Granted, this issue is not on a Duc, but on a GSXR. I have just got the bike out to go for a spin and after a mile or so, when slowing down from around 70mp to stop at a roundabout I felt/heard a nasty juddering sound and immediately pulled over. The front end felt strange and the brake discs were red hot. I had hardly travelled far, maybe 2 miles with only a couple of stops, so I was surprised at the heat they generated. I immediately came home and tried to test the problem out. Im fine when I apply the breaks to maybe 50% max pressure, after this is starts juddering. It also judders on brake release if under 50% max pressure. Any ideas while I have a look around?
I'd be able to tell by having the calipers off of the forks and looking at the condition of the pistons proper? How about the discs? I'll need a runout gauge to check them?
Hold a small steel rule tight against the fork leg and at right angles to the disc so the end just touches the disc...........then spin the wheel with your free hand.....
I cant tell if they are warped or not. I have had the calipers off and cleaned them. They were pretty mucky but are now clean. How freely should the front wheel turn when able to turn frerely and fully assembled? With the calipers off there is no drag and no play in the bearings, they spin freely. With the calipers fitted and the calipers pumped back out to operating distance from the discs, I get around 1 rotation with a hard spin.
Could be many things of course but either worn/loose headstock bearings or brake pad flutter/warped disc(s) come to mind
the headstock bearings can be ruled out as the wheel displays the same resistance when free of a load. It disappears when the calipers are re-fitted so it's either discs or calipers. I'll give them a proper clean after the children are in bed. Can I reuse the seals? Will multipurpose grease (that looks like caramel) suffice?
I rebuilt the calipers last night and there still feels like there is excessive drag on the wheel. Discs weren't warped when placed in to a glass sheet, and pads are mid-life. I'm stuck for ideas.
did anyone mention wheel bearings? haven't read whole thread but easy to check for binding with caliper off.
The wheel runs free and true with little resistance when calipers are removed, so the problem is in the brake system somewhere...
When you say "rebuilt the calipers", do you mean that you took the pistons out of the calipers, cleaned up the pistons and the recesses, cleaned the seals, reassembled the lot, and bled out the system? So how did the pistons, caliper recesses, and seals look? Any corrosion, scoring, signs of leaking or seizing? If all that stuff looks OK, the problem must lie elsewhere. What about the master cylinder? Does the piston return freely on release? Any possibility of it sticking in the ON position? How did the brake fluid look? Clean and clear, or dirty with particles or contamination? Just a few ideas ...
just me maybe, but I wouldn't rule anything out just yet - would be good to hear what the problem turns out to be when you find it PP - as far as suggestions go "i'm out".
No........IMO it will not only bugger the seals up, but it will also melt and get on the discs.... I can't see why you can't do a basic check the disc run-out..........if you use the steel rule method (and tape it on the fork leg, if you can't hold it there with one hand) you can soon tell if there is some amount of warping or not..........either the end of the steel rule touches the disc all the way round or it touches only in one or two places........the latter means some warping..........you can see how much or little there is........in fact you can even hear it.
Arquebus, I did what you suggested. There was no evidence of warping. I've checked the lever to see if it is always on by a small amount. New pads to try and then I'll have to fork out for new discs just incase
Maybe the juddering is a red herring and purely a result of the brakes overheating. Have you removed the pistons and polished both them and the bores with wet and dry? Is there no improvement at all? I think you'd be lucky to get absolutely no drag off the pads as long as it's minimal.
My guesses are: new pads will sort it or, if not that, new wheel bearings. I know Tom said that the wheel turns true with the calipers removed but I'm guessing that there's enough wear/play in them to created the juddering issue when the brake is applied.
What? Am I supposed to read thread titles now? :Bag: I maintain that wheel bearings are the most likely culprit (but that pads are still possibly at fault). Have we eliminated fork oil/springs? Coming off the brakes, the forks ought to decompress at similar rates. Differing spring rates/fork oil quality/air gaps may be a factor ... but I still blame the wheel bearings
