out your street tires. But you autox (in stock class) and occasionally HPDE. Like me. Seems like a little extra caster would be a good move.

-Dan, who is starting to run into problems with asking his car to do every job well

Johnny Mac

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by LudemanDan &raquo;</TD></TR><TR><TD CLASS="quote">
"Some reason" seems pretty obvious: you drive your car as transportation and you don't want to wear out your street tires. But you autox (in stock class) and occasionally HPDE. Like me. Seems like a little extra caster would be a good move.

-Dan, who is starting to run into problems with asking his car to do every job well</TD></TR></TABLE>

I assume you aren't running any static toe out in the front. Talk about wearing out tires - that'll do it.

Mohudsolo

I would think one good reason to want to limit the amount of static cambe is if you enjoy acceleration and deceleration. Having the tire flatter on the ground in a straight line will improve straight line traction. Both matter in autox, braking is probably more important in roadrace conditions since very few Honda products have traction issues under straigh line acceleration at high speeds.

HapaHaole

More caster makes the driver have to exert more force to turn the steering wheel. Having a lot of caster can snap your steering wheel back to center. Of course you can have power steering and then a lot of caster wouldnt matter.

I've been told you want as much caster as you can tolerate!

Johnny Mac

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mohudsolo &raquo;</TD></TR><TR><TD CLASS="quote">I would think one good reason to want to limit the amount of static cambe is if you enjoy acceleration and deceleration. Having the tire flatter on the ground in a straight line will improve straight line traction. Both matter in autox, braking is probably more important in roadrace conditions since very few Honda products have traction issues under straigh line acceleration at high speeds.</TD></TR></TABLE>

Yes, and static camber and the camber gain curve should be a best compromise of straight line braking and cornering power.

Mohudsolo

I have not added any caster to my car and find with the wide autox tires on it needs the steering put back to center. I thought I would do some measuring this winter and see where it is and then consider adding some. I've read a few places to keep caster under 5-6 degrees on front drive cars to prevent torque steer versus 12-13 degrees being OK on rear drivers. I'd be interested to hear anyones opinion or experience with that.

RR98ITR

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Johnny Mac &raquo;</TD></TR><TR><TD CLASS="quote">

Yes, and static camber and the camber gain curve should be a best compromise of straight line braking and cornering power. </TD></TR></TABLE>

So you're saying it's all a giant Compromise?

Scott, who...thought he almost had it....and once again I fell back into my body, found myself finishing a post on H-T...and my mind is as blank as the cover of The Beatles White Album...

Johnny Mac

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RR98ITR &raquo;</TD></TR><TR><TD CLASS="quote">

So you're saying it's all a giant Compromise?

Scott, who...thought he almost had it....and once again I fell back into my body, found myself finishing a post on H-T...and my mind is as blank as the cover of The Beatles White Album...</TD></TR></TABLE>

Yep, that's what I'm saying, and isn't it great that you have to go out and find the best compromise instead of just sitting back in your chair saying to yourself, "I got the best possible setup and there's nothing left to do". Life would be so boring if everything was independently adjustable.

RR98ITR

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Johnny Mac &raquo;</TD></TR><TR><TD CLASS="quote">

...just sitting back in your chair saying to yourself, "I got the best possible setup and there's nothing left to do". </TD></TR></TABLE>

Unpossible...there's always a tenth or two in Tire Pressure.

Scott, who remembers one day he got Two Full Seconds out of careful tire pressure adjustment alone...

Track rat

IMO, caster ranks near the bottom of the list of things that I'm going to want dialed in on my car, as long as it's equal side to side.

The self-centering effect of positive caster is basically just for feel.
The dymanic camber gain is a good thing, but with double wishbones and a good range of static camber adjustment, I just don't think heavy pos. caster should be high on the want list. I too have heard that heavy pos. caster wears out axles.

Once you've got all of your camber, toe, spring rates, tire pressures, brake bias, sway bars, shock valving, corner weights....and especially your driving all dialed in...then worry about that 1/10th of a second that bit of caster might give you .


Modified by Track rat at 8:46 PM 12/16/2005

sdcivic549

Caster is a wonderful thing for the DC5's and the EM/EP's being that we have an evil strut front suspension and have to run a grip of static front camber to get it to hook up. Unfortunately in order to get enough caster for my liking I need to cut up the strut towers

Mohudsolo

Is there any room in the lower control arms to make offset bushings for extra caster?

Track rat

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by sdcivic549 &raquo;</TD></TR><TR><TD CLASS="quote">Caster is a wonderful thing for the DC5's and the EM/EP's being that we have an evil strut front suspension... </TD></TR></TABLE>

Agree. I think it's much more important in a Mac strut car.

solo-x

another drawback to adding caster on a production car is that it changes the bumpsteer curve as well. if your class rules don't allow you to dial out the bumpsteer if you need to you might find yourself in a less optimal situation then before. i know that swapping UCA's on EG/DC2's effects bumpsteer in a bad way for a very minimal gain in caster. not worth it IMO. adjusting it through the lca might have less of an impact on bumpsteer, but at the very least you should always measure bumpsteer after making a change in caster.

nate

CRX Lee

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Johnny Mac &raquo;</TD></TR><TR><TD CLASS="quote">On non-strut systems, you can use more caster if, for some reason, you wanted to run less static camber or your camber gain curve was not agressive enough. </TD></TR></TABLE>
Another reason to run less static camber is if you have a very wide tire and especially a wide bias ply like a cantilever racing slick. Unlike a radial or a narrower tire, they greatly prefer a more evenly loaded contact patch. My 10 inch wide bias slicks will not like more than -2.0 degrees from from what I hear (non-FWD guys tell me that is too much). I have never played with caster hardly at all before but was considering trying more within reason in an effort to gain some dynamic camber change on the F Prod car this season.

Andrie Hartanto

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RR98ITR &raquo;</TD></TR><TR><TD CLASS="quote">
Scott, who saw lots of caster on RTR and Tri-Point cars in 2005... and surely they think they know something...or at the very least they think something...how bout this: there's no apparent dynamic Negative associated with running 6-7 degrees...</TD></TR></TABLE>

From my point of view, it looks like much more than 6-7 degrees. More like 10-12 degrees.

JFYI, NSX comes from the factory with about 8 degree caster. In our car, we ran about 10 degree

LudemanDan

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by solo-x &raquo;</TD></TR><TR><TD CLASS="quote">another drawback to adding caster on a production car is that it changes the bumpsteer curve as well. if your class rules don't allow you to dial out the bumpsteer if you need to you might find yourself in a less optimal situation then before. i know that swapping UCA's on EG/DC2's effects bumpsteer in a bad way for a very minimal gain in caster. not worth it IMO. adjusting it through the lca might have less of an impact on bumpsteer, but at the very least you should always measure bumpsteer after making a change in caster.

nate</TD></TR></TABLE>
Do you mean that more caster will lead to worse tramlining of the tires?

Track rat

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by LudemanDan &raquo;</TD></TR><TR><TD CLASS="quote">
Do you mean that more caster will lead to worse tramlining of the tires?</TD></TR></TABLE>

My guess is that heavy positive caster would lessen tramlining, since positive caster increases steering effort and self centering. Shrug.