A 'new' clutch release bearing

(Joel F Hutchins) #1

First of all my car has an automatic. I read almost all posts and am dumbfounded by the amount of trouble the clutch and it’s assorted items present owners.
I received the new ‘Jaguar World’ magazine recently. In the Q&A section a question about the carbon release bearing was asked. The editor replied that a company in the UK had made or had one available.
I thought some J-L members might be interested. Here is a link.
I don’t know if it will work or not but it sounds workable.

Regards, Joel.

(Robin O'Connor) #2

Hmm not too sure about that release bearing, the Jaguar moves in an arc so effectively slides across the face of the pressure plate whereas a bearing needs to attack in a direct line?

(Mitchell Andrus) #3

A bearing of the roller/ball/pin design must rotate around a defined center. The fact that our fork cannot hold a bearing on a defined center precludes it’s long-term use.

“Looked good in the store”.

(PeterCrespin) #4

I have the Denis Welch bearing and it has three pages of photographic setup instructions. It is dimensioned to work only on diaphragm clutches where there is extra space due to no thrust pad for a carbon ring.

In the website pix you can just see an adjuster screw that is carefully set to rest against the fork, which is itself set up to give closest to parallel with the clutch plate.

The bearing contact face can and does move across the diaphragm fingers with no catching

(Mitchell Andrus) #5

That means the bearing contact face is an additional wear surface. I know these can last as long as the clutch disc itself, we discuss these on other forums. As long we remember to take our stupid foot off the stupid clutch pedal when it doesn’t need to be there most reasonably designed bearings will work.

Trouble creeps in when someone feels that a $30.00 bearing can be abused with reckless abandon regardless the material or design.

(67 OTS S1) #6

I agree, but I ran the GTJ roller bearing setup for years. It came with a collar that kept the bearing centered and a modified fork that let it move slightly as it traveled along the collar. I would still be using it but went to a 5sp with a new bell housing.

(Ben E) #7

That is the ONLY way one of these retrofit roller bearings can work as they are designed to. Sadly, most of these kits aren’t designed as well as the one you described.

People get freaked out by the idea of a carbon bearing that is designed to “skid” on their clutch, so they retrofit some of these other roller bearings, which then does some goofy combination of spinning AND skidding, which it WASN’T designed to do.

In my experience with carbon bearings, the troubles comes when people use inferior, aftermarket carbon bearings. Find a good quality one, and keep your foot off the clutch at traffic lights, and it should easily last 100,000 miles.

(PeterCrespin) #8

Jaguar themselves dropped the carbon and used roller release bearings on all their clutches from 1979-86 XJ S3. 1984-96 XJS,1986-94 XJ40, 1994-97 X300.

I agree the carbon is fine, driving technique is important and any system must be designed properly. High spring pressures in competition clutches are more easily handled by a roller release I suspect. There are reasons other than marketiing why carbon was dropped forty years ago and diaphragm clutches and roller releases are universal today.

(Mitchell Andrus) #9

Here’s the ball bearing TO bearing similar to the one in my 1930 Model A Ford. You will note that even in the 20’s and 30’s manufacturers found a good reason to have the TO bearing travel in a straight line centered on the crankshaft. It travels on a yoke.

British engineering to the bitter end brought them to a bitter end.

(Ben E) #10

I never claimed that carbon TO bearings were great, but simply substituting a roller bearing into a clutch system designed for a carbon one does not get people what they are hoping for without a significant redesign of the system.

It’s sort of like roller lifters on pushrod engines. People hear about failures of poor quality flat tappet lifters, and then go through all sorts of gymnastics to (poorly) adapt roller lifters to their application, when good quality flat tappets are readily available, and last just fine when treated properly.

(67 OTS S1) #11

I think we all agree, improperly done is a disaster! The picture looks pretty close to the GTJ kit.

(PeterCrespin) #12

I agree Ben. I have never had a problem with graphite sliding across a thrust pad and all the models quoted were designed to deliver linear movement. I was largely curious about the Denis Welch part and to try a non-pad disphragm race clutch for the 4.7 stroker engine.