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vibration on front brake just before stopping


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#1 msflanag

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Posted 22 July 2011 - 11:41 AM

Hi,
I'm looking for help in diagnosing a front brake chatter that I get at about 10 mph on down to stop. I have an '06 abs. I looked at the rotors and didn't see any obvious run out. Replaced the pads. lifted the front end up and checked for play in the head set by trying to lift the front tire back and forth. The issue is not there at speed. Any one ever had this issue????
Thanks ahead of time,
Mark

#2 fjrbrad

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Posted 22 July 2011 - 11:59 AM

I have experienced the same thing. I have only had it a couple, maybe three times and it usually happens when I use the front and back brakes together, which I don't do very often. It almost feels like the anti-lock cycling or something to that effect. I usually feel it under moderate to hard braking, and it almost makes the front end shudder. I have come home and checked the calipers and made sure they are tight to the fork legs. I have come to the conclusion it must be the anti-lock sensing something when both front and rear are applied at the same time and it somehow sends a glitch thru the electic portion of the anti-lock. Again that is only what I think or what it feels to be. It certainly is not a comforting feeling to have that shudder come thru the braking system. I am glad that someone else has had the same thing and I am not alone. Now we wait for the experts to come forward.

#3 SLK50

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Posted 22 July 2011 - 12:01 PM

You're experiencing brake squeal, only at a very, very low frequency.

You may have a slave piston not retracting and preventing the brake
pad from cooling adequately, exascerbating the situation.

#4 joebiodiesel

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Posted 22 July 2011 - 12:20 PM

It may be a low speed ABS Activation. It's a common failure on cars. At low speeds the ABS Sensor signal is not strong enough for the computer to see it. It believes the wheel is locked up and activates the ABS to correct it. Fixing it requires making the signal stronger. Somtimes that can be done by making the air gap smaller. Most often the sensor needs to be replaced.

Here is a lab scope measurement of a car that does it. Note the low voltage of the upper signal. As the vehicle slows down, the voltage drops enough that the computer can't measure the frequency of the pulses anymore. That's when the ABS Activates.

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Does it do it every time?
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#5 RaYzerman19

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Posted 22 July 2011 - 12:21 PM

Have you had it in the past or with last pads? Try to determine if it is an ABS modulation taking place. I have felt this occasionally even though in my opinion the ABS shouldn't have been necessary. I don't have an answer for it (yet).

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#6 fjrbrad

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Posted 22 July 2011 - 12:24 PM

Mine has done it maybe 3 times in 7,000 miles. Never high speed, usually under heavier breaking.

#7 ionbeam

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Posted 22 July 2011 - 12:38 PM

Pull the ABS fuse, if the chatter persists it ain't the ABS.

Cheap 'n easy, use a mild Scotchbrite pad (or equivalent) and brake cleaner to thoroughly clean both sides of both front rotors. More work, but recommended is to very lightly clean the pads at the same time even though they are new. Contaminated rotors can mimic warped rotors at low speed. If it fixes the problem good, if it doesn't it was still good to give the braking parts a good cleaning.

It isn't unheard of for a rotor to develop hard spots in the metal which also can cause these symptoms, but this is more common in cars. When a car is parked with very hot rotors and the parking brake is set the pads are pressed against the rotors as they cool can have a bad affect on the rotors in those places.

Well, those are a couple of easy things to check off the troubleshooting list.

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#8 SkooterG

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Posted 22 July 2011 - 12:45 PM

How many miles on your FJR and rotors?

Twice I have had a front brake shudder, or vibration occurr. Both times were with a lot of miles on the rotors. The first time I checked all specs with a micrometer and dial gauge but could not find anything out of spec. Regardless, changing the rotors solved the problem. The second time I just lived with it.

Mine didn't occurr under hard braking however. Only light to moderate braking, 15-20mph and less. Not noticeable at any other time.

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#9 msflanag

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Posted 22 July 2011 - 01:02 PM

How many miles on your FJR and rotors?

Twice I have had a front brake shudder, or vibration occurr. Both times were with a lot of miles on the rotors. The first time I checked all specs with a micrometer and dial gauge but could not find anything out of spec. Regardless, changing the rotors solved the problem. The second time I just lived with it.

Mine didn't occurr under hard braking however. Only light to moderate braking, 15-20mph and less. Not noticeable at any other time.



I have about 28K on the rotors. It does feel like ABS trying to come on. It's actually worse under light braking as opposed to hard. I'll pull the ABS fuse and see if that affects the situation. If that doesn't do it I'll clean the rotors and if that fails I may end up replacing the rotors and rebuilding the calipers.
thanks for everyones help. I'll report back on the fix if there is one.
Mark

#10 C&C

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Posted 22 July 2011 - 02:33 PM

I have had similar experience (periodically) on my '04 (I don't have ABS); my conclusion was that it was glazing either on the pads or rotors. Actually, a couple of hard stops, can remove light glazing and the symptoms may self-correct; I have seen this type of condition come and go.

#11 SkooterG

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Posted 22 July 2011 - 03:54 PM

I have had similar experience (periodically) on my '04 (I don't have ABS); my conclusion was that it was glazing either on the pads or rotors. Actually, a couple of hard stops, can remove light glazing and the symptoms may self-correct; I have seen this type of condition come and go.

Mine was a non-abs 04 too. For the life of me, I could not figure out what was wrong with the rotors. I tried everything - hards stops and even spending a couple hours sanding the rotors. Nothing helped. Nor did I find any anomalies as I mic'd the rotors in a million places around the brake pad swept area.

I figured it was glazing, or hardening, that was simply undetectable. These rotors did have approximately 70k-100k miles on them.

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#12 Richouse

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Posted 22 July 2011 - 04:02 PM

I noticed it also. Fairly light breaking it chattered (sometimes) just before i came to a stop. I checked and checked also... The pads just float in the calipers so I just figured they just chattered a little at slow speed when lightly pressed. It didn't effect braking at all so I didn't worry about it...

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#13 PhilJet09

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Posted 22 July 2011 - 04:07 PM

Thanks for posting this, mine does this too occasionally, always under low speed medium to heavy braking. It isn't consistent enough on my bike for me to spend much time trying to figure it out. Now I have a few things to check.
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#14 mvette

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Posted 22 July 2011 - 05:18 PM

I have felt this also on occasions. Cant make it do it at will. No particular circumstances when it does it

#15 FJRski_2007

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Posted 29 July 2011 - 06:08 PM

My 2007 FJR is as we speak at local Yamaha dealer here in Chicago in regards to this issue.
They had the bike for 2 days and still are looking at it. I will keep you all informed on the solution.

#16 Greb

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Posted 29 July 2011 - 09:00 PM

I've felt this same thing from time to time. It seems from all these posts that it may be a common occurrence.
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#17 rogdeb

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Posted 30 July 2011 - 10:14 AM

Mine didn't occurr under hard braking however. Only light to moderate braking, 15-20mph and less. Not noticeable at any other time.

Same with mine. I've just been living with it so far.
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#18 FJRRider08

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Posted 31 July 2011 - 09:54 AM

Ditto for me too... Cleaned down the rotors and pads with a scotch bright pad and some brake cleaner during the last tire change @ 1,500 miles ago, still had it happen again, not often, just enough to get your attention.
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#19 zed88

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Posted 31 July 2011 - 10:44 AM

Same thing here. Checked out everything on it and looked at calipers, rotors etc. Everything looks good to me, and judging by the other replies here its just a floating calipers issue

#20 FJRski_2007

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Posted 31 July 2011 - 11:05 AM

My bike came back from dealer and dealer concludes that the issue is related to what Joe said above about frequency.