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  1. #1
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    Mimicking bike fit?

    I have two main bikes, a 29HT and a 27.5FS

    The HT is always comfy. The FS, while my favorite shredmobile, is not.

    I get low/mid back pain riding the FS bike on long (4mi, 1000') climbs. While I don't ride the FS bike on those climbs all that often, it's definitely more comfortable.

    I rode both bikes and had my wife take some pics. Yes I felt silly. No noticeable differences in posture.

    Relation between saddle/pedals/bars is very very similar.... about 29" from tip of saddle to bar centerline (60mm stem on HT, 50 on FS), seat to BB within half an inch. Possibly the FS bike had the seat too far forward, so I moved it back and down just a bit (3-5mm).

    So I checked seat height vs bar height. The HT bike has the saddle about 4" lower than the bars, the FS is more like 2". On the FS bike, I always feel kinda hunched, and wind up lowering the dropper on cruise sections to take a break.

    The FS stem is only 50mm, and already in the rise position. Steerer is too short to add spacers. Already have 30mm riser bars. Next step is 50mm risers (new wheels coming, good excuse to change color anyway though I love the green I have now).

    I'm 5'10" and think I'm dead average, maybe long torso, long arms. Both bikes are medium (2014 Taro and Trance).

    My question is this:

    Is there any sense in trying to set up a FS 27.5 based on the fit of a HT 29? It's not really the end of the world here, I can ride as long as I have energy. But I wouldn't mind getting more comfortable.
    2012 Specialized Camber Comp
    2014 Kona Taro
    2014 Giant Trance 27.5 1
    2015 Gravity Monster

  2. #2
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    Usu. I dial in fit to a few millimeters, not 1/2". It sounds like you might want to get a proper bike fitting. The distance that your saddle is behind the cranks probably has a lot to do with your back strain (assuming your seat is not tilted crazily).
    Start with saddle position for proper pedaling efficiency, THEN adjust reach/bar height.
    I usu. aim for similar fit, but my bikes serve different purposes, so the fit is suited for the purpose.

    -F
    It's never easier - you just go faster.

  3. #3
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    Sure. My wife's old bike was perfectly dialed in (in her opinion) so when we updated her ride she was worried about it fitting like her last bike. I made measurements of all contact points relative to the bottom bracket with her on the old bike (to ensure angles relative to shock sag) and then bought matching bars and stem moved her seat over viola, she loved it. To your specific situation, you may find that the exact set-up doesn't allow for the type of riding you intend to do, but if both bikes are ridden under similar circumstances (i.e. XC) verses radically different circumstances (i.e. XC on the Hardtail and DH on the FS), you're probably going to be happy with the result.
    The most expensive bike in the world is still cheaper than the cheapest open heart surgery.

  4. #4
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    Thanks guys -

    Agree that the measurements are not terribly accurate, just trying to get an overall sense of what's different between the two.

    I did notice my knee was a little bit in front of the FS pedal spindle from the photos. I also noticed I look like a dork.

    The HT has higher bars because it's a 29er and has about an inch of spacers under the stem. The FS has a higher seat (relative to ground) because a) I can get away with it, since it has a dropper, and b) the bb's higher.

    I ride both on the same trails... just longer rides on the FS.

    Looking at the images, the hunching is pretty obvious.

    Moving the seat back will make it worse, but getting knee position correct is the first step.

    A shorter stem might help, but the FS is already a 50mm. 50mm riser bars might be the ticket, though I wonder what other effects that'd have on the ride. DH on the FS bike is great, don't want to mess that up.

    It occurred to me that the 800mm bars might be making me hunch even more, so (after hemming and hawing like a moron about which set to swap from another bike) I used my noggin and just moved the cockpit in about an inch on each side. Will try that today.Mimicking bike fit?-leg-angle-fs.jpgMimicking bike fit?-leg-angle-ht.jpg

    There are obviously some differences in angle of the shot, and I probably should have put the bar point on the HT at the average of the two hands, but the back angle is the key, I think.
    2012 Specialized Camber Comp
    2014 Kona Taro
    2014 Giant Trance 27.5 1
    2015 Gravity Monster

  5. #5
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    Your HT is set-up with you more over the BB than the FS. That effect power deliver; thing standing and pedaling vs. a seat way back pushing more forward. That is a stress for sure.

    A cockpit is a cockpit. The position of your set/feet/hands shouldn't have to change with each bike. Set your seat first and adjust your hands to that.

    One method for setting the seat is the slight bend in the leg when the foot is at 6 o'clock. Seat fore/aft is set by putting your foot on the pedal at 3 o"clock and sliding a level seat to where it rests comfortably under you. You may have to go back and for between a bit of height and a bit of fore/aft.

    You cited the 800mm bar. You might simply measure the distance from seat back to grips on each bike to see how those numbers compare.
    I don't rattle.

  6. #6
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    Thanks Mike, appreciate the feedback. Both bikes are the same at 22" from seat tip to center of grip.

    Got a good ride in today, 18.4mi & 2300' - that's a big one for me.

    Knees were complaining on the first segment, so I moved the seat forward. Moved it forward again (to the max line) later in the ride. That helped. Might try swapping in a different seat to see if it'll be more forward.

    Also rotated the seat down, figured that would rotate my hips forward and keep my back straighter - definitely helped.

    Bars being in to about 750 didn't really seem noticeable, though I never really paid attention to wrist angle before. They're now straight in normal riding and slightly out in attack position. Bike felt great on the downhill stuff, so I didn't lose any stability going narrower.

    Might see if I can track down a cheap-o set of 760 +/- x 50mm risers...

    I'm also going to triple-check my rear sag, looking at the images above, looks like way more than 2* difference in HTA (should be 66 and 68)
    2012 Specialized Camber Comp
    2014 Kona Taro
    2014 Giant Trance 27.5 1
    2015 Gravity Monster

  7. #7
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    Knees complaining in front or behind the knee.
    I don't rattle.

  8. #8
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    Heavens to betsy, so many variables. I'd say front of the leg, above the knee.
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    Right where the quad tendon arrow line points would be my guess. Wasn't paying close enough attention other than "this doesn't feel good".

    Post-move, the knee pain went away.
    2012 Specialized Camber Comp
    2014 Kona Taro
    2014 Giant Trance 27.5 1
    2015 Gravity Monster

  9. #9
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    This is a pretty broad statement but it has held up pretty well.

    Pain in front, seat too low. That induces quad-heavy peddling where the knee is too high at the top of the stroke. Bad leverage.

    Pain behind seat too high. Induces over stretching the leg but mostly effects when clipped-in. Pulling up on the back stroke with the leg over extended makes pain. One can do this when standing and peddling under stress absent the proper conditioning.
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  10. #10
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    Thanks Mike - so if I raise the seat, I really do find the bars too low, back too hunched.

    My quads definitely felt it last ride, but it was a long ride for me, and I'd expect to feel it.

    Running flats, so clips aren't a problem. Inconsistent foot placement, maybe.

    Just feels weird, thinking of taking my long, low, slack bike and making it tall and close.
    2012 Specialized Camber Comp
    2014 Kona Taro
    2014 Giant Trance 27.5 1
    2015 Gravity Monster

  11. #11
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    From the photo it looks like that your hands are higher on the 29er. What's the distance from the ground on each bike?

  12. #12
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    Going from memory, and sloppy measuring on an unlevel surface, the HT is about 42", the FS about 40". Chalk that up to wheelsize, head angle, and spacers.

    Very tempted to get a set of 50mm risers, but this whole ordering new parts every day is getting to be expensive.
    2012 Specialized Camber Comp
    2014 Kona Taro
    2014 Giant Trance 27.5 1
    2015 Gravity Monster

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