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PostPosted: Tue Apr 01, 2008 18:51 
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Just to chip in with some summary advice.

Generally I will aim to slow on the approach and do all the braking before starting the turn. I assume you weren't still braking or settling when it washed out?

I wouldn't expect leaves or a small patch of bad road to cause both front and rear to wash out unrecoverably. I've been on high speed courses in heavy rain and had front and rear slide a little, the key is knowing what to do when it happens. Its unusual to lose the rear and then the front unless you were braking or gripping the bars too tight..

There's nothing wrong with Bt020s I've had them for years and found them extremely good in bad conditions. they don't last too well on a track, but they are a good road tyre.

I suspect you need to go back to the basics of cornering:
- make sure you do all your braking before turning in
- you are riding round the bend with the throttle open in the right gear.
- you are controlling the bike smoothly and accurately (i.e. its going exactly on the line you want and not roughly on the right line)

But most importantly you need to pick a speed that has some contingency built in and is not the maximum you and your bike can take the bend at.

So anyone who has their knee down on a bend doesn't have either the ability to see very far ahead or change direction quickly when the unexpected happens.

you can get almost as much benefit by dropping your upper body in and moving only an inch or 2 in the seat.


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PostPosted: Wed Apr 02, 2008 17:44 
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diy wrote:
Just to chip in with some summary advice.


Thanks.

Quote:
Generally I will aim to slow on the approach and do all the braking before starting the turn. I assume you weren't still braking or settling when it washed out?

I wouldn't expect leaves or a small patch of bad road to cause both front and rear to wash out unrecoverably. I've been on high speed courses in heavy rain and had front and rear slide a little, the key is knowing what to do when it happens. Its unusual to lose the rear and then the front unless you were braking or gripping the bars too tight..

There's nothing wrong with Bt020s I've had them for years and found them extremely good in bad conditions. they don't last too well on a track, but they are a good road tyre.

I suspect you need to go back to the basics of cornering:
- make sure you do all your braking before turning in
- you are riding round the bend with the throttle open in the right gear.
- you are controlling the bike smoothly and accurately (i.e. its going exactly on the line you want and not roughly on the right line)


That's the thing - I did all of that. In all my riding I have never ever used the brakes in a corner (well, maybe now and then in town when necessary, but certainly not in proper cornering). I usually don't even brake for corners at all, I roll off to the required speed - and if I do brake I get the braking done a couple of seconds before I turn in.
Straights don't really interest me, you'll find me speeding up for corners more often than you'll find me braking for them. :)
I was using second gear, loose grip on the bars, perfectly relaxed. I never shut the throttle in a bend - keep it neutral and as soon as the bike's leaned over I generally roll it on ever so slightly from that point. I can't say for sure whether I happened to keep the throttle neutral or roll it on at this point.
Line was exactly as I wanted.
After I came off I was lying at I suppose the corner exit really, so I must have been at least half way around. I felt the rear slide out, and then the next thing I know I'm being thrown through the air (or along the ground, I don't really know) - which I figured was caused by the front washing out also.
This had been a mystery to me for months, but I also figured the deep gash/scar/whatever you want to call it on the inside of my right leg and numbness on my right shin must have been caused by the bike falling on my leg as I went down. I can't think of any other explanation for it.
If it helps any, I had put about 5000 miles on the tyres and they weren't new when I got them. They weren't in any danger of being worn out or anything, but I was thinking about replacing them in the near future.
I did have the suspension set up for my weight just about a month beforehand though.

Quote:
But most importantly you need to pick a speed that has some contingency built in and is not the maximum you and your bike can take the bend at.

So anyone who has their knee down on a bend doesn't have either the ability to see very far ahead or change direction quickly when the unexpected happens.

you can get almost as much benefit by dropping your upper body in and moving only an inch or 2 in the seat.


Indeed, indeed...


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PostPosted: Thu Apr 03, 2008 11:29 
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repiV wrote:
After I came off I was lying at I suppose the corner exit really, so I must have been at least half way around. I felt the rear slide out, and then the next thing I know I'm being thrown through the air (or along the ground, I don't really know) - which I figured was caused by the front washing out also.


sounds more like a high side possibly shutting the throttle or the tyre regripping as it exits the slippery patch...

Image


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PostPosted: Thu Apr 03, 2008 12:08 
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I've never quite understood the whole highside thing. I've had quite a few rear slides in the past, sometimes quite pronounced, where the tyre has regripped and the bike has continued on its merry way without jerking me out of the seat. It's happened enough times for me to basically not worry about it anymore when it does.
Would this be different because I was travelling at a higher speed at a more extreme lean angle? I have to say it's kind of an oddity, cornering at speed has always felt extremely stable...it's the slower/wet stuff that gets dodgy.


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PostPosted: Sun Apr 06, 2008 10:21 
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having a rear end slide is no big deal if you are upright. Basically your front should continue to point in the direction of travel and pull the rear back in before it comes too far round. Essentially because motorcycles are articulated, the rear is kind of like a trailer.. providing it remains passive (i.e. not gripping)

However, once the rear comes round more than a few degrees, and then grips suddenly. There is a risk of the bike 'tripping over' as the rear re-grips. It will then catapult you forward. The more cranked over you are when that happens, the more energy that gets transferred in to lift.

In the US (DAS equiv. MSF) they teach you never to unlock a locked rear wheel once it has locked, basically because a low side is preferable to a high side.

I'm not convinced by this, but do generally think that doing nothing is the best way to control a rear slide.


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PostPosted: Sun Apr 06, 2008 19:08 
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diy wrote:
I'm not convinced by this, but do generally think that doing nothing is the best way to control a rear slide.


sadly enough, one has to make all those decisions in fractions of a second. so "experience" plays a big factor here. and by "experience" i mean trying the ugly and the good side of both!


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PostPosted: Sun Apr 06, 2008 22:08 
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diy wrote:
having a rear end slide is no big deal if you are upright. Basically your front should continue to point in the direction of travel and pull the rear back in before it comes too far round. Essentially because motorcycles are articulated, the rear is kind of like a trailer.. providing it remains passive (i.e. not gripping)

However, once the rear comes round more than a few degrees, and then grips suddenly. There is a risk of the bike 'tripping over' as the rear re-grips. It will then catapult you forward. The more cranked over you are when that happens, the more energy that gets transferred in to lift.


Gotcha. I take it there isn't really any way to "hold on" through a potential highside?
I've had a few scary slides while leaned over. Three come to mind in particular.

1. First day on the CB500 doing my DAS. Pissing it down. Wet manhole cover, felt like the whole rear end of the bike moved a foot to the right and then it just straightened out again of its own accord. It was very smooth though, it was more like a slow and progressive snaking movement than a jerk.
2. Coming home in the middle of the night, bend in a local high street, went over a pothole at about 40. Rear end snapped so far out I was certain I was about to crash, but it sorted itself out.
3. Turning right at a mini-roundabout near Boxhill, rear end skipped right out and then regripped. Quite violent, but low speed also.

Perhaps in these cases the rear just wasn't that far gone, but it really feels like it at the time?

Quote:
In the US (DAS equiv. MSF) they teach you never to unlock a locked rear wheel once it has locked, basically because a low side is preferable to a high side.

I'm not convinced by this, but do generally think that doing nothing is the best way to control a rear slide.


It's worked for me most of the time, and in the last eventuality I doubt I would have fared any better in a lowside anyway. Given where I came off, I don't think I could realistically expect a more favourable outcome. :)


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PostPosted: Mon Apr 07, 2008 12:48 
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1 and 2, both likely to be the front pulling you true again.

Hanging on is always usually better than jumping off. Once you've bailed, you definitely have no brakes or steering.


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 Post subject: Re: Cornering
PostPosted: Sat May 31, 2008 18:49 
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repiV wrote:
I had a rather nasty accident back in October presumably involving leaves, so I've had to re-examine some of my thoughts about safe cornering and would welcome any thoughts on the matter.
Quote:


Basically it was a nice right hander, on my favourite local bit of road, which I have ridden at knee-down speeds dozens of times without any kind of incident whatsoever (but that was in the summer). I guess the few months' layoff must have been due to all my commuting making taking the bike out for the same old local play a bit tedious...

Anyway, this time I knocked the bike over into the corner at 60 (as always, something I worked up to over many repeat runs) and take the right line, only this time first the rear steps out and then the front end goes. Result: me into tree, badly shattered tibia, dislocated hip/ankle and some nerve damage.

The road was dry, but there were leaves - I'm not sure why I didn't take this into account. I've since learned that apparently the underside of the leaves can still be wet?

It was kind of a shock to me really because I had considered myself to be a fast but safe rider rather than a nutter, which was generally the accepted assessment amongst friends too, and I've never so much as had any "ohshit" moments in the twisties before then. Complacency?

I had been led to believe that so long as the road surface is decent and dry, the tyres will handle peg-down lean angles without any problems at all (this is a Fazer we're talking about, not a CBRGSZX10000 with knee height pegs...), and that had certainly been consistent with my experience up until that point. Now I'm pretty sure wet leaves must have been the culprit of this accident, but it begs the question, how can you possibly tell the safe lean angle just by looking? How can you trust the tyres to work as they should, when the consequences of getting it wrong are so catastrophic?

I used to be a very confident rider, but now hopefully being able to ride again within a couple of months, I'm left wondering if it's at all possible to have fun in the corners without putting yourself in mortal danger at the same time.
And now I'm worried about diesel and suchlike - I've never been unfortunate enough to hit diesel in a corner, but how the hell do you prepare for something like that? With a leg that's going to take two years to heal properly, I can't afford to come off again.

How do you eliminate this risk without riding as if you have stabilisers on? Is being able to judge the exact levels of grip available something that just comes with experience, much like the "sixth sense" that develops from riding in traffic?


Any number of factors could have caused your get off its easy to overlook the obvious when searching for an answer that doesnt include your possible error!. When you started knee down stuff how often did you do this bend and how often did you check your tyres closely before doing so. Familiarity breeds contempt. Knee down stuff isnt really essential for racers unless they are dropping the bike, like has already been said, go to the track for that kind of riding.


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