crossdrilled brakes on new(ish) cerbs & tuscans...
Discussion
My Sep 02 4.2 cerb has cross-drilled brakes. About 50% of time when I break, I get a very strong judder/vibration through the steering wheel. The other 50% it's as smooth as anything. Castle tell me it is a "feature" of recent Cerbs & Tuscans and has to do with the latest disc/pad combo the factory is using... I however find it somewhat disconcerting, on hard breaking sometimes the whole car vibrates and even rattles the windows...
What I don't understand is how it can be silky smooth one moment, then you let the brake pedal come up briefly and brake again, and the friggin' thing vibrates like mad. Does anyone have this as well and more importantly is it curable (Castle don't seem to think so)?
TIA.
Maarten
What I don't understand is how it can be silky smooth one moment, then you let the brake pedal come up briefly and brake again, and the friggin' thing vibrates like mad. Does anyone have this as well and more importantly is it curable (Castle don't seem to think so)?
TIA.
Maarten
Moved to drilled from solid disks on the cerb and no difference in vibration. More likely to be just warped disks - the drilled disks DO warp, contrary to what some folks say, just less so than the solid rotors.
There is allegedly some play in the hub that 'apparently' makes the disks more prone to warping, but the vibration would not be due to the alleged hub play; it's just meant to make the disks warp more easily, which in turn causes the vibration.
As to the on/off nature of the vibration, then I had it too, and there may be a couple of reasons.
1) the warp will get worse when the disks are hot; also the warp can geterate a hot spot on the disk that makes the grip vary ay diferent points, so it might be smooth on cold/cool brakes and worse when hot?
2) the second theory is mine, but I tested it on the cerb and kind of 'proved' it to myself. Basically it could be doen to 'phasing'. The warp/hotspot or whatever is going to make the wheel grip/retard more/less at a certain point in its rotation. If the 'grip' point is the same on both wheels then the whole car will judder more than if it's out of phase. If it's 180 degrees out, then the steering would judder very badly, but the whole car less so. As a test to this theory, test the brakes a couple of times on a straight road and the judder should be fairly consistent. Go round a corner and test the brakes again. Is the judder the same?
Anyway, all just ideas. I'd get the disks checked out to make sure they're running true and get them skimmed if they're not. Only problem is they could be relatively true when cold, but might get worse when hot.
WB
There is allegedly some play in the hub that 'apparently' makes the disks more prone to warping, but the vibration would not be due to the alleged hub play; it's just meant to make the disks warp more easily, which in turn causes the vibration.
As to the on/off nature of the vibration, then I had it too, and there may be a couple of reasons.
1) the warp will get worse when the disks are hot; also the warp can geterate a hot spot on the disk that makes the grip vary ay diferent points, so it might be smooth on cold/cool brakes and worse when hot?
2) the second theory is mine, but I tested it on the cerb and kind of 'proved' it to myself. Basically it could be doen to 'phasing'. The warp/hotspot or whatever is going to make the wheel grip/retard more/less at a certain point in its rotation. If the 'grip' point is the same on both wheels then the whole car will judder more than if it's out of phase. If it's 180 degrees out, then the steering would judder very badly, but the whole car less so. As a test to this theory, test the brakes a couple of times on a straight road and the judder should be fairly consistent. Go round a corner and test the brakes again. Is the judder the same?
Anyway, all just ideas. I'd get the disks checked out to make sure they're running true and get them skimmed if they're not. Only problem is they could be relatively true when cold, but might get worse when hot.
WB
My '03 4.5 does exactly the same thing. Has done it from 0 miles and is said, again by Castle, to be a feature of the latest brake 'development'. Not thrilled about it to be honest and really can't make out why it happens when it does. I've done track days and can get the brakes really hot and they seem fine braking from 150mph with no problem at all then some other random time I'll get some wobble action through the wheel. I can't be sure yet but it seems to be getting better with miles. I was wondering if I was planing off, for want of a better expression, some imperfections in the disk face caused by the cross drilling? This is speculation though with more than a hint of straw clutching. I'm planning to scrap this new disk/pad combo once the warranty expires next year anyway. I'm looking to go to pucka bell mounted grooved 330mm AP jobs and a sensible after market pad.
Could this all be our fault for complaining about the cost of replacement of the old 4.5 brakes resulting in the disk being substituted with a cheaper alternative?
I've got a couple more track days coming up so I'll see if I can get to the bottom of what's going on.
Washy
Could this all be our fault for complaining about the cost of replacement of the old 4.5 brakes resulting in the disk being substituted with a cheaper alternative?
I've got a couple more track days coming up so I'll see if I can get to the bottom of what's going on.
Washy
Dude do not talk to me bout brake problems on my 4.2 '98 has got the lot vibrations so aggresive you are scared to brake but the very next brake application smooth as silk also brake squeel kin-ell people run and hide when i brake
but again not all the time (hot and cold)alike so far atemps to cure have involved all 4 disc's skimmed, 3 different set's of pads in the front 2 in the back now i'm on new discs up front STILL no cure this hub problem is what im looking into at the moment, i'm talking to some guys who skim your disc's while on the car apparently to keep your disc's in line on your car and not the lathe if this fails i'll need new disc's on the rear and a morgage to pay for it all 
but do i love the car hell yes 
but again not all the time (hot and cold)alike so far atemps to cure have involved all 4 disc's skimmed, 3 different set's of pads in the front 2 in the back now i'm on new discs up front STILL no cure this hub problem is what im looking into at the moment, i'm talking to some guys who skim your disc's while on the car apparently to keep your disc's in line on your car and not the lathe if this fails i'll need new disc's on the rear and a morgage to pay for it all but do i love the car hell yes 
)hi all.
speaking to an AP rep,he said : "our discs don't warp. it's TVR issue" .. hmm .. he suggested it was a resonance in the wheel bearing / hub assembly that was causing the fault.
It's a shame you're on the one piece cross drilled disc cos on the early two piece disc there's a very good upgrade for little money.
you can try having the discs lightly skimmed and bedding the pads in properly to see if that cures it (sometimes does) .. be aware that every skim reduces the heat sink ability of the disc though, and the cross drilled discs can crack easier than the plain discs.
a change of pad may help . I only use mintex pads - TVR have tried several AP compounds to little benefit. Pagid are good (part of AP group) but blinking expensive compared to mintex.
If you car's under warranty I'd still be tackling the dealer about it .. after all brakes are safety-critical and if there's judder at the wheel it implies varying braking effort applied to the wheel, a potential lock-up hazard. If the cross drilled discs suffer more than the earlier plain versions insist on a set of those.
Joolz
speaking to an AP rep,he said : "our discs don't warp. it's TVR issue" .. hmm .. he suggested it was a resonance in the wheel bearing / hub assembly that was causing the fault.
It's a shame you're on the one piece cross drilled disc cos on the early two piece disc there's a very good upgrade for little money.
you can try having the discs lightly skimmed and bedding the pads in properly to see if that cures it (sometimes does) .. be aware that every skim reduces the heat sink ability of the disc though, and the cross drilled discs can crack easier than the plain discs.
a change of pad may help . I only use mintex pads - TVR have tried several AP compounds to little benefit. Pagid are good (part of AP group) but blinking expensive compared to mintex.
If you car's under warranty I'd still be tackling the dealer about it .. after all brakes are safety-critical and if there's judder at the wheel it implies varying braking effort applied to the wheel, a potential lock-up hazard. If the cross drilled discs suffer more than the earlier plain versions insist on a set of those.
Joolz
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