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MG MGB Technical - Hard brake pedal effort

Always looking for ways to lighten/improve the car, I removed the power brake setup. I installed an ealier brake/clutch master setup, from a '70 GT.
This gives me more clearance for the larger K&N air filters, lighter in weight, etc.
However, now pedal effort is quite high, even more than I remember, from previous cars.
The GT has larger rear wheel cylinders, but the Moss catalog only show one master cyliner for '68-74 cars.
One by-product is for auto cross I now don't slow for turns as much as I used to, and that has made me faster.
Any suggestions will be appreciated.
Safety Fast
Dwight
Dwight McCullough

For even more lightness, why don't you chuck the brakes away altogether.
Lech

I really don't see removing the power brake setup as an improvement. Reducing stopping power to increase "going" power seems a bit on the moronic side.
R. L Carleen

Just how much weight did you save anyway? I hope that you measured what you removed from the car and subtracted the weight of what you put back in its place. Let us know. 10 lbs - and from the near centre of the car too. Was it really so important?
Marc

Removing the servo should only increase the pressure required but you should be able to lock up the brakes without it. Do additional leg presses?
George B.

Dwight:The reason they put power brakes in the B was the vast improvment they brought to the system I did a similar change to a 69 C and although the brakes worked well without the boosters it took a lot more "leg" to stop the car. Two new boosters {$$$$}and it stops as it should not alot faster but much easier and more controlable-RIC
R E L Lloyd

Oops!
Looks like I picked 'Flame Wars' and not MGB technical.
Listen you !@#$%^&&*, the first 'B's didn't have power boosters, and they worked just fine.
So there!
Safety [smarting] Fast
Dwight
Dwight McCullough

I don't know about the specifics of the mgb master cylinder, but frequently when going to a power boost manufacturers change to a larger diameter master cylinder to produce more brake power in less pedal distance. If you have a larger diameter master cylinder than the non-power master cylinder you will experience the need for more pedal pressure than stock for the non boosted master cylinder. The advantages of a non boosted master cylinder are 1/ more reliable, 2/ brake power that is consistent under low or high vacuum conditions, 3/ better modulation at the edge of traction, and 4/ less to go wrong. You also get more room to install an air intake system that will produce more horsepower over the stock air cleaner system. You also point out that it is lighter. 7-10 pounds savings may not sound like much. But finding several places to save that kind of weight will result in a car that handles better and is faster than the competition. There is never one magic bullet. Instead it is a combination of improvements that makes the ultimate advantage. You sure are stupid for trying to do better. good luck
Barry
ps check the basics. Are your lines crimped, or the flex lines deteriorated? How hard are your pads? If you have a pressure compensator for the rear brakes is it working properly?
Barry Parkinson

Thank you Barry.
Now there's a voice of reason.
The flex lines are new, braided type. I've bled and bled, and even reverse bled. You know , with a pump style oiler. Yes, I flushed the oil out of the can. I'm not sure about the compensator, or if the car has one.
Thanks again Barry.
Safety Fast
Dwight
Dwight McCullough

And what's more, Dwight, disconnecting the brake booster makes very little difference. If you can't lock the fronts now but could relatively easily before then the replacement MC is a poor choice or faulty.
Paul Hunt

Good choice Dwight. Power brakes, without ABS, do not stop the tires as well as manual brakes and a good driver can out stop ABS in the DRY. Brakes stop the tires, tires stop the car. Bio-mechanics have found that humans judge pressure very well but position very poorly; power brakes turn pressure into position. Bad choice for bio-feedback. Proper race cars use dual master cylinders, mostly for front/rear biasing, but is very good for bio-feedback as the pedal pressure is doubled. My race B with braided lines and properly seated brakes has virtually NO pedal movement; very nice bio-feedback and heel and toe.

Check your brake failure valve if the piston is locked to one side it can restrict flow to the brakes on that end.
Leland Bradley

Thanks Leland.
That's what I'm searching for. I know it's there, because I've driven cars like that.
But there is something I'm missing, and will eventually find.
Maybe it will take a bias bar brake setup.
Safety Fast
Dwight
Dwight McCullough

This thread was discussed between 20/09/2003 and 24/09/2003

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