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How do folks

What is the largest brake master cylinder that will fit the mini? I have seen the racing style ones that have a remote reservoir but I wondered what the largest standard mini one is?

I the brake lines I have, have a larger bore, thus the master cylinder is having to move more fluid.

I was toying with the idea of going from a 0.7 to a 0.75... or should I go bigger still?

Ta

Tom

The brake lines have nothing to do with the amount of fluid you have to move except when bleeding . Once bled and with no air ion the system the fluid acts as a solid link between master cylinder and the slaves at the wheels. What determoines how much fluid you have to displace s the size of the caliper and wheel cylinder bore.

hope this is understandable.

Cheers, what I am trying to do is reduce pedal travel. I've read that a larger master cylinder will reduce pedal travel?

Hi, did you changed your pedal from drum to disc ?

André

Number Six wrote:Hi, did you changed your pedal from drum to disc ?

André

Yes

Yes larger master cylinder will reduce travel but increase pedal effort for a given decel.

Use a master clutch cylinder, this has a larger bore than the largest bore brake cylinder

masnarda wrote:Use a master clutch cylinder, this has a larger bore than the largest bore brake cylinder

not a good idea, the internals of the master cylinder will allow the brakes to drag slightly and soon warm up the discs!

i made this mistake years ago and the discs where glowing red hot after about ten miles!

A larger bore will reduce the pedal travel & as mentioned above will require more effort. This will reduce the 'feel' at the pedal, if you need to reduce travel have you got a problem else where?

COOPERCO wrote:A larger bore will reduce the pedal travel & as mentioned above will require more effort. This will reduce the 'feel' at the pedal, if you need to reduce travel have you got a problem else where?

I've been through the whole system and can't find anything. Its all adjusted up perfectly, no air in the system and no bulging pipes.

The pedal feels ok but I can press it all the way down to the floor almost when I press it hard. I think it would benefit from a firmer pedal as at the moment it is quite light.

Any suggestions as to where I can take it to get advice?

Is this a new build/rebuilt brake set up? Sometimes new seals in the front calipers can 'pull' the pistons back giving long pedal travel. If you press the pedal then really quickly re-apply does the travel get somewhere near where you want it to be? Or if you can get hold of two brake pipe clamps & lock the front calipers off what happens?

Mike.

If the problem is excessive brake pedal travel have you looked closely at the rear drums. If there is any slack then this can take up quite a bit of pedal travel.

Also do you know which bore size of rear cylinders you have fitted? Depending on the year the bore size varies considerably, but as they don't do a lot of work on a disc braked car then you can go for a smaller bore size and still get acceptable performance. The 0.625 bore rear cylinder is plenty for most applications, there are also a couple of even smaller bore options.

It's worth checking out Cooperco's suggestion about caliper pistons being pulled back by the seals,
I had this happen on Cooper S & Metro 4-pot calipers & on the 4-pots, that's a lot of pedal lost!

I had the same problem when I rebuilt my S brake system, I am using a new MS GMC172 master cyl. a lot of pedal travel, I bleed all over the joints, still very low, but the brake pressure is enough to pass the MOT requirement, will it be the problem from the master cylinder?
I am going to replace it with a 998 cooper B cyl and see if the situation would change.


Al

COOPERCO wrote:Is this a new build/rebuilt brake set up? Sometimes new seals in the front calipers can 'pull' the pistons back giving long pedal travel. If you press the pedal then really quickly re-apply does the travel get somewhere near where you want it to be? Or if you can get hold of two brake pipe clamps & lock the front calipers off what happens?

Mike.

Yes, it does exactly that. I can't lock off the front calipers as the hoses are braided...

Thanks for your help Mike