19 replies to this topic

[mini13]

weird question so please bear with me!

i've never managed to get the brakes on my mini so they actually work on the first pump of the pedal.  

 

i've recently rebuilt it with new rear brakes and it has cooper S discs on the front (it's a 1960 model so these were replaced).  i've bled them throughly and there is not air in the expelled fluid.  i've used both a vacuum pump and the two man method and put a whole bottle of fluid through to no avail.  they work great but only after a second pump of the pedal.  

 

the rear drums are adjusted so that i can get 3 clicks (may 4 at a push) on the handbrake.  the master cylinder is original type but it looks like the cooper S master cylinder is the same bore size (0.7") anyway with just a larger reservoir.

 

clearly i've bled brakes hundred of times before on other cars with no issues but no matter what i try the mini still has this issue.

 

what am i missing?

 

i'm wondering if perhaps the MC is actually a clutch MC with a narrower bore or something?

 

 

the hand brake is kinda an independant system, you may need to adjust the square brake adjuster on the back of the drums.
 

[cal844]

Lock the adjuster for the brakes so the wheels can't be turned by hand. maybe even try the handbrake too and try bleeding again. If you need 2 pumps to get a pedal there's air somewhere

[Lplus]

weird question so please bear with me!

i've never managed to get the brakes on my mini so they actually work on the first pump of the pedal.  

 

i've recently rebuilt it with new rear brakes and it has cooper S discs on the front (it's a 1960 model so these were replaced).  i've bled them throughly and there is not air in the expelled fluid.  i've used both a vacuum pump and the two man method and put a whole bottle of fluid through to no avail.  they work great but only after a second pump of the pedal.  

 

the rear drums are adjusted so that i can get 3 clicks (may 4 at a push) on the handbrake.  the master cylinder is original type but it looks like the cooper S master cylinder is the same bore size (0.7") anyway with just a larger reservoir.

 

clearly i've bled brakes hundred of times before on other cars with no issues but no matter what i try the mini still has this issue.

 

what am i missing?

 

i'm wondering if perhaps the MC is actually a clutch MC with a narrower bore or something?

If I'm understanding you correctly the first stroke of the pedal does nothing at all and on the second stroke the brakes suddenly firm up.

 

In that case I'd agree with you that the single stroke of the pedal does not move enough fluid to produce pressure.

 

If the calipers are the right way up (you say they are) and are bled properly, and the pads are tight to the disc, I would be looking at the back brakes since the fluid needed to tighten the calipers against the disc is minimal.  As has been stated above it is vital to slacken off the handbrake completely before adjusting the rear brakes so that the actuation lever sticking out of the bottom of the backplate is as far back as possible and loose.  The shoes should then be adjusted by means of the adjuster at the top of the backplate to give minimal clearance.   Then adjust the handbrake up.  This should reduce the volume of fluid needed in the rear cylinders to the minimum.

[MiniTim71]

I had a similar issue with rebuilt calipers. When the car is at rest, check to see if the pads are loose in the caliper (just poke them and see if the rattle). If the pistons current resting position is too far in, it’ll take the first part of the pedal travel to make contact before you’ll get pressure

A similar concept to making sure the rear drum adjustment is correct - you want all pads and shoes within close proximity to the disc/drum so that all the fluid is used to clamp the brakes and not to push out the pistons a distance first

Hmm, interesting.  I had the Minispares brake reduction kit fitted by local garage and they did say the kit did not contain pad springs which prevent pad rattle, not sure if that is relevant.  How did you solve your problem, I don't see a way to change the piston resting place?

[timmy850]

What I did was remove the pads, push the pistons out a little bit with the pedal and then put the pads back in so they were a tight fit. Obviously don’t push the pistons out all the way or it’ll be a disaster

They normally only go out a small amount and then are retracted by the seals. Worth checking at least

Edited by timmy850, 09 April 2021 - 11:51 AM.