Front Upper Control Arms...

MaysEffect

The SR does not change in this situation. Only the SAI. The SR would only change if you changed the angle of the upright and not the camber and caster.

The only way you'd change the SR is if you change the wheel offset, or somehow modify the upright to change inclination.

Jacking would be increased during turning if you increased caster angle. In this case, don't increase caster.

ValidusVentus

The design of the SPL FUCAs is such that it adds camber by changing the actual length of the upper A arm.

And I tried to go to the link above but it doesn't seem to work on the gov computers unfortunately, they never seem to like links that end in a foreign abbreviation.

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MaysEffect

Right. This only changes the SAI. Because the change in geometry also changes the wheel center line angle, there is no change in SR.

If you increase caster along with camber you will have increased rise and fall.

Adding stiffer components won't help much here. It would mostly just make steering more sensitive.

Rusty

Any adjustable control arm for the Z will change the distance between the ball-joint and the control arm pivots. If you want to change the camber. There is no way around it. You have to live with it. The only way to get around what you are describing, is to move the control arm pivots in or out. Ain't going to happen. With the SPL's. Now you can change the caster too. Slicks need caster. Go to Hooser's web site. They will tell you to run as much + caster that you can. When you start making changes, you will have to live with the compromises.

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MaysEffect

That's an extremely vague suggestion that should be taken with a grain of salt.

Racing tires needed additional camber, adding positive caster is another way of getting more camber with additional steering lock. The tires dont need caster, in most cases its worse for the tires as it pulls the tire away from the road.

Increased negative scrub and wider tires is necessary if you increase camber and caster.

Rusty

A little info from Toyo tires.

Toyo Tires recommends the following general set-up guidelines for the Proxes R888:

Operating Temperature: 160°F to 220°F
Hot Inflation Pressures: 32 to 38 (psi)
Camber: -1° to -3°
Caster: As much positive as possible

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Hotrodz

My r888 setup:
Hot Inflation Pressure: less than 36 psi tire will get squirrelly 36 psi or better.
Camber: -2.26 front -2.00 rear
Caster: 6.5 and I think 7 to 8 would be better

There was another member here running -3.3 front and -1.8 rear with caster at 8 for the same tire. He was running 18x315 and I am running 18x295.

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Rusty

Yeah, I'm running -2.0 camber and +7 caster front and -1.75 camber rear.

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MaysEffect

Have you tries 3 degrees with low levels of caster and less rake? and possibly different shock settings.

MaysEffect

That is equally vague. 32-38psi covers a huge variety of load ranges of about 300ibs per axle. 2 degrees of camber variation is also a huge margin for both steering geometry and tire contact. Changing the caster by that amount (4 degrees to 6 degrees) would possibly change your camber at full lock by 1-4 degrees.

This also doesn't take into account the wide variety of suspension setups these tire companies are advertising to. Cars without sway bars, cars with solid rear axles, cars with McPherson struts.

None of this is a problem for the Z. So additional caster AND camber is not a necessary change, its the reason nissan knocked the Z34 down to -+5 degrees of caster. If you want more response out of the tires, properly match the SR for the given wheel/tire you are trying to use. Not an easy thing to do when dealing with clearance and fitment issues (brakes or fenders). So yes, this is the ultimate compromise. Adding caster and camber ruins your instantaneous roll center. Something that will severely compromise how the suspension balance SHOULD be setup.

ValidusVentus

Could you explain or provide a link explaining this. We have gotten slightly off topic on the thread but its a good discussion. I'm going to do some research on my own regardless.
I am currently at +6deg caster and -2.2 camber up front I believe. IIRC it wasn't possible to get more caster with the SPL arms without forcing the other variables off, though I was under the impression -mostly from scuttlebutt- that even more caster would have been favorable and was seeing this as a limitation for the SPL arms. I know I need additional camber all around (from tire evidence) but I still drove it on the street a bunch over the last few years in Cali; with no AC/blower/interior, race seats and a full cage. Now I'm up in Washington its a different story.

I don't want to turn this into another "what's the best suspension settings!?" thread but I think there is an opportunity to learn something here.

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