Custom brake brackets

[Mikes2]

25.4mm for the master cylinder.

[Alistair C]

According to S2central, standard S2s are:

"The asymmetrical piston diameters of 36mm and 44mm ........."

And my 996s are 2x36mm & 2x40mm.......

I'm sure Marco Put up some calculations before as to the leverage advantages with moving over to multi-pots - can't quite remember where though?

[audiman]

Dunno Lee? Talking of pedal travel...... I have very little using my 4 pot setup with SS braided lines all round. They reduce the size of the pistons in these type of setups so the total displacement is almost the same as the std calipers.

Damn clever! LOL

[Lee]

Thanks for the info.

So, in that case here are the leading figures:
Total piston area stock = 2538mm^2 but this area acts on 2 pads.
My 6 pots = 2507mm^2 per side, all 6 pots are 5014mm^2 per caliper but half of that are acts on each pad
Master cylinder = 507mm^2

All numbers rounded to nearest whole integer.

So, to move pads 0.5mm the following master cylinder piston travels occur:

stock (caliper pistons have to travel 1mm due to sliding caliper) = 5.00mm for each corner at the front (0.5 x 2538 x 2 / 507)
My 6 pots = 4.94mm for each corner at the front (0.5 x 5014 / 507)

This is just about voume ratios for the relevant travels.

So this is about the same. Actually, less travel for my 6 pots

Force at pads are as follows for an applied 500N force on the master cylinder piston. Which would be about 10 kilos (100N) force on the pedal for a 5:1 brake lever

Stock: 500N/507mm^2 = 0.986N/mm^2
At caliper 0.986N/mm^2 feeding 2538mm^2 is 2503N applied by the two pistons. The sliding caliper means that the force at the piston is applied to both pads simultaneously so that means 1251N each

My 6 pots:
At caliper 0.986N/mm^2 feeding 2507mm^2 [piston area per pad] is 2472N which is nearly twice the force per pad.

Marco, check my sums as it's been a long day infront of a PC for me!!

[porkkis]

Errm... The standard pistons are 40+45mm. Dunno where Paul has gotten the 36+44 figures

[Pisobiker]

Calculations look correct to me, Lee.

Just as a "quick guide" for everyone:

A) Force transmitted through pot= (fluid pressure) x (pot surface)

this means at same pressure on pedal, if you double pot surface you double braking force.

B) If you double pot surface you'll need to move double the amount of braking oil to have same pot travel

This means having double the braking pedal travel (of course the eventual "sliding" caliper factor must be kept into consideration as Lee pointed out).
But the "real braking travel" on pedal is only the very last few millimeters, while all the previous travel closes brake pump feeding passages and puts all lines and etire system into pressure.

Take also into accont calipers with higher numbers of pots are "thinner" therefore being intrinsecally stiffer. This means less "expansion" of assembly when braking, thus less piston travel to obtain same braking force.

C) Real BRAKING FORCE is the TORQUE applied on the wheel through the disk.
This means that to have the real braking numbers of your system you need to multiply actual force through pots for the radius from center of disk to pont of disk where braking force is applyed.



for anyone interested I put something about it on the "Guides and Top-Tips" section some time ago.


Marco

[martinjs]

Iwas going to post about this when ive finished making them but may as well do it now, im in the process of making 4 pairs of brackets to suit 996 calipers, so 3 pairs will be 'for sale',been trying to get them finished for the last 4 weeks but havent had much spare time.
i have someone maybe interested in a pair to suit a 323mm disk (what im using) and someone for a pair to suit the 314 disk so there will be a spare set available.
if anyones interested let me know what size disk you'll be using and i'll make them to suit.
they'll be to the same spec/material as lees, but slightly thicker as the 996 caliper is quite wide.
cant give a definate price as of yet, till i get a quote for the hard anodising plus you'll need the bolts to go with them which are an oddish size:wacked:
probably be around the £80 mark (per pair)
ill post a pic when they're done.


martin

[martinjs]

meant to say, will the 314 disk clear the 16" avus wheel with this caliper (996)
i dunno if it will

[Lee]

My brackets are 28mm thick, 174mm long and about 75mm wide.

40 quid per bracket from Al6082-T6, helicoiled and hard anodised!! That's impressive. I'd get that price if I was boshing out a very very large run or if I made the design less structurally sound to cut out some CNC steps. Helps if you are not lining a subcontractors pocket, I guess.

I'd be interested to see the pics once you're done. I need to go to the bolt shop this week so I'll get your fasteners then if you still need them.

Lee

[martinjs]

Lee,
im planning on using capheads for the bracket to hub joint, did your source do these>
these brackets are 38mm thick, so am wanting smallest c/bore possible.
could have spent a lot more time putting fancy rads on etc but cant see the point if their not seen, would add to the cost too.
didnt think these calipers were wider than yours, but my measurement from hub mounting face to c/l of caliper mounting hole needs to be 24mm!!
got a friend to get a quote for the hard anodising, but need to make sure that the price was for the correct treatment, does sound very cheap to me too!

martin

[91_S2]

Originally posted by martinjs

cant give a definate price as of yet, till i get a quote for the hard anodising plus you'll need the bolts to go with them which are an oddish size:wacked:
probably be around the £80 mark (per pair)
ill post a pic when they're done.


martin

Martin,

You have an email from me for the last bracket.

Rich

[martinjs]

I've pm'd you richard.

[martinjs]

Heres a pic of one of my brackets, for a 323mm S8 disk,
have been fitting everything today but have had a slight setback
basically all the nearside brake pipe joins were seized solid, so the union on the pipe which enters wheelarch from abs unit is completely knackered (its only brass so is well soft) so will have to replace that whole length of pipe:wacked:
i'll post some pics when its all sorted

[Jamo]

Trust me to find this thread after Martin's gone away for 18 months!

[martinjs]

Im still here, another week till i go.
But i have finished work

What are you after Jamo?