Why do my brakes "swish" and my pads wear strangely?

[Decker]

Hi, all. My bike is running again, but the brakes are acting up. Specifically, though it does stop nicely, there is a near-constant kinda-pulsating "swishing" light-scraping noise coming from the front forks.

After a quick 5-mile ride to get things warmed up and to verify that I wasn't imagining it, I felt the brake rotors. The right-hand rotor had consistent warmth all around. The left-side rotor, was warm over 50% of the circumference and cool over the other 50%. That's not right!

I took the front left brake caliper apart, and was I surprised.

Look at the brake pad wear, for one thing. These pads have about 150 miles on them. The bright, flecked parts are completely unworn, like new. The darker part is worn down as usual.

For another, the brake rotor was touching the caliper bracket. The other photo shows that the rotor was actually scraping the finish off of the caliper bracket. Note inside the forked part of the bracket that surrounds the rotor, the striations/lines rather than straight black finish.

Do you concur with my diagnosis, of a warped brake rotor? Or any other ideas?

 

[focus frenzy]

yep warped rotor, now would be a good time to do that inverted front end you have been dreaming about.

 

[makenzie71]

...or you could buy another set of rotors. I have a couple sets

 

[Nessism]

I'm thinking your calipers are worn; the sliding pins and caliper mounting bracket binding up.

 

[Decker]

...or you could buy another set of rotors

Rather than confess that I don't even know what an inverted front end is, I went for a new rotor. I already found one, an should have it during the week, for $25 incl shipping. Not bad.

Do they have to be replaced in pairs? Being independent I would think not.

 

[makenzie71]

Nah...just the poor one. It's always better to replace a pair, it's just not a necessity.

 

[TheCafeKid]

Nah...just the poor one. It's always better to replace a pair, it's just not a necessity.

For the most part id agree. However, be constantly aware that your bike may one day start pulling very hard to one side under braking. At that point, it WILL be necessary to replace both sides. That is provided that you didnt wreck the first time it happened.

 

[bwringer]

For the most part id agree. However, be constantly aware that your bike may one day start pulling very hard to one side under braking. At that point, it WILL be necessary to replace both sides. That is provided that you didnt wreck the first time it happened.

Oh, so I need to go out and add another front rotor and caliper to my VX800, which came from the factory with only one? (Err...motorcycles don't pull to one side, even if the front brakes are working unevenly. Many GS models only had one front rotor, and there are a few people who have installed mismatched front rotors to convert a single rotor GS into a dual.)


I'd replace the one bad rotor and go on with life. However, I would also try and make VERY sure to understand why it warped -- is the piston in the caliper sticking? Are the slide pins sticking? Are there any missing or incorrect wheel spacers? Are the caliper and caliper carrier mounting bolts OK? Are the wheel bearings OK?


A buzzing noise when you apply the brakes is completely normal. It's the same on any bike with slotted or drilled rotors.

 

[TheCafeKid]

Oh, so I need to go out and add another front rotor and caliper to my VX800, which came from the factory with only one? (Err...motorcycles don't pull to one side, even if the front brakes are working unevenly.)


I'd replace the one bad rotor and go on with life. However, I would also try and make VERY sure to understand why it warped -- is the piston in the caliper sticking? Are the slide pins sticking? Are there any missing or incorrect wheel spacers? Are the caliper and caliper carrier mounting bolts OK?

Jeeez Brian you never let me have ANY fun

 

[bwringer]

Jeeez Brian you never let me have ANY fun

Oh crap, I forgot that every other even-numbered Saturday is "haze teh n00b" day. :twistedevil:

 

[Stefnwolf]

Could be the caliper

Could be the caliper

I'm not convinced your rotor is the main cause of this.
Its probably warped a bit now, but if it was warped enough to bind against the edge of the caliper mount like that, you would have seen it wobbling just by spinning the wheel with the caliper removed. Must be several mm out of true to cause that.

I would guess that providing the wheel is correctly aligned, and the bearings good, that the sliding part of the caliper is seized. When the brake is applied, it pulls the whole caliper, along with the rotor, towards the worn part of the mount. This would also account for your strange pad wear, as pulling the caliper out of line, the top part of one pad and bottom part of the other are the only bits in contact with the rotor.

Even if I'm wrong, give the caliper a good overhaul before you fit the new rotor, and make sure wheel bearings are good, and spacers are correct.
I'd use a new set of pads too, those are trash now.
However, if you decide to try and sand them flat, wear a breathing mask.

 

[mike-s]

My guess would be maybe warping or quite likely the mounting on the carrier is skewed. Best suggestion i have is to take the disc off everything, get a flat peice of glass and put the cleaned up disc on the glass and see if its totally flat or not. If it's straight then i would suggest you measure up the carrier for straightness.

 

[Guest]

Clean and grease everything well. Except the brake pads of course.

 

[Zook]

I agree withe the seized slider/pins.

And, yes, single discs DO pull to one side. especially if there is plenty of fork flexing, ask how I know.

Why do your brakes "swish"?

Maybe they are from San Fransicko?

 

[makenzie71]

I can firmly attest that single disc bikes do NOT pull to one side.

 

[tkent02]

I can firmly attest that single disc bikes do NOT pull to one side.

How could it, there's only one front wheel.
Probably half my bikes have had single brakes, it works fine.

 

[Nessism]

From an engineering perspective there is a torque moment that takes place with only one offset disk. In reality, the amount of force is not significant to cause any problems. Both sides win. Lets move on.

My vote is binding caliper pins. When this happens both the pins and the caliper hanger need to be replaced...which is not cheap.