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Buell Motorcycle Forum » XBoard » Buell XBoard Archives » Archive through June 02, 2007 » Front Brake: Random Thumpa-thump !?! « Previous Next »

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Swordsman
Posted on Tuesday, May 29, 2007 - 09:35 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

For the second time now, I've experienced an odd thumpa-thumpa-thumpa when applying the front brake. It doesn't do it all the time... very rarely, in fact. However, when it happens, it's quite unnerving. The brake pads are still good, there's no evidence of any debris getting caught in the rotor, and all the peripheral rotor bolts are as snug as they can get. However, I did discover that the rotor has a bit of play at every bolt location; I can flex it inward maybe 1/32" or so at every mounting point despite the bolt tightness. I've never checked this before, so I don't know if that's normal. The rotor has never been removed, and the bike has about 6500 miles on it.

Any ideas what's going on??? I've heard before that in some cases the rotor bolts stretch a bit and should never be reused, but could that have anything to do with what I'm experiencing?

Thanks,
~SM
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Gentleman_jon
Posted on Tuesday, May 29, 2007 - 09:58 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

1. The rotor is a floating rotor, ( unlike the rear which is a fixed rotor with a floating caliper), so the play you report is not only normal, it is necessary.

2. The most common cause of the old thumpa, thumpa is loose steering bearings.

To check this, jack the bike up so the front wheel is off the ground, then grab the fork legs, one in each hand, and check for any play. If you can feel ANY, then that is most likely the problem.

To tighten them, while the front wheel is still off the ground, loosen the pinch bolts on the lower triples, and the the pinch bolt in the center of the upper triple, and tighten the center chrome domed bearing adjustment thingy to about 50 foot lbs.

4. If that doesn't work, check to make sure that the bolts holding the caliper are still tight. If not, tighten them up, and use a little blue loctite to hold them in place.

Let us know...........

PS: Might be a good time to order the shop manual!
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Firebolteric_ma
Posted on Tuesday, May 29, 2007 - 10:48 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

It could also be the build up on the rotor that the stock pads leave behind...Gives the bike a pulsing sensation at lower speeds.

But the "Thump" is most likely the head bearing as Jon has suggested.
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Punkid8888
Posted on Tuesday, May 29, 2007 - 11:14 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

I am wondering about this floating rotor? I have never been able to move mine by hand, should you be able to? I have notice by the dust build up around the bolts that it does seam to move a bit. I initally thought the the rotor bolting system was to allow for thermal growth not so much as a floating system.

its an 06 with 6000 miles and stock everything, nothing has been removed
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Swordsman
Posted on Tuesday, May 29, 2007 - 02:00 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Jon, thanks for the heads up on that. I've been meaning to check the steering bearings out anyway (should have done it at 5k miles!), but just haven't braved it yet. I do have a manual, guess I should go read it!

~SM

(Message edited by Swordsman on May 29, 2007)
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Tank_bueller
Posted on Tuesday, May 29, 2007 - 04:00 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Sword, does the brake lever pulsate when the "thumpin" happens? If not, I'm with everyone else on the steering head bearings. After you torque them properly, you will notice a HUGE difference in feel. Makes the whole bike feel more solid.
(don't ask how I know)
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Prof_stack
Posted on Tuesday, May 29, 2007 - 04:05 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

At 10k the steerings bearings on my XB9S were tightened and it was night and day different; and better.
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Swordsman
Posted on Tuesday, May 29, 2007 - 04:30 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Nope, no feedback through the lever, just through the handlebars and foot pegs. I actually thought it was the foot brake to begin with, but the second time it acted up I managed to test each brake individually as I slowed, and it was definitely being triggered by the front brake.

~SM
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Gentleman_jon
Posted on Thursday, May 31, 2007 - 06:41 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Punk,

The rotors don't move a lot, but you should be able to push them in towards the center of the rim with two thumbs: there is a spring next to each bolt pushing them out.

If they don't move at all, you have a problem. You might try cleaning the areas around the bolts with brake cleaning fluid. That should do the job.

If not, the only thing to do is remove the rotor, and clean everything. Buell recommends replacing the screws after doing this, but the torque values on these screws is not very high, and lots of people reuse them. Loctite blue of course.

While you are at it, cleaning the brake rotors with some fine sandpaper and or brake cleaning fluid is always a good idea, as the stock pads tend to leave quite a bit of residue on the rotors which can cause pulsing.

Now that I think of it, 6K is not a bad time to start thinking about new pads. I like the Lyndall Golds from American Sport Bike, one of our sponsors.

Natcherly once you have the wheel and rotor off the bike you could......................
oh never mind.......
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Txfatcat
Posted on Thursday, May 31, 2007 - 10:36 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

my front brakes were so bad that I stopped using them for a bit...I know wrong solution but just the way was. I was told that the front brake rotor might be warped because of when I first got it I would sit at a stop and hold on the front brake causing uneven cooling. I had Al send me the Lyndall Golds. After going thru the recommended brake in process for the pads all the severe pulsating went away. I also noticed that upon inspection of the factory pads, they were all gualled up(if thats the correct terminology).
I am going to turn 15k here shortly so I think I will check out the head bearings tomorrow.
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Etennuly
Posted on Thursday, May 31, 2007 - 10:56 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Be careful to keep the brake cleaners off the powdercoated rims, it will melt the finish.
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Bad_karma
Posted on Friday, June 01, 2007 - 05:49 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Cliff
When you are sitting at a light have you notice a difference in the shaking in the handle bars when you release the front brake?
Joe
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Punkid8888
Posted on Friday, June 01, 2007 - 06:48 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Really there is some type of spring next to each bolt? I will have to take a closer look at them. I have only tried to move it with very little force. I will try using a little bit more force just to see if I can get it to shift a little.

As for the pads I have been thinking of getting new pads because mine have been leaving the deposits on the rotor. I clean them off every time I wash the bike (once a month). I have noticed it brakes way smoother right after you clean it. But I am kind of frugal and think hey there is still plenty of meat left on those pads so why replace them.

I think I will do the pads the same time I do the tires, which looks like it might be at 8 or 9 thousand. Preferable I would love to make it till the end of the season so I can do it all over the winter. But I got 3500 miles on my bike so far this season and its not even summer yet.

I will let you know what I find tonight when I poke around it.
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Txfatcat
Posted on Friday, June 01, 2007 - 08:39 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Punk,

I think you will be very happy with the Lyndell golds. They provide so much more feedback and feeling than the stocks. I just wish I would Have changed them when i first got the bike
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Ridrx
Posted on Friday, June 01, 2007 - 01:33 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Swordsman,
Have you got the problem pinpointed yet?

Punk,
+1 on the Lyndall golds. Great feel and progression.

(Message edited by RidrX on June 01, 2007)
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Raptorj
Posted on Friday, September 28, 2007 - 06:02 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Had the same problem with a 'clunk clunk clunk' sound coming from my front wheel/head stem area sometimes under braking and when rocking the bike back/forth under brake...

I tightened the head bearings... no change.
Check the wheel bearings for play... nothin'.
Then came the discovery: my rotor was not tight with the wheel and was the source of this 'clunk' sound.

However... I've broken my only size 40 Torx bit just trying to free the bolt holding the rotor to the wheel... damn things are on there tight!
Anyone else had this problem?
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