Brake pads question

[Chris71]

Can you normally wear MTB pads pretty much down to the backing plate?

My front brake seems to have lost some of its power recently. The feel through the lever is the same, but it's not quite as effective and I thought I could start to hear it rubbing so I took the pads out, but actually they don't seem to be that badly worn:



That's a slightly flattering perspective that makes them look like they've got a bit more meat on them than they really have, but still ... shouldn't notice any deterioration in braking at that sort of wear level, should you?

(I have now given the discs a quick going over with brake cleaner, so maybe that will restore things...)

Also, I noticed the discs themselves have a note saying 'resin pads only'. I presume that just means normal sintered metallic pads rather than anything specific?

[cjs]

Have you tried giving the pads a rough up with some fine grit sand paper? Maybe do this and then re-bed them in and see how you get on. Or try swapping the front & back pads? Or just get some new pads, they're only £10 ish a set. What brakes do you have?

[Chris71]

They're Shimano Deore hydraulics.

I've already got a set of spare Fibrax pads (bought for my other bike, but I think they're both Deore...) and I was in the process of changing them when I noticed that the current pads weren't as badly worn as I expected. That got me wondering if you'd expect to wear them flush to the backing plate or if it's normal for them to deteriorate before then.

As it is, I put the old ones back in as I'm guessing the problem lies elsewhere. Thinking about it, I should probably have put them aside as spares and put the fresh ones in to see if that made any difference. didn't think of that at the time.

[Samcat]

I've got a similar brake set-up to you; Deore Calipers with Clarke Discs, and I'm using Fibrax 'Science' pads.
I have also experienced the brake power becoming less, but the lever movement seemed ok , and there was plenty of meat left on the pads.
I put the problem down to glazing on the disc and pad surfaces, so I stripped out the pads and gave them a gentle rub with some wet or dry, and did the same with the disc surface, problem sloved. Just don't forget to bed-in the pads again.

[mk1fan]

Pads wear down to the thickness of the spring used to separate them.

[P-Jay]

Different brakes go to different levels, I've not had any Shimano brakes for years, but I know Avid's can and will go 'to the metal' and somewhat into it too ha ha.

Hope's usually wont.

I would check how centred you're calipers are, and if both pistons are moving at the same rate, you get nice feel from one pad pushing the rotor over to the other pad, without getting any great braking power.

[Chris71]

Samcat said:

I've got a similar brake set-up to you; Deore Calipers with Clarke Discs, and I'm using Fibrax 'Science' pads.

I have also experienced the brake power becoming less, but the lever movement seemed ok , and there was plenty of meat left on the pads.

I put the problem down to glazing on the disc and pad surfaces, so I stripped out the pads and gave them a gentle rub with some wet or dry, and did the same with the disc surface, problem sloved. Just don't forget to bed-in the pads again.

Interesting. Definitely worth a try.

What's the bedding in procedure for these?

Also, good point on the thickness of the spring. The remaining pad thickness can't be much more than that...

[Samcat]

Chris71 said:

Interesting. Definitely worth a try.

What's the bedding in procedure for these?

5 or 6 short sharp stops from about 15mph should do it (without throwing yourself over the 'bars )

[Chris71]

Back on the bike again this morning (with the old pads still in) and, listening harder, there's definitely a faint scraping noise front the front brakes (a bit like V-brakes in the wet). I think that means it's new pads time!

[Chris71]

The new pads are too thick. They were supplied for that bike and they look almost identical when you compare them in your hand, but the pad surfaces are almost touching each other when you put them in and there's not even room to get the disc in between.

I'm assuming the shop just supplied me with the wrong pads, but is there anyway the pistons could be projecting to far out? Is there any form of wear adjustment that needs to be reset or anything?

Apologies, this is turning into a rather commical 'how many former engineers does it take to change a brake pad' thread.

[P-Jay]

Chris71 said:

The new pads are too thick. They were supplied for that bike and they look almost identical when you compare them in your hand, but the pad surfaces are almost touching each other when you put them in and there's not even room to get the disc in between.

I'm assuming the shop just supplied me with the wrong pads, but is there anyway the pistons could be projecting to far out? Is there any form of wear adjustment that needs to be reset or anything?

Apologies, this is turning into a rather commical 'how many former engineers does it take to change a brake pad' thread.

The calipers with 'self adjust' as the pads wear, so you have to push the pistons back in when you fit new pads.

Push the pistons back in so they're flush with the body of the caliper. Then fit the pads, get the caliper DEAD centre of the disc and go from there.

[Chris71]

Doh! I did try pushing them back originally, but obviously not hard enough. Went out last night at about half ten and sure enough a nice big scredriver in the gap levered the pistons back.

Initially they ran fine and I stuck some lights on for a quick ride to bed them in before the commute this morning, but after a few miles they now seem to be dragging a little bit. It's not a lot - you can hear it (faintly) rather than feel it - but they're just close enough to rub on a slight high point. Is that normal?

Please excuse all the numptie questions, I'm not really a simpleton, I promise.

[P-Jay]

Chris71 said:

Doh! I did try pushing them back originally, but obviously not hard enough. Went out last night at about half ten and sure enough a nice big scredriver in the gap levered the pistons back.

Initially they ran fine and I stuck some lights on for a quick ride to bed them in before the commute this morning, but after a few miles they now seem to be dragging a little bit. It's not a lot - you can hear it (faintly) rather than feel it - but they're just close enough to rub on a slight high point. Is that normal?

Please excuse all the numptie questions, I'm not really a simpleton, I promise.

If it's in the first few miles I'd probably ignore any light scraping at this point.

Is is a constant thing, or is it to a beat (if you know what I mean)? sometimes you can warp a disc a bit, but that's usally in really, really heavy use or after a crash.

Carry on with it for a bit, the pads will self adjust to their correct position after a while, or if nothing else wear down to clear.

Have you bled them, or had them bled? you should really bleed brakes with blocks in place holding the pistons completely in, but some people will bleed them with pads in, or worse party worn pads in place, this can overfill the system a bit and the pistons wont go back all the way in, but there a little holes in most systems that will let a tiny bit of fluid leak out if that's the case.

[gp1699]

P-Jay said:

Have you bled them, or had them bled? you should really bleed brakes with blocks in place holding the pistons completely in, but some people will bleed them with pads in, or worse party worn pads in place, this can overfill the system a bit and the pistons wont go back all the way in, but there a little holes in most systems that will let a tiny bit of fluid leak out if that's the case.

i did this, although rushed and on a old set of pads...

a few months past i needed to replace them, totally forgetting about it on a downhill my rear brakes locked up, had to let the pressure out through the nipple on my M4's. luckily my mate had his leatherman on him which i used to crack it off!

[dome]

If it was the original set of pads that came with the brakes then they can be a bit rubbish and fast wearing-your new ones should last a lot longer when bedded in.