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  1. #1
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    Picked up my bike today!

    I did a ten mile first impression ride this afternoon and already ran into a slight problem. I was pushing pretty hard going down a hill and right at 30 MPH I had some violent headshake. I almost lost it, but hit the brakes and got it under control. Has anyone else ever experienced that? If there's a way to fix it I'd appreciate some advice. I do like to go fast occasionally.
    2012 KHS Tempe 29er

  2. #2
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    ive never been that fast, lol. is the star nut tight enough for your headset?

  3. #3
    King of Middle Earth
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    Stand over the bike and lock the front brake. Put your other hand over the upper head set cup and wiggle the bike fore and aft. Do you feel any play in the head set when you wiggle the bike? If so, take it to the shop you bought it from or your LBS and have it adjusted if you are not sure how to do it yourself. BTW, a super tiny bit of movement may be normal but anything else needs attention.

    If there is no movement in the headset after that test, check to see that the wheel quick releases are tight. They need to be cranked down very hard.

    Then try to wobble both wheels back and forth. There should no movement whatsoever there.

    Let us know how it goes...
    fee-fy-fo-fum...

  4. #4
    1*14*29*2.1 & 1*1*29*2.4
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    fork on forwards? Just asking as someone else did this recently!

  5. #5
    R.I.P. DogFriend
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    With a 72 head angle, things could get nervous in a hurry at higher speeds. The XC28 fork, with it's 28mm stanchions, is a likely contributor too, and the wheelset may not be super stiff. It also came with a 680mm handlebar, which isn't super narrow, but isn't wide by today's standards. A wider bar would give you more leverage to hold the bars steady, and a little longer stem might slow down the steering input too (so long as it doesn't impact fit negatively). It's seems most likely that it is a combination of factors that led to your tank-slapper episode than just one thing.

  6. #6
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    I appreciate all the input folks. I'm just getting back into riding after 8 years away, so I'm a little rusty on diagnosing problems. I'll do the test you suggested Hawg, and also make sure the quick releases are tight.

    If none of that works, I have free tuneups for a year from the LBS where I bought it. I can just keep the speed below 30 for a month or so, then take it in and tell the owner about the issue. One thing I know about this particular shop is the guy there knows his stuff. He'll be able to fix it, if it can be fixed.


    jeffj - the angles and fork info make sense too. Maybe I'll just have to settle for not being a speed demon on this particular bike.

    My last MTB was a Giant Rincon, and I once had it at 57 MPH going down a steep hill in Cali. It was wearing some Michelin hybrid tires designed for the street that went to 80 psi. Those tires made a HUGE difference in speed.
    2012 KHS Tempe 29er

  7. #7
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    Dang son! You sound like a speed demon...or your wireless speedo is not accurate ha, just playing. I can't even remember the last time I hit 30mph decending on a xc mtn bike unless it was a smooth gravel downhill. I'd imagine that anything at that speed will feel sketchy, especially with that head angle.

    Could be many reasons but You might want to consider using a much wider bar and shorter stem. It will keep things under control a little better...plus the fork (you didn't mention what kind but someone said it was a RS xc28.) could be a big reason. That fork is not made for that type of riding. I'm thinking stiffer/larger stanchion fork, 15mm thru axle drop outs, wider bars, and shorter stem will correct it. Even an angleset will slacken the headtube...a step in the right direction. Or lastly, check tire pressure or trueness of wheel. Although a completely different application, on a motorcycle...wrong front tire pressure and an unbalanced wheel will shake violently too at high speed.

  8. #8
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    Quote Originally Posted by drz400sm View Post
    Dang son! You sound like a speed demon...or your wireless speedo is not accurate ha, just playing. I can't even remember the last time I hit 30mph decending on a xc mtn bike unless it was a smooth gravel downhill. I'd imagine that anything at that speed will feel sketchy, especially with that head angle.

    Could be many reasons but You might want to consider using a much wider bar and shorter stem. It will keep things under control a little better...plus the fork (you didn't mention what kind but someone said it was a RS xc28.) could be a big reason. That fork is not made for that type of riding. I'm thinking stiffer/larger stanchion fork, 15mm thru axle drop outs, wider bars, and shorter stem will correct it. Even an angleset will slacken the headtube...a step in the right direction. Or lastly, check tire pressure or trueness of wheel. Although a completely different application, on a motorcycle...wrong front tire pressure and an unbalanced wheel will shake violently too at high speed.
    I actually understand a lot of that, especially the motorcycle reference. I've riden close to 200K miles on streetbikes, and have experienced the "death wobble" a couple of times on them as well.

    It sounds to me like I just need to accept my bike for it's intended use, and it's intended use is not speed. The angles are all wrong, the fork is not designed for speed, and ..... shoot. I'm 39. Maybe I should just slow down.
    2012 KHS Tempe 29er

  9. #9
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    Oh, and by the way - that 30 MPH downhill run was on asphalt. I wanted to see what my max speed would be. It wasn't very steep though, and there's another much steeper and longer hill near my house... I guess it's a good thing I didn't try that one first!
    2012 KHS Tempe 29er

  10. #10
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    Keep checking things. Retry the run with the fork locked. Your bike should be able to go that fast on asphalt.

  11. #11
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    If you still have the reflectors on that bike, you may want to consider taking them off as well.
    The little reflector could potentially change the way it handles at "ludicrous speed"
    2013 C-Dale Scalpel
    2013 Scott Genius 930

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