random notes on 964/993 suspension

[Vandit]

Originally Posted by perelet

Bushing geometry.

Most of printed sources put pride on rear trailing arm spring geometry that adds rear toe in (stability) under breaking - Paul Frere covers it deeply in his book.

On other side, front suspension "by design" will toe out under breaking. Surely not best choice for street car. Also maybe unwelcome feature for race car also....

Here are pics of front A-Arm bushings:

I'm in the middle of replacing these bushings w/ polyurethane pieces from Powerflex. My OEM bushes look to be in decent shape, even after 100k miles, but man, they have plenty of flex to them. I can't wait to get it all back together w/ the poly pieces.

[Captain Ahab Jr]

Originally Posted by Bill Verburg

I doubt that they are stronger, just looking at them they all appear to be the same, some of the RSRs used braces to the chassis.

Toe control is more a function of the A-arm bushes, Porsche used 2 different hardness rubber bushes, the RS stiffened the trailing fronts but not the leading one.

So option 1 is to use an RS sport hardness bush in the trailing position to emulate the 993RS

option 2 which is what I did is to use RS sport hardness bushes in both leading and trailing positions

option 3 for a track only car is mono-balls

turn in is also dramatically improved w/ 8.5" vs 8" wheels, even w/ the same tires

Thanks Bill, do you have any photo's of the RSR bracing?

For road your option 2 has to be the best, thanks for the tip, mono-balls would make long distance driving not a lot of fun.

I want to use the 993RS wheel carriers, not just to reduce bump steer but to reduce unsprung weight and because the 993RS track rod is stiffer.

Also I'm sure it would be an improvement to replace the stiffer rubber inner on the 993RS trackrod with a solid section to reduce flex even more. Is there a Porsche Motorpsort part for this?

[Bill Verburg]

Originally Posted by Captain Ahab Jr

Thanks Bill, do you have any photo's of the RSR bracing?

For road your option 2 has to be the best, thanks for the tip, mono-balls would make long distance driving not a lot of fun.

I want to use the 993RS wheel carriers, not just to reduce bump steer but to reduce unsprung weight and because the 993RS track rod is stiffer.

Also I'm sure it would be an improvement to replace the stiffer rubber inner on the 993RS trackrod with a solid section to reduce flex even more. Is there a Porsche Motorpsort part for this?

the things that helped steering the most on my car, in no particular order
8.5' front wheels even if you don't change tires

993RS wheel carriers w/ GT2 monoball inners/RS outers these are no longer being made but there are a few sets left here and there, I believe that Steve Weiner at Rennsport Systems may have a couple sets left theu have gotten to be very expensive since I bought mine

RS sport rubber bushes in both leading and trailing position on the front A-arms

w/ 993 wheel carriers you have to use 993 rotors, 322 w/ big reds or 304 w/ regular 993 front calipers

[perelet]

ABS gear and front Hub.

Porsche factory REALLY struggled with ABS gear and washer during 964 C2 production. Assembly was changed 3 times:



And then in 1994 they said - all previous designs are bad and use this one:



Latest design replaces front hub and washer (abs gear) as pair! Hub is easy - it is 993 hub. But revised 964 45teeth tension ring is impossible to find used, cause you have to find 964 that had front axle repaired at dealer according to bulletin above after 1994...


Gladly, thanks to Rob from DC automotive for supplying various parts to me - one can press out ABS ring from 964 and press it on 993 tension ring. In this case you'll end up with best front hub design ever.





Pressing ring out:



Press rings from this kit from Harbor Freight fit ABS ring very well:






Pressing 964 ABS ring on 993 washer.



Here's 993 hub and matching ring with 964 ABS gear on it:





Oleg.

[Captain Ahab Jr]

Thanks for posting Oleg,

If you have the parts I'd be interested to know if there is a difference in the driveshaft spline and the wheel bearing fitment between the 964 and 993 rear wheel hub.

I'm sure the rear wheel bearings are the same size so I'm assumming the driveshaft spline is the same size.

I know it won't be a straight swap due to wheels and brake disc offsets but for a number of reasons I'm thinking it would be a good idea to fit a 993 rear wheel hub on my 964.

[perelet]

Originally Posted by Captain Ahab Jr

Thanks for posting Oleg,

If you have the parts I'd be interested to know if there is a difference in the driveshaft spline and the wheel bearing fitment between the 964 and 993 rear wheel hub.

I'm sure the rear wheel bearings are the same size so I'm assumming the driveshaft spline is the same size.

I know it won't be a straight swap due to wheels and brake disc offsets but for a number of reasons I'm thinking it would be a good idea to fit a 993 rear wheel hub on my 964.

Ahab, I do not know. Haven't researched that part. I heard that half shafts from current waterpumper GT2/3 cars are much lighter and can be fitted, but task not straight forward.

Also it is known that 993 rear hubs/bearings tend to overheat and leak grease toward axle nut - that's on track conditions. Partially it can be explained by much lighter weight/heat dissipation of 993 rear hub/wheel carrier assembly compared to fat 964 A-Arm.

Maybe some of hardcore track people can add to it.

Oleg.

[rbogh901]

Originally Posted by perelet

Also it is known that 993 rear hubs/bearings tend to overheat and leak grease toward axle nut - that's on track conditions.

Maybe some of hardcore track people can add to it.

Oleg.

I think Bill V has photos of that. He pretty much has photos of everything. And I think he has solutions.

[Vandit]

Solution = higher performance grease

[rbogh901]

Well, this is very useful. I've got my pss9's ready to go and need a little help. I've got the rear washers/spacers all up and going thanks to the following:

Originally Posted by perelet

Rear strut


Order - what parts go on the strut (also see Bilstein documents below):

Now I need to do the same and confirm the order for the front struts. Here is what I have. Does it look like the correct order?

[964TargaC2]

that is whaT I did on mine..

[perelet]

Originally Posted by rbogh901

Now I need to do the same and confirm the order for the front struts. Here is what I have. Does it look like the correct order?
....

Carl, look correct - big washer 1st on the strut. Here's Bilstein installation pic



Oleg.

[rbogh901]

Originally Posted by perelet

Some references
Here are Bilstein specs, quite useful to compare 993 & 964 specs in general:


964
http://www.dvsegmbh.info/PDF/einbau/42011/171/E4-WM4-Y591A00.PDF

Oleg.

Oleg has reminded me that this is covered in the Bilstein pdf reference he linked and looking back indeed it is in the diagram on page 17 of the pdf. This does appear to be the correct configuration for anyone else looking to mount the front struts.

Thanks guys.

[Captain Ahab Jr]

just revisiting this informative thread and thought I'd share some pictures and ask some more questions

I've found some photos of the 964 and 993 front suspension side members and can spot a few differences

964


993 C2


Note the thicker webs and extra web at the forward front wishbone mounting point, also the wishbone mounting axis looks like it is positioned a little further outboard than the 964, does this easily give extra camber??

There is another 993 side member used on the RS and C4/TT but I have not found any photos so am assumming it is stiffer or has extra mounting holes for the front diff than the 993 C2 version

As using a 993 lower wishbone on my 964 is going to help improve toe stiffness it makes sense to me to fit the stiffer 993 side member too, that is if the 964 and 993 chassis mounting holes are in the same postion.

Any comments welcome.

[Bill Verburg]

Originally Posted by Captain Ahab Jr

just revisiting this informative thread and thought I'd share some pictures and ask some more questions

I've found some photos of the 964 and 993 front suspension side members and can spot a few differences

964


993 C2


Note the thicker webs and extra web at the forward front wishbone mounting point, also the wishbone mounting axis looks like it is positioned a little further outboard than the 964, does this easily give extra camber??

There is another 993 side member used on the RS and C4/TT but I have not found any photos so am assumming it is stiffer or has extra mounting holes for the front diff than the 993 C2 version

As using a 993 lower wishbone on my 964 is going to help improve toe stiffness it makes sense to me to fit the stiffer 993 side member too, that is if the 964 and 993 chassis mounting holes are in the same postion.

Any comments welcome.

the main difference between 993C2 and RS/C4 longitudinals is the mounts for the differing brake boosters

993C2 and C2S both have vacuum boosters mounted to the longitudinals as seend here


RS and C4 have electro-hydraulic units mounted in the trunk, that area is clear on those cars


If possible can you measure the A-arm(wishbone) o/s difference? I believe that there is a difference as some 993Cups use the outer mounting holes for the longitudinals even on n/b versions by using special longitudinals which i beliebe to be just re part numbered 964C2 longitudinals.

Both 964 and 993 have the same 2 sets of mouting holes in the chassis for the longitudinals, inner is used for n/b and outer for widebody like RSR and GT2 but not 993turbo

this n/b 993Cup has the longitudinals in the normal inner holes



this one in the outer



both version of 993 Cup use the same wheels and other suspension parts, the main reason to move the bottom of the wheel out and leave the top alone is camber and toe curve correction.

[tom_s]

Originally Posted by Bill Verburg

this one in the outer

looks like this one uses the 964 side member (looking at relative location of the round hole near the front bushing mount). Clever, looks like this arrangement provides an intermediate width.

[Bill Verburg]

Originally Posted by tom_s

looks like this one uses the 964 side member (looking at relative location of the round hole near the front bushing mount). Clever, looks like this arrangement provides an intermediate width.

I agree, though the 993Cup longitudinal has it's own unique part #, I have been told by informed sources that it is indeed the 964C2 part

The recommendation for my 993 track car was to use the 964C2 longituninals in the outer holes

[perelet]

Here's couple of notes on 993RS uprights.

1st. They do not alter steering ratio. Visually RS upright tie rod mount point may look closer to axle, but it is not.






Here are interesting measurements (approximate):




RS tierod inner halfs do look very similar to regular 993 inners



but have different part numbers.



it's been said that rubber inside is harder. I have no means of measuring ...
Oleg.

[rbogh901]

Hi Oleg,

Very analytical as usual. Are you trying to go lower with the RS uprights while avoiding bump steer?

[perelet]

Carl, I do not have (noticable) bumpsteer with my setup,

That said, I think there are so many pros of using 993 rs uprights - they straighen your lowered geometry, reduce unsprung weight, have better heat dissipation, allow brake updates. 993 tierods are big step up from flimsy 964 ones.

Probably only disadvantage is price and need for other things aka brakes, 993 a-arms, and some labor. But hey, i wrench for love of it and relaxation ... there are more expensive hobbies

Oleg

[Captain Ahab Jr]

Just revisiting this very informaive thread and hope someone can help me understsnd the difference between a 964 and 993 rear wheel hub.

If anyone has either one out on a bench and wouldn't mind taking a few measurements for me please PM me and I'll send you a picture showing what to measure