6 replies to this topic

[minimat]

So my girlfriends 1966 austin mini has failed the mot on n/s/r brakes low performance,both handbrake and footbrake.i watched the needles on the brake tester and the n/s was a lot lower than the o/s.I took the drum off expecting to find a seized cylinder but it was as good as new and moved freely,shoes were also very good,adjusted it all up and took it back,this time the handbrake was fine but the footbrake was still low despite being able to lock the wheel up on a dirt road,the tester managed to blow the hydralic brake light switch to pieces pressing the pedal with both feet  .I have since changed the flexi hose and the brake shoes on this side along with the brake light switch bled the whole system and the pedal and handbrake are now really good but with the rear jacked up and an assistant pressing the pedal i can still just about turn the rear wheels,not easily but not to hard either,now run out of ideas the only thing left is the regulater on the rear subframe but i cant see how it would affect one side and not the other,i have not checked the other side other than to adjust it but this was showing ok anyway,both cylinder were the same type and replaced a couple of years ago and have been fine,thanks for any ideas.

[minimat]

All passed now thanks 

[bikenutmart]

What was it ? Mart.

[minimat]

Not really sure as i did all the above work over a weekend but still wasnt confident of a pass as you could still turn the rear wheels with the footbrake on,nice suprise when it pulled up ok but the tester admitted the rollers pull up a bit low on that side!I wonder if it was more noticable on an early mini with not much weight on the back end and not the most powerful brakes in the world than on a heavy modern car, at the moment it only has new shoes on one side as they were unused ones found in the shed but at some point i will get a new set and change them all but its fine for now,got a ticket which is the main thing,the brake pedal feels better than my bora but drums always do compared with discs all round.

[Cooperman]

It is no use just pushing harder as the rear pressure relief valve limits the pressure to a pre-set maximum and continued pressing just puts more hydraulic pressure into the fronts.

On a Mini the rears only do about 20% of the total braking and if the relief valve relieves a bit too much it can prevent sufficient braking for the MoT. You need a tester who knows about Mini braking systems.

The cure is usually to change the pressure relief valve which on a Mk.1 & Mk.2 is mounted on the rear sub-frame. There are adjustable relief valves available.

[minimat]

I had considered this thanks cooperman and its something we may need to do in the future but i cant see how it could affect one side more than the other altough with cars especially old ones anything is possible i suppose,the mini specialist i got the brake light switch from said i would have to be very unlucky for this to happen.

[Shifty]

Also make sure the tester is using the correct weight for the car. The standard one used is way heavy for a mk1. My old one failed on the brakes but when the tester used the correct weight it scraped through.
There is about 100kg difference