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Floating Spline Drive Brakes - Next Upgrade

poppopbangbang

Well-known member
Joined
25 May 2015
Messages
480
I'd like to go to floating discs on my car but everything out there in the aftermarket is a bit "meh", mainly because it's all based on off the shelf motorsport discs and the float is via bobbins which work great on a race car where the brakes are always hot but are mostly annoying on a road car because they are noisy and rattle when you pull up at junctions. The Brembo Track day discs are pretty good but are still £1500 odd which is a hell of a lot for two front discs. Alcon do a kit at £1350 but that uses their 360mm disc (as they don't do a 350 in the right thickness) so you need to ***** around spacing the caliper to use them (and there is no real performance benefit from that small an increase in disc size), plus replacement discs are £450 each.

OEMs like BMW and Merc get around it by having pin drive floating discs where the disc sits on multiple pins arrange vertically from the bell which is great but they are single use i.e. the bells can't be reused so it's an expensive way to do it and not viable for small production. Here's an OEM floating pin drive disc:
11068_x600.jpg


So I've decided to make my own, using a system with a compliant amount of float in it but with an anti-vibration element to stop clacky arrivals at the traffic lights. As always I've looked to F1 for inspiration where for the past few years a spline drive has been used in place of bobbins. Here's Mercs brakes for example:

upmerc1f.jpg


This provides the float required but with less deflection, greater wear resistance, lower weight and reduced failure points. Here's the first draft CAD:



It's a 20 fixing system which captures the disc spline within the rotor spline. The inner retaining ring provides an amount of compliance to allow for float without it being noisy. The disc is used in a GT3 application currently so is well proven. Even better is that replacement discs are around £300 each, so 40 - 50% less than Brembo/Alcon replacement discs and although the bell is a complex piece on tight tolerances as there is no requirement for bobbins the cost is not too different to using bobbins.

I should have them made in a couple of weeks :)
 
Now that's what I call tinkering!! Hat's off to you. Just installed new front discs, pads etc and thought I was doing OK - now firmly back in my lowly place on the tinkerers ladder.
 
coullstar said:
What calipers are these to work with?

I run modified Cayenne 6 pots on mine but the discs are standad 997 Turbo size so this setup will work on 997 Turbo, 996 Turbo & 996 C4S (as a 350mm upgrade), 996 C2/C4 with Cayenne or aftermarket calipers - basically any of the 996/997 which use Turbo size 350mm X 34MM discs.
 
wasz said:
Brilliant 8)

I'm sure you have it in hand, but I just imagined this conversation:

Insurance company: any mods?
popopbangbang: yes, I made my own brake discs
Insurance company: computer says no

Yes I think as the front uprights are laminated with carbon fibre to increase stiffness and there is an extra 30L of fuel where the spare wheel was most normal Insurance companies would be a little concerned by it.

As it is the same company who covers our business operations covers it - I suppose on the basis that if they're covering the public liability of us running F1 cars down the beach front in Spain etc. then a Porsche built by the same people can't be any more risk :D





The brake design I'm producing here is a modification of an 18 bolt application for GT4 (we design a lot of brake components etc. for motorsport). I've gone up on fasteners to allow for some loss of strengh due to aging and corrosion. The bells are way over spec'd for what they are doing and the loads they will see but it's always easier to over engineer and reduce than start on a small strengh multiplier and then have to find ways to increase it!
 
ragpicker said:
Oh my....

....he's at it again.....

:what:

I never really stop - designing new bits for the car is a nice way to spend time when on long flights or waiting around at circuit. It's also had an unplanned break recently as a front wheel bearing failed early so I've refurbed a few bits to avoid it coming off the road in 15K to do them.

Laminated the front uprights with carbon fibre across the high stress areas and replaced the uprights for lower mileage ones with fresh bearings:


Laminated the rear most floor panel as I keep loosing these:


Rethreaded the floor retaining studs to M5 and riv nutted the two push fitting mountings to make it nut and bolt on:


Rebuilt all the Lobros:


Converted the caliper mounting brackets to Ti studs:


(Temp) Changed steering wheels as the airbag kept tripping the SRS light in the old one:


It's never ending - also fresh front brakes, new front TREs, changed the gearbox bush for the upspeced Powerflex one.... not bad going really as it only came off the road on Friday last week :D
 
I'm liking the adjustable suspension and the calipers. Have you a close up photos of them? The caliper looks very machined flat similar to AP Racing in silver finish. What's the story behind them?
 
MNC911 said:
I'm liking the adjustable suspension and the calipers. Have you a close up photos of them? The caliper looks very machined flat similar to AP Racing in silver finish. What's the story behind them?



They are Brembo 18Z Calipers from the Cayenne Turbo S that have been converted to radial mount from lug mount by machining the mounting side of the caliper body down and drilling radial mounts into the body. These then mount to a hard annodised 7075 T6 mounting bracket which adapts the caliper boss spacing and offset of the standard C4 upright caliper mount to suit the modified Cayenne caliper. The flexi - caliper hard line is specific to this setup as there is no standard option that can be used and the flexis are off the shelf HEL.

They are designed to work with the standard (or any disc of the same size and offset) 997 Turbo 350mm X 34mm brake disc.

The original C4 front calipers are now on the rear of the car with 996 GT3 Mk1 330mm discs.

The master cylinder has also been swapped for one of GT3 dimensions but I have retained the standard C4 servo which gives a good balance of minimal travel in the brake pedal vs pedal effort.

It's a very effective setup.
 
Really fascinating, thanks.

My C4 ( a measly 101k miles) has a clonky front CV. Is it a regrease (on or off car) or is it a replacement job?

Cheers Guy
 
Damn, your face must come off when you brake with that set-up :D.

I put Cayenne brembos on a (1600Kg) RS4 and they would almost swap the car around if you braked in a turn.... on a 1300Kg 911; wow.
 

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