Brake setup??
Brake setup??
(OP)
We have a car in that has 4 wheel disc brakes, 4 spot AP race calipers on the front & AP single spot race calipers on the rear. On further inspection it has dual master cylinders & a brake balance bar fitted, it has only the front brakes being boosted by a remote booster & is impossible to brake correctly with the fronts locking all the time.
Could anyone advise me to how this should be setup correctly, my feelings are that the rear brakes should also be boosted & a brake bias valve or proportioning valve should be fitted into the system somehow?
Being an engine builder i need some advice with this to help the customer out, so any & all help will be appreciated.
Thanks
Could anyone advise me to how this should be setup correctly, my feelings are that the rear brakes should also be boosted & a brake bias valve or proportioning valve should be fitted into the system somehow?
Being an engine builder i need some advice with this to help the customer out, so any & all help will be appreciated.
Thanks





RE: Brake setup??
I guess I've read that the bias bar is supposed to have within its adjustment range the best front / rear proportion.
RE: Brake setup??
Thanks
RE: Brake setup??
Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
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RE: Brake setup??
I think your right with the suggestion of a second booster, i will look into it & see how i go!
Do they make a remote booster with twin hydraulic cylinders on it, the remote booster at the moment has a single cylinder on it.
Thanks
RE: Brake setup??
it would help to know what size masters are already on there and the current amount of pedal travel, if you know these please post them.
RE: Brake setup??
Thanks for the reply, the masters are both 5/8", not sure of the current pedal travel as we have the rear end out of the car at the moment, also the engine is out being re-built!
From what the owner has told me the fronts keep locking all the time with or without the booster connected especially when the balance bar is adjusted equally!
Thanks again
RE: Brake setup??
Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Brake setup??
thanks
mark
RE: Brake setup??
Yes, this can be done easily!
Thanks
RE: Brake setup??
Power boosters often do not have a linear force multiplication, because the vacuum from which they operate is finite. So at low force levels you can get more boosting, and when the driver really leans on the pedal there is less boosting.
This is not so bad if the booster operates the brakes at both ends of the car with a conventional tandem master cylinder. But if only the fronts are boosted, with a hydraulic/hydraulic booster I would expect premature front lockup where traction is not so good such as wet or uneven surfaces, and premature rear lockup where traction is excellent on a smooth dry road.
Having a hydraulic/hydraulic booster at each end of the car might only make it MORE unpredictable in my experience, because the force levels and hydraulic pressures will be different at each end of the car.
Best to keep the hydraulics 1:1 and use mechanical boosting between the pedal and the balance bar.
RE: Brake setup??
Could you tell me more about the conventional mechanical boosting setup before the balance bar.
Thanks
RE: Brake setup??
The vacuum booster amplifies the mechanical effort direct from the pedal pushrod to the master cylinder. What you would do is replace the single tandem master cylinder with a balance bar and dual master cylinders acting in parallel. That way the booster acts before the balance bar.
I assumed that if only the fronts are boosted on the existing setup, there was a hydraulic/hydraulic vacuum servo booster on the front circuit only. PPR used to make a VH44 booster which did this, but I think it may now be obsolete, as I have not seen one for a very long time. They used to be fairly common to boost the old single circuit brakes with drum/drum, or disc/drum combination.
Some thought will also need to be given to master cylinder bore size versus, pedal stroke, and fluid displacement. With a tandem cylinder if the total available master cylinder stroke is one inch, each piston moves (displaces) only half that. With a balance bar that has one inch total stroke, each master cylinder could move the full inch. So to displace a similar amount of fluid over the full stroke, the bores of both master cylinders will need to be smaller.
For safety, you will need to still have some pedal height left if you totally lose one hydraulic circuit, so master cylinder bore size is important.
RE: Brake setup??
http://sports.racer.net/brake_bias.htm