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Clutch Pedal Mechanism


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#1 Chris1275gt

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Posted 21 November 2019 - 04:58 PM

Hi

I have 1975 1275gt. I have fitted a new clutch master cylinder and clevis pin. The bite on the clutch is quite low. Had a look today. The pedal moves side to side about 6mm and when pressing down it has 8mm movement before the master cylinder fork starts to move up.

Questions.
Should the clevis pin hole in the pedal arm be a tight fit with the pin?

Does the long shaft that the pedals hang off have the bronze bushes?

I'm presuming if the bushes were renewed the side to side issue would disappear?

If the pin hole on the pedal is worn, with a new pedal not available, what are my options?

I'm planning to take it out tomorrow.

#2 KTS

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Posted 21 November 2019 - 06:45 PM

the clevis pin isn't an interference fit in the pedal, but the hole should be round - they can get elongated with use.  I guess you could either drill it oversize and try and bush it, or weld it up and re-drill the hole if that's happened

 

the shaft runs in bushes pressed into the brake/clutch pedals, and there shouldn't really be any free play of the pedal on the shaft



#3 Moke Spider

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Posted 22 November 2019 - 07:40 PM

The bushes don't control the side play, though, there is always some. I've not measured it, but I'd say there's around 0.5 - 1 mm normally.

 

If the nut on the Pivot shaft is loose, you will get some side play and likewise, of the pedal box or pedlas are badly worn, then that could introduce side play.

 

I've found the best way to sort the pedals is to remove the whole pedal box from the car and sort it all on the bench. You can check the holes in the box for wear, the condition of the Pivot, the Bushes, the studs that hold the Masters in place etc etc and get it all 'just so'. Then it will be right for many years.

 

Trying to do them in car, I found takes a lot longer and is harder to do.



#4 Chris1275gt

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Posted 22 November 2019 - 11:10 PM

The bushes don't control the side play, though, there is always some. I've not measured it, but I'd say there's around 0.5 - 1 mm normally.
 
If the nut on the Pivot shaft is loose, you will get some side play and likewise, of the pedal box or pedlas are badly worn, then that could introduce side play.
 
I've found the best way to sort the pedals is to remove the whole pedal box from the car and sort it all on the bench. You can check the holes in the box for wear, the condition of the Pivot, the Bushes, the studs that hold the Masters in place etc etc and get it all 'just so'. Then it will be right for many years.
 
Trying to do them in car, I found takes a lot longer and is harder to do.


Hi Moke
Took the pedals out this morning. The pivot shaft is clean and tidy and looks quite new though the nut on the end wasn't tight. The brake pedal bushes and pinhole are all nice and snug still. The clutch pedal bushes are not a snug fit and the pinhole is quite oval with a 1.5/2mm gap at the bottom of the hole. I'm getting the hole welded and will drill it back into the correct shape and change the bushes. It was a pig to get the pedals out and imagine getting the pedals back in will be a nightmare so I think I'll take your advise and take the box out and fit it all back together on the bench, that is obviously when my back is feeling much better after this morning!

#5 Chris1275gt

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Posted 28 November 2019 - 08:29 PM

Welded the 1.5mm worn bottom of the pedal pin hole and drilled the pin hole, refitted it back in and fitted new clevis pins and R clips instead of split pins. With the pin now a snug fit the clutch bite point has moved the action 1/2" further from the floor.
Trying to get those clevis pins back in was a challenge so I made a little tool to make it a 2 minute job. One 10" piece of curtain spring wire, 2, 5mm rare earth magnets ans a piece of shrink wrap and an old broken heater knob to pull the pins out.

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