Brakes "Skipping" at end of Braking Cycle

[mzflorida]

I noticed a problem with my brakes the other day. At the end of a deceleration cycle, say reducing to speeds suitable for a right hand turn, I feel a cyclical grab then release from the front brakes. If you think about ABS grabbing and releasing, but with a far lower frequency, it might give you an idea of the conditions I am experiencing/feeling. The pads look good. I cleaned the rotors and the brake assembly. Fluid was changed several months ago. Front bearings have no sign of freeplay. Suspension is fine. Tires are in good shape. Torque values checked. I don't have a caliper to test rotor runout but will order one from Amazon. Anything else anyone can think of? I have a training session this weekend so trying to see if this can be a parts-free remedy so I can still attend. Not too optimistic at this point. Appreciate any guidance.

 

[Rabbit]

Almost sounds like either a warped rotor or the rotor is loose and is grabbing as it turns

 

[dduelin]

Brake rotors can get a hot spot where friction material is adhered to the surface of the rotor. It's thought that when the brake is held tightly against a very hot rotor it sets up the material transfer. You can't even see it but a buff with brake cleaner and a very fine scotchbrite pad should restore even braking again.

A warped rotor usually is felt in a similar manner but the lever or brake pedal has some pulsing feedback.

 

[mzflorida]

Brake rotors can get a hot spot where friction material is adhered to the surface of the rotor. It's thought that when the brake is held tightly against a very hot rotor it sets up the material transfer. You can't even see it but a buff with brake cleaner and a very fine scotchbrite pad should restore even braking again.

A warped rotor usually is felt in a similar manner but the lever or brake pedal has some pulsing feedback.

I have white scotchbrite pads. I’ll clean again while on the next work call. I am not sure about the feedback in the brake lever. Thank you Dave.

 

[mzflorida]

Almost sounds like either a warped rotor or the rotor is loose and is grabbing as it turns

I’m going to “rent” the tool from auto zone. I was going to buy it but 70 bucks for a one shot, I’d be better off buying a new rotor for a few bucks more. I like to fiddle and tinker but generally dislike throwing parts against a problem to see what works. In this case buying the tool vs buying a rotor, the rotor would win.

 

[670cc]

I’m going to “rent” the tool from auto zone.

If you mean “rent” a measuring tool from auto zone, I offer this anecdote. I once had a pulsing front rotor on my NC. There was a visible discoloration anomaly in one sector of the disk. I tried to measure runout, but could not detect any using a dial micrometer. I had strong suspicion that I had every so slightly bent the rotor during a tire change. I cleaned and buffed the disk in all ways I could think of. Nothing resolved the pulsing until I replaced the disk with a used one from eBay.

I concluded that even with a warp or bend not easily measured by a home mechanic, one could still possibly feel the pulsing during brake application.

 

[mzflorida]

If you mean “rent” a measuring tool from auto zone, I offer this anecdote. I once had a pulsing front rotor on my NC. There was a visible discoloration anomaly in one sector of the disk. I tried to measure runout, but could not detect any using a dial micrometer. I had strong suspicion that I had every so slightly bent the rotor during a tire change. I cleaned and buffed the disk in all ways I could think of. Nothing resolved the pulsing until I replaced the disk with a used one from eBay.

I concluded that even with a warp or bend not easily measured by a home mechanic, one could still possibly feel the pulsing during brake application.

That is actually super helpful and interesting, anecdotally or otherwise! Thanks Greg!

I’m riding in some gravel lately to that garden lease I keep mentioning. Wondering if that might have contributed to the issue.

 

[mzflorida]

If you mean “rent” a measuring tool from auto zone, I offer this anecdote. I once had a pulsing front rotor on my NC. There was a visible discoloration anomaly in one sector of the disk. I tried to measure runout, but could not detect any using a dial micrometer. I had strong suspicion that I had every so slightly bent the rotor during a tire change. I cleaned and buffed the disk in all ways I could think of. Nothing resolved the pulsing until I replaced the disk with a used one from eBay.

I concluded that even with a warp or bend not easily measured by a home mechanic, one could still possibly feel the pulsing during brake application.

I’m definitely concerned as it is definitely influencing stopping ability. I don’t feel comfortable with it in its current state of performance other than to test between the two entrances to the subdivision.

 

[davidc83]

A question. If one of the brake pistons were grabbing/sticking, would it cause the same condition?

 

[Rabbit]

A question. If one of the brake pistons were grabbing/sticking, would it cause the same condition?

I would think if they were sticking it would be more constant rather than intermittent

 

[mzflorida]

A question. If one of the brake pistons were grabbing/sticking, would it cause the same condition?

That is what I was thinking too. However, I’m unsure on how to test.

 

[mzflorida]

The only thing I can see that is possibly causing this is the Pad Spring has lost flex for some reason. I've ordered a replacement. But I also decided it was a good idea to bleed the brakes. Unfortunately, one screw head stripped. I had to order a screw extractor small enough to remove it. Very odd as I have the proper JIS head driver for the screw. Anyhow, fingers crossed.

 

[Rabbit]

What screw head extractor did you use?

 

[mzflorida]

What screw head extractor did you use?

I have not yet received it. Brand is Thosaf on Amazon. The link will not work correctly when posted here.