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MG MGA - Holding down the clutch

This is one of those questions that may have old hands rolling their eyes and tutting at my lack of basic knowledge ... but here goes!

when I depress the clutch pedal on my A, and hold it there for any length of time, am I continually causing wear on the carbon face on the release bearing? ... In other words, when I'm in traffic, is it feasible to sit in first gear with the clutch depressed (which is much easier than engaging first gear every time the traffic moves - I have to have the revs at exactly 1000rpm to engage first without grinding the gears).

I can understand that 'riding' the clutch for any length of time - holding the pedal at the point where it's just biting and no more - would be problematic, is there a similar problem if the clutch is fully depressed?

I once wore out the carbon on the bearing when I had a midget, and got stuck a very long way from home, so I'd rather not cause that problem again.

Any thoughts?

Richard Ross

Yes!
D Sjostrom

There's a very simple trick to avoid the first gear graunch...

Instead of trying to go from neutral straight into first, just pull the gearstick down and begin to engage second, but then push the stick forwards to glide noiselessly and easily into first - get the second synchro working for you in first.

This works a treat for me, I can shift into forst with no noise at all - well apart from the noise of the engine.

This way there's also no need to ride the clutch and burn out clutch plate or release bearing. Nor do you hvae to sit with foot on clutch wearing out the carbon bearing.

B clutches are (BTW) rather better than A ones in my experience.
dominic clancy

Thanks for that.

... so sitting with clutch fully depressed WILL burn out the carbon?
Richard Ross

(Echo previous post, Yes) You not only increase wear on the release bearing, you also force the crank forward and increase wear on the thrust bearings. I try to limit clutch disengagement to periods of less than 30 seconds if possible. To minimize the first gear engagement problem, try slipping the lever into second and then quickly into first. The syncro will make a smooth engagement of second which will stop the gears from turning so first gear engagement should be easier. Worked well in my Midget.
Bill Young

I assumed this would probably be the case.

It's always slightly embarrasing sitting at traffic lights, just for long enough for someone to notice the car and make some nice comments, only for the lights to change and then 'cruuuuuuuunch!' - all credibility lost!

How long would you expect a carbon bearing to last in normal usage? Ten years? more?
Richard Ross

Hi Guys:
On my '61A I found the solution was to replace the carbon bearing with an anti-friction (roller) bearing the first time you are down for clutch or trans work.Moss probably sells them.
Chuck

Richard,
Your last question is interesting. It is my understanding that rapid wear on carbon occurs when it overheats from friction. I suspect with minimal "Downtime" one might expect lifetimes comparable to modern roller bearings.
Doug
D Sjostrom

30 seconds? I always freak out if I've held the clutch pedal in for more than 10 seconds! Definately use the second / first trick. I've done that in all my 3-sync cars and never grind a gear. It's much faster than trying to match engine RPMS.
Steve Simmons

In addition to the mechanical reasons for NOT holding the clutch in, it's a dangerous practice. IF you get hit or have a heart attack or whatever unfortunate thing enters your life while you're sitting there with the gears engaged but the clutch depressed, your car takes off with a mind of its own, thus compounding the 'accident'. Sorry to be 'depressing' (pun intended).
Fraser Cooper

FWIW - Another area that is affected by "riding the clutch" is the crankshaft thrust bearings.

Peter
Peter

I have tried to limit clutch depression to 5 seconds, the 2ed gear trick worked for me (I'm about to try a 5-speed). I was also attracted to the option of a roller bearing but stayed with a carbon bearing. This board gave mixed reviews on the subject with expressed concerns on the longevity of the roller bearing. I don't think Moss has them now. They may be availibe through Shade Tree. Steve
Steve Meline

Roller bearings tend to dry out and destroy the bearings due to the fact that there is no pull off spring to pull the bearing away from the thrust face of the pressure plate. The constant contact is enough to keep a roller bearing spinning constantly and greatly shortens their life. The contact is not tight enough to cause excessive wear on the carbon face of the regular throw out bearing. If one is going to use a roller bearing, it is advised that you install the pull off spring and limit plate set up sold by Doug Jackson at: http://www.mgbmga.com/. Click on Technical Information, scroll down to clutch and click on MGA/MGB Clutch Throwout Bearing Problem. Cheers - Dave
David DuBois

This thread was discussed between 30/03/2005 and 31/03/2005

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