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Old 05-04-2018, 01:35 PM   #1
fortyonethirty
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I crashed during practice for the AFM round 2. I got knocked out for a couple minutes, so the whole thing is a bit fuzzy. I have some ideas on what happened, but I wouldn't mind a little BARF wisdom.

What do you guys think?


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Old 05-04-2018, 07:59 PM   #2
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very hard to tell.

I wonder if u chattered the front end. for about 1sec before u actually crash, theres a fluttering noise and some extra shaking on the video. also, the black line that goes by looks to be rubber not a seam. its a broken line, implying the tire was bouncing. do u know what chatter feels like?

did u brake at all? if I get in really hot into that corner, I make sure to brake a little bit to load the front end and tighten my turning radius.
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Old 05-04-2018, 09:19 PM   #3
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Looks like the front tire left a skid mark as it was going down.

Hope you’re okay.
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Old 05-08-2018, 07:16 AM   #4
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Quote:
Originally Posted by stangmx13 View Post
very hard to tell.

I wonder if u chattered the front end. for about 1sec before u actually crash, theres a fluttering noise and some extra shaking on the video. also, the black line that goes by looks to be rubber not a seam. its a broken line, implying the tire was bouncing. do u know what chatter feels like?

did u brake at all? if I get in really hot into that corner, I make sure to brake a little bit to load the front end and tighten my turning radius.
I'm with this. I just had the same front chatter yesterday at Sears Point, woke me right up.
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Old 05-08-2018, 02:55 PM   #5
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You were on the gas then closed the throttle about a second before crashing. From the available info, it's likely you overloaded the front.

It may be that simple, though could have been exacerbated by having had pressure on the bars. We can't tell about that from the video; only you might know whether or not that was a factor. Being off the throttle, it's more likely than not.
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Old 07-18-2018, 10:31 PM   #6
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what would cause the chatter in this case?

Isn't chatter usually caused by bottoming out the forks - so corner speed + closing throttle + potentially weight on the bars = bottom out and chatter?
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Old 07-19-2018, 07:04 AM   #7
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Chances the OP bottomed the front end into Riverside are slim to none. And, bottoming out doesn’t necessarily cause chatter. Chatter is an uncontrolled oscillation where some disturbance creates a feedback loop that leads to all that. Well it can be that. It’s so complicated that it’s hard to nail down w specifics. Nearly anything with a bikes setup can be the cause and fix for chatter issues: springrate, tire pressure, ride height, etc.
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Old 07-19-2018, 08:09 AM   #8
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could a bad tire cause chatter?
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Old 07-19-2018, 12:20 PM   #9
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It could, though if this rider had several laps on the tire already without feeling chatter, that's probably not it, unless something physically failed.
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Old 07-21-2018, 09:57 PM   #10
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it could have been the tire was starting to blister?
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Old 07-21-2018, 10:49 PM   #11
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Given that we can observe riding errors, let’s use Occam’s Razor.
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Old 07-23-2018, 10:20 AM   #12
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I understood "chatter" was the tire slipping slightly and re-gripping in fast succession (i.e., the fork is unable to absorb / control the forces on the tire, including a bottomed out fork or too much rebound potentially, etc.)?

Sounds like that's not right, so just trying to understand what it is... "Uncontrolled oscillation" of what?


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Chances the OP bottomed the front end into Riverside are slim to none. And, bottoming out doesn’t necessarily cause chatter. Chatter is an uncontrolled oscillation where some disturbance creates a feedback loop that leads to all that. Well it can be that. It’s so complicated that it’s hard to nail down w specifics. Nearly anything with a bikes setup can be the cause and fix for chatter issues: springrate, tire pressure, ride height, etc.
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Old 07-23-2018, 02:20 PM   #13
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Given that we can observe riding errors, let’s use Occam’s Razor.
What riding errors do u see?

Closing the throttle there is correct. If anything, it was closed too soon. Perhaps it was closed too fast.
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Old 07-23-2018, 02:22 PM   #14
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Originally Posted by viva_brasil View Post
I understood "chatter" was the tire slipping slightly and re-gripping in fast succession (i.e., the fork is unable to absorb / control the forces on the tire, including a bottomed out fork or too much rebound potentially, etc.)?

Sounds like that's not right, so just trying to understand what it is... "Uncontrolled oscillation" of what?
The forks moving up and down in very fast succession is the chatter part, is the uncontrolled oscillation. But of course u can have chatter at the rear too. Uncontrolled == unstable == does not decrease in magnitude over time. Oscillation == cyclic movement. A tire slipping and regripping could cause chatter, or chatter can cause that.
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Old 07-23-2018, 04:08 PM   #15
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i was pitted with ian in the garage

he was on bridgestones, we (not ian, he was loopy all day after that) were thinking at the time it was a bad front tire

if not the tire, i would be interested to find out the condition of the suspension / suspension fluid

it reminds me of a tank slapper, but going 'up and down' instead of 'side to side'
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