brake caliper piston sizes
Discussion
I don't know about your specific application, but I have an e36 328 that has been up-braked for track use & went from the standard single pot all round set up to an AP 4-pot front & AP 2-pot rear set up without any issues on the standard master/servo set-up.
Don't know the piston sizes off the top of my head as per your original question though.
Also had to machine the caliper spine down to accept the narrower discs from the ones the calipers were designed for.
When I think about it I suppose the increased volume of fluid movement of the original set up pistons as opposed to the new set up is only VERY small as there is theoretically only a few thou' of travel from brakes on to brakes off.
Don't know the piston sizes off the top of my head as per your original question though.
Also had to machine the caliper spine down to accept the narrower discs from the ones the calipers were designed for.
When I think about it I suppose the increased volume of fluid movement of the original set up pistons as opposed to the new set up is only VERY small as there is theoretically only a few thou' of travel from brakes on to brakes off.
Just to clarify, when you say 'single piston' you mean two opposed pistons and when you say 'double piston' you mean four opposed pistons?
Anyway, surely it's not as simple as calculating the area of a 60mm piston, halving it and calculating a diameter from that figure? It depends what you're trying to achieve, more powerful caliper a or just greater pad / disc area.
Anyway, surely it's not as simple as calculating the area of a 60mm piston, halving it and calculating a diameter from that figure? It depends what you're trying to achieve, more powerful caliper a or just greater pad / disc area.
BritishRacinGrin said:
Just to clarify, when you say 'single piston' you mean two opposed pistons and when you say 'double piston' you mean four opposed pistons?
Anyway, surely it's not as simple as calculating the area of a 60mm piston, halving it and calculating a diameter from that figure? It depends what you're trying to achieve, more powerful caliper a or just greater pad / disc area.
The E39 M5 uses sliding calipers, so single piston.Anyway, surely it's not as simple as calculating the area of a 60mm piston, halving it and calculating a diameter from that figure? It depends what you're trying to achieve, more powerful caliper a or just greater pad / disc area.
There is a calculation that I am aware of, but I do not know what it is. Something tells me that 4 30mm pistons have the same area as a 60mm one, but I doubt that is right..
Done some sums and I believe 2x pistons measuring approx. 42.43mm diameter each should have the same area as a single 60mm one (working to two decimal places).
I'm not sure that this is the way manufacturers figure out piston sizes, that is just the size at which two pistons can give you the same amount of travel for a given pedal movement. This size should be treated as a starting point only as of course from here you can either go bigger on the pistons which will give you a longer pedal but greater 'leverage', or smaller which'll give you shorter, harder pedal and probably a slightly more rearward bias.
I'm not sure that this is the way manufacturers figure out piston sizes, that is just the size at which two pistons can give you the same amount of travel for a given pedal movement. This size should be treated as a starting point only as of course from here you can either go bigger on the pistons which will give you a longer pedal but greater 'leverage', or smaller which'll give you shorter, harder pedal and probably a slightly more rearward bias.
Edited by BritishRacinGrin on Sunday 1st June 06:41
Yeah the smaller pistons will necessitate more pedal pressure than larger pistons but a shorter travel into the bargain, and the extra pressure required is probably a non-issue on a power assisted braking system (mine wasn't!). Also front/rear bias is a product of a great many factors apart from piston sizes so is probably not a worry either.
Interesting thread
If I was approaching this conundrum I would look at the area of the circle of the single piston and the area of the circles of the multiple pistons added together
I would assume you want more braking so more area on the multiple piston calipers, this would mean more pedal travel as more fluid would be needed
You then get into master cylinder size, brake pedal ratio, effort and servo assistance multiple
Nothing's simple is it
If I was approaching this conundrum I would look at the area of the circle of the single piston and the area of the circles of the multiple pistons added together
I would assume you want more braking so more area on the multiple piston calipers, this would mean more pedal travel as more fluid would be needed
You then get into master cylinder size, brake pedal ratio, effort and servo assistance multiple
Nothing's simple is it
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