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MG MGB Technical - GT wheel cylinders

I am replacing the wheel cylinders on a 67GT. The 67GT came with a smaller bore cylinder than those on later GT's.

Should I go with the larger bore cylinders or stay with the original size?
Steve Rechter

Steve
I would like to go with the larger bore on my '67 Roadster also but I believe the position of the bleeder valve and or the pin that positiones the cylinder to the backplate may be different on the later 075" cylinder. Would take some sort of modifications , either later backplate or?? sure someone else will know.
Mike
MK Mike

All I can say is that the brakes on my '67 are stock and are perfectly balanced. The later cars were heavier and so may warrant the larger bore.
Steve Simmons

Hi All:
"The later cars are heavier" By later do you mean Rubber lip BGTs? Did the larger rear cyls. not start at GHD4-138401 '67-'80 (which is before the weight increased)? I have just changed out my '74 GT rear diff. with a roadster one and ended up with the smaller cyls. so would like to know what the difference will be in braking.
Godspeed in Safety Fast
Jc
John Crawley

Fitting a smaller diameter cylinder will reduce the braking effect on the rear wheels - i.e. more bias to the front.

On my racing Sprite I fitted the smallest cylinders available - Mini Cooper S - as the rear shoes were always burning out, as were the rubber dust seals on the cylinders.

There are a number of different diameter cylinders fitted throughout the BMC range. The locating pin is in a different position for each cylinder. If you wish to change to a different diameter, the simple option is to drill a new hole in the backplate in order to accomodate the pin.
Dave O'Neill 2

Hello Steve,

I swap rear diff from a roadster and made what suggested Dave: drill a new locating hole. I imagine lager bore wheel cyl were to improve braking a bit due to extra 200 lbs for a GT.

Cheers,

Jean G.
Jean Guy Catford

By later cars I mean anything after 1967. More equipment kept being added throughout the years, from smog gear to anti-burst devices in the doors. Mark I cars are the lightest of the bunch.
Steve Simmons

Hi all,

I've never found the small cylinders to be a problem on my '67 GT, if you really need more rear braking effort then drums may not be for you anyway.

If it's a regular road car, leave them standard - you'd probably never notice the difference :o)

fwiw,
--
Olly
Oliver Stephenson

Steve, Mike is correct - the wheel cylinders are different - the locating pin is in a different place. Check out Paul Hunt's website (pages of vee and bee) where there are some photographs.
Richard
Richard Atkinson

This thread was discussed between 02/06/2009 and 04/06/2009

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