Judder when braking

[BigMark]

When I brake I get a considerable amount of juddering coming up through the bars. It is speed relative almost as if I had something catching on the disc on every rotation. Braking really slowly I can almost certainly feel that there is an inconsistency. Holding the lever with the same pressure develops the judder but more noticeably it seems to have a gripping point followed by the normal braking then a quick grip and so on, fast enough to be related to the disc. Looking at the discs they seem fine, all bolts are tight and the disc appears smooth. Taking the Calipers off the brakes all look fine they are relatively new and the pistons work just fine, plenty of braking fluid.. I was thinking just to replace both discs but if you have any other ideas? Do I need to replace the brakes now or could it be something else?

[John Stenhouse]

Sounds like the classic warped discs

[jammed_stick]

I had my front wheel replaced last week due to the "warped" disc problem.
No more teeth rattling in my mouth when I use the front brakes !

First pair of discs were replaced on 10K km service , after a couple of thousand km , the problem was back.
At second service at 20K km , I complained "it's vibrating again" but decided to wait until 30K km service to have the discs replaced again.
When it was time the workshop told me it's no use to change the discs since the problem resides in the rim ! Several cases where they had to turn (hope it's the right word) the disc seats in the rim to fix the problem.
So I had my front wheel replaced to a used but rimmed one , new brake discs and voilá ... it solved the problem.
Btw: The brakes bites really nice with sintered brake pads.

[Stretch]

I've also seen front wheels that weren't machined correctly.  If the rotor mounting surface on the hub isn't machined perfectly perpendicular to the axle, the rotor will have a slight run-out (side-to-side motion) when the wheel is turning (viewed from the front).

A slight runout isn't a problem initially, because the floating caliper can compensate for the rotor runout for many thousands of miles of normal use.

But there does come a point where the rotor starts to wear unevenly, since the pad on one side of the rotor is pushing against the rotor harder in that one spot.  The same thing happens on the other side of the rotor, 180˚ away.  These two spots eventually grow thinner than the rest of the disc...


Note how the pad on this side didn't make contact with the entire surface of the rotor in this one area, zero degrees of Side 'A'.  The rotor was 'moving away' from the pad on this side, while the pad on the other side of this spot made such hard, complete contact with the rotor, that the rotor is worn thin enough to have a visible ridge of untouched material right near the outer edge.


The other side of the same rotor, 180 degrees from the first spot.  Same as with the other example, the pad didn't make full contact on this side here, but on the other side the pad was rubbing hard enough to wear a thin spot.  


When the front brakes are applied, the caliper squeezes the pads onto both sides of the rotor, but because of the thin spots, the rotor "catches" the pads harder when it rolls back into the thick spots.  That's what you're feeling when you apply the brakes.

The permanent fix is to either replace the wheel, or have the hub's rotor mounting surface trued up on a large lathe.

I believe another possibility would be to make a number of thin shims out of very hard stainless steel shim stock, and experiment with inserting shims between the rotor and hub in some of the mounting points, raising the low spots until the rotor runs true.  This is only a theory, and I would not recommend a rider to run shims of sheet metal, beer can, or other home-grown materials.  A proper machinist can work this out.

And you'll still need to buy a new, unwarped rotor.

I believe a set of replacement aftermarket floating rotors used in conjunction with our floating calipers would eliminate this problem.

[TigerLady]

Stretch:  I had my local mechanic install a set of new EBC rotors last week.  Didn't solve the shudder on braking.  He sent the wheel to a machine shop and they found that the mounting surfaces for the rotors were not true.  They machined the surfaces so they were all even.  I put the old rotors back on thinking that would solve the problem.  Still warped.  I will install the new rotors when I get back from the Central Tiger rally in the U.P.  Work interfered  

The machine shop owed my mechanic a favor so the work was done for a "bag of donuts" (ie: 3 cases of Lienenklugel beer)  :D

I will report back when the new rotors are installed...

[Bixxer Bob]

A lady..... that rides Tigers????  Maybe there is a God after all.... :roll:

[blacktiger]

A lady..... that rides Tigers????  Maybe there is a God after all.... :roll:

that means she must have long legs........nice. :oops: