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Discussion Starter · #1 ·
Hey guys,
So this is a two part post. First I wanted to share my experience this morning and get some input from you all. On the ride to work I was on an interstate and accelerating to around 90mph to pass a group of cars so some lane changing was involved. Not the first time I've done 90mph on this bike. But at one point the head started to shake. Not very fast and lasted for about 5-10 seconds (hard to tell when focused on the road, things seem to slow down). I didn't feel out of control and it wasn't a tank slapper. Road conditions were good: dry, no bumps or holes, maybe higher in the middle of the lane where car tires push down the outer parts. I didn't really do anything different to combat the shake, my panic reactions tend to be pretty mild so I maintained focus and held my speed, continuing to maneuver so I was away from this group of cars. Any thoughts on what I experienced?

This leads me to the second part of this post. I'm about 145lbs with gear and I'm wondering if I need to start thinking about adjusting the suspension. The preload is the same as stock. I won't be doing any track days but I do like to test my skills when I get a chance. Should I move preload a click to account for my lighter weight? And also for my weight should I start looking to change or upgrade parts to get a better ride? Is the head shake a result of setup, my weight, or road conditions? Thanks in advance for any input!
 

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But at one point the head started to shake. Not very fast and lasted for about 5-10 seconds (hard to tell when focused on the road, things seem to slow down). I didn't feel out of control and it wasn't a tank slapper.
Lots of possible causes for this:

The most common cause of headshake, is the front wheel getting light under acceleration while you're also running over rough pavement. Usually only lasts a couple seconds and then settles itself.

It can also be caused by a wheel being out of balance or something similar. Incorrect air pressure (if it's way too low it decreases trail) in the front tire can contrubute to this, as well. If tire pressure IS low, check for a leaky valve using soapy water or for a nail in the tire, causing a slow leak). A lot of times you can push through a headshake with a short burst of more speed, then backing off the throttle slowly.

Driving hard out of corners can also sometimes cause headshake especially if the pavement is a bit bumpy. The front gets light, the wheel is still turned slightly but straightening out, and the tire interacts with the bumps causing a back and forth oscillation that usually damps out quickly.

Replacing the rear tire with a taller one will reduce trail and make the bike more prone to headshake. Lowering the triple clamp downward on the forks (= moving forks upward in the triple clamp) will do the same thing.

I've read that the R3 was designed for riders in the 130 to 160 pound weight range, so the rear shock should be on the correct setting for you, but you can always try different settings to see if they make an improvement.

Here's a real doozy of a tank slapper

https://www.youtube.com/watch?v=LZ1srcQMa_0&feature=related
 

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Discussion Starter · #3 ·
Thanks Fang! I greatly appreciate you taking the time to write this post. This morning was quite a bit more chilly than it has been so I'll check tire pressure as soon as I get home.
 

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Discussion Starter · #7 ·
Thanks for the links pattonme! I'll take a look.

To the other guys, I hadn't either before this incident or after. Maybe it was just the road and the circumstances. ::shrug::
 

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Everyone who rides any length of time will have the (mis)fortune of a tank-slapper at some point. Like Fang sez, usually the front-end gets light but sometimes you get them for no apparent reason. Things I'd offer: You're light, so get weight forward at higher speeds (tuck, chest on tank), take a click or so of preload out of the rear (setting 2 or 3 I'd guess), check steering axle bolt to make sure there's no play or 'clunk' in the steering. Steering damper is nice, but costs coin.
 
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