Oh Bugger - Rear Caliper

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morning all and happy easter...

Changed my tyres yesterday and notcied the rear pads were looking pretty nailed so thought I'd change them (£16 from Hein gericke so not bad ).

Having put the caliper and pads back together it doesn't seem quite right.

If I spin the rear wheel it spins but then gets to a sticky part as if the wheel wasn't straight or the disc was warped, and stops. I can move it on by hand but a little effort is needed.

The rear caliper seems to move a bit side to side with the wheel turning - assume this is part of the same issue??? Ran the engine on a paddock stand and you can really see if moving - its only about 3mm movement.

I have checked that the chain adjusters are in the same place and it looks straight?

The rear brake works but has a lot of traval at the mo - could just be down to thickness of new pads?

THe old pads I took out were Nissin pads (originals?) and seemed to have a backing plate fit onto them - should I have reused the backing plates?

Could it just be:

a. wheel isn't straight?
b. new pads not put in properly?
c. Not put caliper back on properly?
d. just needs time to settle in - take it for a test ride and see?
e. something else?

I will prob go for a little bimble today and see if it settles in.

Worrying me a bit as I need to get this sorted by end of April as I am going to the nurburing where confidence in brakes is always a good thing.


Grateful for any help...

Adam

[sirch345]

I'm not sure about the caliper movement, (difficult without seeing it) are you sure the resistance you're feeling is not from a tight spot in the chain and nothing to do with the brake

I wouldn't rely on the wheel alignment marks on the swing-arm to be that accurate, you're better off using a long straight edge or string to check it

You say there is now more travel in the brake pedal than before, that should return to normal after activating it by hand a few times

Chris.

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I will take a little vid of the caliper movement...

Pretty sure its not the chain as it is fairly new and the spot is the same everytime the wheel goes round. I think the chain takes more than one wheel revolution to go completely round if you see what I mean.

I have tried activating the rear brake several times and whilst the brake seems to work it still has a lot of travel (travels as much as pedal allows.

Planning to go for little ride and see if it beds in???

[Pete.L]

Sounds like the disc is warped and it's pushing the pads back

Open up the pads so they are not touching the disc, lift the rear wheel and spin it. Take note of the position of the disc edge. If it wavers back and forth (about three mm did you say) check the rim of the wheel (not the tyre) and see if that's wavering left and right too. If its not it's most likely the disc if it is check your wheel bearings.
Pete.l

[sirch345]

As Pete said it does sound like the brake disc is warped and now that you've said the tight spot appears every complete turn of the rear wheel it would appear it's probably not the chain, although I would still check the amount of up and down movement there is in the chain at the time you hit that resistance. I've not come across a warped rear disc before, as it's normally the front ones that get all the hard work as the rear doesn't usually get that much use in comparison. I was wondering (if the disc is warped) if you may have a sticking piston, or pistons which caused the disc to heat up and distort. When you fitted the new pads did you have any trouble pushing back the pistons to allow extra room for the thicker new pads or did they retract fairly easily.
The backing plates you were referring to sound like anti-squeak shims to me, they will be not much thicker than a baked bean tin and will probably have traces of copperslip grease on them, if that's what they are, it won't matter if you fit them or not as far as brake performance goes

Chris.

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well went out for a short ride (10 miles into Bath and back).

short story is that the back is not binding (as it wasn't getting hot which I assume ot would do if it was binding.

But the back brake is not really working. I suspect that I have made some school boy error in reassembling. The thread of the front caliper mounting bolt (the 14mm one) stripped - the thread in the caliper body that is which is a bit of an ass.

Decided I should prob replace the whole caliper and their was one on ebay for £10 so took the plunge.

AS for the rear disc being warped I would be suprised as well. The piston wasn't hard to push back in when I took the caliper off and as you say they don't get much work compared to front ones.

Rear wheel bearings - no play in the wheel and when it was off the bearings seemed to turn smoothly. According to th manual there is a 'distance collar between the two bearings - that wiggled a bit but I assume that is no big deal???

Thanks

[sirch345]

Perhaps you have air in the system