MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Hard Brakes

Has anyone had brakes that you have to stand on to stop? I've replaced the rotors,drums,all the cylinders including the master, all new brake lines,new drum hardware and springs, all I can do is get it to slow down, if I ever had to stop short I would be out of luck. Any ideas?
Thanks
Fred

Fred; You didn't mention brake shoes or pads, were they also changed? Did you do all the work
on the brakes because they were hard or for some other reason? Last question, are you a new
MG owner? Assuming you do not have a rubber bumper car the brakes are not power assisted
and they do tend to require more pedal pressure to stop than power brakes. If everything is working
ok the brakes are pretty good. If you didn't replace the pads and shoes, it would be a good idea to
change them and run a few miles to bed in the pads and shoes snd see how they work.
Clifton
Clifton Gordon

If you just replaced the works they will still be seating in and the last thing you want to do is stand on the brakes. Their stopping power will improve as they become matched. My own MG is a 76, which I am running with the brake booster disconnected. I have never found the brakes to be weak or difficult to use, but then again I do not typically drive a newer, over-boosted in every way, car either.

Does your pedal feel hard ? or do you have to push hard to get the brakes to grab ?
What year?
.

I have replaced everything in the brake system, rotors and pads, drums and shoes,master cylinder and brake lines, new rear wheel cylinders and rebuilt the calipers, new flex lines, and new seals in the pressure switch, I never drove the car before taking it apart. It seems like there is low pressure. Is there a difference in the pedals themselves, non boosted versus boosted? I assume it has the right pedals in it but that is the only thing I haven't changed. You can push on the pedal as hard as you can and not lock up the wheels, only slow down. None of my previous Mg's had this problem. It did the same thing with the old master cylinder and before I replaced the rear drums,shoes and hardware.
Fred
Fred

Can't offer any real help, but it sounds like the same experience I've had with both a big Healey and a MGB. Pedal hard as a rock! With both cars it came and it went in less than fifty miles. The only guess ever ventured was heat build-up effecting the fluid. Hope somebody has an answer for when (if) it happens to my current B.
Lowell Wakefield

Fred,
Have a look at the capability of the pedal to put pressure through the system. The pin at the master 9connecting pedal arm and master rod) may have slack. Also chech for sideways play in your pedal (at the pad end). If there is much of it there it can translate into a considerable sideways movement at the master rod end and a potential loss of capability to put pressure through the pipes and hoses.
Regards
Roger
Roger

Let me take a few wild stabs at this one.

You could have ordered or been sent the wrong master cylinder. If the bore is the wrong dia, you won't get proper force.

You didn't mention the year of your B. Do you have a servo assist? My experience with American cars with power brakes is that they don't operate well when the power assist isn't working.

Could you have a servo car with the servo removed? Could the servo have the vacuum line removed or cracked?

Did you buy competetion pads or recieve them by mistake?
Fred Horstmeyer

Fred-
Sometimes it's the little things that cause us to be stumped. Are you really sure that the sytem is properly bled? Sometimes after doing a rebuild of the entire system the mechanic will bleed the system as though he's doing a normal bleed job and figure that the task is complete. This is often a mistake. The system should be thoroughly bled for a second time later on to make sure that no trapped air remains.
Steve S.

The new master cylinder matched the old one and is non-servo (1972) I don't think there is any air in the system and I pressure bled them and the pedal is rock hard, there is no play in the linkage that I can see, and the pedal is high. I had a thought that it might have the wrong pedals and maybe I had a pedal from a servo car (I don't know if the mechanical advantage is the same). I have replaced everything in the brake system but the pedals.
FRED DOHERTY

Are the rears adjusted ?
Have you verified that the brakes are functioning at all 4 corners ?
Do you have any pedal travel before the pedal gets hard ? How much ?
Is it a 72?
.

Rear brakes are adjusted, if I jack up the car and spin the wheels and apply the brakes they stop but I can't lock them up that way. The pedal travels about 1 inch before it gets hard. It is a 72. The brakes were the same before I replaced all the parts. They never got any better. That's why I wondered if I have the wrong pedals in it. I have replaced everthing but the pedals.
FRED DOHERTY

Could the caliper piston(s) be corroded and stuck? The front
disc brakes do most of the work in stopping the car, and it
sounds like the calipers were the only components not
rebuilt.
Ronald

I rebuilt the calipers. I'm pretty sure they are working I can see where they have wiped off the light rust on the rotor and the wheel stops if I jack it up and spin it. I still think it is pressure related
FRED DOHERTY

Fred-
Is it possible that you've installed brake pads with a high-performance type material such as EBC Red Stuff? Some of them are intended for racing use and give awful performance until they get good and hot. Definitely not for street use. If you did, don't feel bad. You wouldn't be the first.
Steve S.

With an assistant pushing the brake pedal can the front wheels be turned by hand? Can the rear wheels
be turned by hand with pedal pushed? I think in one of your posts you said the rear would not lock up. If
the front does lock up that should rule out the pedal being the problem. Can you lock the rear wheels with the hand brake? Can you drive the car away with the hand brake on? If hand brake works you can assume the mechancal components are ok. I believe you said the metal brake lines are all new and not
from a parts car. I'm asking this because my 68 GT had poor brakes on it when I bought it. I found the
rear brake lines had been smashed flat, probably by a tow truck. Same thing on a spare rear axle I
bought. Is there any chance the front and rear lines may be crossed on the pressure failure switch?
Another thought is the 3 way connector on the rear axle and and the in the line connector under the floor. The passages in them are small and could be blocked by trash. I know I haven't given you any good solid
suggestions but maybe one of my questions or remaks will be of some help. Oh, there seems to be
several different brake pedal part numbers, but I don't know what the differences are.
Good Luck. Clifton
Clifton Gordon

Fred,

I don't believe that you have the rear drums adjusted properly. This will definitely affect the pedal pressure, height and overall stopping ability.

You said...

"Rear brakes are adjusted, if I jack up the car and spin the wheels and apply the brakes they stop but I can't lock them up that way."

I would try jacking up the rear of the car and tighten the each rear brake adjustment screws until the wheels will not turn, then back off 1/2 to 1 turn of the screw.

Hope this helps.

Mike


mike

Fred in Florida: In your later post you say the pedal is rock hard, with no play. Is it possible that in replacing everything that you have left no free play in the pedal? There must be at 1/4" to compensate for expansion of the heated brake fluid. There might be travel when the pedal is pushed with a cold system, but after driving the heat builds up and there would be zero travel, just a frighteningly hard pedal and little brake action.
Your 72 has the tandem system found on the MKIIs, and it is easy to overlook the adjustment of the brake pedal switch. If this is screwed in to far it will be exerting pressure on the pedal all of the time and this will result in the system overheating. I first encountered this on an MGA years ago, which has an adjustable pedal pushrod, which I had over-adjusted. You would also smell burning lining and fell a lot of heat on the hubs and wheels.
Andrew Blackley

Air in the system makes the pedal feel spongy, a lot of air will mean the pedal can hit the floor before enough pressure is developed to lock the wheels. A hard pedal with little braking effect is something else. Push back the pads to leave a visible gap between them and the discs - you may have to draw out some fluid from the m/c to stop it overflowing. Push the pedal a little at a time and see if all the caliper pistons start to move and all pads reach the disc with very little effort on the pedal, that should prove the calipers. When you bled them did you get a good flow of fluid through each bleed nipple? I have driven them with and without the servo connected and was surprised how little difference it makes. Is it pulling up in a straight line or pulling to one side?
Paul Hunt

This thread was discussed between 18/04/2002 and 22/04/2002

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.