Bike sizing & fit- Mtbr.com
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  1. #1
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    Bike sizing & fit

    I ride a 19" Spec. RH, it's a 26" wheel bike. Thinking about getting a 29" Kona Unit to build or one already done, the geo is pretty close to my present bike.

    The difference between the 18" and 19" Kona isn't much, like a half inch on the top tube and standover height. Can I overcome that fairly easy with stem and seat position or do you really want to get it right?

    How about going from 26" 19 frame to the 29"? Anyone go a little smaller on the 29" frame to offset the jump?

    Asking cause I have seen size 18 Kona frames or bikes for sale, but not sure about the fit. The 19" Kona has the same seat tube angle as mine, the other a degree more.

    If I got a frame should I go with a build kit like, say, Jensonusa offers at around 700 bucks or better to pick and choose all the components seperate? You can delete a lot of the items off the kit to work around what you already have or want.

    I have been riding my bike stuck in 32/18 the last couple of weeks, didn't take long to get over shifting and I'm sure the power tranfer will be better on a straight SS bike. What 29" ratio will be close to this? 32/20 32/18?

    Thanks all in advance for any advice and insights.

    Glynn

  2. #2
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    My 29er bike frames are the same "size" as my old 26" bikes.

    My 2007 Kona Kikapu Deluxe was a 19". My Fuji Tahoe 29er is a 19" and my Kona Unit is a 19".

    The standover height is just a tad higher on a 29er due to the larger wheels, but I make sure that the actual reach was the same. Measure your 26" bike, and make sure all your measurements match up.

    Seat to bars, saddle height, bar sweep and rise, etc.

    Ratio from a 26" wheel with a 32/18 would be close to a 32/20 or 32/21 on a 29er.

  3. #3
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    I am 6 feet tall with two old 18" kona's and they always feel small. Now I have a 19" unit that needs a 110mm stem to make it handle right but is to long for me even with a 0 degree post and the seat all the way up. I run it with a 100mm stem and it fits perfect but now the front pushes a little. I didnt think 10mm would be so easy to feel a difference.

    Also the 29er slow speed floppy front tire feel goes away with the 110mm stem.
    Last edited by k29er; 11-04-2011 at 06:49 PM.
    2011 Kona unit with some carbon.

  4. #4
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    The Unit's sizing is kinda strange - there's little sizing difference between the 18, 19, and 20. The wheelbases and front-center (bottom bracket to front hub) are all nearly identical. Instead, the the angles vary a bit. I'd guess an 18" with a half inch of saddle/post offset would fit VERY similary to a 19. Of course, a test ride would be best. Also make sure the headtube on the 19" is not too tall - 130 is pretty high if you're not leggy. A flat bar could fix that, though.

    As for build, buying it built up is typically your best value.
    2017 Diamondback Haanjo
    2016 Pivot 429T
    2011 Kona Unit

  5. #5
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    OK talk slow to the new guy, I want to understand all the terms so I make decisions that don't make me buy different components later. Oh well, you know that might not be a bad thing as far as learning goes, just want to get a ride that works for me first.

    k29er, what does "the front pushes a little" mean? Is it better to have the perfect fit with the 100mm or better ride of the 110mm. My stem is a 90mm on the 26" rockhopper, the ETT is the same as the 19 frame Kona, should I stay with a shorter stem or buy a couple and get educated on the feel?

    Ryder1, I'm not leggy, 5'11" w/ a 30.5 inseam, what does the "130" refer to. Planned on using a mid rise 700+ wide bar.

    Thanks for your time.

  6. #6
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    Quote Originally Posted by Glynn Sluder View Post

    Ryder1, I'm not leggy, 5'11" w/ a 30.5 inseam, what does the "130" refer to. Planned on using a mid rise 700+ wide bar.
    130mm. Many 29ers have shorter head tubes to compensate for the longer forks required to fit the 29" wheel. But Kona's head tubes are longer than most 29ers. This can lead to a lofty front end which can make steering feel disconnected and make the front end "push" (not hook up, like a front wheel drive car navigating cones). But with the stock rigid fork (it's pretty short), you should be fine if you go 19" - just move your headset spacers above your stem, or flip your stem.

    The standover on the 19" is quite high at 32.7". If 30.5" is your "true" inseam (not your pant inseam), it might be an issue. Kona measures standover more forward than most bike companies, resulting in a higher measurement. But still - 32.7" is brutal if your inseam is 30.5". That would be a deal breaker for me.
    2017 Diamondback Haanjo
    2016 Pivot 429T
    2011 Kona Unit

  7. #7
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    Googled the correct way to measure inseam and looks like mine is close to 32". My current bike's SO is 31.5 and plenty of room there, makes more sense.

    Gonna keep saving, keep looking.

    Thanks

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