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Front disc brake warp

D

dbutler

Just got it firing!
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New member, old problem...plse be patient - it's been a few years since I have been able to get back on the bike, and that old disc warp problem is back. I had it replaced with an "improved" OEM a couple of years ago and of course the fix hasn't worked.
Can anyone happen to remember if there are any other resources to find a better part? The bike is a 2001 Cali EV and I hate bumping along on it to slow down. the dealer is just going to tell me that he is sure is won't happen again. So no go there.

Thanks again for any info anyone can give.

dennis
 
Guzzi uses good quality Brembo rotors on most if not all of its bikes.
First thing to do is find out what is going on. True warped rotors are pretty rare on motorcycles. Bikes don't weigh enough for how much brake capacity they have to normally get that much heat into a rotor. If they are truely warping then finding out why it is happening would be key. Sticking pistons causing brake drag is one possible reason.
More common "warped rotor" issues are either floating buttons that are binding and not allowing the rotor to float properly or uneven pad buildup on the rotors causing a pulsing in the braking action.
You can buy more rotors, but without determining what is going on and why it could just as easily happen again (as you may have already found out).
 
uh ya...good info! thanks for the hints, I'll look at this from another angle...
 
Mine was caused by a sticking piston on my SP that cause 2 warped rotors, even though I changed the fluid each year. Though this bike has fixed rotors unlike yours.

Since rebuild kits aren't available on for the 2 pin 4 puck calipers for my Breva, not sure what on yours. What I do is to bleed the system every year and clean the exposed edge of the piston with brake fluid and a cotton swab. When bleeding the caliper, I push in each piston all the way and fit a closely cut piece of wood between the pistons to get most of the old fluid out. I zip tie the wood in place. Then blow out the rotor buttons with compressed air and tap the rotor with a mallet and listen for a metallic sound to make sure they are not sticking.

Seems like I'm over doing it but a warped rotor can lock up the wheel if you have to brake hard and happen to be over a surface that is wet or has sand on it.
 
If you are in doubt of the interior cleanliness of your calipers, master cyliners, etc, then after draining the fluid, flush the sytem with methyl hydrate. Works like a charm to clean the sludge out.
 
More common "warped rotor" issues are either floating buttons that are binding and not allowing the rotor to float properly or uneven pad buildup on the rotors causing a pulsing in the braking action
Click to expand...

Right you are! The diagnosis is, in almost all cases, wrong. I thought for a long time rotors warped - that was what I was told and it made sense of the pulsing you can feel when the rotors go off. It is, however, not true and a red herring. The late great Carroll Smith in 40 years of racing never saw a warped disc!

The causes are sticky floaters (if you have em), poor break-in, sticky calipers or the wrong pad material for the application causing excessive heat which leads to the pad material overheating and bonding to the disk ultimately forming cementite.

It is certainly not the cast iron discs - it is still the best material for ordinary riding unless you have an F1 budget and can afford carbon-carbon AND use the brakes like Valentino Rossi going to the corner store. The thickness of the rotor is an engineering compromise: there should be sufficient mass there to allow the rotor to fall below the heat range of the pad after the likely longest application of the brake. Poor racers brake longer than is necessary and they are the ones who 'warp' rotors. I have no doubt that brembo - which does the design for Guzzi and Ducati - were very conservative in how much thermal mass was required to do the job.

Take a look at this - Carroll in his inimitable way makes a complex subject understandable:

http://www.stoptech.com/technical-suppo ... ther-myths

Ta,

Chris R
 
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