Rear wheel skip - why?

[Winston001]

Got a fright the other day. Coming fairly fast into a corner, I braked and may have changed down, not sure. Anyway next thing I notice the bike isn't slowing much and the rear wheel is moving back and forth sideways under me. It felt like it was skipping on and off the road, side to side. Not very far, but certainly out of control.

I have no idea why, its the first time I've ever experienced this. I thought of a tank slapper but that seems to be a front wheel problem and the instability was definitely from the rear.

Went back a day later to check the road. It was clean, no oil on it, the odd very small patch of mud but dry, no tyre marks from the bike that I could see.

It all happened so quickly that I struggle to remember or understand exactly what took place. In fact its taken me a week to even post this, thought I was a gonner.

Any ideas?

[AlBundy]

How much front brake and rear brake do you use? I ask 'coz you state you weren't slowing down much during the ordeal.

Which bike was it on? The Ducati or BMW?

It sounds like you maybe went a gear too low and the compression braking was more than you'd normally experience, which semi-locked the rear wheel, causing it to hop and skip, as well as slide...

Some more info would help in determining or advising further...

[owner]

Do you know how to blip the throttle? ie Match the engine speed to the speed of the rear wheel.

If not, you should google "blip throttle" and learn as much about it as possible.

Everytime I change down after
1;pulling the clutch I
2:rev engine( to the revs I think the motor will be at when I put it in the gear)
then 3;select the gear
then 4:let the clutch out

[Forest]

Check the air pressure in your rear tyre.

[James Deuce]

The rear tyre doesn't have a lot of weight on it during heavy braking and engine braking means the wheel is spinning in spite of the drive train not because of it. Any bumps on the road will biff the rear up into the air momentarily and the wheel stops spinning then hits the ground locked. Tyre grip might overcome engine braking and spinning the wheel back up when it touches down. Sometimes not.

This is what those magical slipper clutches or MV's clever partially open inlet valves are about. They reduce the amount of engine braking the tyre has to cope with and help make heavy braking to hard acceleration transitions really smooth. The old school solution used to be to crank the idle up to 3000rpm, but that would cause other issues. After reading about Mick Doohan racing RVF750s in the Suzuka 8 hour I starting using the clutch to remove some or all engine braking, fully releasing it at or before the apex for maximum drive. On my comparatively weedy RC30 it made sense. On a 200hp modern superbike I think you'd fry your clutch quickly, and slipper clutches make it a redundant riding style.

[imne1]

hmmm I do most of my slowing with engine braking - is this not a good thing? does everyone else just use the brakes only?

[Quasievil]

Got a fright the other day. Coming fairly fast into a corner, I braked and may have changed down, not sure. Anyway next thing I notice the bike isn't slowing much and the rear wheel is moving back and forth sideways under me. It felt like it was skipping on and off the road, side to side. Not very far, but certainly out of control.

I have no idea why, its the first time I've ever experienced this. I thought of a tank slapper but that seems to be a front wheel problem and the instability was definitely from the rear.

Went back a day later to check the road. It was clean, no oil on it, the odd very small patch of mud but dry, no tyre marks from the bike that I could see.

It all happened so quickly that I struggle to remember or understand exactly what took place. In fact its taken me a week to even post this, thought I was a gonner.

Any ideas?

Suspension set up, Chain tightness, Tyres pressures all soughts can contribute to this, you could have run with it and backed it in mate

[Pwalo]

Bit too much front brake. Rear goes light. Change down a gear and the back skips a bit. Nothing unusual, especially on a twin.

Now what you need is traction control like the 1098Rs and then you can bang it down through the gears and get all sorts of banging noises to scare the living daylights out of all and sundry.

[McJim]

I'll set up the camera as promised Winston - I will then film you as you try to replicate the incident and we can see what happened

[The Stranger:Me]

hmmm I do most of my slowing with engine braking - is this not a good thing? does everyone else just use the brakes only?

That sir is a deceptively simple question and can generate pages and pages of debate. Apparently there are those that never use their brakes and this makes them fast, because they are sooo smoooove.
Me, I'm slow and rough - I use my brakes. I use engine braking too, but am more concerned with the appropriate gear and the braking effect is a useful by-product of that process - or an opportunity to lock the rear for the hell of it.

[Bass]

Got a fright the other day. Coming fairly fast into a corner, I braked and may have changed down, not sure. Anyway next thing I notice the bike isn't slowing much and the rear wheel is moving back and forth sideways under me. It felt like it was skipping on and off the road, side to side. Not very far, but certainly out of control.



Any ideas?

Bet you were on the Duc, right?
Been caught out the same way.
I would wager that you changed down too soon under braking. Engine braking on the twin when you do that, is enough to get the back wheel skipping.
I'm with Al and JD on this one

[raftn]

Engine braking, I find on my 955, the engine braking is very effective, coming off the throttle into a corner the bike slows markedly, and i find often there is no need to aply any breaks. On my 675 it's a different story completly, the engine braking is not as noticable and i find myself using the break more often, yet the 675 turns in far easier than any bike i have ever owned, just requires a different riding style.

[imne1]

Ok cool, so I'm prob not doing anything wrong by under-utilising the brakes if I dont need them. I'm still a noob and have experienced the same thing as winston on my lil 250. I've found the applying the rear brake + blip throttle rev matching whilst changing down + easing off rear brake as I let the clutch out ... seems to keep skippy away.

[FruitLooPs]

Nearly binned my 750 doing just that on the port hills after riding my 2-stroke for years I was used to chopping down gears and nearly any rpm.

Learn quick smart though

[Winston001]

Bet you were on the Duc, right?
Been caught out the same way.
I would wager that you changed down too soon under braking. Engine braking on the twin when you do that, is enough to get the back wheel skipping.
I'm with Al and JD on this one

Yep, on the Duc.

Hmmm...good thinking. I suspect you are right. I wondered at the time if I was unconsciously pressing on the rear brake and combined with engine braking, that caused a lock-up.

I have no idea what speed I was doing but knowing me and the excellent conditions at the time, probably 130k approaching. The corner is unmarked (quiet country road) but say 70k bend. However none of that is remarkable, done it before on other roads.

Incidentally this all happened before I was in the corner.

Yes I do use engine braking combined with the front brake normally and probably rely on engine braking a lot because it is so effective.

My point is that I've ridden the bike pretty aggressively over 5000k now (a boy with a new toy ) and if suspension was the problem, it should have shown up by now. If the road surface was uneven, or wet, ok I can understand that. But the sudden loss of control in good conditions is pretty unsettling.