geometry question for a 700c flat bar bike for commute/cross- Mtbr.com
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  1. #1
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    geometry question for a 700c flat bar bike for commute/cross

    Hi All,

    There is a 700c commuter frame available that comes in either disc or canti. I'd like to build up a flat bar roadie capable of taking cross tires for some dirt roads and light trail. My question relates to the right top tube length.

    For mountain biking I prefer a long top tube/short stem. 22.5" effective top tube and 70mm stem.
    However for road biking I prefer a 130+ stem in order to get enough weight on the front wheel otherwise it feels twitchy on the road and wind.

    How would I size a flat bar road bike? Long top tube to go with a short stem like my mtb, or shorter top tube to go with a longer stem?

    I'm leaning towards V brakes just given cost/weight but wonder if I'll kick myself later. There is also a single speed/canti. This is the GT Transeo on sale at Nashbar right now for another two days.

    very best,
    thanks.

  2. #2
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    My mountain bikes (29er) are usually 600 mm TT, 100 mm stem, and then a touch of sweep to the bars, so roughly 700 mm total reach. On my cross bikes, I use around 560 TT, same stem length, and drop bars with about 70-80 mm reach to the hoods, so around 750 total reach. this gives me the front wheel pressure I am looking for in a cross bike. I have tried unsuccessfully using flat bars on several cross bikes, and even with really long stems (120+) I feel totally cramped and the bike is very twitchy. Mathematically, I would need a super long (190) stem or set back post/stem combo to get a similar feel. Everyone is different, so you may not get the same feeling I do with a flat bar setup. I never tried a "alt bar" that has lots of forward sweep from the stem before it beds back at the grips, effectively increasing the reach, so that might be worth considering.

  3. #3
    jrm
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    On my commuter/CX flat bar bike

    im using a frame with a 56.5 cm ETT, a 130mm x 6 stem and a on one freegle bar. This almost gets my hand position over the axle of the front wheel which for me is ideal.

    Somebody walks in the shadows....somebody whispers

  4. #4
    Candlestick Maker
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    Quote Originally Posted by ashwinearl View Post
    Hi All,

    There is a 700c commuter frame available that comes in either disc or canti. I'd like to build up a flat bar roadie capable of taking cross tires for some dirt roads and light trail. My question relates to the right top tube length.

    For mountain biking I prefer a long top tube/short stem. 22.5" effective top tube and 70mm stem.
    However for road biking I prefer a 130+ stem in order to get enough weight on the front wheel otherwise it feels twitchy on the road and wind.

    How would I size a flat bar road bike? Long top tube to go with a short stem like my mtb, or shorter top tube to go with a longer stem?

    I'm leaning towards V brakes just given cost/weight but wonder if I'll kick myself later. There is also a single speed/canti. This is the GT Transeo on sale at Nashbar right now for another two days.

    very best,
    thanks.
    Shorter top tube and upright stem, you're getting old! ;-)

    Seriously though, "Hi" after many years! For commuting, I definitely go with the more upright stance, visibility and comfort rule. But, it's all personal.

    As far as brakes go, pretty much whatever. Disc is always easier to deal with, but you have years of experience dealing with canti's/v's so (again) personal decision. Money no object, get the discs and spend less time with maintenance.
    baker

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