Bill Verburg

There are several mostly race oriented shops that have them in one form or another,
FD has them

spec for Cup & RSR is+3° to +3° 30', I run mine at +3° 30', the lower the # the faster reaction is obtained from the rear on transitions, the higher the slower, set to taste.

DutchNy

Bill Verburg

Save your self a lot of trouble and get RS

Didn't your car have RS wheel carriers w/ the Rs outer tie rod ends?
Here's the difference


You can also use RSR inners w/ the RS outer, that's what I'd recommend.

The RS still have rubber, the RSR are pure spherical,
The upper here is a stock outer/inner, the lower is RS outer w/ RSR inner

DutchNy

Bill Verburg

so something like this?


Are they doing a bump sweep?

DutchNy

Yes, the top one connected to the RSR inner.

What is a Bump Sweep?

Bill Verburg

It's how you know that what you did was right

DutchNy

Tripp993

Will they check bump steer on both front and rear or just rear? I've been following this closely because I've just got the same setup (but with JRZ's), had a very reputable race shop set it up for me and after 2 weekends at the track with their support I was still almost a second slower than before I installed the new parts. I took it to my mechanic at Porsche who does all of my other work and we found that it had a lot of bump steer in the rear. I've purchased the longacre bump steer tool and we are working on that next week. Another thing that was a problem is the JRZ suspension I have was for a RSCS and after installed rear wheels seemed to be droop limited (1" down and 5" up). We have gotten some 1.75" spacers made to move the suspension down to have 3" of travel each way.

Bill Verburg

It's more important in front because you have the steering from the driver and steering from wheel travel, In back it's also important but the issue can be narrowed down and solved far more easily.

Assuming that you car is set up like the factory did for Cup & RSR, as shown here. Use the factory specs as shown.


For both front & rear the less castor the more pronounced any bump steer will be, so too speed an end up lower caster to slow it down decrease caster, Every driver will have slightly different tastes in this regard.
here's a bump sweep for a stock RoW height 993, the reddish curve is the bump, Ideally you want a vertical line, lowering actually puts the car into a better part of the curve, the dashed blue line is lowered to RS height, The RS wheel carriers and tie rods further improve the curve

Tripp993

Thanks Bill. I see that you run 0 toe front and .18 degrees toe in rear and I had my car set to your specs before these modifications. Am I reading this right that RSR/Cup had +0.05 Degrees toe in front and +0.30 degrees toe in rear? Why do you not like those specs for yourself? Some race shops are recommending 1/16" total toe out Front and 1/8" total toe In Rear. Since I using an alignment machine, if I'm not mistaken that's front -0.14 degrees and rear +0.28 degrees. I'm running same tire setup as RSR/Cup but BBS E88 8.5"x18" ET 48.5 and 10"x18" ET63 wheels. What are your thoughts?

Bill Verburg

In front 0 static toe gives better turn in, One of the battles I had w/. the car from day 1 was getting that, things that help, less caster, RSR tie rods 8.5" wheels 235 or 245 tire, less toe some guys evn go to toe out in front.

Similar situation in back, but I like a little slower rear wrt the front so in back more caster, but retain toe in for braking stability

You front wheels imparts a larger scrub radius than mine, you will have better feel and self centering and better turn in, the only downside is less room at the lip

DutchNy

Picked up the 993 this morning. Total weight is 2859lbs

Any input on the spec sheet below.

Bill Verburg

No mention of caster or KT......

sander97C2

Nice! How does it feel? Do you have a pic of how it looks from the side?