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Thread: Bike Shop Woes

  1. #1
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    Bike Shop Woes

    I just went and test rode a Kona Unit 16", and whilst the size of the bike was perfect, the steering was way too twitchy.

    The head angle on the 16" Unit is 70.7 degrees, whilst the HA on the 18" is 72.2 degrees. The "salesman" tried to tell me that the 18" with the steeper HA would be even more twitchy than the 16". Codswallop. The shame was that there was no 18" assembled for me to compare.

    These bikes are hard to come by in Aus, as are a lot of rigid steel 29ers.

    My problem remains thus...

    I can get an 18" Unit from interstate, but that leaves the problem of not being able to ride before buying.

    Can anyone confirm my theory? Is the 18" with the steeper HA less twitchy? Is it that much bigger? Any other choice suggestions?

    I've ridden a 16" Haro Mary (HA = 72 degrees) and it wasn't nearly as twitchy, but it is a different bike altogether. Heavier, as well feeling larger to the point I felt stretched out too much.
    I see hills.

    I want to climb them.

  2. #2
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    Steeper HA = less trail = more twitchy.

  3. #3
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    what do you mean by less trail?
    I see hills.

    I want to climb them.

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    Quote Originally Posted by Stevob
    what do you mean by less trail?
    Trail is the distance between the projection of the steering axis on the ground and the contact patch. More trail = more stability.

    In theory you can slacken the HA ~1 degree for every inch of additional fork length; this may or may not have other undesirable effects.

  5. #5
    AZ
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    A shorter stem will slow it down a little bit . If the 16" frame was a perfect fit an 18" is going to be too big . The increased H.A. is also going to make it quicker steering . You prob. would quickly grow accustomed to the quick steering if you give it a chance , its fairly standard xc geom.

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    Thanks for that. So by that description, trail is an equation of the combination of head angle and fork offset.

    But if you take it to the extreme, a head angle of say 65 degrees will make the front wheel want to lay on it's side with any steering input at all.

    So why does the steeper head angle feel less twitchy to me? When I walked the 16" Unit without hands on the handlebars, the front wheel kept wanting to turn a full 90 degrees. This, to me is way too jittery.

    Obviously things like handlebar width and headstem length play a part in the steering feel, but...but...but...

    Oh, I don't know anymore...

    Has anyone had the same decision to make?
    I see hills.

    I want to climb them.

  7. #7
    AZ
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    You are over thinking this , get on the bike and ride it . If its right you will know it .

  8. #8
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    Quote Originally Posted by fallzboater
    Steeper HA = less trail = more twitchy.
    +1. The steeper the angle gets the twitchier the handling gets. You can shorten the stem and widen the bars to tone it down a bit.

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    Quote Originally Posted by AZ.MTNS
    You are over thinking this , get on the bike and ride it . If its right you will know it .
    Herein lies my problem. The 18" isn't ready to ride. Think I'll give that shop a call.
    I see hills.

    I want to climb them.

  10. #10
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    Quote Originally Posted by Stevob
    Herein lies my problem. The 18" isn't ready to ride. Think I'll give that shop a call.
    How tall are you? If the 16' size was perfect then you don't want an 18" - you either want a wider bar and shorter stem on the 16" or different model. Going to a bigger frame will introduce a longer top tube, completely changing the fit (not to mention the different angles here).

    Post up your height, shirt sleeve size, and inseam and we can figure out which size bike is more appropriate.

  11. #11
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    Though the salesman said that the 16" was "perfect" - how tall are you, inseam, etc.? I won't be helping much in the tech department, but FWIW, I just built up an 18" 2009 Kona Unit with the Project 2 fork and love the way it rides. It's far from twitchy to me - in fact, it feels very balanced yet handles quickly enough for a very smooth and fun ride. I agree with AZ.MTNS, you may be worrying too much. Make sure you have the correct size first, then enjoy the ride - I haven't heard too many complaints about the handling of the Unit (uh, huh, huh). I do understand your stress over not being able to try the 18" but you should be able to get pretty close based on your measurements and previous frame sizes.

    Good luck and keep us posted!

  12. #12
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    5'6" and around 30-31 inseam. Where from/to do I measure sleeve length?
    I see hills.

    I want to climb them.

  13. #13
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    The other thing I forgot to mention is that I "sat" on a 19" Unit last friday (that one wasn't ready to ride either) and it didn't feel as large as the 16" Haro Mary I sat on 30 mins earlier.

    I'm going to ask the shop to set up the 18" so I can compare.
    I see hills.

    I want to climb them.

  14. #14
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    Man.. 5'6'' on a 18" seems like its pushing it. I'm 5'8'' on a 17.5 and its just right. However my inseam is 31. I guess do all you can to ride before you buy. Do the 29" wheels change TT height?

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    Being a 29'er the sizing is a little different. Assuming you like Kona's appriach to geometry in general (shorter top tubes, longer stems), the 22.4" effective top tube on the 16" is appropriate for your height. Going up to an 18' frame increasres the ETT but 1.1 inches, which will dramatically alter your position on the bike. To compensate, you would need to put a ridiculously short stem on the bike, which in turn will unweight the front wheel and make it wander on climbs. Not to mention, the standover height on the 18" is bigger than your inseam, so you junk would be resting on the frame straddling the bike, and the chance for a more high impact introduction between the two is likely.

    At your height, it sounds like the 16" is the right size. Going on to an 18" will stretch you out a ton, and with it's steeper head angle and the need to switch to a much shorter stem, you will have a very twitchy climber. The larger bike (according to the numbers) would also be twitchier downhill, so it seems that you would be making a move in the wrong direction.

    That is, unless you have monkey arms. If you are some kind of 5'6" freak with arms that go down past your knees then none of this matters :-)

  16. #16
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    hehehe...my only resemblance to a monkey is my ears and my hair and my tendancy to throw my poo at people watching me through my cage...other than that, well, we're chalk and cheese.

    Ok, I went back and rode the 16" again, but for longer. Spent enough time on it to really get a feel for it. First thing, the 32/18 geering combined with the 175mm cranks is too short for me, but that's a non issue. I found myself sitting right on the back of the seat, with my hands wanting to drift forwards in front of the handlebars. This bike had the seat set right back too, and it had a 75mm stem. The handlebars were wider than any of my other bikes (680mm).

    The shop is getting an 18" in for me to try, and should be ready tomorrow sometime. I thought that they already had one, but it was a 19" I'm told.

    FWIW, my old Giant Yukon rigid circa 1996 has a 17.5" frame, but I'm unsure as to the HA on it. My current 2006 GT Avalanche is a small frame, but I don't know the exact size or HA of that either.

    I've sort of come to the conclusion that some manufacturers might make their small size frames with slacker HA's so that the wheel doesn't contact the frame when turned 180 degrees (speculation only). Toe rub on this bike is an absolute impossibility unless you're Bob Terwilliger so what other reason could there be?

    The wait continues...
    I see hills.

    I want to climb them.

  17. #17
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    Obviously, getting that 18" built up and testing it out is the way to go. I know many folks ride a touch smaller frame but a while back, I test rode a 17" Redline Flight deciding that a 19" was totally out of the question. For giggles, I asked to try the 19", rode it and felt totally comfortable on it. Really didn't feel that much bigger than the 17 to me. Each manufacturer is a bit different - I'm 5'10" with a 32" inseam and the 18" Kona Unit seems to fit like a glove. Keep us posted on what you find - again, if you decide on the Kona, I think you'll be really happy!

  18. #18
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    Another one crossed off the list.

    GT Peace 9r medium. Too heavy. Too big. Too stiff. Too much air pressure in tyres Mr Bike Shop Mechanic Man.
    I see hills.

    I want to climb them.

  19. #19
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    Had to abandon a ride tonight. The rear wheel on the GT has stuffed bearings and I bent the derailler hanger which my tensioner is on (couldn't get it straight after stuffing around for ten mins).

    So the pressure is on. Time to buy a bike. Or no ridies for me.
    I see hills.

    I want to climb them.

  20. #20
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    I ended up buying the 2009 16" Unit.





    I love it.
    I see hills.

    I want to climb them.

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