Ap Discs and pads?
- Thread starter Mikey_Boy
- Start date
Yes, Reyland have the cheapest front discs, followed by Performance Friction then AP. Stick with the standard BMW rears unless you can't get on with the mismatched drilled rear/slotted front look.
TomK managed to crack one of his Reyland discs after a heavy session at a wet Castle Combe trackday, although mine were fine although didn't see a track before selling them recently.
As for pads, it depends on your budget. Pagid RS29s were awesome but for me were too noisy, dusty and expensive, so I was happy with EBC Bluestuff NDX at less than a third of the price, bought direct from EBC. Be aware that neither are RD90 labelled so strictly speaking not to be used as a road pad (they are too good at stopping :roll: ). TBH the calipers are so good that you could probably use blocks of wood as pads and still headbutt the steering wheel with a good prod of the middle pedal.
TomK managed to crack one of his Reyland discs after a heavy session at a wet Castle Combe trackday, although mine were fine although didn't see a track before selling them recently.
As for pads, it depends on your budget. Pagid RS29s were awesome but for me were too noisy, dusty and expensive, so I was happy with EBC Bluestuff NDX at less than a third of the price, bought direct from EBC. Be aware that neither are RD90 labelled so strictly speaking not to be used as a road pad (they are too good at stopping :roll: ). TBH the calipers are so good that you could probably use blocks of wood as pads and still headbutt the steering wheel with a good prod of the middle pedal.
Yes I cracked my Reylands after less than a year, that said I also managed to crack my AP discs previously.
Those who know a lot more about these than I do suggest Performance Friction discs are the best for the AP setup so hopefully 3rd time lucky I won't get a disc that cracks after a year! They come in less expensive than the AP too, but considerably more than Reyland, around £560 a pair iirc.
Martin at http://www.raceparts.biz/ is your man for AP/PF stuff, otherwise Reyland for the cheaper option.
Those who know a lot more about these than I do suggest Performance Friction discs are the best for the AP setup so hopefully 3rd time lucky I won't get a disc that cracks after a year! They come in less expensive than the AP too, but considerably more than Reyland, around £560 a pair iirc.
Martin at http://www.raceparts.biz/ is your man for AP/PF stuff, otherwise Reyland for the cheaper option.
Rs-29.
I'm trying to look into what's going on further. A friend of dave who's a race engineer for AP kindly gave us some temp paint and stickers for the calipers. A brief investigation end of last year showed that the discs were getting close to the upper end of operating temp at about 600c but should have been fine, caliper temps look OK. I'm off to Donnington and spa in the next month so will be doing more checks, fed up of buying discs!
May well invest in some of these and ducting, I believe they can be made to fit
http://www.rennline.com/bmw-cooling-backing-plate-bbk-big-brakes-track-fade-pads/productinfo/HM-157/355MM/
I'm trying to look into what's going on further. A friend of dave who's a race engineer for AP kindly gave us some temp paint and stickers for the calipers. A brief investigation end of last year showed that the discs were getting close to the upper end of operating temp at about 600c but should have been fine, caliper temps look OK. I'm off to Donnington and spa in the next month so will be doing more checks, fed up of buying discs!
May well invest in some of these and ducting, I believe they can be made to fit
http://www.rennline.com/bmw-cooling-backing-plate-bbk-big-brakes-track-fade-pads/productinfo/HM-157/355MM/
They’re pretty expensive Tom. I’ve cobbled together cooling ducts for the front brakes through modifying a method described by Exdos. Mine don’t vent directly into the disc hat as do those in your link, but they are directed onto the discs.
I bought Dave’s AP BBK and Reyland will be making me a set of J Hook rear discs once they’ve restarted production after moving premises. I’m not sure if I’ll fit in any track days before shipping my car to Aus but if I do, I’ll report back.
On a separate note Tom, did you manage to code out the brake assist function?
I bought Dave’s AP BBK and Reyland will be making me a set of J Hook rear discs once they’ve restarted production after moving premises. I’m not sure if I’ll fit in any track days before shipping my car to Aus but if I do, I’ll report back.
On a separate note Tom, did you manage to code out the brake assist function?
Hmm if your getting up to 600degs I reckon the chances are your overheating the rs29s hence braking harder hence killing the discs (I've had a similar issue before on another car where the disc cracked in half).
I'd go for some higher friction pads without a doubt, and some work on the cooling, have you got the backing plates removed? They OEM ones are shite and don't help at all with cooling...
I'd go for some higher friction pads without a doubt, and some work on the cooling, have you got the backing plates removed? They OEM ones are shite and don't help at all with cooling...
It has crossed my mind, however so many other people run with this combo without issues. AP discs are well known to crack so I'm hoping the PFs will be ok in combination with cooling to the disc.RedUn said:
I haven't removed the backing plates so far because I'm a little concerned with the 32mm disc how close it is to the track rod end etc, bearing in mind it is reaching 600c, but you are probably right and I should ditch them
Yes I've seen exdos' great how to for that, very helpful, I know the plates are probably overkill but they do look like they'd do the job properly. Nice to have some matched rotors front and rear, it always slightly bugs me having slotted front and drilled rear but can't face paying AP rear disc price for something pretty much the same as the BMW but 3 x price, maybe I should put a call in to Reyland :scratchhead:BMWZ4MC said:
Re the brake assist, yes that looks to have been done I'm pleased to say, however I haven't tested it yet. I will write up a thread how to once I have, it's pretty simple. 8)
I might tolerate the mismatched discs but my OEM rears are completely shagged after 50K miles including of many, many track miles!
I’ve had them skimmed at least once and there are now tiny cracks propagating from the cross-drilled holes. Somehow they’ve resisted the erosive forces of half a dozen sets of EBC Bluestuff pads on occasion cooked to the point of smoking.
I’m very keen to deactivate the brake assist. It turns braking into an unpredictable affair usually at the most critical point at the end of a high speed straight. I’d like to keep the ABS though - I presume that isn’t deactivated too?
I’ve had them skimmed at least once and there are now tiny cracks propagating from the cross-drilled holes. Somehow they’ve resisted the erosive forces of half a dozen sets of EBC Bluestuff pads on occasion cooked to the point of smoking.
I’m very keen to deactivate the brake assist. It turns braking into an unpredictable affair usually at the most critical point at the end of a high speed straight. I’d like to keep the ABS though - I presume that isn’t deactivated too?
I suspect the surface of the discs is getting hotter than 600 degrees. Where did you put the heat paint? On the rim of the disc?TomK said:
I cracked numerous discs in my old S2000 and spent a lot of time and money getting a disc and pad combination that brought the temperatures down so that the discs survived. Additional brake cooling works, but i don't recommend removing the heat shield as the heat shield is protecting a few sensitive components from the radiated heat.
Higher friction pads are the way to go. However, discs are generally treated as a consumable by race teams so its always going to be an uphill battle finding a combination that gives discs longevity as the higher friction pads usually cost considerably more so you end up trading pad cost for disc cost.
50k! That's pretty good going, are they still above minimum thickness?BMWZ4MC said:
Yes brake, hill and wet pad wipe assists are all individually able to be turned off separate to dsc or abs
I have been close to pulling the ABS fuse in the past I hate the brake assist so much!As AP suggested the paint was on the rim. The final pink paint was for 620c and there was still some pink showing so I suspect I'm running slightly below 600, which is right in the operating range of RS-29.Lower said:
Friction At 300°C 0.47
Friction Max at (@ 550°C) 0.49
Constant working temperature: 400 – 700°C
Max temperature for short period only: 750°C
Do you have any suggestions for a higher friction pad? I'm not aware of many pads that will be able to deal with those sorts of temps, maybe something from endless or project mu, as you point out though I don't really want to be spending much more on pads, £600 is enough
Personally I think the AP cracked because they are well known to and the Reyland, given that I cracked it on a wet day was most likely due to thermal shock from water onto the disc, I have an idea of how that might have occurred. Some additional cooling definitely can't hurt though!
You're looking at it from slightly the wrong angle.
If you go for a higher friction pad (coefficient of friction at 0.4 or higher) you get more initial bite for a lower pedal pressure and the disc/pad temperatures reduce as a consequence. You also don't necessarily want a pad that keeps working at massively high temperatures on a car you're using to track days because you have no way of knowing that you're overheating the discs. A little bit of fade at high temps can actually be a good indicator that you should allow the brakes to cool a bit.
I had success with Dixcel pads in the S2000 (R01 on the front and Z on the back), but i don't know if you can get them for the Z4M and different makes/compounds do seem to perform differently in different types of car so i can't really help with specific advice. It is quite hard finding the proper coefficient of friction figures for some pads so i ended up trying loads and cracked a number of discs along the way. Ferodo DS2500, Spoon, Porterfield R4S, RS9, etc etc. but the dixcel pad on a DBA4000 disc worked the best where the discs survived with excellent braking performance that didn't tail off. Worked well enough from cold too.
If you go for a higher friction pad (coefficient of friction at 0.4 or higher) you get more initial bite for a lower pedal pressure and the disc/pad temperatures reduce as a consequence. You also don't necessarily want a pad that keeps working at massively high temperatures on a car you're using to track days because you have no way of knowing that you're overheating the discs. A little bit of fade at high temps can actually be a good indicator that you should allow the brakes to cool a bit.
I had success with Dixcel pads in the S2000 (R01 on the front and Z on the back), but i don't know if you can get them for the Z4M and different makes/compounds do seem to perform differently in different types of car so i can't really help with specific advice. It is quite hard finding the proper coefficient of friction figures for some pads so i ended up trying loads and cracked a number of discs along the way. Ferodo DS2500, Spoon, Porterfield R4S, RS9, etc etc. but the dixcel pad on a DBA4000 disc worked the best where the discs survived with excellent braking performance that didn't tail off. Worked well enough from cold too.
I don't understand how higher friction pads gives the discs an easier life. From my high school physics, surely you are just converting the kinetic energy of the car to heat energy in the disc. The AVERAGE of the two must match, whichever way you do it to arrive at the same corner speed.
If you use a higher friction pad (which presumably reduces the DURATION of the braking), surely this results in a HIGHER peak temperature but for less time. The thermal shock on the disc is INCREASED! You also get closer to the traction limit of the tyres. Seems a little disingenuous to me, although I'm no expert by any means.
If you use a higher friction pad (which presumably reduces the DURATION of the braking), surely this results in a HIGHER peak temperature but for less time. The thermal shock on the disc is INCREASED! You also get closer to the traction limit of the tyres. Seems a little disingenuous to me, although I'm no expert by any means.
Lower said:
Yeah, I see what you mean. Thing is the friction coefficient is pretty high (0.49) already, I'm also weary of putting anything with even more bite will be like head butting the steering wheel on even the lightest application with these calipers.
The discs should also be able to cope with those temps I was seeing.
I'll see how I get on with some more cooling and perhaps switch to RSL-1 next time round (pagid seem to have a new lineup of pads these days http://www.pagidracing.com/en/products/racing-brake-pads/product-family-rsl.html), I'm hopeful the PF discs will be better in any case.
Cheers