Front brake would pulsate and I assumed it got warped when i accelerated w/ the disc lock on. Got a oem rotor from ebay to replace what i thought to be a warped rotor. Now, the pulsating got a lot better BUT ITS STILL THERE... Did I get a rotor that is less warped than the one i was replacing but still warped nonetheless? Anyway to find out what the heck I should do? [bang]
Was thinking of bleeding but I don't think it would pulsate even if air in the line. I'm stumped.
See if there's any way that you can double check the integrity of the rotor. Place it on an exceptionally flat surface. If it appears to be straight/flat, then check to see if there's actually contact being made when the wheel is spinning. Prop the bike up and spin the wheel around, be very thorough.
I don't actually know what I'm talking about but this seems like the obvious first step.
Hm, well I really didn't want to take it off again but I guess I'll have to. As far as spinning the wheel I did that before I took it out for a test ride. Doesn't seem like it was spinning freely. Got about 2 spins before it would stop. Rotor is definitely rubbing the pad. I'll take it off and see if the other one is making the same rubbing sound.
I got two new 5 hole Brembos. Never been on a bike. ;D
LA
Quote from: uclabiker06 on February 15, 2010, 03:58:03 PM
Hm, well I really didn't want to take it off again but I guess I'll have to. As far as spinning the wheel I did that before I took it out for a test ride. Doesn't seem like it was spinning freely. Got about 2 spins before it would stop. Rotor is definitely rubbing the pad. I'll take it off and see if the other one is making the same rubbing sound.
You should def be able to get more than 2 revolutions on even a light spin of the wheel. Maybe check the torque on the axle nut or check to see if the brake pads are retracting all the way after you release the brake lever. If the pistons are sticking, they will put a lot of drag on the rotors.
My new rotors (ISR dampened) on the wheel removed the pulse I had previously felt at the lever. Also, they are lighter, look great, and really provide loads of stopping.
IMPORTANT NOTE:
With everything torqued to spec, you may not necessarily get a freely spinning wheel. Two reasons:
1) Brake pads/calipers are designed to constantly 'kiss' the rotor when not engaged. You don't pull the lever to move the pistons a distance before the pads contact the rotor. You grab some lever, you get some brake. The pistons just don't retract further than they need to.
2) If your speedometer is driven off the front wheel, as on older Monsters, you will be spinning a set of gears and the cable up to the speedometer. This is not a drag-free system by any means. The spinning wheel is slowed by the speedometer. Is this significant? Yes. To feel it, remove wheel, remove speedo-drive, and tinker with it in your fingers. When you are good and messy, re-grease and reinstall.
Make sure the buttons on the rotors can move, clean the friction surfaces on the rotors with a Scotchbrite and brake cleaner, sand glazing off pads and bed in brakes.
Couldn't the pulsating be the other rotor? (having some built up hard spots?)
Howies advice should fix that, if that's what's going on.
Not an expert, but what about forks or axle bent/misaligned from the mishap?
I has pulsing Brembo rotors I converted them to fully floating and that cured the problem
Um, yeah I don't know... kind of confused. disc lock was on the right rotor and so that is the one i replaced but there is a lot of drag. The lock hit the bottom of my calipers but i don't think it would have done anything to my forks. I also re torqued the front wheel so its not that. We'll see how it goes
Have you already ruled out a damaged caliper? When I took off w/ a wheel lock still on the rotor, the rotor was fine but I busted one of the mounting bolts for the brake caliper.
Caliper mounting screws fit fine; nothing detectable by my eye. Besides if it was the caliper I don't think I would get less pulsating after replacing the rotor. Rotors float back/forth freely.
There is a little notch in the right side of the wheel axle and usually when I replace the wheel I put an allan or something in the notch to keep it in place but I didn't do that this time cuz I forgot.
I figured since my forks aren't adjustable it wont matter if that notch is lined up or not. Would not holding the notch in place while torquing the axle nut make a difference in my torque reading for the axle nut? Just trying to think of all possible angles....
How you tightened the axle is not the problem, you are correct, the notch only matters on adjustable forks. Did you clean the rotors with a Scotchbrite pad and brake cleaner and deglaze the pads? Small amounts of brake material transfer to the rotor. Uneven transfer or brake materials that don't like each other can cause a pulsation. Also, what is the condition of the rotor? Is it excessively grooved? Worn below limits?
Quote from: howie on February 15, 2010, 11:32:31 PM
Make sure the buttons on the rotors can move, clean the friction surfaces on the rotors with a Scotchbrite and brake cleaner, sand glazing off pads and bed in brakes.
+1. Completely solved my pulsing front brake problem. It also greatly improved the braking performance.
Scott
The rotor seems fine. I'm not really good at using my micrometer but it seems fine. Surface is flat to the touch so no grooves. I think I am just going to bleed the brakes and instal a new pair of ferodo platinum pads that i got a while ago. Maybe that will solve the rest of the pulsating issue.
Even with new pads, be sure to scrub the rotors down with brake cleaner and a ScotchBrite pad.
Scott
Ok, so I just took the bike to Nick from Valley Ducati Service. He said the wheel spins freely enough and the drag wasn't excessive. He doesn't think the rotor is bent. He didn't even make me wait to make an appointment... Just took me right in....(THANKS)
Anyways we decided the best thing to do for now is to hit it with the scotch bright and brake cleaner. I went to home depot and got scouring pads. I don't know what scotch bright pad is but Nick showed me and the pads I got from home depot look the same. I should have some brake parts cleaner lying around the house.
So how hard to i need to scrub the rotors? Like for hours or what ? Never done this before
And go through the process to properly bed them in. It's a waste of time if you don't.
edit:
You shouldn't have to spend too much time cleaning. The key is to get an even deposit of pad material on the rotors.
i think for braking performance that a proper bed-in is more important than the cleaning. You want as much friction material all over that-there rotor as possible.
Scrubbed the rotor w/ scour pad and brake cleaner then took out for a test and still pulsates just like i thought it would. >:(
Don't know what else to do so I will install new pads to see if that helps but don't think pulsing has anything to do w/ the pads. Maybe i'll try the scour pad again and rub harder. Thanks anyways to all for the suggestions.
Scotch Brite is a brand name from Scotch brand products. It really is very different from the cheap knock offs that look exactly the same. The pad has a microscopic abrasive (aluminum oxide I think) embedded in the plastic that is amazingly hard and works worlds better than one that's just scrungey plastic. It's hard enough to scratch chrome, ask me how I know ;)
The first time I cleaned my rotors it didn't make a difference even though I had a real Scotch Brite pad and brake cleaner. Then I did it again and scrubbed my heart out. Then worked on every disc button to make sure they moved freely. That and a quick sanding to break the glaze on the stock pads and it was all better.
Cleaning the buttons is obvious, that frees the rotor to move which is what a semi-floating rotor should do. If they stick then you might get some pulsing or other odd vibes. There's some weird science behind all the scrubbing and bedding in.
When you properly bed in brake pads you take a perfectly clean rotor and perform a series of hard braking exercises. These repeated brakings get the pads hot and when they get nice and hot (but not too hot) they start to actually leave a thin coating of material evenly over the rotor. It's this thin even coating that the pads grab and really take hold of, not the steel surface. Getting that coating nice and even takes a series of hard stops followed by a nice long run to cool the discs evenly. If you don't get a nice, thin, even coating then some spots on the rotor have more friction than others and you can get pulsing.
Getting back to cleaning before new pads...
If your pulsing is caused by a warped rotor cleaning won't help. If your pulsing is caused by uneven brake pad deposits on your rotors dropping new pads in may not help. Even if you try to bed them in properly you're doing it over a spotty coating and not on a dead clean rotor surface. You get another uneven coating and pulsing. But now you're convinced the rotors are warped so you order two new ones, drop in your new pads, bed int, and things are fine.
What's the point of all this rambling? Maybe it's the pads, maybe the rotors are warped. Either way, seriously cleaning the rotors, really scrubbing, with the right pad and brake cleaner will take an hour of your time and cost about $10. Pads are usually around $100 and up, discs around $300 and up.
My brakes pulsed so bad I could sweat the rotors were warped. But with those kind of prices I scrubbed the crap out of the discs before I was going to drop that kind of coin. Turned out a good cleaning was all I needed and the braking performance was much improved to boot.
Scott
Don't mean to ramble. I got a used rotor from ebay and installed it to replace the rotor i thought was warped after taking off w/ the disc lock on, yet there is still some pulsing. Thought that was clearly stated.
The scour pads I got are green ones made by 3M. I'll give it another shot and scrub the crap out of them. Didn't scrub to hard initially cuz didn't want to take too much off the rotors and thin them out. I didn't really scrub the buttons though.
The rotors are stainless steel if they are stock. The most you will do is scratch them up a bit, which would be good for bedding. To clean them effectively you should remove them from the wheel. The only resistance in the rotors should be the springs. You might want to search the board for Norm's method to turn semi floaters into full floaters if you don't have a fear hitting expensive parts with a big hammer and like the clang clang of a full floater.
The theory:
http://www.stoptech.com/tech_info/wp_bedintheory.shtml (http://www.stoptech.com/tech_info/wp_bedintheory.shtml)
The procedure:
http://www.stoptech.com/tech_info/wp_bedinperformance.shtml (http://www.stoptech.com/tech_info/wp_bedinperformance.shtml)
Thing is I had more than 8K miles on the bike w/ no problems so I don't think bedding is the issue w/ the current current setup. It was after the disc lock hit that the pulsing started. Thanks for the tips. I know what bedding is and I will definitely bed in the new pads when i instal them. I want my rotors to function w/ out pulsing before I worry about turning them into fully floating...
The green scrubby pads from 3M are the ones you want. Again, cleaning is cheaper than replacing. Even if you don't want to turn them into full floaters cleaning the buttons and making sure they can move and turn is part of this. If all that doesn't work, try the new pads. If it's still pulsing, yeah, you may have a bent/warped rotor :(
Scott