Pre-Loaded Clutch Release Bearings

[kradicke]

Is it necessary, or even a good idea, to apply a minimal load to clutch release bearings of the ball bearing variety?

Load would be induced by something like a 25# spring acting on the clutch lever (in the bellhousing).

Thanks.

 

[GregLocock]

And the difference between this and 'riding the clutch' is what exactly?

Cheers

Greg Locock

 

[kradicke]

Hey Greg, yes I realize that, and that is exactly my thought as well. The reason I ask the question is because the bearing supplier recommended to me that I should preload the bearing, this did not make sense to me as the original application was not set up this way...

Your opinion is always a good one, and since it reinforces my own, I'll keep the setup as is... unloaded.

Thanks,

Kai

 

[funnelguy]

There are 2 benefits on racing vehicles...

1. Life is made easier for the diaphram fingers and bearing by not constantly accelerating from 0-10,000 RPM instantly every time the clutch is dipped (for those who use the clutch).

2. No loss of motion at the clutch caused by vibration knocking back the piston/bearing assembly.

That's the theory, anyway. I've only ever failed one, and that was on a Ralt with the typical hydraulic unit.

 

[patprimmer]

If I were to do it fro the reasons above, I would use a 1 or 2# spring, so as to have absolute minimal preload.

Will the bearing wear out or overheat as I presume they are only designed for short duration operation

Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Rob45]

Greg:
You wrote: "And the difference between this and 'riding the clutch' is what exactly?"

The answer is, preloaded clutch release bearings don't rattle, for one thing;
if I could find a release bearing that would survive preloaded in a Class 8 (heavy) truck application, I'd release it (no pun intended) in a minute to solve a nagging problem I've got with release bearing rattling on the input shaft.

Preloaded release bearings seem pretty common in passenger cars with self-adjusting hydraulic release mechanisms, aren't they?

 

[PEW]

My little off-road trials car is based on (UK) Reliant 850cc mechanical parts. These little engines and transmissions are based on the ancient Austin 7 designs.

When I built it, using a complete 3-wheeler Reliant Rialto 850 as a donor, it turned out the clutch fitted to the donor transmission was already brand new so I just used that. It is of the earlier, non-diaphragm spring type, with a carbon ring release bearing which must definitely NOT be pre-loaded.

Shortly afterwards I was offered a replacement clutch kit at a very good price and I bought it to keep for when the day comes, as trials cars do get some hard use. When it arrived it turned out to be of a later diaphragm spring design with a ball-bearing release setup. I will need a couple of extra parts from a later Reliant 850 to adapt it to fit my car, but no matter.

There has been some recent discussion on the Reliant Kitten Owners' Club website, and elsewhere, of late on how to change a Reliant clutch from old type to new.

The important thing is that the expert advice I have been given tells me that the ball type release bearing SHOULD be lightly pre-loaded and we are to change the original operating arm return spring around so it changes from holding the bearing "OFF" to holding it "ON".

I queried it as it seems to me not very logical, but that is how it's supposed to be.