Hey guys,

When I bought my RVF400, the front discs were covered in grease and the bike did NOT stop. Anyways, I cleaned the discs, flushed the fluid and put new DP Sintered HH-rated pads on it. It stops a lot better, however when I'm at less than 40km/h the front end shudders and it feels like the front wheel is going to come off, even when I'm not braking. I can feel slight pulses through the brake lever when it happens. So I'm guessing the brake pads are dragging.

The discs aren't warped and they have ample thickness (3.9-4mm). I've pulled the pads back out and the only thing I can find that's unsual is that the backing of the new pads seem a bit too wide, and they keep catching on the sides of the caliper when I sit them up against the pistons. To sit them in there properly they have to be pushed on completely straight. I'm thinking that maybe one piston is being pushed easier than the other, meaning the pad is pushed out on an angle and it can't retreat back, and is therefore stuck on an angle and half of the pad is touching on the disc?

The wear on the pads look pretty normal now, but when I took them out after I first discovered the problem, on 2 of the pads, only half of the pad had been used.

When I put the new pads against the ones that came out they don't look wider at all, but the difference would be sweet fuck all I'd imagine. The old pads seem to slide in easier, without touching the sides of the caliper.

My questions:
1) Has anyone heard of this problem before?
2) The old pads had a metal backing plate on them with holes in it. Should I take them off the old pads and put them on the new ones? What's the point of them?
3) I was thinking of taking a little bit off the sides of the brake pad backings - what should I use to do this? It probably needs a fraction of a millimeter off each side..

Cheers

1) The pads always drag, although it's a very negligible amount.
2) The old pads with the metal backing was to dissipate heat better, so less heat is transferred to the caliper and then fluid.
3) Don't touch the pads, you are relying on them to save your arse, so don't fuck with them in any way, shape or form.

The old pads were easier to put back into the caliper because they were worn, and hence thinner, so more room to slide them in. Obviously when changing pads, you unbolt the caliper and push the pistons back into the caliper, to help get the pads in and slide it over the disc, then you pump the lever to push the pistons back out so the pads are in contact with the disc.

I'm going to say you need to strip your calipers and clean them all out and replace seals. One of the pistons in your caliper is obviously having a problem moving smoothly, so rebuilding the calipers and replacing seals with new OEM seals will fix your issue, I bet.

I know they always drag, but this isn't normal. So I should reuse the metal backing?

I know the new pads will obviously be thicker, but that's not what I'm talking about in this case. The backing of the brake pads is wider, which means the sides of the pads are hitting the sides of the calipers.

When I push the pistons all the way back, and sit the old pads in place they can move left to right a millimeter or so. These ones can't move side to side at all, so I think they are getting caught on the side when they are meant to return.

I hope I explained it a little better this time.. Here's a diagram to explain what I mean by the width of the backing..



EDIT: Here's a dodgy mockup to explain exactly where it is a tight fit...

Did you buy the correct pads? Don't put the metal backing on the new pads if they didn't come with one.

If the pads don't fit, then you have bought the wrong ones or you have done something wrong.

Which pads are they?

I had some Ferodo pads that were too tight a fit in the caliper. I took the grinder to the backing plate and shaved a few mm off them.

How did you check your discs for runout(warpage?)

It sounds like the discs are warped (or not fitted flush)

I've had pads that fit more loosely than some other brands but they are secured with the retaining pin so can't fall out... only maybe cause a slight 'knock noise' if they move up and down.. this should not cause the pulse or binding feeling though.. I can't see the pads twisting and causing an odd binding due to the retaining pin.

Tape a stick to each fork so it just touches the disc (hardley any touch) and spin the wheel.

If you get a change in rubbing sound then either your discs are warped or they are not fitted properly to the wheel

I'd also be inclined to give the brakes a good service. Strip them right down and give them a good clean. Check all the seals as well and make sure they are in good condition and replace if necessary. It will rule out stuck/dragging pistons.

yes it's probably the pistons sticking !

I tested the calipers one at a time and the pistons are moving quite freely. When I try to pull the calipers off the disc with the new pads they are hard to pull off (because they are caught on the sides of the calipers) but with the old pads they slide off easily, as they should.

So I'm 99% sure it's just because the backing is too wide, and the pad is getting caught on the side of the calipers, and therefore can't retract back. I've ordered some EBC HH-rated pads and will swap them over (I know I can grind them a bit but I choose not to). Hopefully this fixes it! (:

Thanks for all the advice.