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  1. #1
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    Small frame 29er for leadville?

    I have option to ride a small size BMC 29er hardtail for Leadville. I normally ride a medium 26" FS mtb(rode this in Leadville 2011), but with a longer stem and sliding the seat back a bit I can get the BMC pretty close in terms of saddle to bar length, and seat height is okay. Any concerns about trying this??

  2. #2
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    What's the measurement from back of saddle to centre of BB on your old bike (drawing the line vertically down from the back of the saddle)? Can you replicate this measurement on the BMC and have it still fit? If not and you have to move the saddle further aft than you are accustomed to I would say NO, that's a compromise, don't do it for such along race, if however you only need to do a longer stem, then go for it, the 29" wheels will roll so sweet on the Leadville "trails"
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  3. #3
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    saddle to bar measurement is important, but only after getting the saddle to bottom bracket setback correct. If you can't put the saddle in exactly the same position relative to the BB on the 29er AND get the bars in the right spot without resorting to some sort of whacky stem selection, then don't even think about it.

  4. #4
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    Try a few long training rides on it first, otherwise I wouldn't change anything. I tweaked my saddle height a few weeks before my second Leadville and it was a mess. Cramped 45 miles in and barely finished. Ended up with a slower time on a carbon 29er hard tail than I did the year before with 26" wheels and 5" of travel on a 28 lb bike. I think small changes that you may not notice on other rides make a difference on that distance and altitude.
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  5. #5
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    Quote Originally Posted by mudge View Post
    saddle to bar measurement is important, but only after getting the saddle to bottom bracket setback correct. If you can't put the saddle in exactly the same position relative to the BB on the 29er AND get the bars in the right spot without resorting to some sort of whacky stem selection, then don't even think about it.
    Yeah,

    Pretty unanimous feedback, and exactly what I was thinking.

    What I'd add is, have you ever gotten any bike fitted, or at least checked for Knee Over Pedal Spindle? Do you even know that your 26 FS bike fits?

    In my opinion, saddle position--height and setback--drives everything else. There's some controversy about KOPS (Knee Over Pedal Spindle). Some people say it's the absolute and un-wavering standard for saddle position relative to crank center. With cranks horizontal, is the point of your knee in a perfect vertical line with the spindle of the pedal; at the saddle height that is correct for you?

    I think of KOPS as a guideline, but it's pretty damned close to right for everyone. Maximizes power, and allows the knee joint and hip sockets to move in a way that is most sustainable. For me, I like to be slightly forward of KOPS. But millimeters forward.

    Here's the key thing I'll say: when you are young, or if you don't ride all that much, fit is less important in terms of comfort. In my experience, you can have some pain and discomfort when you are young, and you've forgotten about it before bedtime. But as you get older, or as you ramp up your riding to 5,000 miles/year or more, these things start to degrade and you get repetitive use injuries. And if you care about power, fit is important.

    For me, at 49 and 5K-10K miles per year, a bike that doesn't fit will ruin my body. Saddle position off by more than 5mm? My knees AND hips will start hurting me after just a couple rides. But it won't get that far now because I can feel that it's wrong in 5 minutes of pedaling.

    So you have an optimum saddle height/setback. From there you have the position you want your bars to be, reach and height. You can tinker with that using stems. But if you're doing it right, you will NEVER fsck with saddle position. That's just a constant.

    Some bikes will never fit you. Once you have your own understanding of your dimensions, you can typically spot that without even saddling up. For me, to get the saddle position I want since I have relatively long femurs, a bike that has a seat tube angle that's steeper than about 73.5 is iffy. A typical bike with 73, I'll need a setback post. To get the reach I want, I need an effective top tube a little over 24". My acceptable range is probably 24-24.75. If a head tube is very short, I may not be happy with the amount of spacer offset and stem rise I'll need.

    Basically, I can shop for a bike and know what size will work for me, or whether a given bike could ever work just by looking at the geometry table. For example, I really like a bunch about the Kona Hei Hei. But it has a 75 degree seat tube angle. Deal breaker. I wouldn't even bother test riding one.

    If you are going to be doing stuff like Leadville, spend some time learning about what fits you. You should never just randomly slide saddles up and back to make a bike fit. Because you won't be making it fit unless you're saddle position is pretty close to right.
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  6. #6
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    Thanks for the replies. My first go-round at Leadville (2011) was on my 30 pound 2004 Stumpjumper FSR, which I still ride due to financial reasons. I am adamant about bike fit- I use a plum bob (for KOPS) and ruler pretty religiously on my mtb, road and cross bikes. I know the set-up on the BMC will not be ideal in all likelyhood, but I seem to be fairly adaptable when it come to hopping on other frames, albeit not for 103 miles! If the discrepancies are too much then it's back to the stumpy, but the BMC is so tempting. So is the cross bike!

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