Vibration under braking

You can buy a basic runout gauge at harbor freight or auto parts store. Fix the bars/forks in place, clip or magnetically attach the gauge holder/bracket somewhere close to the brake (on the forks or onto something else that isn't spinning, obviously) and place the gauge tip on the rotor and spin the wheel. Your rotor/s are probably warped IMO, and as far as I know they can't be turned and must be replaced.

I would just make a quick jig of sorts to run closely to the rotor for starters. That will give you an idea if you will need more sophisticated equipment. I do think you are on the right track, good luck.

+1 @1KPerDay . Here's a simple way to check without a gauge.

how to check motorcycle brake rotor run out

Duane

Gunnert said:

+1 @1KPerDay . Here's a simple way to check without a gauge.

how to check motorcycle brake rotor run out

Duane

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Great video thanks @Gunnert (Duane)

Check the front tire for cupping also.

Have you isolated which end the vibration is coming from? If it' the rear, I'd suspect the caliper is not free floating; e.g. with pads removed you should be able to move caliper back and forth once mounted.

Duane

Gunnert said:

Have you isolated which end the vibration is coming from? If it' the rear, I'd suspect the caliper is not free floating; e.g. with pads removed you should be able to move caliper back and forth once mounted.

Duane

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Duane,
Rear brake is smooth as glass when using that brake only. When using the front brakes is when I feel the vibration and it "feels" that it is on the front. Going to use your posted video homemade run out gauge this afternoon to test further.

This might be the phenomenon BMW referred to as "brake judder". One of their recommendations was cleaning the rotor. I've used lacquer thinner on a rag with good results. Of course, keep it away from painted surfaces.

@joe schmoe , odds are the rotors are fine. I'd suspect a stuck piston in one of the calipers.

Duane

aggieengineer said:

This might be the phenomenon BMW referred to as "brake judder". One of their recommendations was cleaning the rotor. I've used lacquer thinner on a rag with good results. Of course, keep it away from painted surfaces.

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I did use brake cleaner and a rag to wipe down the rotors when I cleaned the calipers right before I replaced the front pads

Gunnert said:

@joe schmoe , odds are the rotors are fine. I'd suspect a stuck piston in one of the calipers.

Duane

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Duane, you think so, even after cleaning the calipers (Jay Bear Video) and compressing them open all the way in to allow for the new brake pads? I wondered about a stuck caliper, but figured with doing the previous that it rule out a stuck caliper?

Unless the piston was removed from the caliper during cleaning, it would be difficult to be sure that it was a truly clean and smooth bore. You might try measuring the thickness of the rotor in several places with a micrometer. If the uneven braking is obviously a function of the wheel RPM, I'd still be suspicious of the rotor. I'm thinking runout, uneven friction at the surface, or uneven wear. Interesting mystery.

joe schmoe said:

...and last winter had the dealer do the brake fluid service as part of the 18K service.

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Did you have this issue before the dealer did your brake fluid service? If not, it's possible the dealer didn't bleed the brake lines correctly and air is causing an uneven pressure on the front calipers.

I use 1500 grit sand paper to clean my rotors. Also did you re;place the pads with OEM or aftermarket and were you having the problem before you replaced the pads?
The rotors are supposed to float. Something else to check are the wheel bearings. My bike acted weird when mine were going bad.

An important clue would be the frequency of what you are feeling. Is it something that only occurs once or twice per wheel revolution, or is it more of a low frequency buzz, perhaps even audible?
If the latter, wheel bearings would be a worthwhile thing to check. Something loose in the brake/wheel assembly could be vibrating at a natural frequency. Hope you can figure it out.

I went and purchased the Harbor Freight clamp on dial indicator. Checked both front rotors and they are perfect. I could nudge the front fender to verify the gauge was resting against the rotor.

Someone had mentioned the brakes? What else is left for checking the brakes? Is there something I can check using the GS-911?


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Couple people have mentioned the bearings… have you checked them? You can remove the front wheel and stick your finger inside and turn the bearings and feel for free movement/grit/grinding. Personally I’m surprised the brake rotors checked out based on the behavior. I’m at a loss. Maybe something loose in the front end???

I'm still thinking "sticking brake caliper piston". I know you cleaned them.. I use brake cleaner for the caliper/piston/etc. and lube with Permatex Ceramic Lube. But there are many lubes that work. To clean pistons I push them out slightly using brake lever, clean, and then lube before retracting piston and reinstalling,

BTW, I have an 8 ounce jar of lube that I bought in KNOW at least 10 years ago. I use the lube on when I do brakes on bikes and cars. After 10 years I've still got about 1/2 jar left; e.g. this stuff goes a lonnnng way,

Duane

1KPerDay said:

Couple people have mentioned the bearings… have you checked them? You can remove the front wheel and stick your finger inside and turn the bearings and feel for free movement/grit/grinding. Personally I’m surprised the brake rotors checked out based on the behavior. I’m at a loss. Maybe something loose in the front end???

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I have not checked the bearings. I will do that tomorrow...