25 replies to this topic

[Chris1275gt]

Hi all! Just got my mini to the point of test driving it after a full restoration, but the brakes seem to not work properly. The whole braking system is new and running 8.4" discs at the front and drums with 1/2" cylinders in the rear, aswell as a GMC227 master (the yellow tagged one). So the problem is that it does indeed brake a little, but I'm unable to get any wheels to lock up and the brakes just seem kinda "sloppy". The pedal feel however is decent I think (never driven another Mini with a properly working braking system so not 100% sure) and I've bled the brakes multiple times and got just clear fluid with no bubbles coming out in all corners. Any idea what might cause the issue or how I should try to fix it?
 
Thanks in advance!
 
- Toffe 

Hi
I've noticed on Minispares flow chart for braking systems that the GMC 227 master cylinder is only used with the .75 rear cylinders GWC1102 not the .5 rear cylinders.

[sonscar]

People who know nothing about cars other than the monthly payment buy them in their droves and the brakes just work out of the showroom without any skimming,bedding etc.How does the manufacturer achieve this and why can't we?Steve..

[unburntfuelinthemorning]

I've recently converted my front drums to discs.  Unlike modern cars my unservoed brakes have little initial bite with a light touch but put a little effort in and it stops well.  The drums bit more initially too because of the self servo effect.  I've taken it easy on the brakes for a while as the pad advice slip decreed but have not worried about it too much.  The markings on the disc are nice and even and the same width as the pads. The pads are EBC which Minispares supplied with the kit and they supposedly have a coating to help the initial bedding in.  They did not come with advice for bedding in like the advice posted above. 

[gazza82]

Blimey.  Think I'll use a different make then.

 

What pads are you using? Some EBC pads are not designed for road-use and have to be heated up a lot to work.

[unburntfuelinthemorning]

 

Blimey.  Think I'll use a different make then.

 

What pads are you using? Some EBC pads are not designed for road-use and have to be heated up a lot to work.

 

These which came with the disc brake kit. 

 

I'm happy with them, my previous comment was merely a way of expressing astonishment at the endless bedding in procedure Quinlan Minor posted.

[cal844]

All I do when bedding in brake pads is to drive 3 miles of left foot braking, then spin round and do the 60 to 10mph stops, until the wheels are warm to the touch (usually within the 3 miles, doing a 60 to 10mph stop every half mile)

Side note, make sure the route you use is quiet and that there are no vehicles following you for safety reasons.

I then simply drive as normal afterwards.

[Toffe98]

Well just realized I'm an idiot, got the lines between MC and the brake limiter valve the wrong way round  from the limiter on everything's correct though, I'll just have to get some new lines and connect the 12mm union on the MC to the REAR brakes, not the fronts 

[Quinlan minor]

Well just realized I'm an idiot, got the lines between MC and the brake limiter valve the wrong way round  from the limiter on everything's correct though, I'll just have to get some new lines and connect the 12mm union on the MC to the REAR brakes, not the fronts 

That'd explain the problem.

Well done for finding it. It's the hardest thing to do: checking your own work.

[Ethel]

Reading my way way through the thread wondering when somebody was going to pick up on it being a yellow band stepped bore master.

 

The bottom outlet is M12x1 and goes to the rear brakes as it's the larger bore with least mechanical advantage.

 

That's the other way round to the earlier dual masters so the pipes to the Fam7821 valve need swapping over. The connections for the front circuit are directly opposite each other. The outlet for the rear circuit is offset closer towards the end of the valve body because only the inlet is blocked off by the shuttle so the pressure in the rear brakes can return the valve when you let off the pressure in the front brakes.

 

1/2" wheel cylinders will give you a bit less rear braking effort, but will reduce the pedal travel. Might be a good move if you're an "enthusiastic" driver and nobody is brave/stupid enough to get in the back of your Mini! 

[Toffe98]

Reading my way way through the thread wondering when somebody was going to pick up on it being a yellow band stepped bore master.

 

The bottom outlet is M12x1 and goes to the rear brakes as it's the larger bore with least mechanical advantage.

 

That's the other way round to the earlier dual masters so the pipes to the Fam7821 valve need swapping over. The connections for the front circuit are directly opposite each other. The outlet for the rear circuit is offset closer towards the end of the valve body because only the inlet is blocked off by the shuttle so the pressure in the rear brakes can return the valve when you let off the pressure in the front brakes.

 

1/2" wheel cylinders will give you a bit less rear braking effort, but will reduce the pedal travel. Might be a good move if you're an "enthusiastic" driver and nobody is brave/stupid enough to get in the back of your Mini! 

 

Well if they're flipped from the earlier master cylinders then that explains why I got it wrong when using the old lines as models, thanks for confirming that!   I think I'll have some braided lines made instead of the copper ones, saves the hassle of getting the bends right and looks neater, and also leaves more room for a dual carb setup, or maybe even a supercharger 

 

Yep, got the 1/2" cylinders on already and I do believe it's what will stay on, would consider myself an "enthusiastic" driver and might even take it on track every now and then, even if it's more built as a fun road car 

Edited by Toffe98, 09 May 2020 - 03:22 PM.

[Ethel]

I'd stick with solid lines. flexies want to go where the unions point and can't make as tight bends.

 

You can get a pipe bender for not much money. Minispares also do a pipe kit, but if your car's LHD...