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  1. #1
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    Top Tube Length/Stem Length

    I'm 6' 3", normally ride a 25" top tube with a 120mm stem. Looking at a frame with a 25 1/2" top tube, but I would need to switch to a 110mm stem -- would this help or hurt in weighting the front end for climbing steep hills? Which set up would be better for cross country riding? Shorter top tube/longer stem? Longer top tube/shorter stem? My main concern is with weighting the front end on very steep hill climbs. I realize that the wheel base is also getting longer as you lengthen the top tube by 1/2" -- is that a positive or a negative?

  2. #2
    www.derbyrims.com
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    Quote Originally Posted by ventana man
    I'm 6' 3", normally ride a 25" top tube with a 120mm stem. Looking at a frame with a 25 1/2" top tube, but I would need to switch to a 110mm stem -- would this help or hurt in weighting the front end for climbing steep hills? Which set up would be better for cross country riding? Shorter top tube/longer stem? Longer top tube/shorter stem? My main concern is with weighting the front end on very steep hill climbs. I realize that the wheel base is also getting longer as you lengthen the top tube by 1/2" -- is that a positive or a negative?
    I'll break out the factors separately (in my opinion):
    Going to a shorter stem on the same bike, changing nothing else, will reduce upper body weight over the front wheel, and straight arm seated position is more upright. Flat smooth corner handling will have less front tire traction. Body postion is further behiind the front wheel enabling ability to brake harder, which is an advantage for more nimble handling for difficult trails and downhill. Seat climbing will require bending elbows more and tensioning arms more reducing efficient effort.

    A longer TT with NO change in stem length and no other changes will increase forward reach and lower the upper body more forward adding weight bias to the front tire. This brings increased front traction, reduced braking power, and slower handling response due to the longer wheelbase and lower upper body ride position.

    Combining both to have no seated fit position change using a shorter stem but longer TT and downtube will blend both factors. Less weight on the front wheel reducing flat trail cornering front wheel traction. Ability to brake harder downhill, and you can brake later entering flat corners to help maintain front tire traction initiating turns. Not much change in climbing except the longer wheel base will require more attention to balance the bike at very low steep climbing speeds.

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