Uneven wear on brake pads ...

[Roy]

Another - anyone had this or know what might be causing it

I installed new front pads just after xmas; the old ones were evenly worn. My bike isa 2006 streetbob.

Just changed the front tyre and noticed the pads (so because of a broken ankle taking me away from biking for 6 long weeks - this is after 3.5k miles) are unevenly worn. I would usually expect to replace my front pads at least after 10k.

Can't get a decent photo, however if you look at the pads with the locator holes towards the top, then the pad thickness is about 3 mm at the bottom and 2mm at the top.

I have chucked new pads in; the piston action on the calipers seemed okay - no obvious seizing or apparent weakness.

I replaced the fork springs for progressives just after xmas and had accidentally overfilled the fork oil which has been corrected now.

Any clues anyone?

[banquo]

Mine wear evenly on each pad, but the inners on both front and rear wear quicker than the outers (PITA, as you can only see the outers at the rear). If the pistons move freely, could be stiction on the location pins, assuming yours are similar to mine? I use a little copper grease on the pins, and on the back of the pads. Don't know if it does any good, but makes me feel better...

[Trevor]

Problem I have had on a 03 glide was that the pads had worn more on the top than the bottom. The brake became spongy but no amount of bleeding would cure it. I know the disc is a bigger circumference on the outside but I have never heard of it before. It first started about 3k.

[banquo]

That kind of unbleedable sponginess is often caused by the pads being pushed back from the disc, so they have further to travel when the brake is applied. I used to get this on cars, when rust built up on cast-iron discs. When you fitted new pads, the new material was bearing on disc areas where thick rust had built up, and this forced the pads out. As the pistons at the slave cylinder are large diameter, any slight travel at that end results in a much larger travel at pedal or lever. On the Harley stainless discs, rust isn't a problem, but pads can get knocked back by slightly warped discs too. Might be worth getting yourself a dial guage, and measuring for warping on the discs. Warping might explain the uneven wear too, and I've heard of it happening on Glides, especially when heavily loaded, with a lot of downhill work.
Severe rattling can let the pistons withdraw too. If I'm riding a bumpy highland road, sometimes the front brake has a huge travel the first time it's used, and needs pumped to push the pistons back out again. The lever and pedal travel are based on the assumption that the pads skim the disc all the time, and only have to move a tiny amount during braking.

[Trevor]

It was only the original pads, put the pairs together after taking the wheel out and noticed that the backing pads were not parrallel. Changed pads and I have done 4K without any problems. Dial gauge proved the discs as that was what I thought was pushing the pads back slightly.

[banquo]

Non-parallel backings doesn't sound good. Too many issues with Moco brake pads for my liking...