Rear brake mis-behaving

Just finished some work on the bike - oil and filter change, new chain and sprockets and replaced the pads on the rear brake. Bike is an '04 Transalp and something is amiss.

The problem is that the rear wheel is stiff to turn but put this down to the new and cold grease slicked chain and the brake pads not sat quite right.

A spin, literally round the bloke, had the rear disc is rather hot to the touch - uncomfortably so. And this is without using the rear brake - other than to test it worked before setting off. Though the disc didn't take too long to cool down, I'm sure that this ain't right.

The pads are Brembo and the correct ones for this model. But the backing plate for the pads is a little thicker than on the original pads - 4.0mm as against 2.9mm. Curiously, another set of pads that I have (how did that happen?) also has a 4mm backing plate - and they're a different manufacturer.

The pads fitted the caliper ok and the whole lot was a snug fit to get over the disc, but you'd expect this with new pads.

As appears common to this particular caliper, the original "static" pad is hardly worn and the "movable" pad has worn much more.

Confused of Galway.

I have found that un-even pad wear - moving side of caliper as against non-moving side, was caused by either the locating pins sticking in their respective rubber housings or the pad securing pin having worn groves in it. Either or even a combination of these will caused un-even pad wear in my experience.

As for the new pads - how far into the body of the caliper did the pistons have to go before you could get the new pad equipped caliper over the disc?

Could be that you have run out of movement on the piston . . . . . or the piston is stuck and not moving back into the caliper body a bit once the brake has been released.

If not already done, a good clean of the caliper piston would possibly help, moving it as far out of the body of the caliper as is possible without popping past the seal, light coating of silicone grease or some brake fluid, push it back into the caliper and repeat several times till it moves freely. Thats what I do twice a year to my brake calipers, before and after winter use.

Just my mutterings.

Steve T

I tend to keep the calipers clean as a matter of course. A quick clean and the piston slid right back into the caliper with no bother at all.

I also fitted a new pad pin as there was a groove developing in the old one. All other mountings cleaned and greased as required - no problems there.

How about t'other end ... is the master cylinder adjusted for some free play, to allow the fluid back into the reservoir? What's the brake hose like? sometimes, with old age, the lining can deteriorate and form a flap that acts as a one-way valve, restricting fluid flow back to the reservoir. ( It happened to the clutch on the land Rover ... admittedly the hose was probably 20 years old, but stil l....)

Uneven pad wear WILL be caused by the sliding side of the caliper sticking, as Steve says. It happened on my Transalp and is starting on the GS. You need to split the caliper halves and clean and grease the two sliding pins and make sure the rubber boots are good. A new pad retaining pin wouldn't go amiss either. If it isn't seized its an easy job done without needing to undo the hose. If it is seized though the calliper will need to be removed from the bike and some heat and big levers applied. Probably easier to get a new/2nd hand calliper at this point though.

Master cylinder is absolutely fine - and no adjustment possible. Hose is also fine - was replaced with a HEL braided hose some time ago. Anyway, the piston slide back into the caliper with no bother at all. Didn't even spill any fluid from the reservoir.

Caliper cannot be split as it's all one piece.




Caliper pad pin has been replaced with a new one and the other pins thoroughly cleaned inspected, greased and replaced.

Pad retaining spring in the right way round. All rubber boots are sound.

Like I said earlier, the only thing that I found was the new pads having a thicker backing plate - and two different manufacturers have the same thicker thickness backing plate.

Could someone measure the thickness of their pads' backing plates?

A couple of things come to mind although I'm sure you will have already checked.
Is the brake pedal sticking & not allowing the pedal/piston to return?
Is the anti rattle spring that clips into the caliper installed the right way round?
Other than usual binding, or some misalignment somewhere, I guess you need to lift the caliper & pump/release the pedal to see wether the piston extends or retracts, indicating wether the problem is in the piston/hose/pedal/m cyl or in the sliders/misalignment etc.

First port of call would be pedal pivot.

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on my RD400 i had a similar problem , it turned out on the master cylinder where the pipe from the reservoir enters there are 2 holes , one is just a pinhole , it was blocked, and the fluid could not return from the caliper

Mervin said:

on my RD400 i had a similar problem , it turned out on the master cylinder where the pipe from the reservoir enters there are 2 holes , one is just a pinhole , it was blocked, and the fluid could not return from the caliper

Click to expand...

That happened to a chap I know that has a (very nice) CBX1000. It took him ages to find!

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All good with the master cylinder and brake pedal returns as it should. Anti-rattle spring is in the right way round - I have checked. Piston extending and retracting as it should.

Really stumped with this one.

OK, its been a while but I battled with my TA's rear calliper lots of times. IIRC the calliper moves on the pins and associated rubber boots - parts 7/13 & 8/12/16 which screw into the bracket. I betcha these are seized up - item 12 especially. If the calliper can't slide then only the piston side pad will wear as its that side that pressed harder against the disk. Of course your brakes' efficiency is reduced- not that it matters that much on the rear. I seem to remember (and we know how good my memory is) that when I eventually got into mine it was in two halves, but may be confusing that with the front. Good luck

austin said:

IIRC the calliper moves on the pins and associated rubber boots - parts 7/13 & 8/12/16 which screw into the bracket. I betcha these are seized up - item 12 especially.

Click to expand...

All appears good there - but I'll have to have another check. But not today, as I'll be very busy keeping my head down 'cos of Ophelia.

All the calipers are one piece items by the way.

Caliper on the bike, pistons pushed in, pads out. The caliper should slide nice and easily on the two pins. Then put pads in and it should still slide - unless the pin is catching them.

We have a winner! Thanks Austin, I owe you a beer.

austin said:

IIRC the calliper moves on the pins and associated rubber boots - parts 7/13 & 8/12/16 which screw into the bracket. I betcha these are seized up - item 12 especially.

Click to expand...

I was fooled by the state of the caliper pin bolt (item 16) which was pristine and the apparent state of the sleeve (item 12) and the boot (item 8). The ends and inside of the sleeve were fine - but the outside most definitely was not.

Thank goodness David Silver's have the boot and sleeve as a stock item.

Right, on with the packing...........

Oh, and I need a new rear wheel for my bicycle.

We'll never get moved at this rate.

OK, time to 'fess up.

What came out of the caliper -




The new bits that are going back in -




And finally a comparison of old versus new -



I'll take measurements of the new sleeve in case anyone wants to get a stainless one machined up.

A wee bit of west coast corrosion there Tony.

Andy.

outrunner said:

A wee bit of west coast corrosion there Tony.

Andy.

Click to expand...

Yer not wrong there, Andy. There's not a trace of grease inside (what's left of) the boot nor on the outside of the sleeve itself.

You did well to get it out in one piece Tony. When I eventually got round to doing something proper about my seized slider it took loads of heat, levers, drifts, big hammers and eventually drills to get it out. It was right mess and I probably ought to have replaced the caliper - I did buy a used one but it was from a 600 and had the banjo hole was in the wrong place. I suspect this is a common problem on these Calipers as its not immediately obvious that just greasing the pin is not enough. IIRC this design of caliper is throughout the Honda range.

the brembo brakes on my Vigor are no better

If anyone has any doubt as to how the sleeve should slide in the caliper, then have a gander -