Shuddering when braking

[scream aim fire]

So just bought a bike (zx6r p7f) and when I brake over 40/50mph The front end seems to shudder, The seller thought it was the brakes so put new pads on it and checked the pistons but its still doing it, The lever feels fine when braking its just the front end of the bike.

Any ideas what it could be?
____________________
CBT PASSED 18/01/09 THEORY PASSED 14/04/09 DAS PASSED 17/04/09 3 minors wet test.
Bikes: 2009 Aprilia RS125 (PX'D) - A1P ZX6R - Stolen -Triumph Daytona 600 -wrote off via BMW
Current bike: P7F ZX6R

[at106]

Could the discs be slightly warped?

[scream aim fire]

[CaNsA]

either warped discs, wheel bearings or headstock bearings.

[InspectaBike]

[CaNsA]

Another thought, check the tyre pressure and inspect it for any signs of damage.

[scream aim fire]

[CaNsA]

[InspectaBike]

Putting my neck on the line a little and diagnosis without seeing the bike but I have seen a fair few bikes warp discs when stood for prolonged amount of time especially winter mths

What happens is the pads sit on one area of the disc and when stood through winter mths in a cold garage the disc slightly warps because of the cold weather..as cold effects metal just like heat does

I had one chap leave a bike in a garage for just 2 weeks in really cold weather and when he returned after just said 2 weeks had a serious brake judder..turned out to be discs had warped.
____________________
www.inspectabike.co.uk

[scream aim fire]

[scream aim fire]

[Noxious89123]

There have been threads before about "juddering" brakes, by myself and also by TUG.

We've both tried many things and found nothing to solve it. Seems to only be an intermittent thing too, doesn't always happen!

Can't remember what TUG tried, but personally my bike has had;
New head bearings.
A few pairs of tyres, all correct pressures + sizes.
New brake discs and pads.
New front wheel. (And thus new bearings).
Forks rebuilt.
Brakes rebuilt with new seals.
New brake lines.

And pretty much everything else that has been suggested. I would point out that some of those things weren't done *because* of the judder, but and things that I have done and it hasn't effected it.

Oh, and the discs aren't warped. Apart from having this with both the old and new discs, the new ones were checked for run out when fitted. It was noted on one MOT though that on the "roller brake test" that braking effectiveness varied.

One thory that I read online, and it seems to be the only one that seems to make sense to me, is that when you use the brakes some of the friction material transfers onto the disc. If this material on the disc is uneven, you can get areas of varying grip on the disc, causing this juddering. I find that If i clean the discs with brake cleaner and rub them lightly with some wet & dry paper, the juddering dissappears, but only very briefly before it returns.

Only feel it sometimes, and usually only at about 10mph after slowing from high speed.
____________________
'06 Honda CBR125RW-6 ~ '00 Honda CBR600F-Y ~ '07 Honda CBR600RR-7 ~ Bikeless
'53 Ford Ka 1.3 ~ '03 Vauxhall Astra SRi 1.8 ~ '52 Vauxhall Astra SRi 2.2 ~ '53 Vauxhall Astra GSi

[Ariel Badger]

Fairys Attack disk.
____________________
Bikers make great organ donors, get 115 on your licence today.

[kestrel]

[mudcow007]

to check if disks are worn could you not just remove them an put the disk/ rotor on something totally flat (glass table) an see if the disk rocks/ wobbles

not very scientific but it will give you an idea

headstock bearings. stop bike, put front brake on an rock the bike forward an backwards, if the bearings are goosed you "should" feel movement in the forks

[InspectaBike]

[kestrel]

[Noxious89123]

[scream aim fire]

[Noxious89123]

[Vincent]

[CaNsA]

@ InspectaBike
Not the advertising campaign you thought it would be is it?

[Casper]

[AlexW]

One would assume bike brake discs can warp due to their design and simply how thin they are, but I know with car discs they aren't normally warped, its normally pad material on the disc surface, like when you brake from high speed hard and then keep on the brakes while sat still.

[InspectaBike]