Rotor weirdness

The front brakes on this XJ650J weren't working properly when I bought the bike earlier this summer. Despite some trepidation on my part, I recruited the help of a more experienced friend and disassembled the front brake system, with the exception of the caliper.

In addition to some grit and varnish in the master cylinder and the fact that the twin hoses and bracket have been replaced with a single line, I found mud - yes, MUD! - in the caliper.

*sigh*

Sprayed all that out of the caliper, gave everything a reasonable cleaning, put it all back together, and - Lo and behold! - brakes work a lot better!

However...

I noticed that the brake pads had worn at a sharp angle, rather than parallel to the surface of the pads, like this:

|/ /|

Sure enough, the rotor seemed to be passing through the front fork at an angle. It also seems to be extremely close to the outer edge of the fork, rather than in the middle of the space for it (see pics - LARGE!). I included pics of the front wheel mounts, in case you all see something obvious that I'm missing completely...

Rotor through fork:
http://www.neoquasar.org/~rhys/BikePics ... r-Fork.jpg

Front axle, left side:
http://www.neoquasar.org/~rhys/BikePics ... e-Left.jpg

Front axle, right side:
http://www.neoquasar.org/~rhys/BikePics ... -Right.jpg

For this and other reasons, I haven't ridden it since I rebuilt the brakes, but there has never been any pulsing in them, so I don't think the rotor is warped. I'm thinking either there is a spacer missing somewhere, the castellated nut is torqued down far too tight, or the fork is bent.

(Though if the fork was bent, wouldn't it have problems compressing and rebounding? It works perfectly, though both forks need new seals.)

 

Try Lubricating (graphite, some grease) the PIVOT BOLT and the PIVOT BOLT TUBE that holds the rotor. When that little puppy seizes up after sitting for a while, it won't allow the caliper to rotate properly and that may be the cause of your problems......

 

Funny you should mention that because I made the same mistake, too. I thought I had a caliper that was jacked to one side causing the pads to wear exactly as you described. I ordered a set of pads from Bent Bike, and when I got 'em do you know what I discovered? They're cut right out of the package beveled like you described. It's in the design.

Go; ride your bike. It's suppose to be that way.

 

Interesting. It sounds more like a quirk, then, because I also have a parts bike to compare to. While it was extremely stripped down already when I got it, one thing it did have was a front caliper. I took THAT apart and looked at the pads. They were worn evenly.

The front wheel assembly on the parts bike is missing all of the spacers and spedo gears, so I can't use it as a good example of how the rotor should pass through the fork, but with everything loosened, it seemed to pass through dead center and parallel. Coincidence?

I've had this bike for less than a year and being a bike mechanic is definitely more of a hobby than my primary area of expertise, but it did seem to me like that's an awfully small tolerance in that rotor slot if that's the way it's supposed to look. I'm surprised it doesn't grind against the outside edge.

Needs a battery, working blinkers, new mirrors, new plugs, oil change (at least once), gear oil change, new coolant (just kidding)... bike needs some love.

Also needs new forks seals in front and possibly replace the springs, remove the chrome from the (single!) exhaust can and just polish the metal. (Has a 4-into-2-into-1 header.) On and on... But natually, brakes are kinda first!

 

Quirk? Maybe... All I know is I got the brand new set of pads sitting on my desk right in front of me and the pads are wedge-shaped.

Here's a link to Bent Bike's online cataloge. Have a look for yourself. (Mine are the 91-62205 pads.)

 

If you have not yet done so .. DO.. REBUILD the calipers as well.
It makes Huge difference., and imo, really dumb not to.

 

I plan to rebuild the calipers at some point, but I have a limited funds situation and there are a lot of things going on (not all concerning bikes). Fortunately, I do have two calipers to work with, so once I get this bike up to what I consider the minimum, I'll start ordering parts to rebuild the spare caliper. Swap, rebuild first one. Shelve it.

As for the pads and rotor position, I guess I don't have a problem, then! Good deal. That frees me up to concentrate on the intruments for a while (starting with the blinkers and mirrors, which are MISSING).

Once the thing is *properly* street legal, I'll get it some plates and get down to really cleaning it up. Luckily, I should be able to do the same thing with the fork tubes as with the brake caliper. Pull tubes from spare bike. Disassemble. New seals. Get to where I know wtf I'm doing. Get damper rod holding tool along the way. Re-assemble. Swap for tubes on running bike. Repeat.

Thanks for the advice, all!