10-18-2017, 02:23 AM
How did you clean them? Did you rebed the pads after doing so?
Discs being physically warped is a far less common cause of this than pad material buildup. You can clean them with scotchbrite and brake cleaner but anything more aggressive should be done with care. Spinning the wheel and pinching can prevent hi/low spots. After doing this you will want to follow a bedding procedure to re-bed the pads (see the internet for plenty of arguments on the best way to do this). Be careful as braking will be diminished right after cleaning the rotors as you will have removed the necessary layer of pad that is transferred on to the rotor which increases friction.
If you get through all of this and still have a shimmy here's a list of things you can measure/check to try to eliminate the issue:
1.) Measure runout of rotors for physical warping (mentioned above) You can often rent a dial gauge from an auto parts store if you don't have one.
2.) Remove and inspect the pads and clean and lubricate the retaining pins to ensure they are in good working order
3.) Check balance of tire, you may have lost a wheel weight
4.) Check tire for cupping, uneven wear, flat spots etc.
4.) Inspect wheel bearings, replace them if there's any question whatsoever
5.) Check steering stem tightness (hold front brake and rock bike forward and aft-- if there is clunking in the steering tube, you need to tighten it up or replace bearings if shot)
6.) Ensure you have fresh brake fluid and no air in the system
Another thing to try and focus on is if the pulsating is felt in the lever or in the bars. This can be very difficult to distinguish but is very indicative of the problem system.
If you're certain that all of the above is OK, you're in "unlikely land" and you might need to start throwing money at the problem to figure it out such as an internal tire defect not externally visible.
Unfortunately I've been battling the same issue. I believe my issue is tire or bearing related but still haven't gotten to the bottom of it and it's not that severe so I am waiting for winter to tear into it.
Discs being physically warped is a far less common cause of this than pad material buildup. You can clean them with scotchbrite and brake cleaner but anything more aggressive should be done with care. Spinning the wheel and pinching can prevent hi/low spots. After doing this you will want to follow a bedding procedure to re-bed the pads (see the internet for plenty of arguments on the best way to do this). Be careful as braking will be diminished right after cleaning the rotors as you will have removed the necessary layer of pad that is transferred on to the rotor which increases friction.
If you get through all of this and still have a shimmy here's a list of things you can measure/check to try to eliminate the issue:
1.) Measure runout of rotors for physical warping (mentioned above) You can often rent a dial gauge from an auto parts store if you don't have one.
2.) Remove and inspect the pads and clean and lubricate the retaining pins to ensure they are in good working order
3.) Check balance of tire, you may have lost a wheel weight
4.) Check tire for cupping, uneven wear, flat spots etc.
4.) Inspect wheel bearings, replace them if there's any question whatsoever
5.) Check steering stem tightness (hold front brake and rock bike forward and aft-- if there is clunking in the steering tube, you need to tighten it up or replace bearings if shot)
6.) Ensure you have fresh brake fluid and no air in the system
Another thing to try and focus on is if the pulsating is felt in the lever or in the bars. This can be very difficult to distinguish but is very indicative of the problem system.
If you're certain that all of the above is OK, you're in "unlikely land" and you might need to start throwing money at the problem to figure it out such as an internal tire defect not externally visible.
Unfortunately I've been battling the same issue. I believe my issue is tire or bearing related but still haven't gotten to the bottom of it and it's not that severe so I am waiting for winter to tear into it.