Change height of spindle on Bilstein strut?
 

Car is a 74 911, lowered front and rear, otherwise stock suspension except for bigger sway bars and some bump steer washers. I'm about to swap out the front Bilstein struts for 3.5" spaced units in order to use A calipers vice the stock M's. The car gets light weekend and track use. A friend suggested I really should lower the spindle height appropriately while I'm swapping the struts. I know this is thought to be a desirable modification, but will I actually notice an improvement anywhere, or is it just one of the many smart changes you should make to get the most out of a track car? Opinions? Or, even better, facts?

Fact: you would raise the spindle and, yes, this is desirable if you want the car set up for the track (low).

Fact 2: this is more easily done with a Bilstein strut.

Ah raise. Well I was almost right. But what does this do for me? (The opinion part, I suspect.)

If you are going to lower it to track heights, raising the spindle will help to preserve the suspension geometery that the factory intended.

Milt is right...raising the spindle on Bilsteins is feasible, doing it on Koni or Boge struts is not so easy due to the tappered housing above the sprindle collar.

To raise and gusset the struts, contact Clint at RebelRacingProducts...he does great work and at a very good price. Tell him Souk sent you.

http://www.rebelracingproducts.com/Suspension/Steering.html

Here's an exaggerated sketch...you'll get the idea.

http://forums.pelicanparts.com/uploa...1223596415.jpg

My friend does them all the time, this will give you more info- http://www.rebelracingproducts.com/Suspension/Steering.html
Oops! I just notced that this info was already posted above. DUH!

Many thanks. Souk, the drawing is good. Can I infer that the roll center at the front of a 911 is maybe 6 or 7 inches off the ground, and that a 3/4" lowering of it would yield something like a proportional benefit...say .75/7 or maybe 11%? Or is that too simple minded to be useful?

911's were designed with a specific ride height in mind, but it's not the height that they were delivered in the US. Porsche had to raise the cars to meet US headlight height requirements. I don't remember how much exactly but my feeble brain says 1.25". Somebody else should know. Obviously you could lower the car to meet European specs and it would benefit from the change. It would be adjusting beyond that point that you would start to see a negative change.
Then you would need raised spindles or a bump steer kit or both to manage the geometery.

According to my Spec Book, the difference in front ride height between US and the RoW is only 9mm which comes out to less than half an inch, if I'm not mistaken.

Raising spindles is also advisable with larger rims, if you read the book "The Unfair Advantage" Mark Donohue goes into depth about how important suspension geometry is and how when fully utilizing the full range of the suspension any 'bottoming out' at high speed is a bad, bad thing. My spindles have been raised 19mm.

+1,000 about Rebel Racing, their RSR struts are on my 935 project...and his customer service is out of this world. I'd recommend their parts to a family member :)

for more info, you should try contacting Clint Smith at Rebel Racing Products,
he is almost done with mine,this is a service that he offers,and he is a very approachable guy and has a wealth of info.
his number is:

805-440-9849