brake balance valve

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peter freeman
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brake balance valve

Post by peter freeman » Thu Mar 10, 2016 6:09 pm

Got my MB MOT'd today and it passed - but to my surprise the handbrake was better than the foot brake on the back wheels. My question is - is the brake balance valve adjustable. I changed the valve a while ago as the old one was leaking and falling apart but I did not think about it being adjustable at the time.



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Re: brake balance valve

Post by philhoward » Thu Mar 10, 2016 6:20 pm

Check the cylinders first - if one piston has seized, you'll only get half "push"?

Ironically, it's probably better on the "Emergency Brake" than the service brake anyway - you need most of the effort on the front. Overdo the rears and they'll lock up too easily?


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Re: brake balance valve

Post by peter freeman » Thu Mar 10, 2016 6:23 pm

Not a cylinder problem as they operated together and the chances of both being faulty at the same time by the same amount ! The rears locked up on the handbrake but not on the foot brake which makes me wonder - my MOT man made no real comment but seemed to be surprised.



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Re: brake balance valve

Post by philhoward » Thu Mar 10, 2016 6:31 pm

If the rears passed OK as a service (foot) brake I think you might be reading too much into it.

You should be able to lock the rears up on the handbrake (have with virtually all my cars, anyway) but struggle to do so with the footbrake.


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Re: brake balance valve

Post by Roger Pennington » Thu Mar 10, 2016 6:40 pm

I'm inclined to agree with Phil, you don't really want to be locking the rears early with footbrake operation, so it's probably ok?

To (hopefully) answer the other question, I'm more or less certain that the valve is not designed to be adjustable (in fact I'm not even convinced it's designed to be serviceable?)


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Re: brake balance valve

Post by peter freeman » Thu Mar 10, 2016 6:45 pm

Last year I could not lock the backs up with the hand brake but it passed because checking the efficiently against the cars weight it was ok - I do not know if it locked up with the foot brake last year. I expect my MOT man having seen it lock up with the hand brake expected it to do the same with the foot brake - I have been "at" the hand brake prior to the MOT. Going to have it and my SS1 MOT'd again in the summer ( SS1 done last month ) as I am too old now to be under the car in the winter. So 6 MOTs this year instead of 4 but it also will get the MOTs away from the road taxes which are due soon which can't be bad.



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Re: brake balance valve

Post by peter freeman » Thu Mar 10, 2016 6:47 pm

Did not look at the valve when I fitted it Roger but I could not see any adjustment screw etc. The end was coming off the old one so servicing it was not a consideration at the time.



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Re: brake balance valve

Post by philhoward » Thu Mar 10, 2016 6:52 pm

I don't think they're serviceable either - and suspect they are mainly to limit the pressure to the rear to stop (prevent) them locking up in the first place? I did see a writeup on how they work many years ago but can't remember the detail!


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Re: brake balance valve

Post by peter freeman » Thu Mar 10, 2016 7:02 pm

Never mind it did pass the MOT so all is well - the car in front of me did not ( hole in the sub frame ) and my MOT man said it was because it was old, I pointed out that it was much younger than any of my cars.



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Re: brake balance valve

Post by Roger Pennington » Thu Mar 10, 2016 7:06 pm

Yes, I think you're right Phil. All the workshop manual says is that one is fitted, and no more than that - there are no instructions for it, and no diagram, so I suspect that their intention was very much that it should be a "black box".

Re MOTs, I know what you mean about grovelling around in the cold, the SS1 and the Yellow Peril run out in Nov. and Dec. respectively, but the trouble with moving it to the summer is it's difficult to find a spare window with all the shows and events going on. At least they fall in a bit of a "dead spot" in the calendar... :)


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Re: brake balance valve

Post by peter freeman » Thu Mar 10, 2016 7:10 pm

No shows during the week for me. As long as I avoid June which is the international month I am fairly free most of the time. I cannot get a car in my garage - full of spares and tools.



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Re: brake balance valve

Post by scimjim » Thu Mar 10, 2016 9:07 pm

Scimitar MOTs should all be done in early August :mrgreen:


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Re: brake balance valve

Post by CNHSS1 » Thu Mar 10, 2016 9:31 pm

On the sierra and used on my old TVR, was a brake balance valve that sat at an angle, nose up facing front. Basically it limited the braking when the nose dived and arse went high, normally this would unload the rear wheels and lock them up, potentially dangerous. The valve was a ball bearing in theory, that under harsh or emergency brake was propelled forwards closing off the valve slightly. The angle of the dangle could be adjusted to alter its effect. They could stick though, were cheap enough from ford though, to just replace. No idea if its the same sort of device on yours Peter?


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Re: brake balance valve

Post by peter freeman » Thu Mar 10, 2016 9:33 pm

My plan Jim is to have the Sabre in May, the SS1 in July the MB early Aug and the Coupe late Aug - cannot have them all in Aug - what if I have a failure - screws up the rest of the MOTs.



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Re: brake balance valve

Post by peter freeman » Thu Mar 10, 2016 9:36 pm

The MB uses a SD1 balance valve - so do the later GTEs and GTCs I believe - sited just behind the chassis cross member behind the radiator. Not sure about the earlier cars.



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