Hey guys,
I've been looking for the answer to this for a while now. Lets see if anyone on the forum can answer this.
Before I get into the subject at hand, let me back up a little. I do a lot of work on NSX's. I set them up for track sessions, racing, etc. An NSX runs 8 degrees of caster in the front suspension. As most of you know, caster helps the car turn better by tilting the tires in the direction of the turn. If you turn left, the left front tire will tilt more toward 0 or even positive camber. (caster affects camber by allowing the tires to tilt in a turn). NOW, back to the original question. I have a 93 LS special. I'm building it for roadcourse racing. Nothing professional, just for personal fufilment. You know the deal. I just bought an alignment machine for my shop. I was checking the specs on the 90-93 integras. The camber spec is 1.5 degrees. NOW, the camber specs for the 94 and up Integras, including type R's is 1.17 degrees. This is counter intuitive for tuning. BUT the Integra type R is well known for it's ability to turn and handle well. So this is my question. Why would an Integra with the ability to turn well have less caster than an older model?
The more positive caster you put in the more the tires will tilt. Why would they back off the spec for the caster? Especially in a car that is a Front wheel drive Front motor design. Normaly a FF car will have a ton of understeer. This would tell me that more caster would be needed to turn the car in a high speed turn. Am I missing something here?
Next question. I'm thinking about taking the factory radius rods off the front and modifying them to put more caster in my car. BUT, if someone will tell me a reason why I shouldn't I'd like to hear why.
Thanks guys, have a great weekend,
Barn Man..

 

out of camber, spring rate, dampening, and caster, i would consider caster the least bit of worries.

i dont know anyone who would play with caster prior to playing with the other 3 first.

the itr has good handling because of a few things which include combination of weight distribution, chassis rigidity, aerodynamics and spring/dampening setup

 

I agree, all of these things make a tremendous difference in handling. I'm looking at doing what I can at this moment. I'm thinking that the difference in the NSX and the Integra as far as caster goes is the placement of the motor. I'd like to run about 3 degrees of caster and see what it feels like. I can always move it back to stock setting or even tweak it more.
I took my car up to Michigan and ran in on the roadcourse at Gingerman. The car did much better than I expected originally, but initial turn in was a little slopy. I'd like to sharpen it up a bit. I'm about to invest in the equipment to corner balance it, but that's a way out as far as cash goes. I can't help but think that adding a little caster would help my turn in.
I've raced a supercharged NSX on the same track a couple years ago. It felt nice. At low speeds it has a little understeer, but at speed the back end can become a little evil if your not ready for it. It's a balancing act to get it right. But that's the fun part.
I passed a couple S2k's and a WRX on the course, but I'm sure most of that was due to driver experience. It still felt good!
Barn Man..

 

I know my ITR came 'out of spec' on caster, I think one side was slightly negative caster *shrug*

Maybe it improves the feel, i.e. makes the car feel darty? Or maybe it's because it's FWD, you want to keep the drive wheels as parallel as possible.....

It's a very good question that I have no answer to

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ccfries &raquo;</TD></TR><TR><TD CLASS="quote">Maybe it improves the feel, i.e. makes the car feel darty? </TD></TR></TABLE>

I agree it still doesn't make much sense to compromise steering effort vs. potential g-forces and straight-line stability. And caster should serve to keep the tire flatter against the road as the camber is changing/body is leaning.. so I'm going to chuck that theory.

http://www.ozebiz.com.au/racet....html

Positive caster tends to straighten the wheel when the vehicle is traveling forward, and thus is used to enhance straight-line stability. The mechanism that causes this tendency is clearly illustrated by the castering front wheels of a shopping cart (above). The steering axis of a shopping cart wheel is set forward of where the wheel contacts the ground. As the cart is pushed forward, the steering axis pulls the wheel along, and since the wheel drags along the ground, it falls directly in line behind the steering axis. The force that causes the wheel to follow the steering axis is proportional to the distance between the steering axis and the wheel-to-ground contact patch-the greater the distance, the greater the force. This distance is referred to as "trail."

Due to many design considerations, it is desirable to have the steering axis of a car's wheel right at the wheel hub. If the steering axis were to be set vertical with this layout, the axis would be coincident with the tire contact patch. The trail would be zero, and no castering would be generated. The wheel would be essentially free to spin about the patch (actually, the tire itself generates a bit of a castering effect due to a phenomenon known as "pneumatic trail," but this effect is much smaller than that created by mechanical castering, so we'll ignore it here). Fortunately, it is possible to create castering by tilting the steering axis in the positive direction. With such an arrangement, the steering axis intersects the ground at a point in front of the tire contact patch, and thus the same effect as seen in the shopping cart casters is achieved.

The tilted steering axis has another important effect on suspension geometry. Since the wheel rotates about a tilted axis, the wheel gains camber as it is turned. This effect is best visualized by imagining the unrealistically extreme case where the steering axis would be horizontal-as the steering wheel is turned, the road wheel would simply change camber rather than direction. This effect causes the outside wheel in a turn to gain negative camber, while the inside wheel gains positive camber. These camber changes are generally favorable for cornering, although it is possible to overdo it.

Most cars are not particularly sensitive to caster settings. Nevertheless, it is important to ensure that the caster is the same on both sides of the car to avoid the tendency to pull to one side. While greater caster angles serve to improve straight-line stability, they also cause an increase in steering effort. Three to five degrees of positive caster is the typical range of settings, with lower angles being used on heavier vehicles to keep the steering effort reasonable.

 

If you want more caster, Take the left and right upper control arms and swap them.

This is a trick that has been around for awhile.

On my ITR, I run -2.0 of camber at all 4 corners, O toe in the rear and slightly toe-out in the front.

After swapping the front upper control arms: Turn in is much qwicker at any speed, but not "darty". I do not think that high speed straight line stability is any differant than it was.

The only down side is moving the car around at parking lot speed with no power steering. It is harder to turn lock to lock at 5mph (not really a concern)

Mattj

 

Thanks Dropspeed,
This is what I was looking for. That will be much easier than modifying the radius rods.
If you have a wing (bigger than stock), 0 toe in the rear may be ok on high speed sweepers. If you trailbrake into turns, 0 toe in the rear may cause the back end to come out a little. But, some guys like to use this to steer the car. If you get the back end unsettled, then as it starts to come around, you can get back in the throttle and settle it back down. It's good for sharp corners after long straights or long sweepers. But if your car can turn well, you can do the same thing by going in hot and lifting off the throttle. With the weight transfer to the front wheels, you can get the car to turn without the rear coming out of shape. Much more desireable.
I aligned my Teggie to the ITR spec. It felt much better than the stock setting on the track. Then I tweaked the *feel* by adjusting my Koni's and changing tire pressures. When I finaly get some scales, I'm gonna use the Ground Control coil overs to set the corner balance. This should make the car feel MUCH better. Thanks again.

 

by radius rod, do u mean the ball joint on the upper control arm?