Front brakes were dragging when stopping hard, discovered that the left outside pads were shot, one was nearly to metal. Strange thing is, the right side pads (both inner and outer) look nearly new, with 15K miles on the bike. It seems pretty obvious that the left brake assembly is doing all the work, while the right assembly seems to be almost new. changed all the pads, bled the brakes, including loosening all the line connections and bleeding, in case there might be air trapped. was thinking that maybe air in the right side lines might cause the left side to do all the work, but very mimimal air bubbles observed when bleeding either side.
loosened the caliper bolts, and before tightening, ran the bike forward a bit and clamped down on the front brake to hopefully center the pad and rotors.  went for a test ride and, when I stopped, I felt both front rotors. the left side rotor was much hotter than the right side, which was nearly cold.
appears that the left side is still doing all the work.
any suggestions on how to balance the braking on both sides? seems like I have only a single disk in the front right now.

would appreciate suggestions, advice, experiences, etc.
thanks
Ron
08 C-14, Penrose, Colorado

It sounds like the pistons on the right caliper are stuck or frozen in place. It happens sometimes, especially when motorcycles are not ridden for a while and the brake pistons develop a small line of corrosion against the seal. The only way I know of to fix it is to remove the pistons from the caliper, clean and inspect all of them for any flaws, corrosion, discoloration, etc. and reinstall them. Also check the seals to be sure they are clean and do not have a ring of debris along the outside edge. Finally, thoroughly clean and dry all parts including the calipers themselves, wet the seals and pistons with new brake fluid and reassembly. Some people do not think a brake seal should be used again after removal but I have done it successfully for many years. Oh and by the way, check the seal slots in the calipers to make sure there is no debris or corrosion down in the groove as that tends to make the seal grab the piston harder than it should.

You should be able to move all pistons in the caliper with nothing more than thumb pressure. If they are more difficult to move than that, something is wrong and will need to be addressed.

You can buy seals (both the main seal as well as the outer or dust seal) as individual components, as you can with pistons. So after you inspect all the parts you will only need to replace anything that is worn, damaged or unserviceable in some way. You do not have to buy everything new to refurbish a caliper.

Brian

Front brakes were dragging when stopping hard, discovered that the left pads were shot, one was nearly to metal. Strange thing is, the right side pads look nearly new, with 15K miles on the bike. It seems pretty obvious that the left brake assembly is doing all the work, while the right assembly seems to be almost new. changed all the pads, bled the brakes, including loosening all the line connections and bleeding, in case there might be air trapped. was thinking that maybe air in the right side lines might cause the left side to do all the work, but very mimimal air bubbles observed when bleeding either side.
loosened the caliper bolts, and before tightening, ran the bike forward a bit and clamped down on the front brake to hopefully center the pad and rotors.  went for a test ride and, when I stopped, I felt both front rotors. the left side rotor was much hotter than the right side, which was nearly cold.
appears that the left side is still doing all the work.
any suggestions on how to balance the braking on both sides? seems like I have only a single disk in the front right now.

would appreciate suggestions, advice, experiences, etc.
thanks
Ron
08 C-14, Penrose, Colorado

I was thinking maybe that was the problem. when I replaced the pads, the right side pistons compressed fairly easily, but I've been riding in the rain quite a bit the last couple of months and maybe it's time to pull the calipers apart.
I'll dig in and do some cleaning this weekend:)

thanks a lot
Ron

IIRC the brake hose goes to the left side caliper and then loops over the fender to the right caliper, or is it vice-versa?
If that hose over the fender were kinked or blocked then that could also cause the problem.
You can test easy enough by bleeding a half pint or so of fluid through the right caliper.
If it doesn't want to bleed through then ya have a blockage.
Seized pistons are a possibility but less likely unless the left side ones are not returning and therefore it's dragging on the left side. This would cause more heat & wear on the left side.

Hose goes right over to left side, good thought, tho. Hose is in good shape, bled just as smoothly as the other side. was 'hoping' to see more air in the crossover line and that would fix it, but no joy.

Will try the remove, clean, and replace thing this weekend and advise.

removed calipers, disassembled and replaced all seals last week. bled brakes, (speed bleeders are my friend) including all banjo joints. pistons all seemed perfect. went for short test ride and then longer ride (50 miles to work) and the right rotor is still quite a bit warmer to the touch than the left at end of ride. I think that is telling me that the left brake is still doing more work than the right brake:( just like before, but not as bad.

I'm not sure what to do now. could the fact that the brake line goes to one brake and then loops over the tire to the other brake cause a change in brake fluid pressure to affect left and right brakes differently?
Is there anything else that might cause the application of the front brake to be unequal between the two?
Thnking maybe I should change the brake lines at the triple tree connection to two equal length lines and eliminate the crossover, but I don't want to change the lines if it won't make a difference.

any ideas?
thanks

the right rotor is still quite a bit warmer to the touch than the left at end of ride. I think that is telling me that the left brake is still doing more work than the right brake:( just like before, but not as bad.

If the right side is warmer that would tell me that either the right side is dragging or the right side, NOT the left, is doing more work.

more braking = more heat

You should be able to see if it is dragging by putting the bike on the center stand, jack the front wheel off the ground and see if it turns freely and if you can hear it drag from either the left or right.

Unless the hose connecting the two calipers on the front of the bike is clogged (highly unlikely), it is the nature of any hydraulic system to be self balancing. As pressure is applied to the brake fluid in the system, only the diameter of the pistons will have any effect on how much force is put on the individual brake pads (although a sticking seal can change this it is a relatively small consideration).

Any difference in temp. you can feel with your hands between the two front rotors is really insignificant as when the brakes are operational and being used, the surface temperatures are much, much higher than anything you could stand to touch. What I think you are feeling is just the difference in the running drag of the two sets of brakes and does not really indicate how much actual braking is being done by each rotor.

There is a certain amount of drag in disc brake systems and that along will cause a bit of increase in rotor temperature. As there is always some thickness variation and some run out in all rotors, it is that very small change as the rotor rotates that tends to push the pads back and the caliper pistons back in their respective bores. In the normal variation of things, one rotor will be less true than the other (statistically it will just work out that way) so while both may appear 'smooth', the rotor with the greater run out will push the pads back faster and a bit further, and that will reduce the friction and heat caused on that side. Same thing goes for the seals- some are tighter than others, and a tighter seal (easy boys!) will tend to hold a piston and brake pad closer to the rotor than a looser seal would.

The only way to really check on braking action would be to either install a pressure gauge on both calipers and watch them as the brakes are used (you can be stopped for this test although a moving test would be more useful) or put temp. sensors on each rotor and note the temps. the rotors achieve, again when actually being used and loaded.

Otherwise I would just assume all is within a normal range. It IS normal for some pads to wear sooner than other pads on the same caliper; mine tend to wear on the insides of the rotors faster than those on the outside of the rotors. To get maximum life out of the pads, some people swap the positions so each one gets its 'turn' in the high and low wear place.

Brian

removed calipers, disassembled and replaced all seals last week. bled brakes, (speed bleeders are my friend) including all banjo joints. pistons all seemed perfect. went for short test ride and then longer ride (50 miles to work) and the right rotor is still quite a bit warmer to the touch than the left at end of ride. I think that is telling me that the left brake is still doing more work than the right brake:( just like before, but not as bad.

I'm not sure what to do now. could the fact that the brake line goes to one brake and then loops over the tire to the other brake cause a change in brake fluid pressure to affect left and right brakes differently?
Is there anything else that might cause the application of the front brake to be unequal between the two?
Thnking maybe I should change the brake lines at the triple tree connection to two equal length lines and eliminate the crossover, but I don't want to change the lines if it won't make a difference.

any ideas?
thanks

RHino, sorry, don't know left from right sometimes, you are correct:)

BDF, Thank you for your insight. I guess I'm just a bit skittish, since i just changed the pads and the outside right set were worn almost to metal while all the left side pads looked nearly new.
guess I'll just ride it and be checking the pads frequently.

That isn't normal. It's possible that the left caliper line  or caliper could be blocked. You could take of the right caliper and place  block in it so the pistons don't shoot out and apply the brakes to see if the left side is actually working. (Done on the centerstand with the front end up.) Don't know how accurate it would be, but it would tell you if it is not working.

Try loosening the axle clamp bolts then hold the front brakes then pump the forks vigorously at least five times. Then tighten the right axle clamps bolts then the left. This is my version of the manual front wheel installation instructions (which are incorrect) but the point is to "seat the front axle"  which if not done may be the cause of your uneven brake wear. My theory is that this "axle seating" procedure centers the wheel and axle assembly (and rotors) in the sweet spot between the two calipers such that all pads get equal attention and remain happy.

- small note here : my mech advises that the brake fluid be changed regularly because he has found that over time the internal portion of the various brake hoses will deteriorate and result in particles forming in the fluid. He thinks that this is particularly an unhappy situation for ABS equipped bikes.

- not sure how accurate it is , but he's very much a "bike person".

.

I had a similar situation happen to me but it was caused by a warped rotor (I warped it through mishandling during a tire change).  Assuming the pistons are moving freely (easily checked) then it has to be something external to the caliper and that leaves the rotor or it's alignment to the caliper per Lather.

- small note here : my mech advises that the brake fluid be changed regularly because he has found that over time the internal portion of the various brake hoses will deteriorate and result in particles forming in the fluid. He thinks that this is particularly an unhappy situation for ABS equipped bikes.

- not sure how accurate it is , but he's very much a "bike person".

.

Every vehicle manual I ever read  required regular brake fluid changes. Brake fluid absorbs water and will eventually go bad and the water will mess up the brake system parts.

There ya' go Bob, fixed it up for ya'.

There really isn't any way to have a hydraulic system 'bias' or 'favor' one part over another. Unless there is something terribly wrong like a big ring of debris / rust around the piston up against the seal that does not let the piston retract, the system really will be balanced.

Brake pads wearing at different rates on the same bike is pretty common, especially on bikes that have one pad per piston and multiple pads on each side. Unless the wear rate is more than something like 50% difference, I would just push it off to the randomness of the cosmos. Or a <k-word> problem, which is really the same thing. Quite a few people move brake pads around between rotors and between inside / outside to even out the wear imbalance.

Brian

Try loosening the axle clamp bolts then hold the front brakes then pump the forks vigorously at least five times but if you do it more than fifteen times it is more for you than the bike. Then tighten the right axle clamps bolts then the left. This is my version of the manual front wheel installation instructions (which are incorrect) but the point is to "seat the front axle"  which if not done may be the cause of your uneven brake wear. My theory is that this "axle seating" procedure centers the wheel and axle assembly (and rotors) in the sweet spot between the two calipers such that all pads get equal attention and remain happy.