MG MGB and MGB GT Tech Talk
Guys,
Aside from the obvious extra oomph from the servo, is there anything preventing me from removing the servo and putting in the brand new master and switch manifold I bought for the 73.
Moss wants $89 for a rebuild kit for the servo and the Yankee in me is having trouble spending that.
Thanks,
John
The last time I looked the front calipers calipers are the same for boosted brakes and non-boosted brakes. Therefore pressure to operate them is the same. If you lock them up with non-boosted system, the boost system would just let you do it with less pedal force. No change it the stopping effectiveness. Check the pedal ratio (length above the pivot and the length below divide the two)to verify that the non-boosted pedal doesn't have a larger mechanical advantage.
I have had no problems in stopping with the non-boosted system in my 1964 B.
I have a 79 and a 71, the only difference I can feel is more sponginess in the 79, there is no difference in the effort necessary to operate them.
Go with the 73 master, it just feels better.
Chris,
The pedal length and travel is identical.
And Mike,
I like firm brakes better, don't you?
You guys just saved me 89 bucks.
Thanks,
John
A year ago I would have agreed with you guys. My '76 always stopped but took a lot of pedal pressure that I thought was par for the course. For some strange reason, my servo started working again after a very hot trip in parking-lot like conditions on the highway. Now the pedal needs less than half the push and, to my mind, gives a much more controlled stop.
Now this revelation didn't come "free" as I now have some vacuum issues that I didn't have before. The car is a little harder to start when cold and coming to a stop when warm the rpm drops down to less than 500 and then slowly stumbles upwards to about a 1000. I did have a leak between the master cylinder and the booster, detected with carb cleaner, (Why is there no gasket between the master and the booster? I know there is a cup seal on the master's penetration into the booster but shouldn't bolted together metal-to-metal surfaces always have some some sort of gasket?) but now all is tight. I'm starting to wonder if isn't some sort of intermittent leak at the right-angle non-return valve at the bottom front of the booster as this fitting is kind of a loosey-goosey fit.
When I was planning the restoration on the Iris Roadster I decided to add a servo, V8 Greenstuff pads and slotted rotors. My '74 GT has stock braking and the difference is incredible. The Roadster stops like a modern car. In time I will replace the pads and rotors on the GT. A servo may not happen as I'm pondering adding a supercharger.
If you go with the earlier brake system, you'll end up with a set-up that looks like this in the attached photo. This is my V8 which started life as a '79 but now uses a non-boosted system.
You'll need the pedal box frame and cover, MC, pedals, new lines and the distribution valve if you decide to use it. In this photo, you may notice I don't have the valve assembly and have created a true, dual-circuit system.
To install the pedal box assembly, you'll have to drill a couple of new holes but not much else. The hole where the pedals drop through on the late car is bigger than the early cars but the box assembly covers it all.
I thought there was a difference in the length of the short lever arm. That piece of the brake pedal arm on the other side of the fulcrum pin.
My '67 has a single circuit system and the total pedal travel is about 3/8". It is as hard as a rock and stops the car on a dime. Brakes, if kept in proper working order on the B, don't need a booster. The original design was overkill for its time. The rotors are larger that most other cars of that era and the drums are huge by comparison as well.Most of the weak braking problems, that I have encountered on Bs are due to sticking calipers and rusty wheel cylinders. Throw in your share of crushed rear brake lines and you have a poor braking system. RAY
Another option I've seen here some time back, (I tried a quick search and didn't come up with anything) was to modify the brake pedal arm at the top where it hooks to the M/C rod. I can't remember who did the mod, I was going to try it eventually. Someone here may remember who it was and where the article is located.
In a nutshell, the top of the pedal arm was built up by welding, then a new hole was drilled lower (IIRC) down the arm for better leverage. A plate was welded to the M/C support bracket with holes drilled to mount the M/C lower to be in line with the new hole in the arm. It gave better leverage and therefore easier pedal effort for the same movement than before. Made sense to me, but I've not been able to find it today...
