Bill Verburg

It's way below that

right around where I run 94/98, RS is 124/127+/-10

boomboomthump

@Bill Verburg That last pic you posted...

What is up with that wheel for the speed sensor? I don't see the normal M22 bolt that passes through the sensor wheel and the hub? I also don't believe I've ever seen an RS specific part for this, so I'm scratching my head.

Is it some older 964 part? How does it mount? (just some Sunday morning curiosities while I sip some coffee)

Bill Verburg

Its a 964

boomboomthump

Ah, ok. Thanks... had me wondering.

nk993

Just wanted to resurrect this thread a bit as I am trying to decide between uprights. As per Bills information above, the RS uprights were designed really for RSR and GT2 ride heights rather than RS, but still work well with RS.

But we also have now the BBI and the ERP uprights. As per this threads measuremeants: https://rennlist.com/forums/964-foru...ights-etc.html the ERP uprights raised the spindles another 10-15mm. So does this mean the ERP uprights would be even LESS suitable for someone running RS ride height and not GT2/RSR? Ie better off to go with stock RS? @Bill Verburg
thank you

boomboomthump

Take a look at my posts 28 & 29.

Factory RS/GT2 uprights are for RS and lower heights but should be used with RS dampers, which have shorter bodies. If you use them with non-RS dampers at RS and lower heights, you have very limited suspension travel (riding on bump stops).

The BBI uprights are designed for running at RS and lower ride heights but with standard (Non-RS) dampers. The shock mount is lower, which means you’ll have more range in suspension travel (vs above which is a problem without RS dampers).

If running higher than RS, neither upright is a good choice. Stick with stock uprights and bump steer correction.

nk993

Sure, I get that, but lets remove the shocks from the equation and assume they will be custom made for the application. Range of motion is only one thing these uprights are supposed to solve at the end of the day. The rest is bumpsteer/toe change as per the above.

With that in mind, and assuming exactly RS ride height, I am specifically curious about whether the ERP's extra 10-15mm as per the thread in the 964 section (if that is even true, because ERP quotes the same 50mm as BBI, which if measured from US OEM is just RS) means that the stock RS uprights will be better for EXACTLY RS ride height.

Bill Verburg

bump steer is a continuum, it doesn't turn on or off like a light.

bump steer or roll steer is the change in toe induced by wheel travel.

this is BBI's measure of toe change for the RS and their wheel carrier.

This data is for a single ride height which i don't know. At that ride height there is little difference between RS and BBi, BBi is a bit better, and either is way better than the stock 993 wheel carriers


change the ride height an this graph changes.

So in general RS curves gets better as ride height goes from RS to RSR and BBi will be slightly better than RS.

There are other considerations as well

I really like the Eisenlohr Racing Products versions sold by Tarett.

But any of them will do the job at lowered ride heights

You do want to use a shorter shock though, I use Bilstein Cup shocks which are the same length as b8s and PSS


also don't forget that you need the RS outer tie rod, even better is the RSR outer & inner

upper here is stock, lower is RSR which has the RS outer and a mono-ball inner


The RS tie rod mounts differently to the wheel carrier than stock.

boomboomthump

Exactly. There's only two questions here IMO.

1) What ride height do I want to run?
2) What type of shock bodies to I want to run? (shorter RS style or not)

Pick your wheel carrier based on those two. You cant ignore #2. It's as important as #1.

Bill Verburg

The other thing that the above wheel carriers do is raise the roll center, the further the axle is raised relative to the ball joint the further the roll center goes up.

This is good because the closer to the Mike axis the lower the roll couple the lower the amount of roll, in this regard the BBi and Eisenlohr carriers are superior to the RS versions.

What the raised axle does is lower the outer end of the Aarm, the roll couple is a function of the length of the line from the roll center to the CoM, the front and rrear roll centers determine the roll axis and the front and rear CoM determine the MIKE axis

here A1 is shorter than A2 so the same force causes less roll, because of the shorter lever arm.

ToSi

What's a 'mike axis'?

Bill Verburg

imaginary line through front Com and rear CoM

ToSi

Ah, are you referring to what Carroll Smith calls the mass centroid axis? It doesn't really work that way since a solid(ish, to the extent it matters here) body can only have a single center of gravity but sure, higher roll centers mean less roll.. usually. Then there's roll inertia and the rest of the fun stuff..

nk993

Sorry guys I guess my question wasnt clear, and maybe I should have put it in a different thread.

To answer @boomboomthump question: The car will be RS ride height and is already running RS spec dampers (ie the shorter ones).

My question is specifically about the new ERP (Eisenlohr) carriers In the 964 thread linked above @Peteinjp seems to have measured another 10-15mm difference between these ERP uprights and the stock RS uprights and he will therefore run 10mm lower than RS. So WITH THAT IN MIND, for exactly RS ride height and exactly RS dampers, is one better off with ERP or RS uprights?

ToSi

the easy answer is to match the drop to the parts & stick with the RS. The published toe curves are a wash but the erp parts will have some additional camber gain, whether or not this is beneficial to your application is more complicated to answer since it depends on the rest of the setup and will require some amount of testing to optimize. Very well might not matter in the end. A practical consideration and more significant for a street car IMHO is the erp upright uses a heim joint tie rod end, vs the more durable weather sealed ball on the factory RS parts.