So who's right? Anyone actually tried rears without doing the maths and noticed/compared the difference?
Paragraph lifted from article about calipers efficiency i just stumbled upon during quick google sess "Each piston in a floating calliper has twice the effect it would have in a fixed calliper because the reaction from the piston is used to apply the same force to the 'other' side of the disc"
Or does this open up another point for discussion and disagreement? Floating, fixed, sliding, dual.... I will just agree to disagree
Bigger aint always necessarily better, with many things. Bigger at the expense of what? Pedal travel?
Bigger pistons = more pedal travel yes. Pad areas do not matter for braking force created, they do matter for heat dispersion and wear characteristics though. This is a whole new ball park though.
Pads area indeed do not matter for force created but DOES matter in how much friction is transfered over to the disc and this is where pad size makes a big difference especialy in multi pot aplication as they will not flex
you only take 1 side of the pistons when working out the forces, now obvi0usly a 4 pot is a better design for pad stability and stiffness, but in this case the rears are just not up to the job, and belong in the made up folklore that you get on the internet. there are loads of big 4 pot front calipers that will fit under 16" wheels, the ones on my E38 stop a 1900kg car from 3 figures better than the mk2 with 280s did from 70
I was trying to lighten up the thread! But its a mk3 20v so asuming running a reasonable mc. My 996 fronts with 22mm m/c - pedal travel and feel are spot on. Better than 54mm 280s on a 19mm 8v m/c. Anyway this is getting off topic!
And precisely that is the problem, mismatch between master cylinder size and porsche rear calipers as they are obviously designed for a different ratio! Also what diemeter discs did these people use porsche rears on? Anything smaller then they are designed for and braking will be reduced as you will agree So lets compare effectivness of these calipers on rear engined porsche with as much weight over them if not more then mk2 golf front You really think porsche would use them if they offered less braking capability then standard mk2 golf fronts? It just cant be People get poor results due to mismatched components
Yes mismatched components, so are you suggesting everyone who fits the rear calipers from a porsche to the front of their golf should go and find a matching set of even smaller pistoned calipers to go on the rear to make up for it?
i think its but the pads are narower so they dont cover all the golf 312 disc you have 10 to 15mm thats not covered on the inside leon cupra r calipers are the same piston size as the 996 fronts the Piston areas are golf 54mm 3.142x27x27x2=4581 LCR/996 fronts 3.142x19x19x4=4537 996 rears 3.142x14.5x14.5x4 = 2642.422
No i am not suggesting anything and to be honest i will not be doing any of these brake conversions and dont egg anyone on to do so All i am saying from begining of this thread that small Porsche rear calipers have to be more powerfull and better than mk2/mk3 standard fronts and that pots diameter is not the full story as long as they coupled to matched components As for problem with uneven braking what is the problem in using bias valve? I think this thread has gone off topic for far to long now and maybe we need a thread split? I would love to see experiment carried out in braking force between calipers tho Surelly there is some data from mot like brake test machines?
Had a Godspeed Porsche conversion on my mk2, 325mm with porsche rears(same car that is in the Haynes Golf manual) Think they were 32/28's, but not 100% on it. Worked amazingly well. Pedal felt right, with the pedal stroke feeling stock with the std master cylinder.
they are a backwards step, obviously the master cylinder needs to be the right size, but I wouldn't reccomend anyone use the porsche rears, unless you find some that have a piston area around 2200 Sambo, I'm not attacking what you've said, but it might be worth digging around and reading up on the basics of hydraulics
nope. sorry. my personal experience on customer supplied set on leon cupra: boxter rears = solid pedal and not much brake effort, far worse brakes than std horrble setup/mis,match of cyl to piston ratios
