Discussion
Bang some AP 6 pots on with 330mm floating rotors on solid bells. Put some pagid Yellows or Greys in and short of going to 380mm discs and water cooled monobloc calipers, etc, you probably won't stop quicker. Cost, circa GBP 1500.... a bit more than 500, but worth it. THe M5 is a heavy, wallowy beast at around 1700kg and needs some controlling!
fergus said:
Bang some AP 6 pots on with 330mm floating rotors on solid bells. Put some pagid Yellows or Greys in and short of going to 380mm discs and water cooled monobloc calipers, etc, you probably won't stop quicker. Cost, circa GBP 1500.... a bit more than 500, but worth it. THe M5 is a heavy, wallowy beast at around 1700kg and needs some controlling!
The 330mm AP's are smaller than the stock M5 brakes so I would go for the 380mm kit personally - although £3k is a lot of money for brakes.
The brakes are probably fine - it is the driver using them incorrectly that usually shags them quickly. If you come steaming into the corner and then slam on the brakes then you're not doing it properly. Get some instruction and you will see that although the car feels smoother and you don't brake as hard, you are getting better lap times (not that I condone timing on a stricly non-competitive track day of course).
Oh, and it's also much cheaper than replacing the brakes!
>> Edited by m-five on Wednesday 24th September 15:49
I thought that most race drivers were either 'on or off' with the brakes (in the right part of the approach to the corner obviously - not wishing to unbalance the car) then maybe trail brake through the corner to help settle any understeer? If you trail the brake up to the corner rather than through it surely you just overheat the things that way?
If a car can only corner at one given speed, then the only way to increase the lap time surely is to maximise the time spent at max speed down the straight, i.e. leave the braking as late as possible to allow a greater distance to be travelled in a shortened time?
I agree with your point about the disc size, but how much pad area do the APs allow pad to disc contact with in contrast to the standard brakes. Also do the standard (4 pot?) brakes have independant pistons?
Even if the disc is bedded in properly, both the disc and the pad must be treated as consumables surely? If the disc is properly bedded and allowed to cool evenly, then it will 'wear' rather than warp. If in doubt, get some ducting into the centre of the back of the disc to allow cold(er) air to be drawn out through the vanes?
>> Edited by fergus on Wednesday 24th September 16:05
If a car can only corner at one given speed, then the only way to increase the lap time surely is to maximise the time spent at max speed down the straight, i.e. leave the braking as late as possible to allow a greater distance to be travelled in a shortened time?
I agree with your point about the disc size, but how much pad area do the APs allow pad to disc contact with in contrast to the standard brakes. Also do the standard (4 pot?) brakes have independant pistons?
Even if the disc is bedded in properly, both the disc and the pad must be treated as consumables surely? If the disc is properly bedded and allowed to cool evenly, then it will 'wear' rather than warp. If in doubt, get some ducting into the centre of the back of the disc to allow cold(er) air to be drawn out through the vanes?
>> Edited by fergus on Wednesday 24th September 16:05
Go direct to AP racing and they will make you a set of discs to your specifications. (these will fit on a standard bell for a given hub size...)
NB if you get an 'upgrade kit', make sure you get road rather than race calipers as the race ones do not have the same sort of seals as the road ones and will get shagged more quickly...
>> Edited by fergus on Wednesday 24th September 16:38
NB if you get an 'upgrade kit', make sure you get road rather than race calipers as the race ones do not have the same sort of seals as the road ones and will get shagged more quickly...
>> Edited by fergus on Wednesday 24th September 16:38
I was once told by a very exsperience ex fomula 1 driver/manager that when taking a road car on a track you should do never more than 4 laps if you don't want things to wear out. 1 slow lap to warm everything up. To chargers and then one slow lap to cool everything down followed by a 20 minuite rest to allow the car to cool down before going out again. If you do 10 or more fast laps you will shag a road cars brakes suspension and tyres in no time and the only solution if you want to do this is either go out in a track designed car or upgrade the road car to track spec.
The AP Racing kit is 343mm for standard wheels or 356mm for 18" aftermarket wheel both with 6 pot calipers. I think they come with Ferodo DS2500 pads. The kit for std wheels is CP5555 - 1036
www.apracing.com/roadcar/brakekit/data.asp
Also available are American pads by Axxis, the Ultimate spec would be a good match for the std rear discs. Also Stoptech SS brake lines and good fluid would help (unless they are supplied in the AP kit?). Four wheel kits exist for aftermarket wheels with 4 pot 355mm discs all round or Brembo 8 pot 380mm fronts and Brembo 4 pot 345mm discs for the rear.
www.zeckhausen.com/BMW/E39_M5.htm
No matter what option you should open up the brake ducts as detailed in the following articles to get some cold air to the brakes.
www.bmwm5.com/greg/brake_ducts/
www.louv.tv/cars/m5/ducts/
I am in the process of changing to Axxis Deluxe Plus pads, std discs, SS lines, AP racing fluid and open brake ducts. I should be finished in a couple of weeks.
sohlman's advice is very good for the M5, basically do not do more than 5 or 6 fast laps even with upgraded brakes because the road tyres will overheat and understeer badly then fall apart in chunks. Even top brakes will not like slowing a 1.8 ton car for more than 6 laps.
>> Edited by ColinM on Saturday 27th September 18:59
www.apracing.com/roadcar/brakekit/data.asp
Also available are American pads by Axxis, the Ultimate spec would be a good match for the std rear discs. Also Stoptech SS brake lines and good fluid would help (unless they are supplied in the AP kit?). Four wheel kits exist for aftermarket wheels with 4 pot 355mm discs all round or Brembo 8 pot 380mm fronts and Brembo 4 pot 345mm discs for the rear.
www.zeckhausen.com/BMW/E39_M5.htm
No matter what option you should open up the brake ducts as detailed in the following articles to get some cold air to the brakes.
www.bmwm5.com/greg/brake_ducts/
www.louv.tv/cars/m5/ducts/
I am in the process of changing to Axxis Deluxe Plus pads, std discs, SS lines, AP racing fluid and open brake ducts. I should be finished in a couple of weeks.
sohlman's advice is very good for the M5, basically do not do more than 5 or 6 fast laps even with upgraded brakes because the road tyres will overheat and understeer badly then fall apart in chunks. Even top brakes will not like slowing a 1.8 ton car for more than 6 laps.
>> Edited by ColinM on Saturday 27th September 18:59
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