MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG Midget and Sprite Technical - rear brake cylinders

Are the rear brake cylinders on a 1275 hand. I am assembling the rear axle with a pair of new backplates from Rich Wooley, and the peg hole for the brake cylinder is on the wrong side of the bleeder / pipe holes to be able to mate it to the backplate. Is it possible he has sent me a backplate from another car (mini?) that is incorrect ?
Dominic Cancy

Mini backplates are easy to spot as they only have three mounting holes.

Lockheed produced the twin-piston wheel cylinder with a number of different bore sizes and came up with a foolproof way of preventing people from fitting the wrong wheel cylinder to any particular car. The locating pins are fitted in different positions for each size.

There were three different sized wheel cylinders fitted to Spridgets, so when changing backplates, you need to make sure you have the correct ones.

You could try drilling a new hole in the backplate, or pull the pin out and redrill the hole in the wheel cylinder.
Dave O'Neill2

They are not handed.
The peg mismatch indicates a potential wrong cylinder.
There are six different cylinders which all look the same from the outside. The difference is in the size of the pistons. The peg is in a different place for each size of wheel cylinder.
If you have two cylinders which have the pegs in different places then the cylinders are different sizes.
If the peg on the cylinder doesn;t match the backplate, then the cylinder is not the size originally fitted.
If both cylinders are the same and the backplates differ, then the backplate has been made wrong.
Paul Walbran

The cylinders are original Lockheed, and are the same and have the same part number, and correspond to what the Parts book says they should be. So it appears I have the wrong backplate, even though it is a mirror image of its twin. So I will probably just drill a hole in the backplate.

Thanks for the inputs, this is a detective job at every stage as I didn't take the car apart and the Heritage shell is also not always provided with the correct holes in the correct places

Dominic Clancy

I just replaced the rear cylinders on my '71 1275. The ones I removed had no pin fitted (although there was a hole) so I removed the pins from the new ones. Did I read somewhere that the pins are unnecessary as the cylinders need to ' float ' on the backplate? Should I refit the pins?
Thanks!
Simon Fryer

You need the pins. The cylinders need a little movement, but don't need to move anywhere they feel like.

Having said that though, there are people who've bolted the cylinders to the back plate, and not encountered problems. In fact, they've removed the problem of the bloody horse shoe clip that otherwise fixes the cylinder to the backplate.

So your choice.
Lawrence Slater

Theoretically, the bleed screw *should* prevent excessive movement of the cylinder, although I would prefer to keep the pin.

Having said that, I used an M5 button-head socket screw in place of the pin on my race car, as eluded to by Lawrence.
Dave O'Neill 2

Thanks guys -appreciate your experience. I guess I have to re attack. Maybe I can get the pins in from the back and avoid battling the circlip again.
Simon Fryer


For those who hate the E clip that comes with rear cylinders, here are the proper retaining rings and spring washers that match the original factory ones, and as a bonus, are available in stainless steel:

Grainger #5DA81 = 11/16" external retaining ring, stainless steel.
Grainger #6ZA12 = 11/16" wave washer (3 wave), stainless steel.

http://www.grainger.com/Grainger/static/products.html

Because they are only available in packs of 10, you will have enough of them to last for 100 years (at the rate of once each 10 years).

Another easy source for these parts would be Fastenal. Another member bought them there for $1.50.

The other alternative of pulling the roll pin, tapping the hole and attaching with a small hex head screw. Though, perhaps the original design which allows some "float" helps the shoes to seat better. The rear brakes do so little of the work that it might not matter a whole lot, either way.


Norm
Norm Kerr

Simon,

Without any shadow of doubt, rip the e clip thing off and throw it away then remove the pin and drill and tap the hole it sat in to M5, using the pin as a depth gauge to make sure you don't drill down too far. Cut down an M5 hex headed bolt or similar to size and just bolt the cylinder in from the back, attach the brake line and away you go. So much easier when you want to remove the cylinder in the future. I don't tend to bolt them up too tight so there's still a little bit of movement if needed.
Matt1275

Why the hatred for "E" clips, they are easy when you know how.

Dave
Dave Barrow

Thanks for the specifics Matt.
Simon Fryer

Dave,
Because they are not stock, they are some cheap substitution.

True, there is a knack that can make them possible to put on, but they are still a pain.
I'd rather use something that is as simple as a C clip (easy to pop on or off, when the cylinder inevitably starts leaking in a few years and needs replacing again).


Norm

Norm Kerr

This thread was discussed between 02/02/2014 and 22/07/2014

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.