random notes on 964/993 suspension

[perelet]

Some of this information is covered here and there on the net, some I haven't seen. Hope it can be helpful for DIY and tinkerers.



Front struts.

Front struts for 964 and 993 are pretty much interchangeable, here's reference pic:



valving is pretty close according to Bilstein specs (see below).

Major difference is that 993 struts use M12 and M14 mounting bolts and 12mm and 964 uses 2 12mm bolts. Lower hole in 993 strut is 2mm wider.



If you'll need to use 993 struts on 964 wheel carrier you'll need to reuse 964 M12 lower bolt and also 4 12-14mm spacers for proper strut fitting. I got spacers from Jeff @ Rothsport





Also here's pic of Koni adjustable inserts in 964 strut. Pretty good setup IMHO, but not popular for some reason:



Here are measurements of RUF lowering collars. Collars go in place of stock adjusters and will let you lower car with minimal investment:



IMHO they are best used with stock springs. I tried them with Eibach springs and car was way too low.

Note on PSS10 vs PSS9. Because of TUV regulations Bilstein changed thread size on PSS10. In this sense PSS9 has much more freedom in height adjustment and can use springs of different lengths:



Comparison of stock and pss9 assembly:



Front wheel carrier

993 aluminum wheel carrier will fit 964. You'll need to rebore 964 lower strut hole to 14mm (see above) or use 993 front struts.

Now and then it was mentioned that flange dimensions are different. Not that I can see:






Oops run out of image per post limit. See next post.

Oleg.

[perelet]

One fact worth to mention (as discussed on rennlist) is that 993 ball joint will fit on 964 arm, but it will have 2mm play, because 964 knurled screw (p/n 964 341 465 02) is M10 and 993 is M12









See next post

[perelet]

Rear strut

There's a lot of new vs old style 964 rear strut confusion. My car is 90 - old style.

New style 964 struts or 993 struts will fit "older" body with proper adapters, I bought mine from Jeff @ Rothsport



Here are some details:

Newer 964 struts are similar to 993 with exception of upper mount. 993 uses 4 studs 964 uses 3 (which are different from older 3 pattern ). So for older 964 easiest and no brainer way - go for 993 rear struts + adapters.



Here are spacer measurements for reference:





Side view of 993 top:



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




Here's mounted spacer with 993 top mounts:



and comparison to stock rear strut assembly (with Eibach spring):



Oleg.

[perelet]

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

993
http://www.dvsegmbh.info/PDF/einbau/42011/171/e4-wm4-y592a00.pdf

964rs
http://www.dvsegmbh.info/PDF/einbau/42011/171/E4-WM4-Y602A00.PDF

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

Oleg.

I'll add more notes most probably over next winter.

[porterdog]

Cool.

[Jim Richards]

Great thread, Oleg. I would love to see this as either a sticky or somehow tied to the 993/964 systems analysis sticky we already have. Thanks for posting it.

[David in VA]

This is great, thanks for posting.

[Bill Verburg]

Originally Posted by perelet

S....
Now and then it was mentioned that flange dimensions are different. Not that I can see:






....
Oleg.

I don't know where the caliper mounting flange thickness was ever discussed,
there was some discussion wrt the strut mounting flange which I believe was measured to be the same on the steel 964/965 wheel carriers and the 993 aluminum wheel carriers, the struts ought to have the same width.

There are 4 different wheel carriers that were used on 964 and 993
base 964 used a steel axial caliper mount wheel carrier


964RS and 964t used a steel radial caliper mount wheel carrier


base 993 and 993t used an aluminum radial caliper mount wheel carrier w/ long steering arm(on left) 993RS/Cup/RSR/GT2 used and aluminum radial caliper mount w/ short steering arm(on right)


the 993 alumium wheel carriers each have a dedicated steering arm connection each w' it's own unique geometry to accommodate a lowered car
top is stock 993/993t w/ rubber inner bottom is 993RSR/Cup w/ mono-ball inner


stock 993 w/ rubber inner(top) 993RS w/ stiffer rubber inner

[Bill Verburg]

Originally Posted by perelet

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

993
http://www.dvsegmbh.info/PDF/einbau/42011/171/e4-wm4-y592a00.pdf

964rs
http://www.dvsegmbh.info/PDF/einbau/42011/171/E4-WM4-Y602A00.PDF

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

Oleg.

I'll add more notes most probably over next winter.

Are these documents available for the Bilstein HD and Cup shocks? H&R shocks? Motons?

I don't see the spring rates in the documents they do have the wire specs the most interesting part to me was at the end where they have the shock dimensions, you can see that the shocks are shorter for use in a lowered car, it would be very interesting to see these dimensions for all the available shocks from Bilstein, H&R, Moton, Motion Control, JRZ etc.

[perelet]

Originally Posted by Bill Verburg

I don't know where the caliper mounting flange thickness was ever discussed,
there was some discussion wrt the strut mounting flange which I believe was measured to be the same on the steel 964/965 wheel carriers and the 993 aluminum wheel carriers, the struts ought to have the same width.

Bill, my pics/measurements are for strut mounting flange not caliper. Also, thanks for additional pics!

Originally Posted by Bill Verburg

Are these documents available for the Bilstein HD and Cup shocks? H&R shocks? Motons? ..

Bilstein used to refer to those docs from German page, I do not see links anymore, but you can try to dig there or by model number. I've seen KW specs. Those docs are part of German TUV approval so they should be available.

Originally Posted by Bill Verburg

I don't see the spring rates ...

You can calculate relative rates based on dimensions in Bilstein spec.

Oleg

[rbogh901]

Oleg,
How do you like them?
Did you, (should I?) replace your upper strut mounts when you did your install? Stock mounts or monoballs?

[perelet]

Rbogh,

I like pss9's. My previous setup was way too low/slammed - RUF collars, koni adjustable fronts, RUF rear shocks plus Eibach springs. With pss9's I have more car than I'm driver. And I'm pretty lame driver. I do not day drive my car and mostly drive to time trial events - autocross on steroids, speeds below 110mph, usually held on huge helicopter field or short road tracks. Suspension is perfect for that. Suspension is not harsh, driving on the street does not feel uncomfortable.

Sway bars have huge effect on car, I'll dig pics and post sway bar combinations/comparisons. Also suspension alignment is big factor, I use homegrown laser setup to do alignment.

I haven't used monoballs, I think it is one of fine tuning elements and at my driving level I may not notice


Oleg.

[rbogh901]

Good. It sounds like you used your stock strut mounts. That is what I would like to do for street use but some people claim that replacement is necessary. 400$?

[perelet]

Here's another piece of information.

Front control arms.

Overall dimensions and geometry of 993 and 964 A-Arm are identical. 993 parts are definitely "beefed up" and a bit heavier.

Weight without bushings:
964 - 3.4lb
993 - 4.3lb

Stock front bushings weight (per side) 1.2lb

Few pics:









4 Tonns of force will break 964 arm:


In real life situation this is more than 6G breaking, no tires will withstand that, so practically this is crash limit.

In race situation when car hits curb under braking ..... momentary load it may get close... , factory never used updated A-arms on 964 cup cars. But still they updated them for 993 ... there must be a reason for that.


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:








Oleg.

[perelet]

Another list member is doing 993 PSS9 conversion on 964 and he brought up another difference that I forgot. Thanks Carl!

Lower hole on 993 shocks is 12mm. Some 993 aftermarket shocks been shipped with 14mm hole and metal cylindrical reducer to 12mm. Measure hole, if it is 12mm it needs to be re-bored to 14mm.

964 (early and late) uses M14


993 uses M12



Oleg.

[creaturecat]

good info.
thank you.

[redturbo911]

Wow this is a good read. Thank you.

[Captain Ahab Jr]

great thread and thanks

I'm now going to add a pair of 993 front lower wishbones to my parts to collect list for my lightweight 964 project.

The 993 parts maybe heavier but increased toe stiffness while under braking has a huge effect on the the overall stability of a car.

Does anyone know if the 993 front suspension alumnium chassis frames are any beefier than the 964 parts or are they both the same part?

[Bill Verburg]

Originally Posted by Captain Ahab Jr

great thread and thanks

I'm now going to add a pair of 993 front lower wishbones to my parts to collect list for my lightweight 964 project.

The 993 parts maybe heavier but increased toe stiffness while under braking has a huge effect on the the overall stability of a car.

Does anyone know if the 993 front suspension alumnium chassis frames are any beefier than the 964 parts or are they both the same part?

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

[paul284pt]

Loving this, thanks!