Changed rear tyre, back brake doesn't seem 100%

[alan0259]

As above, changed it on my CBR 600 F3 (1998) and just took it out for a spin to make sure everythings ok.

On the center stand the wheel spins freely as it should and the back break operates, but when I took it out it just seemed like I had a lot less breaking power than before.

I've had a look at each pad is at either side of the disc, just don't know what else to look at or test?

Cheers

[Dazbo666]

- make sure the brake fluid reservoir is at the right level
- maybe bleed the brake asap if possible
____________________
1st bike (Sept'06 - May'10) : 1991 GPZ500S / Current bike (since Nov 2009) : 2003 Suzuki Bandit 600N
Word of the day : DILLIGAF

[alan0259]

[alan0259]

Forgot to mention, I used about half a tin of WD40 cleaning everything while it was in bits

I didn't touch the brakes with it but could have got some overspray on the disc.

What can I clean this with just to make sure?

[Chalky.]

You should have burnt off your WD40 on your ride if there was some on the disc.

I use a bit of rubbing alcohol, it soon evaporates after.

There should be no need to bleed it.

Check the wheel is aligned correctly, and the top part of the caliper has slotted in to the metal slider as it should on the right hand side.

[jjdugen]

Disk brakes are great, as long as they are properly aligned.
On the rear wheel, there is always the posibiity that the disk is not running exactly center in the caliper (due to slight wheel misalignment). If the disk is at an angle to the pads, it will feel very spongy as the pads have further to travel before biting, and will only have part of the full face of the pads in hard contact with the disk.
Try realigning your back wheel again, loosen it and adjust until the brake pedal feels firm again.
BTW, I align rear wheels by making sure the sproket runs in the middle of the chain and the brake feels firm. I would rather have a slightly misaligned rear wheel with chain and brake properly aligned than try to get an absolutely perfectly in line wheel.
Another BTW. I your front brakes feel spongy, check for air in the lines, of course, but if no improvement, check the alignment of the calipers. Most are out to a certain degree.

[MickC]

[alan0259]

Before I started this thread I only took the bike around the street and brought it back in the garage as I wasn't sure if there was a big problem.

Took it out for 2 hours this morning, after a few miles they went back to normal Can only assume I got WD on the disc...

Another thing I've noticed is that when its on the center stand, if I spin the wheel I can hear a slight scraping noise, is this normal or anything to worry about? There's a couple of inch where it's silent so I'm assuming it's a slightly warped disc as if it was something else it would happen for the whole turn