fork flex?

[wayne cooper]

Had my first street crash the other day. Not bad for 38 years of riding. Both the bike and myself are lucky. Me for having riding gear and the bike for not sustaining any real damage.
After going back to look at the skid marks so I could figure out why it washed out in front as it was doing good on dry pavement with the front wheel locked. I noticed that the mark went from straight and true to a set of three hash marks that were on about a ten degree angle. It almost seemed that the front wheel tried to curl up under the bike due to a flexing of the front forks. I know that at high speed (240 kph+) there is a discerning flex in the tubes. Being as I am seldom over 200 kph I set aside the fork brace as a possible winter add on.
I have just ordered one.

[fgh]

Huh! You locked the front and wonder why you go down?

[TheCafeKid]

sound almost like a tank slapper minus the crazy bar action..

[Grandpa]

Had my first street crash the other day. Not bad for 38 years of riding. Both the bike and myself are lucky. Me for having riding gear and the bike for not sustaining any real damage.
After going back to look at the skid marks so I could figure out why it washed out in front as it was doing good on dry pavement with the front wheel locked. I noticed that the mark went from straight and true to a set of three hash marks that were on about a ten degree angle. It almost seemed that the front wheel tried to curl up under the bike due to a flexing of the front forks. I know that at high speed (240 kph+) there is a discerning flex in the tubes. Being as I am seldom over 200 kph I set aside the fork brace as a possible winter add on.
I have just ordered one.

BS, first-class BS. The lack of fork brace didn't cause your crash; you caused your crash!

[Steve]

So, according to you signature line, were you living yet or not?


"I know that at high speed (240 kph+) there is a discerning flex in the tubes."

"I am seldom over 200 kph"

240 kph ~ 150 mph
200 kph ~ 125 mph

Life begins at 140

And you call this a "street crash"? Thankfully you are not near any of my streets. :shock:

No fork brace that I know of will prevent flex due to braking. All the braces I know of clamp to the tops of the lower tubes and help stabilize the forks when sideways forces are applied, as in turns. This keeps the two lower fork tubes moving up and down together, minimizing strain on the axle. If you were braking hard enough to lock the tire, you reduced your fork flex as soon as the tires started skidding. When the front tire skids, you will go down, unless you are extremely lucky.

IF your forks flexed due to braking, they would have moved back, toward the engine. A fork brace will do NOTHING to prevent that motion.


.

[wayne cooper]

RE crash

Dear Grampa. The incident happened at less than 40kph and was the result of some fool who decided to move to the right hand lane in order to gain a couple of car lenghts at a stop light. The speed listed was only to point out that the GS is well known for being a little bit flimsy. I was looking for some feed back as to the angle of the front tire prior to the crash. In case you are wondering I had less than 2 car lenghts to bring everything to a halt. I guess hitting the car and launching myself over it and bending the front end would have been a far better decision. Heck no sense riding home, and later on that evening with a skinned knee and a scratched fairing when you can break bones and trash hundreds of dollars worth of front end components. I ride less than 10 kph over the limit in the city and the roads I apply a more spirited style to are familiar with long sight lines through the curves.

[Grandpa]

Dear Grampa. The incident happened at less than 40kph and was the result of some fool who decided to move to the right hand lane in order to gain a couple of car lenghts at a stop light. The speed listed was only to point out that the GS is well known for being a little bit flimsy. I was looking for some feed back as to the angle of the front tire prior to the crash. In case you are wondering I had less than 2 car lenghts to bring everything to a halt. I guess hitting the car and launching myself over it and bending the front end would have been a far better decision. Heck no sense riding home, and later on that evening with a skinned knee and a scratched fairing when you can break bones and trash hundreds of dollars worth of front end components. I ride less than 10 kph over the limit in the city and the roads I apply a more spirited style to are familiar with long sight lines through the curves.

Whatever...

[49er]

Dear Grampa. The incident happened at less than 40kph and was the result of some fool who decided to move to the right hand lane in order to gain a couple of car lenghts at a stop light. The speed listed was only to point out that the GS is well known for being a little bit flimsy. I was looking for some feed back as to the angle of the front tire prior to the crash. In case you are wondering I had less than 2 car lenghts to bring everything to a halt. I guess hitting the car and launching myself over it and bending the front end would have been a far better decision. Heck no sense riding home, and later on that evening with a skinned knee and a scratched fairing when you can break bones and trash hundreds of dollars worth of front end components. I ride less than 10 kph over the limit in the city and the roads I apply a more spirited style to are familiar with long sight lines through the curves.

It's more likely that your front dampers are too soft causing your tyre to judder under the high braking load. What type of bike are you riding?
It's never a great result once you lock up the front end, especially on a wet road!

[fgh]

After I read your first post I had the impression that you were locking the front on previous occasions. Hence the first smug post which I now most sincerely apologize for. Steve was pretty thorough in his reply. When the front locks the bike can be kept up but it has to remain in a straight line and straight up, something that can't be repeated sucessfully by even the most experienced riders. No kind of modification or addition to the front end or any part of the bike will help. The only real solution is anti-lock brakes. Those must be engineered into the bike when its designed and aren't available as an aftermarket mod. When in a panic stop its very difficult to moderate the braking effort, but it can be done. Yours and everybody elses bike will stop its quickest at the point where the control pressure is maximized without locking either wheel. I practice on mine with some frequency. If there's a stop light ahead and no one behind you then throw the brakes to her. Each practice gets you closer to perfect.