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MG Midget and Sprite Technical - Master cylinder clevis pins

I've assembled the pedal box with new master cylinder (older dual type) but had forgotten to order new clevis pins. I thought it would be a simple matter of inserting new pins when they arrive but I can't get the old ones in as the wider end part won't clear the pedal box side. It looks like I'd have to take the pedals bolt out and raise the pedals a little. Surely it can't be this awkward can it?


Bill Bretherton

As you describe Bill, that’s what I had to do recently.
Philip Sellen

Thanks Philip, another job to postpone then.
Bill Bretherton

As I recall, the pedal pivot bolt won't quite withdraw underneath the footwell lid, as it catches on the reinforcing ribs with the pedal box bolted down. The modification is to grind down a flat on one side of the bolt head. It will then just clear the reinforcing web on the underside of the footwell lid.

Only thing is I cannot remember if this was on the Frog, or the later car. Or if it applies to both!
GuyW

Its certainly true of all the cars with a dual cylinder! The image suggests its not bolted to the car yet so all may not be lost...........!
Bob Beaumont

Thanks Guy.

No, not bolted in yet Bob as I always assume the worst with these things so not too much repeat work to do! Unfortunately it is a TRW M/C bought some time ago before I became aware of their shortcomings so I hope it doesn't leak!
Bill Bretherton

I would check and see if the bolt will clear those reinforcing ribs and withdraw, before moving the pedal box.

If not, then lift the pedal box until the bolt can be withdrawn above the level of the footwell top. Then grind down one flat of the bolt head flush to the bolt shank. This will mean that in the future you can withdraw the bolt without having to undo and disturb the pedal box itself. It will still insert and tighten up properly like this, and still function correctly. It won't help the job now, but will make things much easier in the future should you ever have to remove the pedals.
GuyW

Bill
Have a look at the MGA Guru website with regard to your TRW master cylinder. There is a small modification that can be made to avoid 'residual brake pressure' that you may want to consider now rather than later.
Alan
Alan Anstead

Guy, the bolt head is well within the rib which must be deeper than original. So, in case of issues, the pedal box will have to come out which is a pain. I suppose I could grind the rib back but awkward where it is.

Thanks Alan.
Bill Bretherton

That's odd, Bill. I just checked my cars. I couldn't remember which one I did this on, but it's the frog. One flat of the hex head ground down to the level of the bolt shank. Rotating the bolt so this aligns with the edge of the reinforcing rib and it would just clear it. The rib in both cars 1960 & 1971 is 1/2" deep. It would of course also depend on the pedal box frame being pulled down tightly .

The other mod I did, though this time only on the '71 car, was to drill and tap the pedal bushes and fit a grease nipple to each. Reached from the top by removing the plate cover. I did this following a torrid time when the brake pedal pivot rusted and fused itself to the pivot bolt. Pedal still moved relative to the car, but only because the bolt was turning with it. Didn't manifest itself until I needed to dismantle it and the bolt turned freely but wouldn't detach from the pedals. Ended up cutting the bolt through twice with a bare hacksaw blade. A slow, painful, nasty job working in the confines of the footwell
GuyW

Guy thats exactly what happened in my pedal box. At some point I need to do the grease nipple mod.
Chris Madge

Some useful background info on residual valves (7/8" dual master cylinders on front drum braked MkI & early MkII Sprites and early Mk1 midgets all with 948cc engines) and restrictor valves (on later MkII Sprites and MkIII Sprites with 3/4" dual master cylinder and front disc brakes and 1098cc engine):
https://www.gerardsgarage.com/Garage/Tech/DbrakeUg.htm

(Read with http://www.gerardsgarage.com/Garage/Tech/DBrake/TandemMC_Part1e.htm)

Alan - what is the MG Guru link please? Some info: http://www.mg-cars.info/mg-midget-sprite-technical-bbs/refurbishing-twin-master-cylinder-2017062111263131648.htm


Cheers
Mike
M Wood

Mike
google MGA Guru. Although aimed at the MGA it has some really useful information. Some time back I got his permission to reproduce an article in Mascot magazine.
Alan
Alan Anstead

Can't you put the clevis pins in from between the pushrods?
Rob
MG Moneypit

Sorry Guy, missed your post - It's not as bad as I thought but my flange is about 5/8" so may still be "tight". I could grind the flange a bit where the bolt head is.

Mike, thanks, I've read that. Mine is a 3/4" cylinder.

Rob, there isn't enough width.
Bill Bretherton

Bill,
Clearance may well be harder if the pedal box isn't fastened down tiught. Especially ifyou have a gasket of some sort under it?
GuyW

Thanks Alan for the tip about into on MGAGuru website:
http://mgaguru.com/mgtech/brakes/bt101a.htm
http://mgaguru.com/mgtech/faulty/ft046.htm

Best wishes
Mike
M Wood

Guy,I have a gasket but haven't screwed the pedal box down yet and noticed it's a bit proud around pivot bolt position so tightening it will reveal bolt head a bit more beneath flange.
Bill Bretherton

Bill, to fit the clutch clevis pin push the brake pedal clevis out the way and vice versa.
Rob
MG Moneypit

Rob,of course! D'oh, why didn't I think of that!
Bill Bretherton

Use an R clip as well. So much easier.
Rob
MG Moneypit

This thread was discussed between 20/04/2020 and 23/04/2020

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