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Custom Brake setup
jimgiblett - 9/9/10 at 05:18 PM

I am looking at seriously upgrading the braking on my Alfa project and was hoping that I might be able to get some guidance from the ever knowlegable LCB community to help me self build a solution rater than handing over £750+ for an off the shelf solution.

If I go from 2 pot to 4 pot calipers and want to retain the existing M/cylinders what formula do I use to calculate the piston sizes?

I plan to go for larger disks. If so the pads will be further from the wheel centre and thus have less rotational force exerted upon them so should this be compensated for in either m/c or piston size?

Thanks in advance

- Jim

clairetoo - 9/9/10 at 07:35 PM

Piston area is - pie x (radius squared) x the number of pistons .
As for larger discs - I have changed my Fury front's from the stock 247's to a home-brewed 285mm setup - and the improvement is dramatic , to say the least .
Less pedal pressure gives the same braking effect - all to do with more torque at the contact patch (as in - 20% larger discs gives 20% more braking for the same pad pressure)
As I understand it !

RichardK - 9/9/10 at 07:43 PM

Stole this excel spreadsheet from somewhere! Dont understand it but you might!

Linky

Cheers

Rich

jimgiblett - 9/9/10 at 07:47 PM

quote:
Originally posted by clairetoo
Piston area is - pie x (radius squared) x the number of pistons .


Thanks Claire

So I should try to keep the same piston area to keep the same pressure from the m/c.

I am scouring the brembo catalogue to find a vented setup. And then I'll probably buy a pair of Wilwood midilights.

- Jim

Dusty - 9/9/10 at 08:32 PM

What pads do you currently use? I went from greenstuff to mintex 1144 about two months ago and nearly doubled my braking power!!!!!

jimgiblett - 9/9/10 at 08:39 PM

quote:
Originally posted by Dusty
What pads do you currently use? I went from greenstuff to mintex 1144 about two months ago and nearly doubled my braking power!!!!!


Fair comment on different pads. Not sure of the make, but they are pretty good for what they are. The reason I need to sort the brakes is that I am doubling the power maybe triple.

I think I need more than just a pad upgrade

- Jim

[Edited on 9/9/10 by jimgiblett]

interestedparty - 9/9/10 at 09:05 PM

Worth remembering that as the brakes get bigger, your unsprung weight will go up.

JF - 9/9/10 at 09:20 PM

Usually yes... but not always. quite a few of the large diameter discs have alu centers. And therefor not that much heavier, or in some cases even lighter then the standard discs.

v8kid - 10/9/10 at 05:23 AM

Are you sure you need vented discs? Usually locosts are so light that vented discs do not get warm enough to work properly.

I found brembo catalogue great just cos it gas a good search facility. Ended up with SLK rear discs that after machining only weighed 20% more than the alloy center front discs at 33% of the cost.

Def worth the effort on trolling through the catalogues as there are some unlikely combos that can work well.

Cheers

jimgiblett - 10/9/10 at 06:49 AM

quote:
Originally posted by v8kid
Are you sure you need vented discs? Usually locosts are so light that vented discs do not get warm enough to work properly


This is for my project car which although light by tin top standards (c. 900kg), is still a bit heavier than a 7. With 300hp and some track use planned I thought vented might be a sensible upgrade.

I have been going through the brembo catalogue but havent fount a good alternative so I may try wilwood universal bell and rotor option.

- Jim

interestedparty - 10/9/10 at 07:46 AM

quote:
Originally posted by v8kid
Are you sure you need vented discs? Usually locosts are so light that vented discs do not get warm enough to work properly.


Very good point. IIRC Westfields don't normally have vented discs