Bandit 600 brake judder

Hi,

I've just noticed a judder from the front end under heavy braking. Most
noticeable from 20-40mph.

It may have always been this way as I rarely jam my brakes on below 40mph -
but do regularly from high speed, but it doesn't seem to happen above 40.

I've taken both calipers off and they seem OK. The head bearings seem smooth
and there's no play I can feel. I've checked the fork clamp bolts for
tightness.

What shall I look at next?

Cheers.

 

Warped discs?

 

Warped discs is most likely as the fella above ^ said.

However, sometimes if a bike is used in the wet and then not used for
a few days, the the pads leave corroded and pitted patches on the
discs - Pro-lites are prone to this. This is also worth checking.

 

Curiously, I used it in the wet on Wednesday (which I don't do often), so
I'll look down this avenue.

 

What frequency is the judder?

If it was the head bearings or forks I'd expect more of a single 'thunk'
than a repeating judder.

Check if it's warped disks by fastening something flexible to your fork
leg which is barely - almost - just touching the surface of the disk.
When you rotate the wheel, it should be obvious if the disk is running true.

You should also examine the circular fasteners that hold the outer disk
(the braking surface) to the inner disk, if there is excessive play in
any of them then this could be the cause.

If the problem is either of those 2 then it's new/replacement disks.

If it isn't, get them physically checked by your preferred, trustworthy
mechanic.


Chas.

Life lesson No' 842
"I can handle the arguments . . . but not the silence in-between".

 

I'd say about 10 times a sec and only under serious heavy braking.

 

How much play is there in the bobbins between the disc and carrier?

Sounds like a warped disc though. You got 'em really hot recently?

 

If you've had a recent front tyre, check that the wheel spacer is right
up against the bearing, if it's not, then it'll cause the disk to bend
out slightly.

 

Muck says...

I'd have thought that the pads would just move over to compensate for
the offset disc, if it's only out by 1mm or so.

 

Kevin Stone scribbled:

If it is this then a couple of good runs along the twisties should wear
the discs down again, reducing the judder to barely noticable.

 

Maybe, but when your whole wheel is moving side to side by about 2mm, it
does do funny things to the disks, like bend them into the caliper mount
so that one _just_ touches and scrapes when cold.

Putting the front end back to what it was supposed to be like cured the
problem.

 

Nope, I did change the rear pads today (and tightened chain), but I can't
see how this is related.

 

Check front discs are running true as someone ^upthere recommended, a bit of
blue tack with a pin or nail in running close to the disc will help you see.

 

Will be doing this on the morrow...

 

Should, yes, but IME, depending on the disc material, not always.

 

Well, duh..

 

Pip Luscher scribbled:

It worked on my AT a couple of days ago which has been standing outside
for months. And costs peanuts (petrol) to do

 

frag wrote:

Seems to be much better today, so could have been this. Haven't yet checked
to see if the disks are warped thought.

 

I mentioned it just in case. You just never know!

 

Kevin Stone scribbled:

Good stuff. Same for me and my bike, had a blat on it today and there's
no trace (to me) of the juddering it had.

I would have thought if they were warped it wouldn't get better by
itself, but SWK will know better.