Really hot rear brake disc

[Warthog]

I just had a new rear tyre fitted, and at the same time the mechanic noticed I was almost out on my rear pads. So he prised apart the pistons, removed the pads and stuck in some new Bendix (?) ones witha load of coppergrease. When the wheel was back on, he spun in and there was a faint metal on metal sound on the odd turn of the wheel, like a chef sharpening a knife. Wheel turned ok though. So I rode home. Now I have ridden to work, normal commute, using front brakes to do the slowing, just dragging the odd back brake round slow roundabouts and parking etc, and the front discs are lukewarm as you'd expect, but the rear is very hot. Like you can tap it but not hold it hot. There is also a rainbow discolouration of the pads, like when you heat metal with a blow torch. This would suggest to me that the brakes were binding, but when I have it up on my paddock stand, the wheel spins very well. Better than my front did before I cleaned the calipers, it would hardly turn if mounted wrong. So my questions are these:

1) is it normal for new brake pads to go all rainbow colour where they are touching the disc?

2) why is my rear disc so hot if the wheel seems to spin fine??

3) is it damaging i.e. going to warp my disc or set my ar$e on fire??

[petevtwin650]

Hi Nick, I would say the pads are binding except that don't appear to be when it's up on the stand. Maybe they've cooled down and withdrawn slightly by then.

I'd take out the pads and pump the piston out a bit and clean them up. Damage may already be done to the seals though. Sometimes the dust seals get jammed too.

Could definately warp your disc IMO.:(

[the_lone_wolf]

could the disc be bent? when he took the wheel off did he lean it on the disc side?

if it's bent it'll rub against the pads at certain points of the revolutioin, and make that knife sharpening noise

try gently using it, if the pedal feels like it's pulsing it could be that perhaps?

[petevtwin650]

could the disc be bent? when he took the wheel off did he lean it on the disc side?

if it's bent it'll rub against the pads at certain points of the revolutioin, and make that knife sharpening noise

try gently using it, if the pedal feels like it's pulsing it could be that perhaps?

Good point TLW or the disc could've been warped before the pad change.

[Warthog]

Didn't feel noticably juddery, and now the metal scraping noise is gone, it was just the pads bedding in. Basically you can see the pads working with the lever, they break well, wheel spins fine, everything looks good, just it gets mega hot :(. If you spin the wheel, break, then release, they spring back fine and the wheel can turn again. Perplexing...

[G]

Could your foot have been resting on the brake lever by mistake?

[the_lone_wolf]

Didn't feel noticably juddery

it wouldn't feel like a judder, the pedal would pulse slightly, tbh you may well not notice it through a boot. i'd be tempted to fire it up on the paddock stand, bung it in first and let the wheel spin* and then lightly apply the rear brake by hand, as you gently increase the pressure you may or may not feel the pedal resistance changing, but as it's not making the knife sharpening noise i'd be inclined to think it was the pads settling down

*keep pets / kids / loose clothes / treasured anatomical bits away from the moving chain...

[Warthog]

it wouldn't feel like a judder, the pedal would pulse slightly, tbh you may well not notice it through a boot. i'd be tempted to fire it up on the paddock stand, bung it in first and let the wheel spin* and then lightly apply the rear brake by hand, as you gently increase the pressure you may or may not feel the pedal resistance changing, but as it's not making the knife sharpening noise i'd be inclined to think it was the pads settling down

*keep pets / kids / loose clothes / treasured anatomical bits away from the moving chain...

That sounds like a good test for the juddering. I could see when they were fitted that they pressed unevenly against the disc (as the disc and previous pads had been so worn down together and the pistons had to be completely pushed back again). Now they seem to sit fine and evenly. When the mechanic pushed the old pads apart, some brake fluid squirted out of the reservoir. Don't think that has anything to do with it, as the brakes are too good, not too bad! Maybe loosen the lid in the reservoir to releive some pressure if there is any? TBH, all this would be something to do if the wheel was clamped tight, but it seems fine :(.

[Sosha]

That sounds like a good test for the juddering. ......

It ain't "Juddering" it's "gently pulsating" (ooer) & believe me - I am now fully qualified in how to tell the difference.....

[Sosha]

When the mechanic pushed the old pads apart, some brake fluid squirted out of the reservoir. Don't think that has anything to do with it, as the brakes are too good, not too bad! Maybe loosen the lid in the reservoir to releive some pressure if there is any? TBH, all this would be something to do if the wheel was clamped tight, but it seems fine :(.

Wider pads mean pistons pushed in further - which means less space for brake fluid - worth checking resevoir not overfilled and wapping lidd off.

[the_lone_wolf]

It ain't "Juddering" it's "gently pulsating" (ooer)

what he/she said^^^

could be described as a throbbing perhaps;)

[Sosha]

or "Flexing".... :smt104

[Warthog]

Well what ever it is, I don't think the disc is warped yet, jus that it is hot and might warp soon! I am going to go outside and take the caliper off, see if I can see anything...

[Warthog]

fixed! I think ;)

I dismantled eventually using cruddy work tools, and found that (bear with me as I don't know the right names for things!) the little thin metal assmbly that sits behind the pads, kind of springy, had gotten mashed when the new pads were put in, so half of was bent in sticking between the pads. This was then rubbing against the top of the brake disc, so much so it had worn a shiny disc-sized groove into it. This was then superheating the disc and making my pads go a rainbow colour. I took it out, straightened it with some pliers and put it back in behind the discs. It seems well out of the way now, but when I tested it up and down the car park, I was braking heavily, making my rear wheel skid, and so when I felt it it was hot again #-o. Now I just have to let them cool down, then ride normally and hopefully it will be fine. Rear wheel spins fine again now too.

Question: Do I ring up the mechanic in question and bollock him or ask for a discount?? It was an honest unlucky mistake, but we were spinning it and both heard the metal noise at first...

[the_lone_wolf]

brakes will get very hot when you use them, jump off the bike after a gentle ride and spit on your finger then quickly touch the disc, it'll probably boil and hiss because the disc is so hot. sounds like you found the cause

[petevtwin650]

Call them and at least give em a b0ll0cking, then ask for a discount:D

Sean C had a similar thing with his front pads on his last fateful rideout. Mechanic there had assembled one of the fronts wrongly. Luckily Tilt sorted that out for him. Make you wonder about these "mechanics" sometimes. :smt013:smt067:smt075

[Alpinestarhero]

Call them and at least give em a b0ll0cking, then ask for a discount:D

Sean C had a similar thing with his front pads on his last fateful rideout. Mechanic there had assembled one of the fronts wrongly. Luckily Tilt sorted that out for him. Make you wonder about these "mechanics" sometimes. :smt013:smt067:smt075

Definatly; there was a guy at uni with a bandit who had his bike serviced, and the mechanic hadnt torqued up the rear caliper bolt correctly. It had vibrated loose, then the whole caliper was flapping about on the wheel.

I only let my dad fix my bike, and I am trying to learn as much as I can to be able to do it myself - I think possibly I could trust a few of you lot on here aswell. I find it very hard to trust anyone with fixing something on my bike which, if it isnt done properly, could result in an accident and my injury.

[Warthog]

http://alpha-sports.com/suzuki_parts.htm

According to this it is number 4 part the ".spring, pad" on the rear caliper that was mangled.

[Warthog]

Definatly; there was a guy at uni with a bandit who had his bike serviced, and the mechanic hadnt torqued up the rear caliper bolt correctly. It had vibrated loose, then the whole caliper was flapping about on the wheel.

I only let my dad fix my bike, and I am trying to learn as much as I can to be able to do it myself - I think possibly I could trust a few of you lot on here aswell. I find it very hard to trust anyone with fixing something on my bike which, if it isnt done properly, could result in an accident and my injury.

Well I try and do most stuff myself, but as he was changing the tyre, he noticed the pads were gone so I thought lets just bung new ones in as I have an MOT booked tomorrow morning. Just thought he would do it right!

[Alpinestarhero]

Well I try and do most stuff myself, but as he was changing the tyre, he noticed the pads were gone so I thought lets just bung new ones in as I have an MOT booked tomorrow morning. Just thought he would do it right!

Na, I'm not questioning you for a second :D I would expect someone to do it properly too, and not only that, to investigate any abnormalities after doing something...like metal-on-metal noises :smt104