C4 Widebody conversion - Proper suspension conversion
02-04-2011, 09:55 PM
#1
Rennlist Member
Thread Starter
C4 Widebody conversion - Proper suspension conversion
I recently bought a C4 WB conversion, but the suspension was not converted to WB position and specs. So, the only conversion was to use a combination of lower ET offset wheels and spacers. I am concerned that this is a far from ideal geometry for the front suspension. Some questions:
- Is there a Safety concern with the handling behavior?
- What will the symptoms be of this poor geometry? Will the car tend to "dart" from side to side? or??
- Can someone point me to a good reference with explanations of impacts of suspension geometry variables - specifically with large changes in wheel offsets (spacers).
- In referencing the differences in track width between NB and WB, I found that the difference is 27mm on each side in front, and 57-60mm on each side in rear. The front wheels are ET23 vs ET55 stock turbo, so the change is 32mm which positions the wheel very close to the WB position. The rear wheels are ET15 plus 21mm spacers, vs ET55 stock turbo wheels, so the change is 61mm and matches the WB position.
- What is the impact or risk of using spacers+offset on the rear wheels vs. using the Turbo trailing arms? Does this put extra stress load on the wheel bearings?
- What parts and procedure are needed to do the proper front suspension conversion? move upper shock mount to outboard position, move lower suspension mounts to outboard, longer axles for C4, wider sway bar?, longer brake hoses, longer tie rod sleeves, longer ABS sensors?, what else?
- The cost for new C4WB front axles is quite high. Can longer shafts be machined and fit to the existing CV joints?
- Anyone have experience with this conversion? or any of these things just lying around?
THANKS in advance,
I am attaching quote excerpts from a recent thread with expert commentary by our friend Geoffrey:
"All 964 widebody cars, and 993 race cars (RSR, GT2) and 993 911 GT (GT2) street car have the suspension side members installed on the outboard position which widens the track about 25mm per side. This requires different tie rods, sway bar, movement of the orientation of the dampers, brake hoses, and may be others I'm not thinking of at the moment.
If you look in your trunk by the ABS pump you can see the chassis to suspension member mounting holes. There are 3 of them, with the suspension member bolted to only 2 (inner and middle for C2), (outer and inner for C2 Turbo).
It makes a noticable difference in handling due to the scrub radius changes.
The 964 WB will have worse bump steer than a NB due to the fact the tie rod is longer so it moves a greater distance for a give compression or rebound of the damper. A WB with correct front suspension position mounting has much better geometry than a WB with the front suspension left in the NB position.
some people convert a NB to a WB but do not understand about the suspension settings. I've noticed it on almost every conversion that I've seen.
The WB does have a better overall geometry, but by the nature of the longer tie rods will have worse bump steer to manage ie reduce the suspension travel, use a bump steer kit, etc."
- Is there a Safety concern with the handling behavior?
- What will the symptoms be of this poor geometry? Will the car tend to "dart" from side to side? or??
- Can someone point me to a good reference with explanations of impacts of suspension geometry variables - specifically with large changes in wheel offsets (spacers).
- In referencing the differences in track width between NB and WB, I found that the difference is 27mm on each side in front, and 57-60mm on each side in rear. The front wheels are ET23 vs ET55 stock turbo, so the change is 32mm which positions the wheel very close to the WB position. The rear wheels are ET15 plus 21mm spacers, vs ET55 stock turbo wheels, so the change is 61mm and matches the WB position.
- What is the impact or risk of using spacers+offset on the rear wheels vs. using the Turbo trailing arms? Does this put extra stress load on the wheel bearings?
- What parts and procedure are needed to do the proper front suspension conversion? move upper shock mount to outboard position, move lower suspension mounts to outboard, longer axles for C4, wider sway bar?, longer brake hoses, longer tie rod sleeves, longer ABS sensors?, what else?
- The cost for new C4WB front axles is quite high. Can longer shafts be machined and fit to the existing CV joints?
- Anyone have experience with this conversion? or any of these things just lying around?
THANKS in advance,
I am attaching quote excerpts from a recent thread with expert commentary by our friend Geoffrey:
"All 964 widebody cars, and 993 race cars (RSR, GT2) and 993 911 GT (GT2) street car have the suspension side members installed on the outboard position which widens the track about 25mm per side. This requires different tie rods, sway bar, movement of the orientation of the dampers, brake hoses, and may be others I'm not thinking of at the moment.
If you look in your trunk by the ABS pump you can see the chassis to suspension member mounting holes. There are 3 of them, with the suspension member bolted to only 2 (inner and middle for C2), (outer and inner for C2 Turbo).
It makes a noticable difference in handling due to the scrub radius changes.
The 964 WB will have worse bump steer than a NB due to the fact the tie rod is longer so it moves a greater distance for a give compression or rebound of the damper. A WB with correct front suspension position mounting has much better geometry than a WB with the front suspension left in the NB position.
some people convert a NB to a WB but do not understand about the suspension settings. I've noticed it on almost every conversion that I've seen.
The WB does have a better overall geometry, but by the nature of the longer tie rods will have worse bump steer to manage ie reduce the suspension travel, use a bump steer kit, etc."
02-08-2011, 06:25 PM
#3
Rennlist Member
lucky you - do know how many guys wish they had the narrow body trailing arms? It will allow you to run 11 or wider rear wheels with very deep outer lips should you choose to use 3 piece wheels. This is a very popular conversion on the rear. On the fronts, so what running either a 1" spacer or a 1" wider outer front lip assuming again you are running 3 piece wheels is another sought after mod from the 965 guys. Standard wheels are 8 & 10's x 18 on the 3.6 Turbo - many would if it would fit run 9 & 11 or larger, most do not want to roll the fender lip or the other mods necessary to run wider wheels. Elliott on the 965 board has a Turbo that did not change the front suspension and just runs a spacer as I remember. Just so you know the 1978 and 1979 930 ran a spacer on the front to move the wheels out to increase track width. Starting in 1980 Porsche made a 930 front hub that moved out that amount an just made the track wider. They had turbo trailing arms on the rear and still used a spacer to move everything out. Should be no issues for you, I think a plus. Jim
jdorociak@gmail.com
jdorociak@gmail.com
