4 pot brake help needed

[toymex]

Does any one use there standard master cylinder with 4 pot calipers ,i have bought some compbrake calipers that are supposed to be designed to work with standard master cylinder but i cant get them to work i have got a decent feeling pedal but they just dont slow aswell as my old 16v brakes this is a racecar so i need good brakes any help appreciated:thumb:

[novaguy08]

They all bled up ok?
What pads are you using?
everything is clean?

[toymex]

yes m8 bled them loads of times, using pads compbrake supplied hawk hps everything is clean got a good pedal but they just dont slow you as you would expect not as good as my old setup 16v grooved discs,ds2500 pads

[Pistol Pete]

How many miles have you done to bed them in?

[toymex]

its a race car so i have only done a test session but had to call it a day as the brakes were crap just not sure the master cylinder is up to the job i might have to look at a bias box before the first race in may

[Pistol Pete]

They will need time to bed in before they become effective.

[toymex]

i did 4 ,15 min sessions but no improvement ,was starting to get a bit of brake dust so guessing they were bedding in ,i am just unsure whether the master cylinder is man enough and whether anybody has used the original master cylinder effectively with 4 pots

[Pistol Pete]

What master cylinder are you running at the moment?

[toymex]

i think it is a gsi one but am unsure how to tell exactly as it came on my hillclimb sport that was rolled last year

[Stuart]

is there a consistent colour across the disc surface? if not then the pads wont be bed in properly. Did the pads come with instructions? as I know the likes of mintex 1144/55's have different bedding in procedures etc.

Maybe look at a new (not second hand) master cylinder (although the cost of that VS a bias box might make a bias box a better value option).

Also be aware that if they are the same diameter discs/calipers as the 16V stuff, the actual stopping power wont be much different as its all down to the caliper radius rather than number of pistons etc

[novaguy08]

I agree here, your not supposed to belt about a track on a test session to bed pads & discs in, you need to make sure that they are worn in gently to get the full effectivness of them. I know you said its a trackday car but if you use it on the road as well then take it for a cruise for a couple of hours making sure you have plenty of stop & starts, Stuart is also right, you can put 32 pot calipers on there but so long as the surface area is the same you will end up with the same braking power.
If your pedal is still nice and stiff then you dont need to worry about the MC as its a direct connection via the booster so thats not the problem, make sure that the pads are bed in well and truly and if they still not the same then upgrade the pads to something from EBC like red dot The discs stil grooved? same discs you were using from the 16v setup?

[Stuart]

I didnt say surface area ;) the size of the pad dictates wear rates. I was on about the effective leverage (ie disc radius/caliper radius).. you can have a pad the size of a 5pence piece and it will stop the same as a pad the size of the disc, only the one the size of the disc will last more than one stop lol.

fwiw the 1155 bedding in procedure is to get the pads/discs warm with 5-10 30-5mph stops then 8-10 90-30mph stops. DONE

[toymex]

thanks for the replys ,its a race car not a trackday car the discs are grooved and slightly bigger diameter than the 16v stuff ,i am not using the servo and understand that i will need a lot more pedal pressure,the pads were bedded as per compbrakes recommendations and there is even colouring across the discs i am unsure if it is pad material or master cylinder the ds2500 were really good so i might try them but i have got my first race soon and as i cant try them on the road wanted to ask if anyone is succsesfully running 4 pots with the standard m/c that should then take this out of the equation and point to pad material /bedding in