Hi All,

About three months ago I had problems with the front brakes juddering. The general consensus on the forum was warped disks, and the bike shop thought so too, so they were replaced with EBCs (with new EBC pads too). Now the new setup is juddering, and there's a strange wear pattern on the disks... agh!

Strange wear pattern on both disks, on boths sides (click for larger version):



Closeup of wear pattern (click for larger version):



The juddering started again when I went to my first track day, but is now doing it even with light braking, every time I touch the lever. The whole of the front end vibrates (so not just the lever pulsing) at around 40mph, and I can see the front forks vibrating forwards and backwards (not just up and down) when it happens. The lever is firm with no spongy feeling or travel, and a dial guage shows the disks are within limits, so it doesn't seem to be warped disks this time. The pads mostly look fine when I took them out to look at them; all had worn evenly. One of them had two pits, and a score mark that lined up with a score mark on the disk:

Pad with score mark and pits (click for larger version):



Disk with score mark corresponding to pad score mark (click for larger version):



There doesn't appear to be any play in the head bearing, nor in the wheel bearing, though all I did to check this was to get my girlfriend to push down on the back with the bike on the centre stand and wiggle the wheel and the forks around vigorously.

Anyone with any ideas? I've completely lost confidence in the bike at the mo, as the front brake has never been right since I've had it!

Cheers,
Ed

Have you rebuilt the calipers? Got braided hoses? I'm clutching at straws here mate.

The disc has been checked as having how much run-out?

Give the pads a scuff up with some 80grit paper. They look like they've got a bit warm.
This will also allow them to re bed in, take it steady for a while tho. I would also clean and check your calipers to make sure there's no sticking pistons.

It is possible that the problem stems from a worn stepped tyre.

Apparently, worn fork bushes can cause juddering while braking.

Are the wheels balanced?? I had massive judder when braking, and also when riding at certain speeds. I could actually see the forks moving back and forwards at 70mph

The front wheel was WAAAAAAYYYY out of balance.

Wheel balanced, problem gone.


The strange disc/pad wear could be a symptom, not the problem.

Hi Ed,

Sorry to hear your troubles have returned.

The pits in your pads lining up with the score marks on your disks look to me like you had a stone embedded in the brake pad as some point. Did you hear any scraping?

You say that the disks are within limits of runout according to the dial guage. However I must say that the marks you have are identical to the ones that I had when my new disks warped again. My money is on warped disks again.

I like you lost complete confidence in my bike, having also replaced the disks, but having a front brake that was never quite right.

I, like you, was keen to rule out a warped disk when the problem returned so quickly.

In the end I replaced the disks again (under warrenty from Sandy Bike Spares) and at the same time had the front calipers rebuilt. Ever since then all has been great with my front brake. So much so that I have now realised how bad the back brake is on the ZZRs... whereas I was quite happy with it before.

I could not explain why my bike warped its second set of disks so quickly, but the guy at Sandy Bike Spares was happy to swap it out, and said that "these things sometimes happen during manufacturing".

Let us know how you get on.


Paul

like Sandy has said, id go with a stone/debris causing the marks on the pads disks and stuck pistons causing warping again. Has anyone checked the head race bearings for the vibration side of things. Could be the bushes worn but they would have to be really shot to give that much grief IMO

Anyone else notice that the radial marks coincide with the inner and outer drill holes?



My guess is that they were drilled at the end of the manufacture and weren't deburred.

Hence the pad was 'lifted' off the rest of the disk at that point, causing the light wear marks. Eventually the burrs would have worn level, but by that point there is already a radial ridge in line with it, and will continue to be as it won't ever flatten off. Hence the judder.

Manufacturing fault. Return them.

Hi Guys,

Thanks very much for the support!

My first thought was the head bearing (or something in the forks), but I waggled the forks around good and proper and couldn't feel anything.

I've cleaned out the calipers, but haven't rebuilt them. In getting the pads out I pushed the pistons home and they all moved fine, and moved back into contact with the disk fine one I put them back on and pumped the lever, so I don't think it's a stuck piston.

I hadn't thought about wheel balance. That's an interesting one, though I would've thought that would've given vibration without braking too.

My dial gauge measurements claim one disk varies by about 0.1mm and the other by about 0.25mm. According to my Haynes manual, 0.2mm is the norm and 0.3mm is too much. But if it was one warped disk, I'm surprised I'd be getting wear marks on them both...

It could also possibly be the brake lines or fluid; I have a suspicion both are the original 8yr old ones!

It goes back to the bike shop tomorrow, so I'll let you know how it goes...

Thanks again for the support, guys!

Yours,
Ed

Any news Ed?

Ahh, well...

The bike shop confirmed there's a problem (so I'm relieved it's not just me being a noob). They also confirmed the disks aren't warped, but are catching somehow, giving the strange wear pattern.

They've been on the phone to EBC, who they think will want the disks sent back to them. So I'll be taking the bike in tomorrow evening and leaving it with them. The shop are being really good and have said, since it's not my fault, they'll loan me a bike while mine's off the road (some sort of old Bandit, I think). At least that will give me something to compare mine to when I get it back

Fingers crossed it's just a dodgy set of disks (both of them!), and a new set will have me good to go!