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random notes on 964/993 suspension
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. |
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 |
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 :rolleyes:). 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. |
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. |
Cool.
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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. SmileWavy
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This is great, thanks for posting.
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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 |
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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. |
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Oleg |
Oleg,
How do you like them? Did you, (should I?) replace your upper strut mounts when you did your install? Stock mounts or monoballs? |
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:confused: Oleg. |
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$?
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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: Olg. |
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. |
good info.
thank you. |
Wow this is a good read. Thank you.
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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? |
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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 |
Loving this, thanks!
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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? |
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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 |
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. |
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. |
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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. |
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I think Bill V has photos of that. He pretty much has photos of everything. And I think he has solutions. |
Solution = higher performance grease
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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:
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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? |
that is whaT I did on mine..
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Oleg. |
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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. |
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. |
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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. |
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The recommendation for my 993 track car was to use the 964C2 longituninals in the outer holes |
993RS uprights
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. |
Hi Oleg,
Very analytical as usual. Are you trying to go lower with the RS uprights while avoiding bump steer? |
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 |
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 |
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