MG Sports Cars

I understand that in 1972 power brakes were option but I really don't understand how it would work with the Mastercylinder located where it is?? And is there a easy way to convert to power brakes by using off the shelve parts/junk yard and fabracation?? I want to improve my braking but don't have the time to have my only piece of transportation down for a week. Any thoughts or advice would be greatly appreciated.

Dave

The brake servo may have been an option for the home market, but I don't believe it was made available in North America until 1976 for the MGB.

The servo does not really increase braking ability...it makes for a little easier braking effort on the pedal. It's not going to make you stop any shorter. (The North American market MGC ran two servos; the home market only had one. MGB did not receive a servo for the North American market until 1976.)

I ran my MGC without servos for two years. No difference in stopping distance noticed when I installed the servos.

If you want, you can incorporporate the brake pedal box, brake m/c, and servo unit from any 1976-80 MGB into your 1972 MGB. I did this for my 1974-1/2 MGB/GT conversion.

You'll need to drill new mounting holes on the ledge for the pedal box...that's about the hardest part, other than making new brake lines.







Edited 1 time(s). Last edit at 02/01/2012 03:10PM by mowog1.

What do you hope to accomplish? To my of thinking, there are three main criteria: (1) stopping distance, (2) resistance to "fade", and (3) pedal feel. Power brakes don't help with the first two criteria at all, and whether they help with the third is arguable and/or subjective. Fitting stickier tires is usually the best way to improve any car's stopping ability. That said, IMHO usually the cheapest/easiest way to improve stopping distance and resistance to fade is to fit better brake pads, and the cheapest/easiest way to improve the pedal feel is to fit residual pressure valves. Some people swear by EBC's "Green Stuff" pads. (Moss and others supply them.) I'm pleased with EBC's "Yellow Stuff" pads. (I got mine from John Targett.) The search box above will help you find articles on this site that describe Wilwood's residual pressure valves and show photos of them installed.

If you have big sticky tires, a "big brake kit" should help quite a lot with stopping distance and fade resistance... but on general-purpose modestly-sized wheels/tires, stock well-maintained MGB brakes will have no difficulty locking the brakes over and over again.

I'd like to see a well researched and written report on the significance of tire/wheel rotating inertia on stopping distance. In principle greater wheel/tire/brake weight should all significantly increase stopping distance. We hope that wider tires and bigger brake rotors will offset the inertia effect of those four big flywheels. I'd like to see the trade-off quantified, especially for cars in our size/weight class. Many of us are fitting much bigger wheels/tires/brakes than MGB vintage racers, and I wonder if we're really getting the performance benefits we expect.

A long time ago, I swapped rear axles without much thought to how the new (Ford Mustang) drums compared to the MG drums. That seemed to have the effect of shifting brake bias forward, which meant that the rear brakes didn't seem to be doing their job. Later, I swapped from Mustang to Ranger rear wheel cylinders and I think that helped improve brake bias a bit. Incidentally, I believe I should have gone with rear disc brakes when I did the axle swap because (a) they're lighter and (b) they're a bit easier to service.



Edited 1 time(s). Last edit at 02/01/2012 03:02PM by Moderator.

Everything in the braking system is proportional from the liking of how it feels to fuel economy. Like Curtis mentioned, we modify these vehicles and increase the rotating inertia (matter in motion) by modifying the wheel/tire/brake assemblies mass. You can built a car to under brake or over brake or even brake excellent for three or four clamp down sessions and then fade comes in. A lighten engine's flywheel can even help brake by reducing its rotating inertia while letting the engine act like a "Jake brake" does.

As also mentioned, larger rotors and hydraulic components are only as good as the stopping power of your tire grip; after all, locking up tires will not give you the shortest braking distances or vehicle control. In fact, this is why cars are fitted with anti-lock brakes especially rear wheel anti-lock. Velocity and inertia are two different factors to consider when working with braking systems; the higher the car's speed, the higher the velocity which translate in stopping kinetic energy. Transferring the inertia energy to the rotors/drum is another physic's phenomena.

Although, I do understand your concern; I have driven cars where I wonder if I had enough leg strength to apply panic braking duties. On the other hand, I've driven cars that locked up the wheels at the smallest commanding push of my foot. I like predictable braking effort, not too touchy and not too demanding in force.

Manufacturers have to also worry about getting all of this mass going and the energy needed to do so which translate in "fuel economy"; this is why they'll built a street automobile with respect to fuel economy and moderate highway speed for braking duties. They also apply common sense on their high performance cars by increasing braking component size with disregard to a small fuel consumption increase.

I know that I'm getting away from your original question and here's where I would start; install or have someone install a brake pressure gauge at each brake bleeders (one at a time) and write down the pressures recorded on each wheel. Do it from maximum leg effort; they also make a gauge to measure pedal effort if needed.

You should have higher reading to the front from the back, however, if the highest reading (should be front) reads around 800 PSI of pressure there should not be a pressure problem. If it reads 350 PSI or lower, then there's a problem either within the hydraulic system or elsewhere; it also could be that your brake pedal leverage is wrong. If everything checks out right then adding a booster may help reduce pedal effort to match the capability of your car design.

I hope that this can be of help to you and again as Curtis mentioned, trying brake pad with different compound materials can help. A softer material will usually brake harder but not last as long. Also, make sure that your pads are not glazed or contaminated, the brake hoses are not swollen internally, the calipers float freely etc., etc... I'm certain that someone else can chime in with better advice on pedal effort as I have read some serious postings that reflect experienced advice.

Cheers,

Here is a good resource. I read all of the tech articles and found them most helpful.

[www.essexparts.com]

JB

I'm not trying to hijack this thread but I have a quick question -
I've driven glenn towerys car with power brakes and now my '79 and I cannot get use to the feel of the power brakes.. My fathers '72 has manual brakes and I have to use less force and have way more feel...

Is there anyway to get more feel in these brakes?

That is a very good point sir I would enjoy hearung others opinions on it.

Dave

Although it's unlikely Glenn T's car would have a faulty power servo that is one possiblilty. For me the only time an MG with power brakes took more force was when the booster was not working correctly or disconnected. Both the 2x power servo MGC, and the B with single booster. The brakes still work, you just have to push harder. Glenn may have a mix and match wheel cyl and master sizes going. my 2 cents db