Warped Rotors?

I just got this bike and the only thing I notice that may be wrong with it are the rotors, or so I think. When I am just on the rear brakes I am fine, but if I get on the front brakes I get a pulsing action (ie. stop, go, stop, go) It is actually more noticable at low speeds I think because the rotors are spinning slower. Anyway, I was wondering if anyone has had to replace the rotors? The guy I bought it from has already done the pads all the way around and he thought he did the rotors but wasn't sure. The bike has 37000, so it may have been awhile since he replaced them. What is it going to cost to replace them and should I replace them with stock rotors or are there other options? Thanks, I love this forum.

 

Sounds like they are warped. OEM rotors will be expensive. I would consider aftermarket, maybe even wave-type rotors. My front brakes ahd a spot where it was like they went from light to full on. I just finished a little while ago bleeding my brakes and clutch and the front brake feel is a whole lot better and smoother than before. Anyway....to see if the rotor is warped, remove the front wheel and us a straight edge acros the rotor and look for gaps. There are also tools you can buy that will do the same thing but this is a more simpler way. Removal of the rotor from the wheel may be necessary but most likely not since the mounting points are close to the hub. Someone else here may have a better way to check. I don't know if motorcycle rotors can be turned ot not. I have never tried it.

 

Thanks for the info. I wasn't sure if maybe the brakes did need bled. I bet that is good times with the linked brakes! They don't seem soft though, just off and on like you said.
The old owner didn't even notice it enough to even know there was a problem. He said it may have crept up on him so gradually that he didn't even realize it. I probably won't worry about taking care of it until I put it in the shed for the winter. Thanks for the help.

 

Dial indicator - that's the word for the tool I was thinking of. And mello has a good point that if the rotor is bent, getting the front whel off the ground and spinning it may allow you to tell. Just dont get the tire wear mixed up with a rotor beng bent or warped. I looked at a friends CBR and at first (correctly) I thought he had a bent rotor and I could tell the brake was binding on someting when just roling the bike and applying no brakes. Then I thought it might just be the way the tire wa wearing a (optical illuision and all that). ALso, at some point along the circumferance of the rotor, the brake lever would go all the way to the grip, indicating to me a rotor was probably bent.

 

I had the same problem with my bike when I bought it. I was a little worried about it because I thought it might get worse. I talked to my local motorcycle mechanic, and he said that it is a common thing. His explanation was that when they make the alloy for the rotors, any heterogeniety in the metal will cause uneven expansion when the brakes get hot from use. As a result you get a high spot on the rotor. He also said it shouldn't affect the performance of the brakes and that I would probably get use to it - which I did. It never really did get any worse, if it isn't really bad, I wouldn't worry about it.

Good luck,

Mel

 

Check this out. The Galfers are very expensive and about the same as OEM, but the EBC's are a little ($100) less.

http://www.bikebandit.com/partsband...~product_dept_id~2158588~selection_Path~3.asp

 

Thanks for all of the info. mwohlgem, I have gotten somewhat used to it, but it is still bad enough that I will probably try to take care of it before next riding season. I am going to check it out in the morning and see if it is visibly bent.
Thanks for the link Zonaman

 

good responses so far.

i replaced rotors on my 93 gixxer sixxer out of absolute necessity. two new EBC rotors cost me about $300. you can expect between 150-200 a piece for standard EBCs. they're perfectly fine for street use.

someone mentioned turning them and it is not possible. i looked into it and they are simply to thin. nothing to turn!

it's quite easy to check for warped rotors.

drop the center stand
put a weight on the back seat
spin the wheel​

you're looking for smooth rotation. there'll always be the gliding noise because brake pistons don't disengage, they just stop pushing. you can hold a straight edge against the side of the rotor so it is flush with the braking surface top and bottom. spin it again.

if it's that hard to distinguish, you're in no immediate danger. ride it out for the season and replace them this winter. if its a rough pulse, change em dude

its very simple to do this yourself. maybe 2-3 hours if you have no experience. no more than unbolting from the rim and bolting the new one up!:third: