17" & 18" wheels problem and solutions?
11-10-2002 | 07:09 AM
#1
Thread Starter
Burning Brakes
Joined: Oct 2001
Posts: 818
Likes: 0
From: Abbotsford, B.C.
17" & 18" wheels problem and solutions?
As many of you know, Porsche does not recommend running 18" wheels on any 944 series car, and 17" with the proper modifications to the suspension. The main problem is the increase load on the front spindles can cause them to shear off and possibly cause catastrophic(sp?) damage. I wonder if anyone considered staggering the wheels with 17" fronts and 18" rears. Would that work? Some of you know that I run 18" Kinesis Supercups on my '86 non-turbo 
with '86 turbo suspension. I will be running Big Reds behind those wheels, therefore the unsprung weight and load on the spindles will increase. I have had Lindsey Racing magnaflux and cryo-treat a spare set of '86 951 spindles that I hope will be up to the task. Some believe that this spindle failure can occure only on track cars, but I have heard otherwise. And as for the wheels they were on a Boxster, 8.5x18" and 9.5x18". Only the fronts have a 21mm spacer while the rear fits under the quarter panel without any body mods ie rolling the lip. Those that went to Whistler in October know what I mean. So what do you guys think?
with '86 turbo suspension. I will be running Big Reds behind those wheels, therefore the unsprung weight and load on the spindles will increase. I have had Lindsey Racing magnaflux and cryo-treat a spare set of '86 951 spindles that I hope will be up to the task. Some believe that this spindle failure can occure only on track cars, but I have heard otherwise. And as for the wheels they were on a Boxster, 8.5x18" and 9.5x18". Only the fronts have a 21mm spacer while the rear fits under the quarter panel without any body mods ie rolling the lip. Those that went to Whistler in October know what I mean. So what do you guys think?
11-11-2002 | 02:40 PM
#5
Race Director
Joined: Jul 2001
Posts: 14,075
Likes: 3
From: Santa Barbara, CA
I think the '86 spindle-failure is over-rated. I believe it's a statistical analysis and data-interpretation issue.
There were more '86 951s built than all the rest combined. They are also older, meaning failures would start showing up first.
So if you were to assume that the '86 spindle and the later ones were the same, then you should expect to see failure-rates of 10:1 for the SAME durabilityi.
However, if you assume that the '86 spindle is weaker, you would have to measure failure-rates higher than 10:1.
I don't think we have the comprehensive data on ALL spindle failures ever to draw a definite conclusion.
But to be on the safe side, I've had my spindles shot-peened and nitrided. Then I have a spare set I bring to the track and they both get manafluxed yearly. But I would think this should be done to ALL spindles that see track usage, regardless of the model year.
There were more '86 951s built than all the rest combined. They are also older, meaning failures would start showing up first.
So if you were to assume that the '86 spindle and the later ones were the same, then you should expect to see failure-rates of 10:1 for the SAME durabilityi.
However, if you assume that the '86 spindle is weaker, you would have to measure failure-rates higher than 10:1.
I don't think we have the comprehensive data on ALL spindle failures ever to draw a definite conclusion.
But to be on the safe side, I've had my spindles shot-peened and nitrided. Then I have a spare set I bring to the track and they both get manafluxed yearly. But I would think this should be done to ALL spindles that see track usage, regardless of the model year.
