Non Ducati but I wanted to ask as we're at a loss. The angry Italian lady that lives in my bed had a ~4th gear rear wheel lock up on the Snetterton straight last week which sent her into a 120mph breakdance spin down the pits. She was actually quite excited about the whole thing as she felt like MotoGP Ionnone style and I even got the business several times that night which was cool (but I'd rather not resort to 120mph to get giggity giggity). Anyhow I digress .. we're supposed to be at Mugello and Imola in a few weeks and those are the last places you want a surprise rear wheel lock up but can't work out what caused it? The only smoking gun after the event was that the chain was very tight and the axle had pulled back a little on the other side. There's no sign of damage or marks on the swingarm and from people I've spoke to they think it very unlikely the wheel moved enough to hit the swingarm but the tight chain is the only obvious sign of something being wrong? The bike looks to run fine in every gear, I havn't been able to push it hard anywhere but did cycle through the gears with no problems. The rear bearings all look good, everything feels rock solid as it was all rebuilt by the previous owner. No signs of damage on the sprockets or inside the front sprocket cover. What are peoples thoughts on the chain being tight, is there anything else other than hitting the swingarm that could cause it??
Think I'd have wheel out, chain right off and check every bearing, turn g/box sprocket by hand and feel for any roughness/tight spots etc also look for witness marks round rear wheel area, if it did catch on something there should be a big mark visible somewhere. Good luck.
I had a similar experience a long time ago now, on a CB500 whilst doing 70 on a motorway. It happened momentarily and very quick but when I stopped and checked everything I realised that one of the axle nuts was loose on one side which had caused the wheel to move out of alignment which had caused the chain to over tighten. The bike had just been serviced so obviously the axle bolts had not been tightened to the correct torque. May this have been the problem?
It seems like the only explanation but it just didn't look like the wheel could move by the amount needed for it to hit the swingarm? There's a big gap.
I'd suggest that if it had moved enough to lock the wheel there'd be some type of marking on the swing arm and the tyre. Other than that no idea.
Given that the chain was tight and the axle had pulled back then the wheel couldn't have been fully tightened. So it would be reasonable to assume that it had moved. You would think that the first thing that would contact would be the tyre and the swinging arm but is it possible that something contacted within the brake? Whatever, I'd be stripping it down to find out.
Do you mean the rear brake pads accidently got applied? I'm pretty sure its near impossible to lock the rear wheel when on the power (she was accelerating still). I've locked the rear accidently when hard on the brakes when the rear has been in the air, but I dont think it's possible when accelerating?
Not necessarily the pads, but something must have contacted pretty substantially to cause the lock up. Nothing short of a full inspection is going to show up the cause. I'm sure you don't want to risk it happening to her again.
I think the rear axle wasn't torqued correctly, it should not be able to move if it was correct. Possibly any chain adjusters weren't snugged against the any axle plates too. I'd check a parts or workshop manual diagram to ensure you have all the (right) bits around that area too. Aside from the axle movement - I've locked the rear solid after adjusting the rear brake pedal to get the free play out (thinking it would be better, more instant, etc), took a fair bunch of miles before it happened but it locked the rear totally solid, had to drag the bike out of the way. About ten minutes later (smoking a few fags and swearing a lot) it was if the problem never happened and the bike rolled freely and the rear brake worked fine. As I'd taken all the free play out, the pads at rest were too close to the rear disc and the small amount of friction generated heated up the pads/pistons/fluid which caused the pads to contact a bit more, and so on - when it all cooled down it was fine. IIRC it took about 20 or 30 miles before it locked up, can't say I'd noticed anything different until the rear was going sideways all by itself.
Check the rear brake pads. If the wheel had moved it might have snagged on the caliper / pads and jammed until the power was off. As Derek said it would have to be something quite significant to lock the wheel.
Was thinking about this. Could it be that the brake overheated and stuck on? Happens a lot with older Ducati's even if they aren't being used. Just one tap, doesn't return, gets hot, expands and boom locks. May be worth looking at the disc for any overheating signs?
We couldn't see any signs of overheating on the rear, Vale was looking for that yesterday. Sounds like a possible culprit though.
Insufficient free play at the pedal can mean that the piston doesn't travel far enough back to uncover the bleed hole back to the reservoir creating exactly this effect.
Was the lockup instantaneous or did it the bike decelerate a bit first? I think it is unlikely to be anything within the engine itself. Mechanical failure within at those speeds usually breaks something. You might want to drop the oil and check just in case, though. Have you checked the chain and sprockets carefully in case something got caught? If the axle has moved it either wasn't done up properly or something got in between the chain and sprockets. Friend of mine had a rear wheel bearing collapse which caused a similar lock up. He was going through miss-kiss-miss at the Ring at the time. Threw him off the bike, but somehow both rider and bike missed the barriers.
I forgot to say that yes we already dropped the oil and its completely clear. The axle definitely moved back on the other side to the rear sprocket despite being properly torques as Vale is very careful about this and doesn't let me and my huge Ducati breaker bar near her bike! I just wouldn't expect the wheel to be able to move so much that it locks against the swingarm? I'm going to get in the garage and loosen it off and actually try and make it do it later. The chain and sprockets looked fine. I took a look as we figured there would be damage to the alloy sprockets if a bolt or something had jammed in there. It might just be me looking for stuff but there seemed to be black oil from the chain link rubbers which I wondered if it was due to the chain being very tight? Jesus, thats not the place for it!!
I'd defo be double checking the rear break. Make sure it's not been over adjusted, the plunger mustn't be tight into the M/C. This could cause the problem Derek described. It would also unseize once cooled off.
Exactly - the lack of free play was pre-loading the hydraulics and not allowing enough release of the pads from the disc. End result is a thermal cycle that results in a locked rear wheel.
I still can't get my head around something Guy Martin mentions in his autobiography- that when he's doing one of the Northern Island races, his rear brake disc is glowing red as he's accelerating hard and using the rear brake to stop the front wheel coming up , both at the same time. I'm not a racer and find it hard to understand that this isn't self defeating ,as surely the drag from the rear brake is slowing him down, wouldn't he be better off not accelerating quite so hard therefore not needing to use the rear brake and not not slowing himself down so much. I am of course making the assumption that he knows what he's doing, although entertaining though he is , I sometimes doubt it!
