dandan

Stoptech

Rotora

KAD KAD 17" Wheel Kit - 6 Piston G caliper on UK front disc (46mm pad depth) with a UK rear setup Braking torque: 7.8% reduction Front/rear bias: 2.7% extra to rear KAD 18" Wheel Kit - 6 Piston H caliper - 356mm disc (46mm pad depth) with a UK rear setup Braking torque: 0.6% reduction Front/rear bias: 0.2% extra to rear KAD 18" Wheel Kit - 6 Piston H caliper - 356mm disc (46mm pad depth) with a UK rear disc and KAD rear caliper (49mm pad depth - can someone confirm this please?) Braking torque: 5.1% improvement Front/rear bias: 3.9% extra to rear KAD 19" Wheel Kit - 6 Piston H caliper - 378mm disc (46mm pad depth) with a UK rear setup Braking torque: 4.3% improvement Front/rear bias: 1.3% extra to front KAD 19" Wheel Kit - 6 Piston H caliper - 378mm disc (46mm pad depth) with a UK rear disc and KAD caliper (49mm pad depth - can someone confirm this please?) Braking torque: 9.9% improvement Front/rear bias: 2.3% extra to rear

AP AP Road Kit CP5555 6 Piston caliper - 356mm (54mm pad depth) with a UK rear setup Braking torque: 0.5% reduction Front/rear bias: 0.1% extra to rear AP Road Kit CP5555 6 piston caliper - 356mm (54mm pad depth) with an AP 330mm rear (44.1mm pad depth) Braking torque: 2.7% reduction Front/rear bias: 1.4% extra to front AP Race Kit Pro5000+ 6 piston caliper - 362mm disc (54mm pad depth) with a UK rear setup Braking torque: 0.9% improvement Front/rear bias: 0.3% extra to front AP Race Kit Pro5000+ 6 piston caliper - 362mm disc (54mm pad depth) with an AP 343mm rear Braking torque: ??% improvement Front/rear bias: ...(need rear caliper info)

Brembo Brembo 6 Piston Monoblock - 14" (51.75mm pad depth) with a UK rear setup Braking torque: 4.6% reduction Front/rear bias: 1.5% extra to rear Brembo 6 Piston Monoblock - 14" (48.7mm pad depth) with a UK rear setup Braking torque: 3.9% reduction Front/rear bias: 1.3% extra to rear Brembo 6 Piston Monoblock - 14" (51.75mm pad depth) with Brembo 13.58" rear and Brembo "C" caliper Braking torque: ??% reduction Front/rear bias: ...(need rear caliper info) Brembo 6 Piston Monoblock - 14" (48.7mm pad depth) with Brembo 13.58" rear and Brembo "C" caliper Braking torque: ??% reduction Front/rear bias: ...(need rear caliper info)

Here are a few comparison figures I have generated for our common big brake kits. All calculations are based on some assumptions and come with some caveats: 1. Pads sit in 0.5mm from the edge of the disc. 2. The same pad compound is used for every comparison 3. All kits are listed as "improvement" or "reduction" with a percentage based on their comparison to the UK spec setup ("improvement" means it is more powerful than UK spec) 4. Front to rear bias change is calculated relative to the UK spec setup 5. UK spec front pad depth = 58mm - could somebody verify this please? 6. UK spec rear pad depth = 49mm 7. Use at your own risk - I worked these out for my own benefit when looking into buying a BBK off the shelf 8. I am sharing the numbers here for interest's sake - not to start any arguments or for anyone to go away and build their own kit based on my calculations 9. If you have any piston diameters or pad depths for the applications where I have gaps in the data then please let me know. 10. Please let me know if you think there are any mistakes or contradictions. 11. This data relates to actual braking capability based on the dimensions of the disc, pad and caliper. There is no accounting for temperature, heat capacity, feel and pad knock back, rotating mass, unsprung mass, caliper stiffness, pad choice etc. Some of these are subjective whereas others can be quantified (another post coming on that soon). I'll add more to this list and fill in the gaps as I get the time and extra info (e.g. Brembo's "C" non-monoblock rear caliper that they sell to go with the 14" monoblock front kit). Rear caliper info is generally very hard to come by!

Yes - you'll get to a point where the pad geometry looks a little off and also the disc will start running very close to the caliper at the extremities. That's not to say a small increase would be impossile though, I've never looked. You could do a lot worse than a floating UK size disc, excellent pads and titanium caliper pistons for a minimum hassle "heat tolerant" approach for a track weapon.

Wez, With the Alcon 4 pot caliper you would need a 356mm disc (that gets you within 0.6%). A 343mm would mean you were 4.8% shy of the UK specs. The Alcon 6pot on a 324mm disc would be 0.4% better than UK's. The Alcon's piston area is actually slightly less but the pad is shallower, increasing the effective radius for brake force squeeze onto the disc is a little larger.

Yes, the piston area is huge and it's very suprising when you start looking around. When you ditch the UK calipers for AP/KAD/Brembos the disc size generally has to get up to ~350mm or more to match the UK's braking torque for identical pad compounds. I know the AMG also uses very deep pads and this reduces the effective radius and braking torque a little bit too....they're not the ridiculous, ABS inducing overkill people seem to think. When I get to work tomorrow I will dig out the spreadsheet and post up some comparisons for our most common big brake kits...plus your Alcon numbers. I may need some pad depths or profiles for some of these brands though...like KAD and D2.

If your ones are the same as the SLR 8 pots then they should be a staggered 32mm and 28mm combo up front in the 8pot beasts. This works out to be a shade smaller than the UK specs...just shy of 99% of the UK's piston area.

Good point, but I haven't come across any calipers that have a bigger piston area than the UK specs yet so I doubt people will run into issues with their master cylinders when swapping out a UK setup. However, I don't have any info for Paul's AMG babies, Stoptech or any 10 or 12 pot calipers yet.

One has four 31.8mm pistons (this is what I have for the rear) and the other has a 41.8 and 38.1mm staggered combo. Their piston area relative to the UK front caliper is 86% for the staggered and 55% for the 31.8mm version. Not off the top of my head but I have it somewhere... If you want - I can tell you what size disc would be needed on the front with the Alcon 4 pot Monoblock to give you the exact same braking torque as the UK setup (with all other things equal such as pad compound).

Paul, Do you know what the piston diameters are in your front calipers? I've got a monster list of caliper piston areas for various brake kits and OEM calipers but haven't found anything about these....

You might think that idle is the time you’d get the least vacuum due to limited exhaust flow but I didn’t see that at all. With just the two exhaust vacuum sources I could get decent enough vacuum at idle to hold a playing card against an open hole on the catch can - no problem. Something to bear in mind with something like this is the exhaust design seems to be very important. I have an oddball exhaust where I can switch between a triple silenced 3" system or a single silenced 4" system. The 4" is only about 3ft long and exits near to the diff area, the extra 3” section continues full length exiting at the back of the car. Obviously the 4" route is far less restrictive - we had an instant boost rise to 1.8bar (rather than the 1.6bar the ecu was trying to hold) when we first set out to do the remapping to suit so it makes a big difference. Point being - this affects the breather system... Before I added a vacuum feed to the turbo intake I could see positive pressure in my catch tank when running through the 3" system...this is bad. With the 4" short and unrestricted exit opened up I got no positive pressure at all irrespective of boost/rpm. (Both gave vacuum at idle as I mentioned before). If I had an exhaust as free flowing as my short 4" section I would have left it at that and stayed with just the slash cuts in the exhaust. However, as I drive round in "quiet mode" quite a lot I added a turbo intake feed to provide additional vacuum for those situations. Basically don’t try tghis system if your exhaust is at all restrictive

I think I would revise my system slightly if for some reason the downpipe etc had to come off the car or I was doing it on another car. My slash cut pipes are a long way down the midpipe and they are plumbed back to the engine bay with hardpipe (aluminium bent to shape the path up past the downpipe). Those two pipes are pretty long, probably around about 5ft each. The one way check valves are right next to the catch can and therefore along way from the heat source in the exhaust. This is great as it means the valves run cooler and I'm sure this is the reason they are lasting without issue. However, I now think that I could shorten the length of the aluminium piping and possibly put the slash cuts into the start of the midpipe or maybe even in the downpipe with only a couple of feet of the aluminium piping to keep the valves away from the heat. The upside to this would be less pressure lost (or in this case gained) along the length of the aluminium pipe giving me a tiny bit more vacuum than I have now with these long pipe routes. However, that is a lot of ballache for potentially negligible gain. Slash cut entry points can be seen in the kit pic; other pic shows the valves. I will get a photo of the intake plumbing and valve at the weekend, I've got a few parts at the powdercoater now so there's no catch tank or intake pipe in the engine bay

Uh oh - the pressure is on

Well done mate!

I have a dash 10 from each cam cover to the catch can, then two dash 8's into the midpipe via one way valves and slash cuts and then I also have one dash 12 to the turbo intake via a third one way valve. I've done about 5k on this setup and haven't fried any one way valves yet. When Ryan gets back I'll aim to do a back to back on the rollers with and without the vacuum to see if there's any measureable difference.

Sorry to hear that Paul, best of luck with the teardown.

I used to really like the look of facelift lights but now prefer the UK specs (or even the prefacelift J spec ones as long as they are immaculate) on most colours as I think they look more modern and inkeeping with today's new cars. IMHO certain cars look better with facelift but on black I definitely prefer the "pre" version. Geo's looks lovely here...

Nice motor, glad it's all sorted again - well done and good luck with the sale. I think it would look great with very dark wheels and also a set of facelift front lights would suit it well (I normally prefer UK or prefacelift but IMHO the darker facelift ones would look nice here).

Good progress mate, keep up the hard graft.

Me too, every time.

Great post - thanks.

What do you mean by wrong?