brakes

[robo]

Just trying to soak up some of the info on braking systems for my build. From what i have gathered without an adjustable pedal box there is a good chance of the rears locking up on track cars or on wet roads. This must get worse with the heavier engined cars. With the sierra running gear would it not be prudent to rob the abs system and fit the whole lot and forget the adjustable brake bias boxes. At the end of the day you can only adjust them for conditions on the day and on a road car that changes on every corner you go round.Would another alternative not be to fit those load compensating valves fitted to lots of small hot hatches and light vans that automatically lessen the pressure to the rear as you get load transfer to the front. Views?
Bob

[flyerncle]

Fit normal m/cyl and system and if needed a pressure reducer valve in the rear line or alter rear cylinder sizes to suit.

[robo]

Is that method ok with sva? How would that affect an mot brake test where they are looking at braking efficiency as a percentage related to axle weight?Or am I reading to much into this and its not really an issue?
Views

Bob

[SeriesLandy]

If I recall ashg changed his rear wheel cylinders after his first iva test.To change the brake distribution.
I may be wrong though.

[flyerncle]

As Steve says a few have done this and passed IVA,Spuds car has a standard setup and went through fine,Sierra m/cyl and disc/caliper front and 10 in drums rear,as far as I remember no reducer valve.

If they use a roller brake tester with axle weighing facility (and I am fairly sure they all do)there are calculations as to weight and balance and pedal force used.
Someone who has a car passed will tell you better and I think Adrian H has put this on the forum previously.

[robo]

Lots of mention about drums on the rear in the forums. The car i am breaking is disc brake rear ,is this going to be to fierce?
bob

[flyerncle]

Comes down to balance from front to rear,the donor weighs possibly three times the weight of the roadster so its pro rata in braking force and it will be overbraked so you may need a reducer in the rear or the dreaded balance bar.
The race car I have built has a twin cylinder balance bar setup and is proving to be a pain at the moment to setup but hopefully wednesday will sort it at the track.

Once you have it all up and running find a friendly MOT station with ATL and you will get some idea of the forces involved.

ATL will weigh axles and give brake force in kilo's and some idea of split front to rear.

[robo]

That has to be a good case to try the load compensating valve. They have a simple drop rod attached to lower wishbone that is fully adjustable.So you could in fact test system on any mot station rollers before going to iva.Brake lockout on rolling roads is a major problem and changes with different tyre compounds so in theory that might be the answer.They wont look at it as somthing alien as its fitted to dozens of cars.One other thing that comes to mind is the use of braided brake hoses, i have built several kit cars and on one occasion i was failed at a test station because the brake hoses did not carry a bs number. Is this still the case or did i just come across a complete twat?
Bob

[robo]

That gadget that adrian h has got has to be the answer. With some roller time at a friendly test station you must surely be able to produce a test result comparable to iva whatever system you have.
bob

[MarkB]

Don't folk use the Sierra's brake valve thingy found on the bulkhead anymore?:confused:
I thought it got mounted down in the tunnel at a certain angle to do that "don't lock the arse end up please bit"..

[AshG]

it was adrian that changed the size of the rear cylinders. i have got 9 inch drums on mine and it went through without any modifications what so ever.

[robo]

tyre diameter must play a large part in this as the larger diameter is going to lessen the braking effect, also tyre width is going to affect tyre lock out in the rollers. Is it the guys running the smaller tyre diameters that are getting the locking rears?
Bob