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What Did My Front End Do?


pantablo
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A few weeks ago I had a 'pucker' moment on one of my canyon rides. I've been trying to understand one aspect of what happened.

 

I was riding at a good pace on a deserted canyon road. It was my usual Angeles Crest ride but this was a new canyon road for me, that I usually dont do nor would I probably do again (due to logistics). I was going about 70mph in a left hand bend. I was hanging off a bit, looking through the turn, etc. Then the front end washed out and the front of the bike felt like it went to the right, having lost traction. It chattered a bunch, feeling like the front tire was trying to regain traction (The road was slightly rippled here on further inspection later). Then IT happened. The handlebars quickly went to the left stop ( I mean they felt like they snapped to the left hard). Thats the part I dont understand-what caused it to do this? I quickly saved it and kept riding. I just dont understand that left stop business...When it did this I thought to myself-thats it, Ive done it and I'm about to crash...

 

Anyone know what the front was doing that caused this?

 

In hindsight, I dont think I did ANYTHING like tensing up or "trying" to recover it. That probably saved me. It all happened so fast I didnt realize what it was doing or what was happening until it was over. Its possible I rolled off the throttle but I doubt it. I definitely didnt TOUCH the brakes. I was loose on the bars as far as I know, always am very conscious of that. That probably helped save it too. I dont recall if it fell into the corner more when the bars went left but it definitely didnt stand up.

 

A little background on me might help too. I've been riding now for 2 years. I currently have a 2004 600RR that I have owned for about 5 months, and 4300 miles. Previous to this I learned to ride on a gs500, putting 9000 miles on it. My riding consists (and has always consisted) almost entirely of canyons. No commuting or much street riding, except to get to the canyons. I currently have been riding friday and sundays up at Angeles Crest Hwy in the Los Angeles area and have been for quite some time. I am doing my first track day at Willow Springs in a couple of weeks and look forward to doing several track schools, in order to give me a bigger safety margin on the road. This is my first post but I've been lurking here a bit, off and on.

 

Thanks in advance...

pablo-

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63 views as of this moment and not one theory? Stumped ya.

 

I was reading November's Cycle World TDC column by Kevin Cameron:

 

"...If the [front] tire is operating near the limit of its adhesion, the rear portions of the footprint are under enough side stress to begin sliding. Because this loss of grip begins at the highly stressed trailing edge of the footprint, the rider may feel this as a reduction in the self-centering action of steering. This is why the steering "goes light" as the limit of front grip is approached."

 

Only confirms what I already knew-that I'm one lucky SOB...

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Think about it from a physics point of view

When cornering the tyre isn't completely straight in line with the chassis, it's turned in towards the inside of the turn.

 

Because of the force on the tyre, it naturally wants to turn in on itself, so when the tyre finally lets go, the front wheel is free to turn the way it wants to until the bars hit the stops.

 

Not a good explanation but it's why it happens.

 

I've lost the front end many times and every time, the front folded.

I've just been lucky enough to save it every time so far *knocks wood*

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  • 2 weeks later...

In common vernacular, your front end "tucked". You exceed the traction limits of the tire, which can be caused by too much weight bias toward the front. This can be caused by many factors; one is being off the gas, or not on the gas hard enough and overloading the the front. Another is braking deep into the turn, and another is suspension. Your suspension may be set up in such a way that it can't handle the rapid bumps at that speed and your front tire lost contact with the road.

 

The physics explanation is correct, but I think what you are more concerned about, although not mentioned in your post, is how to avoid this in the future. When something that severe happens to me and I don't know why, I turn around to see if I hit sand any thing loose on the road. It is usually the case. Other times it is fear to let off the brakes, or missing a downshift and coasting through the turn.

 

The beauty of the track is that you don't have to worry about sand or gravel in the turns and you can experiment with the limits of traction. On the road you just have to dial it back or be willing to take a gamble that stacks the odds against you sometimes.

 

Glad to hear you pulled out of it. It sound like you didn't give up on the bike and it rewarded you by keeping you on the road. When I feel the front going, I hold the inside grip so that the tire/wheel cannot tuck on me and it has worked in the past, but I don't think it is in anyones teaching technique - it was just gut reaction.

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