Brake disc help please
Discussion
Can anyone help? I have a 4.5 Cerbera that has had the standard AP Racing front discs replaced by the new RR/Tuscan cross drilled discs because they were warped (and by then too thin to skim). Now they have warped again - within 750 miles! I have a big argument going on with the factory because they say that I am the only person in the universe to have warped the new style discs. Is this true? Has anyone else had a problem with the new discs?
Interestingly, the new discs' venting vanes are angled, implying that they are/should be handed. In fact, a chat with AP Racing confirmed that if the vanes are angled then (depending on the angle) they should only be fitted to the correct side of the car. In my case, both the warped pair of discs (that have now gone back to the factory via the dealer) AND the replacement discs that I had to buy (because the factory refused to supply free replacements) are near side brakes - ie all four discs are identical and all four should be fitted to the near side. The factory say this makes no difference.
And before you ask, no I didn't do a track day and yes I have run them in properly.
Interestingly, the new discs' venting vanes are angled, implying that they are/should be handed. In fact, a chat with AP Racing confirmed that if the vanes are angled then (depending on the angle) they should only be fitted to the correct side of the car. In my case, both the warped pair of discs (that have now gone back to the factory via the dealer) AND the replacement discs that I had to buy (because the factory refused to supply free replacements) are near side brakes - ie all four discs are identical and all four should be fitted to the near side. The factory say this makes no difference.
And before you ask, no I didn't do a track day and yes I have run them in properly.
quote:
Can anyone help? I have a 4.5 Cerbera that has had the standard AP Racing front discs replaced by the new RR/Tuscan cross drilled discs because they were warped (and by then too thin to skim). Now they have warped again - within 750 miles! I have a big argument going on with the factory because they say that I am the only person in the universe to have warped the new style discs. Is this true? Has anyone else had a problem with the new discs?
Interestingly, the new discs' venting vanes are angled, implying that they are/should be handed. In fact, a chat with AP Racing confirmed that if the vanes are angled then (depending on the angle) they should only be fitted to the correct side of the car. In my case, both the warped pair of discs (that have now gone back to the factory via the dealer) AND the replacement discs that I had to buy (because the factory refused to supply free replacements) are near side brakes - ie all four discs are identical and all four should be fitted to the near side. The factory say this makes no difference.
And before you ask, no I didn't do a track day and yes I have run them in properly.
I suspect your problem is actually nothing to do with warped discs. There's a very interesting article at www.stoptech.com/whitepapers/warped_rotors_myth.htm which suggests a far more likely explanation - and a cure.
that's a great piece of info peter, and is pretty much what i heard had been said by an AP rep. curiously he also commented that there was another possible reason for the vibration on the cerbie and that is a resonance between the hub / wheel bearing assembly. I wonder if this could really be the case bearing in mind that TVR have just recalled almost every cerbie and tuscan with the "thin wall" front hub castings due to the wheel bearing / hub face corrosion cracking the hub alloy casting. now if the casting isn't up to the job and there's hairline cracks appearing this would allow the bearing to move as the AP rep hinted. indeed I've changed these uprights where the casting is only held together by the wheel bearing outer carrier and the brake caliper... alarming stuff.
Also peter .. how much time do you spend on the net finding all this wonderful info for the rest of us?? .. whatever it is please keep up the good work :-)
Also peter .. how much time do you spend on the net finding all this wonderful info for the rest of us?? .. whatever it is please keep up the good work :-)
quote:
Spot on, Beej. As you say, AP discs with angled vents are handed. They need to be fitted to the correct side of the car, so that they scoop air at the top of the disc when the car is moving forward. I was told this personally by a technician in the race department at the AP factory.
That's puzzling, I would expect the rotors to suck air in the middle and blow it out round the outside, rather than the other way round?
yep you should have been recalled as far as I know all cars should be checked. however the first cerbies had a brilliant thick wall casting as std that doesn't need changing, it's maybe after the first year of production that they changed to the weedy casting that's giving all the trouble. it's a free changeover if they need doing, but make sure it's done correctly - I've seen cases of tracking not being checked after or camber, and steering wheels pointing anywhere but straight ahead etc etc...
So it sounds like the vanes should point backwards at the outer edge - but either way, one assumes, they should both be pointing backwards, not (as currently) one backwards and one forwards. My point is; this is how they were delivered from the factory... twice. Has anyone else out there got a Red Rose Cerby that they can check? The factory have said that these discs are NOT handed. AP have said that they are.
Don't confuse the drilling with the vanes. I have Tuscan S discs on a Cerbera and the drilling suggests that they are both left side disks. However, the vanes inside the disk are actually straight so the disks are not handed and will fit either side. Unless your disks are different to mine, check the vanes not the drilling. Direction of spiral drilling makes no difference to the disk.
haha. well after all the talk I actually managed to drag myself across the workshop to look at a pair of rr discs i have on the floor, bugger me backwards if beej isn't right .. they only do them one way, so one side of the car will be fitted the wrong way around. muppets. I've checked with a rr customer of mine and his car is exactly the same ie one the right way and one the wrong way. maybe TVR got them cheap by only buying all one side, or maybe it's a purchasing cock-up at the factory? whichever it's definately a cock-up
:-(
:-(
If you visit the AP Racing web site they clearly talk about handed discs... www.apracing.com/car/brakedisc/identification.htm
Most AP Racing Brake Discs feature Curved Vanes. The brake discs are handed and should be installed with the cooling vanes running back from the inside to outside diameters in the direction of rotation as indicated in the sketch.
Rich...
Most AP Racing Brake Discs feature Curved Vanes. The brake discs are handed and should be installed with the cooling vanes running back from the inside to outside diameters in the direction of rotation as indicated in the sketch.
Rich...
are the discs actually by AP though ..? they don't have AP anywhere on them, and my AP distributor says he's never seen the smaller cerbie disc and suspects those aren't AP .. although he could just be telling me that to keep AP happy .. what's the betting they're just cheap shite though
OK so that sorts out the handing issue but does it explain why my discs started juddering after 750 miles? Probably not. My car is currently at Fernhurst for a service (totally p****d off with them so far) so I asked them if they had come across "warped" new style discs on either a Cerby or a Tuscan. No comment was the reply.. don't want to damage their relationship with the factory.
PS. If its all the same with you Jools I'd rather not take up the buggering offer.
PS. If its all the same with you Jools I'd rather not take up the buggering offer.
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