Hi, there all! I have a quick query. I am getting a scraping sound from my front wheel when pushing my bike, i have lifted the bike and have spun the wheel freely, there appears to be an uneven resistance? probably caused by my front pads or discs? it is stiff at first then spins free again, then stiff again, as if there is a slight buckle in the disc? My question is how much permanent resistance (if any) should there be? many thanks. P.s the pads are good and brakes are working.

 

Could be a couple of things, in order of likelihood (imo)...

Warped rotor, frozen hanger-pin on a caliper or sticky piston behind the pad(s).
If the wheel doesn't have any side-to-side movement at the axle,
it's probably not bad axle-bearings.

If you have average wrenching skills, you could do a little research,
get a manual and do a complete caliper over-haul.
That only involves seals (which are cheap) and is a good idea anyway.
Especially, if it's been a while. The grease in the hanger-pin boots tends to dry out eventually,
and then the calipers quit 'floating'.

Some drag is inherent in the system, since the hydraulics only force the calipers
closed. Not much more than a whisper, though.

Hope this helps, Ern

 

Do you have a dial indicator? A couple quick and free things you might try: resetting the caliper or like Ern said , get a manual and check your service limits for your front rim and brake disc. The service limit for my disc is .30mm (.012 in.)

 

you're always going to hear some of that.... it's called 'kissing'. the brake pads can't be forced all the way off the rotor, otherwise your first lever pull would come all the way back to the bar until you got the brake pads to touch the rotor again. i guess i'd have to check it in person to see if it's abnormal and really inconsistent. sometimes it'll sound a touch louder in one spot than another - and thats okay.


it's not okay when you're riding and you feel the bike lunging during braking. that could mean like ERN said - a warped rotor. you would also feel a warped rotor in the lever as well. it would pulse along with the lunging that you're feeling. that would require, at minimum, new rotors and new pads


if the bike still lunges under braking and you don't feel any pulsing in the lever, it means that there is excessive brake pad build up on the rotors. that would require you to get new pads (unless they're almost new) and lightly buff the rotor with a scotch brite pad or something similar to remove the brake pad build-up that gets on the rotor after a long time.


if your bike is completely normal under braking - i'd say it's just normal kissing. the braking system works when the bike is under way. that should be your judge instead when you're pushing it around the driveway. one thing that causes kissing to become louder than normal is your brake pistons being dirty. when dirty, you'll find that one may stick a little more than the others, causing the back or front of the pad to still touch the rotor a little more than it would/should. they should move evenly with each other. if you haven't cleaned them in a while, take the pads out (remember which one goes to which side), push the pistons out a touch via the lever, and clean them with a soapy old toothbrush, until they are shiny like new.

 

Yep, I think that just about covers it all.