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993/964 RS top mount uniball joints

colt

colt

PCGB Member
Member
Gentlemen, I have with assistance from the net ( USA) found the part number and supplier of the bearing itself for the suspension strut top mounts fitted to front and rear of both 993 and 964 RS models. We can obtain them from the uk concessionaire for hirschmann bearings, the oe manufacturer. Priced at 28.10 plus vat each , I don't think they will get any cheaper ever! The price improves a bit if we order ten or more and there would be a modest pound or two for postage.
Who is interested in getting some spares for their respective cars. These are consumables as far as suspension goes and the rubber dust boots should be renewed any time the strut is removed from the top mount as these are crucial to the longevity of the joints. We would need to get these from Porsche (964 343 186 80)
Christian......
 
This is good news as previously a few specialists have told me the uniball is only available as a complete assembly from Porsche for £££.

Christian, if they're definitely the correct size and specification I'd certainly be interested in taking a set.
 
Well give it a few more days then I'm going to place an order .
Christian..........
 
Right gents, I placed an order for some bearings and they have arrived several weeks ahead of schedule. I have checked the dimensions and fitted one to an empty top mount case and can confirm that they replace the original items in all respects. Let me know how and when you want to pick them up/ delivery etc.
Christian.....
 
Are they steel ball in phosphor bronze race, or steel in steel? Thanks, Paul.
 
Okay great job.

Can you let me know how much and I would prefer posting to West Sussex. Obviously no hurry so donkey service is fine.

I can let you have my email so you can send me bank details and I will transfer money.

Ken
 
Hi Paul, they are steel in steel but as you know, the ball runs on a self lubricating Teflon liner in either case. This is the part that wears and creates the free play. The only possible downside I could see with the outer material being steel is the very remote possibility of it becoming corroded inside of the housing if it got wet, making it difficult to remove if worn at a later stage.Protected against by a smear of grease upon assembly and moreover the sealed top nut and weather proof boot on the underside of the mount would protect it anyway. Plus I could buy at least four of these bearings for one rear 993 RS top mount ( without the nut) I understand 964 mounts are more expensive . Given that the original failed before 35k road miles and a replacement from Porsche had to be returned because it had play before it was fitted, rather like the gt2 Evo steering rack arms which were faulty and then Porsche dropped the part and told people to use 993 RS rubber ones, quality at Porsche has slipped of late?
Christian.
 
Ok that makes sense now. I wondered how you could get them so much cheaper than me. I buy in bulk and have them in stock, but I always get the correct heavy duty phosphor bronze type as specified by Porsche. The steel on steel will wear quicker that is why they are a cheaper bearing. The phosphor bronze has the correct characteristics needed. They naturally have play before fitting and torquing the large lock nut cap. Once fitted and torqued they will tighten up. The bearing manufacturers spec will show both the unfitted and fitted play tolerance. Cheers, Paul.
 
I don't see how the outer material has an effect on wear as the Teflon liner separates the parts. Nothing is moving against the steel outer race? Looking at the specification of the bearing on the web site, no mention is made of free and fitted play ? How much longer do you expect the bronze case ones to last ? The last bearing I removed from a mount was not a tight fit and was removed with a tap from a plastic mallet? if you tighten the nut down it would only pinch the ends of the bearing and not clamp it around In all directions?It's not usual to have play on a spherical bearing before you fit it into something?
Christian..
 
I've fitted quite a few spherical bearings in my race GT2s and RSRs and these cars have every single joint as a bearing. On the 993 GT2s I have and the 993 RSR all the rear arm rubber bushes are replaced by the factory with spherical bearings. These are also phosphor bronze outer race material. They have play before fitting and go tight after fitting. The bearings in the arms rely purely on an interference fit to keep them in the arms. These bearings do not have to rely on Teflon or PTFE coatings as the steel on phosphor bronze is good without it and very durable. An unfitted phosphor bronze bearing has more unfitted play than a steel in steel bearing. The specs will show you a minimum and maximum play.

I cannot say for sure how long the life difference will be but I remember when racing formula renault the bearings in the A arms were steel on steel with PTFE from a very good manaufacturer and would have play before the season was out. With any of these bearings it is a compromise between cost, application and longevity. Phosphor bronze bearings are always a more costly alternative to steel in steel of an equivalent size. Either bearing type is cheaper than the factory only alternative of a complete top mount.
 
I see your points Paul. I have just been out in the shed looking at the two bearings fitted in the mounts. The steel in steel is certainly tighter than the bronze cased version ,but then the steel is new and the bronze is 35k miles both have the top nuts loose. Interestingly the bronze version is a loose fit in the housing to the point that when i attached it to a shock to operate it, it popped out of the housing in a stroke or two. The steel on the other hand was dropped into the housing by placing the bearing in the fridge for twenty minutes and placing the housing on the top of the aga for the same time, it was an easy fit and seemed less stressful than knocking or pressing it in, although it would only require modest pressure to install those ways, it certainly fits the housing well, as it showed no signs of moving when subjected to the same test as the original one. I shall next torque up the top nut and see how it affects the tightness of the ball to move, little change i should expect due the steel not being easy to compress by an alloy nut in a thin alloy case. Your point about the Renault bearings is interesting ,but i bet those bearings were open and not weather sealed and also they would have been quite small relative to the load for weight and aerodynamic reasons? The top mount bearing in these cars is big and weather sealed, i see other marque aftermarket uniball topmounts and note often they are not weather sealed and at least half the size of these items if not smaller and it's no wonder they don't last.
Am i right in saying that the 993 rsr/gt2 race rear control arms have uniball joints that are not replaceable installed within them and they are open with no weather sealing at all? talking more specifically about the lower A arm the ball joint and front uniball joints are the std production car items with only the rear rubber bush changed to an open uniball held in with what looked like grey epoxy resin?

Christian..................
 
Hi Christian, this has changed things a little as I thought you were getting a like for like bearing ! Is there anybody using this design of bearing in this application? I know you said you found the info from an american site ? One concern I have is that I wonder if the steel / steel bearing will transfer more of the load into the alloy casting?
 
Yes the rear arm uniballs are open, but they definitely are replaceable. When the standard ball joint end of the arm wears out I buy standard C2 arms, remove the rubber bush end and fit the correct spec phosphor bronze spherical bearings. As I say they are a tight interference fit so as you suggest I heat the arm and leave the bearing in the freezer, it then pushes in nicely. As the phosphor bronze material is more springy than steel the tight interference fit tightens the bearing when everything resumes ambient temp.

Tightening the top cap nut with the steel on steel bearing is unlikely to change the bearing clearance / tightness due to the material properties. This is why steel in steel are made with less unfitted play.
 
Lawrence, obviously anyone who has doubts about the suitability if this bearing for the application is under no obligation to take any. I will take more than this hiccup to bankrupt me!
Christian
 
For anyone who is interested in these bearings I don't see any issue with them, and it shouldn't put you off. It was just an observation that the price differential between the bearings I buy and the ones Colt has sourced. I bought in bulk last time and was surprised Colt bought some les than half the price I could achieve, but all is now clear.
 
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