Warped Rotors? Or just over sensitive rider?

[ViperThreat]

Hey Guys, Want your opinion on this.

A few months ago, I started to notice a subtle pulsing in my brakes at low speed - Below 10mph, under really light braking, I could feel the brakes catch & release. Above 10mph, or with anything more than a light touch, the pulsing feel disappeared.

When I jacked up the bike, and free-spun my front wheel, I could hear the rotor making the "shing shing" sound, and could see that the rotor was wobbling slightly (maybe 1/32nd of an inch in movement).

As a result, I tossed on a set of spare rotors I had, and some new pads while I was at it.


3 Months and maybe 300 miles later, I'm feeling the same thing.

I read online that the floating-rotors are supposed to prevent this, but i see conflicting information in my searches.

Can anybody point me in the right direction?

 

[OaklandF4i]

Clean the buttons that allow the rotors to "float".

 

[auntiebling]

you could also have a sticking caliper piston

 

[ViperThreat]

Clean the buttons that allow the rotors to "float".

Do you have recommendations on what to use to clean them? Brake Cleaner? WD40? soap& water?

 

[OaklandF4i]

Soap (degreaser) and hot water. Brake cleaner after. I wouldnt put WD40 on for fear of contaminating pads. This is where I would start. If after the buttons all move freely and the problem persists. Throw a gauge on the rotor to see if its truly warped. If not, then check calipers, wheel bearings and so on.

 

[ViperThreat]

Soap (degreaser) and hot water. Brake cleaner after. I wouldnt put WD40 on for fear of contaminating pads. This is where I would start. If after the buttons all move freely and the problem persists. Throw a gauge on the rotor to see if its truly warped. If not, then check calipers, wheel bearings and so on.

Thanks, will try this tonight.

 

[ST Guy]

The big question is do you feel the pulsing in the lever? Or, do you only feel it through the bike itself like the brakes are grabbing a bit more, then a bit less, then a bit more as the wheel turns.

If the lever is actually pulsing, then you likely have warped rotors. However, what is far more likely is that you have dirty areas on your rotor and that changes the coefficient of friction and thus how effective the brakes are at any given point around the rotor.

This latter scenario is far, far more common than rotors that are actually warped and often a good cleaning and rebedding of the pads and rotors takes care of it.

Dirty rotors will often exhibit what you are noticing. You can feel the uneven braking at lower speeds but not higher speeds. If the rotors were really warped, you'd feel it just the same, only at higher speeds the frequency of the pulsing at the lever would be higher.

I'm betting you have dirty rotors.

 

[ViperThreat]

Honestly dont feel it in the lever so much as I feel it in the seat of the bike.

I've cleaned the bike pretty thoruroughly, even going so far as to steel-wool the brake pads as was suggested on another forum post I saw.

I'll try cleaning again tonight as well.

 

[Donelop]

Not to thread jack but I'm having a similar problem. For me my brake lever feels squishy, and coming to a stop my forks dive and bounce as the rotor pulses with more and less friction. There is absolutely no float in the rotors either, so I'll try to see what i can do with that first.

 

[auntiebling]

Squishy:
assuming you've bled the air out, squishy can be a sign of the rotor pushing the brake pads back because it's actually warped. if that's the case the pistons are too far away. the first bit of lever travel is just extending them to where they should be, THEN contact with the rotor happens.

btw, a pointy object like a pen or pencil can be fastened to the fork leg to check runout. a rubber band works fine. you won't have a number for runout but you'll have a good idea if that's the problem

 

[FLH03RIDER]

Donelop, Viper,

As "auntiebling" suggested check the runout on the rotor(s). If you don't have stands have a friend help you raise/block the bike up so you can easily spin the wheel and check for runout.

As for the Buell there is a good possibility the rotor is warpped, pretty common issue. Most noticeable at low speeds through bike feedback versus the "squishy" brake lever. Loved the ZTL setup on my 1125R but did have to replace the warped disc and pads. If the rotor is ok, bleed / flush the front brake with fresh fluid.

Might also want to look at Eric Buell's site for this mod. http://www.erikbuellracing.com/store/models/xb12/front-brake-rotor-mounting-kit.html

 

[Donelop]

For clarification on what I mean by "Squishy," there's a significant amount of lever travel before I feel ANY resistance at all. Slightly different from air in the system. I've done EVERYTHING to rule out the possibility of air, down to replacing all the washers and banjo bolts to make sure there weren't any cracks or gaps and the problem still persists.

 

[inthewoods]

Buy a rotor hone and clean all that pad residue of your rotors.

 

[bcv_west]

For clarification on what I mean by "Squishy," there's a significant amount of lever travel before I feel ANY resistance at all. Slightly different from air in the system. I've done EVERYTHING to rule out the possibility of air, down to replacing all the washers and banjo bolts to make sure there weren't any cracks or gaps and the problem still persists.

The simple test for air is to put a rubberband compressing the brake lever overnight. If it gets better in the morning, you've probably got air in the system.

If they take awhile, but bite hard when they get there, probably not air. From the sounds of it, you've tried to rule it out. I'd guess you either have not enough fluid in the system, so your pistons are coming back too far, and too much lever travel before they engage. Or, your pistons are sticking. Old seals, dirty pistons. With the pads out and a thin piece of metal between them, do the pistons slide out easily, and back in easily? If so, try adding more fluid with the pistons out a bit, that will put their 'at-rest' position further out, so less travel to engage. If not, rebuild the caliper.

OP, same advice but in reverse. Could be a bit too much fluid so your pistons aren't coming back far enough. Or a sticking piston, as already suggested.

 

[Ironbutt]

For clarification on what I mean by "Squishy," there's a significant amount of lever travel before I feel ANY resistance at all. Slightly different from air in the system. I've done EVERYTHING to rule out the possibility of air, down to replacing all the washers and banjo bolts to make sure there weren't any cracks or gaps and the problem still persists.

Your description makes it sound like you still have air in the system tho.

Maybe your master cyl is leaking internally and it's shagged? It needs a rebuild?