Clutch Release Bearing to Pressure Plate

[BrianAz]

Just about to put on a new clutch assembly on my 1980 Spider 2000 and refit the transmission when I noticed that the new release bearing barely contacts the lamells on the pressure plate. Compared to my old assembly the internal diameter of the hole of the lamells on the new pressure plate is 39.5mm. The ID and OD of the contact face of the bearing are 36mm and 43mm meaning that there is 4.5mm of contact "thickness" between the bearing and the lamells.
On my old assembly the ID of the lamells is 35.7mm. The ID and OD of the contact face of the bearing are 40mm and 47mm meaning full contact between the entire bearing face and the lamells. I called the supplier, Vicks, and they assured me that what I got is correct. IAP also have the same dimensions of their release bearing, not sure about their pressure plate.
Has anyone come up against this problem?
I have just assembled the transmission and it is on the engine ready to be put back into the car over the weekend. I decided to use the new parts except for the release bearing which is the old one.

Thanks,
Brian.

[fiat218]

im gonna comment on all this , but i would think u would be foolish to put back a old bearing!!! that just opinion, that makes no sense to me

[ventura ace]

I've seen a lot of variation in the sizes of the clutch pressure plate fingers and the throw-out bearing, also, but nothing as drastic as the measurements that you have. I would go back to Vick's again, and let them know that they need to research it further. In your case, half of the surface of the T-O bearing is hanging off in the air and not touching anything. This is not right. You calculated 4.5mm contact thickness, but consider that is a diametrical measurement -- the contact is really only 1/2 of that, or the radial mearsurement of about 2mm. If things run a little bit of off-center, as could easily be the case, since the T-O bearing slides along a guide tube with some clearance, this gets down to 1mm perhaps on one side. It would still work, and you could choose to use it if you were way out in Timbuktu with nothing else available, but since there is better stuff available, I wouldn't use it.

One set-up that I took apart had a 31mm ID on the pressure plate fingers, and the T-O bearing dimensions were 39mm x 46mm. This had a really generous overlap of (39-31)/2 = 4mm radially.

Another set that I used had a 35.5mm ID on the pressure plate fingers, and the T-O bearing dimensions were 37mm x 43.5mm. This had a scimpy overlap of (37-35.5)/2 = .75mm radially, and worked fine.

Yours has (36-39.5)/2 = 1.75mm underlap on those inner edges. Not good.

Your're debating on using the old T-O bearing. How does it feel and sound when you rotate it. Put it on a flat surface and put something heavy on top of it (25# or more) and spin it like a lazy susan. Compare the old and new. If they behave about the same, I 'd consider reusing the old one. But, if the old one has any roughness or drag, I wouln't reuse it.

Alvon

[Kevin1]

I'm running a clutch/pressure plate/throwout bearing from Vicks. Been in the car for 4+ years, and no problems. It's difficult to find parts that are identical to the originals sometimes, but if they work, they work.
Looking at Alvon's post, if his worked with .75mm overlap, then your should work with the 1.75mm (43-39.5/2=1.75) that it has. It may be different than the original parts, but I'm willing to bet that if you measured the parts in ten "original" Fiats, you'd get at least three different results . . . . How many miles on that old bearing? Before I buttoned everything up I'd give a little more thought about using an old bearing in there.

[ventura ace]

Kevin,
His new bearing is not overlapped, it is underlapped. This is much different than my case that I threw out for comparison. Half of the T-O bearing contact surface is hanging out in the air. The OD of his T-O bearing is just barely making contact. I wouldn't use it. Vick's should be able to come up with something that mates better.

Alvon

[BrianAz]

Thanks for the inputs guys. Yes, I have UNDERLAP and therefore have decided to go with the old bearing. It makes a bit of noise but that is better than the underlap situation. Funny thing is, Vicks assured me that I received the correct parts. Also, the TO bearing from IAP is the same as Vicks, as I confirmed with IAP on the phone. Don't know about the pressure plate comparison between Vicks and IAP, but the underlap just did not look right and in the event of some extra play between the bearing and the shaft it is riding on, it could have meant disaster. I have some pics of the old and new TO, Pressure plate combination that I took before rebuilding the engine so I will post these.
Thanks,
Brian.

[BrianAz]

Hi again,
Here are the photos of the TO bearings and pressure plates, new and old. You can understand my concern about the lack of contact surface between the new bearing and new plate. Therefore, I used the new plate and the old bearing. I hope to finish the engine and start the car this weekend, so we will see how it all works.

Brian.

[So Cal Mark]

tvstar (Tom) had his car towed to me yesterday with a broken clutch pedal and firewall. While looking it over I noticed that it has the same bearing-pressure plate issue that Brian is concerned with. It could be this is the cause of high-pedal effort that causes component failure

[trippbannister]

Brian,

As for the tongs of the new pressure plate touching the bearing -- I had the same exact problem with mine. In fact I took pictures very similair to the ones you posted and sent them to Vick's and asked what was going on. Csaba assured me it was the correct one, so I went ahead and bolted it in. Sure enough, as the bolts sucked the pressure plate to the flywheel, the tongs were pulled in closer and the bearing fit over all of them much better.

Hope you get this in time! Otherwise I'm sure it became apparent during assembly.

Tripp

[BrianAz]

Thanks for the replies,
I didn't think about rechecking the TO bearing fit to the pressure plate after bolting it to the flywheel. Anyway it is assemblied it using the old bearing.

Brian.