Brake caliper set ups

[catswhiskers]

Has anyone got any experience as to whether there would be any inherant problems associated with fitting two brake calipers to one disc?
I am suggesting two identical calipers mounted opposite each other and plumbed with a 'tee' connector to feed both calipers equally.
Taking into account all the standard available donor parts, this should work out much more economical than fitting competition discs and 4 pot calipers shouldn't it?
I am only talking of road use, not track or rallying mind you.
Thoughts?

Mick.

[David May]

I've seen Hawks fitted with two calipers at the rear (to increase the rear bias) and it appears to work well. Cheap and very cheerful with only the unsprung weight penalty. Even easier on a Corse I which has twin pickup points on the hub carrier.

[tryphon]

Usually the 2nd rear caliper is used for the mechanical handbrake required by regulations, only the hydraulic caliper is used when the brake pedal is pressed.

[colin artus]

F1 cars used to use twin caliper setups before the advent of exotic multi-piston calipers/carbon discs et al. There are no technical reasons against it other than complication and unsprung weight.

Colin

[gdr]

You might generate excessive heat by adding a caliper if the car is being used hard and has good tyre grip. In this case need bigger or vented disc to dissipate extra heat.

[catswhiskers]

Thanks for the input guys.
David, it was the very fact that I have ordered a Corse that prompted my enquiry. When I got the cast uprights, I noticed the twin mountings and thought mmmm. I wonder.
I think that excessive heat shouldnt be a problem because I'm only planning to use the car for road use. This solution, as I hoped will give me more rear braking without it being excessive.
The corse also has a brake balance bar fitted to fine tune things.
Thanks again.
Mick

[Chris J]

Apart from the caliper lugs, are Hawk/Transformer rear uprights handed?

[gdr]

Remember that the overall brake clamping force is proportional to caliper piston area and inversely proportional to master cylinder piston area. Assuming you'll be using a twin master cylinder brake pedal box, you might find that you need to increase rear master cyl bore (or decrease front) if you double up on calipers to avoid too much rear bias.
Presumably the pedal box supplied with kit has master cyls sized to suit the kit weight distribution and recommended braking components(single caliper)? As stated, bias bar for fine adj only.

[catswhiskers]

From my understanding of the pedal box/master cylinders, it is designed to be suited to racing 4 pot calipers at the rear without modification but I have to say that at this point, I will 'suck it and see'
I am proposing to use Alfa 164 rear calipers which have smaller pistons than the front ones so watch this space.

Mick

[David May]

The master cylinders that Huigh suplied me with (Corse I) were very much biased to the front, and I used a 40% smaller rear to get anywhere near balanced brakes. I wish I had thought of twin calipers back then - I'm spending a fortune on (thin) Ferodo 2000 pads which only last a few events.

[Arthur]

Mick,

More rear braking? Harder you go, the less rear you want, or can safely use. (Unless you're one of these "rallying" types, and want to use a LOAD of rear bias to get it sideways quickly - road tarmac and circuit stuff is what I refer to).
I'm still using the standard Ford Granny stuff supplied by Hugh with the CorseI, and am running something like 60% bias forwards on the bar, and remember the rear master cylinder of the standard set-up is a size larger than the fwd one, so a deal less pressure is sent to the rears anyway. Plus there's more pad area front as well.

So as the guys say, there is no technical reason why not, but as well as the weight penalty, you'll be shunting more fluid, so you will have more pedal travel as well. So unless you need more brake full stop, you'd get better performance for less weight with larger diameter discs. To shift bias around, use the bar first, and thereafter the cheapest method is to bugger about with master cylinder bore sizes. Smaller bore, more pressure, but more pedal travel. Larger bore, less pressure, but harder pedal feel.

Arthur