Tweet
There's a bit of snake oil attached to drilled/slotted rotors IMO, at least as far as motorcycles are concerned. Comparing the benefits that a car sees to a bike is particularly tough. I've been more than a bit skeptical of the trick car rotor tests I've seen as they invariably install new 'recommended' pads when changing rotors so it's not a true 'a-b' test; how much of the improvement is due to the rotors, and how much to the pads? This is rarely answered...
One thing to remember is car rotors are vented, something our bike rotors are not. You'll also notice that when car rotors are slotted, the slots extend to the outside edge. And if they're drilled, the holes vent into the internal venting, not just to the other side of the disc. So in this case, any outgassing actually has someplace to go; unlike a bike, where any gas is trapped in the hole between the two pads. I'm not saying it doesn't help on a bike, but it's simply not as effective. Yamaha tried vented rotors (the early FJ bikes come to mind) but wasn't able to make them work and quickly abandoned them.
Floating rotors? Now 'required' on performance bikes, the 'floating' feature is a waste of money if you're still running stock calipers. A good upgrade if you have rigid-mount (non-floating) calipers, but the OEM floating calipers won't see any benefit from this feature. These do offer a weight loss with alloy centers which will improve ride/handling, but that in itself doesn't offer any real braking gain. It's interesting to note that the rotors 650 Central sells come with 'special' pads and a smaller-bore master cylinder, and I suspect most of the claimed improvement is due to them rather than the rotors. One thing not mentioned either is pad/rotor life.
Rob mentioned honing the master cylinder and caliper; doing the MS is a good idea, but there's little benefit to doing the caliper and you want to be real careful not to enlarge the bore, as this can allow the piston to 'cock' in the bore. Yes, clean the piston bore out and make sure it's smooth, but the critical sealing surface is the piston; if you have pistons with any pitting (and who doesn't?), replacing them to ensure smooth piston movement will restore them to the best operation. I'm not saying that lightly pitted pistons won't work, but they won't be as good. And once you have rust on them, it will be back...
One thing to remember is car rotors are vented, something our bike rotors are not. You'll also notice that when car rotors are slotted, the slots extend to the outside edge. And if they're drilled, the holes vent into the internal venting, not just to the other side of the disc. So in this case, any outgassing actually has someplace to go; unlike a bike, where any gas is trapped in the hole between the two pads. I'm not saying it doesn't help on a bike, but it's simply not as effective. Yamaha tried vented rotors (the early FJ bikes come to mind) but wasn't able to make them work and quickly abandoned them.
Floating rotors? Now 'required' on performance bikes, the 'floating' feature is a waste of money if you're still running stock calipers. A good upgrade if you have rigid-mount (non-floating) calipers, but the OEM floating calipers won't see any benefit from this feature. These do offer a weight loss with alloy centers which will improve ride/handling, but that in itself doesn't offer any real braking gain. It's interesting to note that the rotors 650 Central sells come with 'special' pads and a smaller-bore master cylinder, and I suspect most of the claimed improvement is due to them rather than the rotors. One thing not mentioned either is pad/rotor life.
Rob mentioned honing the master cylinder and caliper; doing the MS is a good idea, but there's little benefit to doing the caliper and you want to be real careful not to enlarge the bore, as this can allow the piston to 'cock' in the bore. Yes, clean the piston bore out and make sure it's smooth, but the critical sealing surface is the piston; if you have pistons with any pitting (and who doesn't?), replacing them to ensure smooth piston movement will restore them to the best operation. I'm not saying that lightly pitted pistons won't work, but they won't be as good. And once you have rust on them, it will be back...
Comment