[t783vkj]

Which is better, 4 smaller pistons or 1 whacking great one?I assumed 4 pot the way to go,but does anyone have any data reguarding stopping distances?Is it correct that early cosworth sierras where 4 pot,but later models adopted a single pot floating caliper?If so what was the reason behind that, manufacturing cost or design improvement?

[eldoodarino]

A two piece aluminium design bolted together should always be stiffer by design and give stiffer pedal than a single piston design..... this is why 4 pots are used.. not for stopping distance....

this is exactly related to your question.... but is still relavant... http://www.stoptech...._monobloc.shtml

personally i think 4 pots are a more accurate way of braking, and more responsive to pedal pressure.... with careful choice of pad they can be Extrememly effective...

Chris

[t783vkj]

Did I read that correctly,your saying 4 pots give a firmer pedal,not shorter stopping distances?

[martinthrapston]

doesnt take much to work that out,you got 4 pistons applying equal pressure,ie 2 pistons on both sides,1 piston applying pressure to 1 part of the caliper and also pulling the opposite side of the caliper aswell is not really working effectivley compared to 4 smaller pistons which is where you get the firmer pedal pressure from.....

[eldoodarino]

 t783vkj, on 05 June 2010 - 11:16 PM, said:

Did I read that correctly,

no... what i said was .. a 2 piece caliper bolted together (in the case of a good 4 pot aluminium caliper)...produces a very stiff mechanism and excellent pedal feel...

this is the key point of the design.... not the difference in stopping distance, as this would be marginal..

[t783vkj]

Im kind of in two minds,I like the idea of uprating the brakes,300mm vented disc with cosworth 4 pot calipers is what Id priced up,but on the other hand,the car is more or less standard engine wise,and the mods I intend carrying out ,the usual exhaust ,cam & head ,wont produce huge horsepower.The standard brakes to be honest seem up to the job,& Im unsure as to weather big brakes are warranted,especially given they will increase the unsprung weight.

[FlashBastd]

How are you planning on fitting a 300mm disc inside a Cossie caliper? Cossie's were all 278mm.

FYI the 2WD Cossie's had 4 pots, the 4WD's had single pistons.

[t783vkj]

......no comment on the actual point I was making then....

[t783vkj]

FYI I was referring to a set of aftermarket AP calipers for the sierra cosworth,that I had found 2nd hand,they run larger than standard discs.

[FlashBastd]

If you can get hold of 4 pots for a sensible price, then go for it. I was pretty underwhelmed by the Mk3 Mondeo AND ST170 calipers.

[ScubaSteve]

i dont think 4 pots will make much difference in all honesty, the problem lies with the master cylinder IMO, which will be proven or not soon

what master cylinder does the frp use?

[FlashBastd]

Both, as the changeover was mid FRP build, and apparently there is little or no difference between them, which is why I kept postponing it. However Jack on zsoc does reckon it has improved things, as does Tedley IIRC.

[ScubaSteve]

thats also the reason im keeping quiet about it, i dont want to go about saying im doing this and that, then others to do it aswell only for it not to work

I have a far fetched theory, which is probably a load of bollocks but i like to think things logically haha

as the early setup only used 238 or whatever they were discs and smaller calipers, so the master cylinder was made stronger to make the smaller brakes better, then when they decided that bigger more progessive brakes were better but thought that the stronger early master cylinder was too overkill with the bigger brakes so put a weaker one on to match the bigger setup

as said probably just me and my over active imagination,lol

but i will give you a 100% honest opinion when i do mine

This post has been edited by ScubaSteve: 09 June 2010 - 10:11 AM

[FlashBastd]

I suspect the later design was just cheaper to make, but then I am cynical!

[ScubaSteve]

saying that im still impressed with my upgrade over the standards, especially for 100 quid or so it cost me all in, although you still have to push the pedal a fair bit to get them working they seem a lot sharper and slow the car noticably harder, also you dont get fade, at all, which was my main gripe with my originals, getting severe brake fade down through Ex-Muhle at the ring convinced me to try something else lol

i did overhaul the calipers before putting them on, wether that made any difference i dont know

This post has been edited by ScubaSteve: 09 June 2010 - 10:48 AM

[t783vkj]

I decided to take the plunge,got out bid on the AP caipers so had to resort to plan B .Standard 4 pot cosworth calipers,posted for £60 the pair.I'd appreciate advise as to which model/mark/year mondeo discs I need to suit the intended installation.

[FlashBastd]

I think you just need 2WD Cossie discs, to go with those calipers.

[t783vkj]

Cheers.

[eldoodarino]

 ScubaSteve, on 09 June 2010 - 09:55 AM, said:

thats also the reason im keeping quiet about it, i dont want to go about saying im doing this and that, then others to do it aswell only for it not to work

I have a far fetched theory, which is probably a load of bollocks but i like to think things logically haha

as the early setup only used 238 or whatever they were discs and smaller calipers, so the master cylinder was made stronger to make the smaller brakes better, then when they decided that bigger more progessive brakes were better but thought that the stronger early master cylinder was too overkill with the bigger brakes so put a weaker one on to match the bigger setup

as said probably just me and my over active imagination,lol

but i will give you a 100% honest opinion when i do mine

for some unknown reason the early servo and master cylinder is MUCH MUCH easier to get a firm pedal on....

I did a guys FRP last weekend (late system).... sure enough after we were all done (been round all bleed screws etc etc) cap back on...pedal was soft as hell..

went out for a spin anyway...

came back

went all round the 4 corners again...

cap off the reservoir....

Pedal SOLID AS HELL..like a brick!

started the engine...test pedal...still solid

cap back on...pedal goes softer again..(but still usable)... no idea why.. really pisses me off....

happened loads of times...just can't do anything about it..

never have this issue with the early one...like a brick everytime...well, unless it's mine...lol

Chris

[ScubaSteve]

hence why im swapping my mates s reg puma early style master cylinder and servo with my later one tomorrow

hes getting my old 258mm brakes out of the deal, dont thin khe really cares too much about soft pedals

will let you know the difference

This post has been edited by ScubaSteve: 11 June 2010 - 05:26 PM