A question regarding the cross drilled rotors..
Discussion
The car has done 2k miles and i was cleaning it the other day when i noticed that around the cross drilled holes there are some really small little cracks. I have seen this on turbos with much more mileage. But i hadnt expected it to happen so soon. Why does it happen and also does it affect the braking performance..
Any info would be greatly appreciated, cross drilled rotors are new to me
all the best
adam
Any info would be greatly appreciated, cross drilled rotors are new to me
all the best
adam
Cross-drilled rotors, just say NO! The cracks form because the body of the disc heats and cools slower than the outside. This happens for all types of brakes, but seems to be worse around the cooling holes of drilled discs. Not a problem until the cracks join up, but eventually it can weaken the disc to the point that it fails catastrophically. It's happened to me and to several other sprinters. I'd suggest you stick to plain or grooved discs.
Adam.
A thread I started a month ago may be of interest.
www.pistonheads.com/gassing/topic.asp?f=48&h=&t=34201
As an update, following the most recent Bruntingthorpe exploits the car is booked in to have replacements next week, following the cracks growing from 5mm to 8mm. I think it's only sensible with a trip to Nurburg at the end of the month. Porsche GB say these rotors are servicable with hairline cracks upto 7mm. I'd be very interested to hear if your supplying dealer (ie Alois himself) has any suggestions toher than Ceramics which wear out pads too quickly to even last a weekend Nurburg trip
cheers
DAZ
Porsche GB say this is normally caused by an abusive braking style. WTF.
How else can you slow from 190 down to 50 in less than 500 yards at Bruntingthorpe....
>> Edited by dazren (moderator) on Tuesday 6th May 17:52
A thread I started a month ago may be of interest.
www.pistonheads.com/gassing/topic.asp?f=48&h=&t=34201
As an update, following the most recent Bruntingthorpe exploits the car is booked in to have replacements next week, following the cracks growing from 5mm to 8mm. I think it's only sensible with a trip to Nurburg at the end of the month. Porsche GB say these rotors are servicable with hairline cracks upto 7mm. I'd be very interested to hear if your supplying dealer (ie Alois himself) has any suggestions toher than Ceramics which wear out pads too quickly to even last a weekend Nurburg trip
cheers
DAZ
Porsche GB say this is normally caused by an abusive braking style. WTF.
How else can you slow from 190 down to 50 in less than 500 yards at Bruntingthorpe.... >> Edited by dazren (moderator) on Tuesday 6th May 17:52
Paul.
I am currently avoiding the ceramic route as I am aware of a Turbo owning Nurburgring junkie who had problems when he upgraded to such an unacceptable level that he reverted back to the original steels.
Only this weekend over on another forum I read a report of an accomplished Ring driver who had a 526bhp GT2 at the Ring over easter and he had to go to a garage mid weekend to get replacement front pads fitted at a cost of 750 euros. This would imply they may infact not be cheaper to run even if the ceramic discs last as long as they Porsche claim.
With new rotors and pads going on next week I shall be keeping an eye on them over my Nurburg weekend at the end of the month. I am beginning to think the problem with my first set was the two Bruntingthorpe Vmax speed sessions.
DAZ
I am currently avoiding the ceramic route as I am aware of a Turbo owning Nurburgring junkie who had problems when he upgraded to such an unacceptable level that he reverted back to the original steels.
Only this weekend over on another forum I read a report of an accomplished Ring driver who had a 526bhp GT2 at the Ring over easter and he had to go to a garage mid weekend to get replacement front pads fitted at a cost of 750 euros. This would imply they may infact not be cheaper to run even if the ceramic discs last as long as they Porsche claim.
With new rotors and pads going on next week I shall be keeping an eye on them over my Nurburg weekend at the end of the month. I am beginning to think the problem with my first set was the two Bruntingthorpe Vmax speed sessions.
DAZ
Daz,did you ever go down the additional cooling duct route you mentioned ?
When you are at the ring try to clear the clogged brake pad dust from the holes at the end of each day,this is supposed to make a difference.
Thinking about it after a hard day ringing,I don't suppose the above looks too attractive compared to a few beers.
When you are at the ring try to clear the clogged brake pad dust from the holes at the end of each day,this is supposed to make a difference.
Thinking about it after a hard day ringing,I don't suppose the above looks too attractive compared to a few beers.
Daz, I was under the impression that the ceramic discs AND pads would last 100k miles or so, making the cost along the same lines as the reds. In normal driving, with a normal GT2, would this br the case? I suppose any form of proper motorsport, including the ring, will cause major wear.
CS - Haven't got the GT2 cooling ducts yet. Waiting to see if I get any brake fade whilst playing at the Ring. I'm beginning to feel the problems are caused by my antics at Bruntingthorpe in which case I doubt the cooling ducts would offset the pounding I give the brakes in contrast to my mechanically sympathetic driving style at the Ring.
RR - I have read the same about the ceramic rotors that they should last at least 100k miles. I did not read the reports to include the pads lasting the same distance even with just slow numpty road use. From discussions with people who have the ceramic system and occasionally track their cars it appears that the pads are used at least as quickly as the original fit pads to the steel rotor systems.
DAZ
RR - I have read the same about the ceramic rotors that they should last at least 100k miles. I did not read the reports to include the pads lasting the same distance even with just slow numpty road use. From discussions with people who have the ceramic system and occasionally track their cars it appears that the pads are used at least as quickly as the original fit pads to the steel rotor systems.
DAZ
Cross-drilled discs are predominantly for appearance, not performance! Which is why I am amazed that manufacturers of high performance cars still use these in place of grooved discs. To substantiate this look at competition cars – they are scarcely used!
If you regularly perform hard braking on the road or do track days, then you are going to be continually be plagued by this problem. Also using race pads such as Pagids are going to cause the same problem, as excessive heat will be generated. If you do brake hard then I would recommend grooved discs with race pads, otherwise drilled should be fine, but use less abrasive pads. I am not sure if Porsche can supply grooved replacement discs – anybody know?
If you do decide to change then there is no need to go for complete set of new brakes, just new bell and disc. I know that AP will manufacture a bell to fit any car, to which their standard grooved discs will fit. Also, having separate bell and discs reduce the likelihood of warped discs, which I am sure some people will be familiar with if they do a lot of track days.
Also, if you are looking to do track days (Nurburgring included) then you should ensure that there is adequate cooling to the brakes, as there is nothing more frightening than hitting the brakes hard from 150 into a corner and finding nothing there!
Aside - It’s funny when people talk about improving their lap times on track they always talk about increasing the performance! What they seem to forget is that suspension set-up and brakes (as well as driving instruction) will also make a significant difference in lap times and will be safer!
All IMHO!
If you regularly perform hard braking on the road or do track days, then you are going to be continually be plagued by this problem. Also using race pads such as Pagids are going to cause the same problem, as excessive heat will be generated. If you do brake hard then I would recommend grooved discs with race pads, otherwise drilled should be fine, but use less abrasive pads. I am not sure if Porsche can supply grooved replacement discs – anybody know?
If you do decide to change then there is no need to go for complete set of new brakes, just new bell and disc. I know that AP will manufacture a bell to fit any car, to which their standard grooved discs will fit. Also, having separate bell and discs reduce the likelihood of warped discs, which I am sure some people will be familiar with if they do a lot of track days.
Also, if you are looking to do track days (Nurburgring included) then you should ensure that there is adequate cooling to the brakes, as there is nothing more frightening than hitting the brakes hard from 150 into a corner and finding nothing there!
Aside - It’s funny when people talk about improving their lap times on track they always talk about increasing the performance! What they seem to forget is that suspension set-up and brakes (as well as driving instruction) will also make a significant difference in lap times and will be safer!
All IMHO!
If you opted for AP discs and pads, would you also need to change the master cylinders? Also, would the power be up there with the big reds?
Alternatively you could also look into G-Force's ceramic racing brakes:
www.g-force-motorsport.co.uk/PFC/pfc.htm
Alternatively you could also look into G-Force's ceramic racing brakes:
www.g-force-motorsport.co.uk/PFC/pfc.htm
No you wouldn't need to change the master cylinder! I mentioned bell and disc only, not callipers!
If you start changing complete braking systems then you are looking at a few grand, this way it should cost you £350 a corner for the bell + disc. But then you don't have to replace the bell again, just the disc.
I am definitely going down the same route for my car. Just spoke to the guy who looks after the car, and the discs, new two track days ago, are cracking quite severely - maybe one track day left!!!
>> Edited by Mark_H on Thursday 8th May 15:29
If you start changing complete braking systems then you are looking at a few grand, this way it should cost you £350 a corner for the bell + disc. But then you don't have to replace the bell again, just the disc.
I am definitely going down the same route for my car. Just spoke to the guy who looks after the car, and the discs, new two track days ago, are cracking quite severely - maybe one track day left!!!
>> Edited by Mark_H on Thursday 8th May 15:29
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