by vCLaW » Wed Jul 04, 2012 11:52 pm
This may depend on what make /model of brakes you are using, worth checking.
The discs shouldn't need cleaning, unless you have somehow got oil / grease / brake fluid on them. If they do need cleaning, you can buy proper disc brake cleaning fluid, or something like isopropyl alcohol or methylated spirits should work. Though don't get any of the cleaning fluid on the pads, it will probably wreck them. If its just mud/dirt on the discs, then just wash it off with water.
Assuming they are hydraulic disc brakes, replacing the fluid and bleeding the brakes may help. Some makes of disc brakes are easy to bleed, others not so much. You can buy the kit and fluid to do it yourself, or it shouldn't cost much to get it done at a decent bike shop.