How to fit a bike- Mtbr.com
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  1. #1
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    How to fit a bike

    What sort of measurements and adjustments should I make to a bike to ensure it fits me properly?

  2. #2
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    how tall are you, what kind of trails you riding, what kind of bike are you buying?
    I'm 6'1"
    I have a 62cm roadbike (that's about a 25", max extension and reach)
    a 56cm surly steamroller (bit shorter than ^^ for urban flicking)
    a 15" banshee scirrocco (short for quick handling)
    a 19" santa cruz heckler (tall because it's big suspension and I needed the length)
    a 20" surly 1x1 (tall because it's the trails I'll ride it on are just different compared to the heckler and being a single speed leg extension's important)

    in general:
    shorter bikes = quicker handling bikes
    longer = more stable, and allow your body to stretch out comfortably
    some people will run looong seatposts and stems to get the handling of the short frames with the stretch of the bigger ones, but then they also sometimes clip their feet with the front wheel since larger bodies usually means longer feet...
    If steel is real then aluminium is supercallafragiliniun!

  3. #3
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    I more meant after purchase. I already figured out my frame size (I'm 5'9" and just bought an 18.5" Motobecane Fantom Comp DS). I'm talking about stem adjustments, handlebar height, etc.
    Last edited by Nikhil42; 12-08-2009 at 06:05 PM.

  4. #4
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    Quote Originally Posted by Nikhil42
    I more meant after purchase. I already figured out my frame size (I'm 5'9" and just bought an 18.5" Motobecane Fantom Comp DS). I'm talking about stem adjustments, handlebar height, etc.
    For best handling stems should be 50-80mm long. Much longer than that and you weight gets to far forward and the bike "steers" awkwardly. An old rule of thumb is your bars should be 1-3" lower than your seat when it is at the height for proper leg extension. I have found this to be a good starting point. When the bars are level with your seat or higher it make climbing, wheelies and cornering a little harder and when more than 3" lower it starts to get uncomfortable.
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  5. #5
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    its mostly about feel.. if a mtb feels good to you, it fits well enough to not really worry about it much.

    when you get into things like sore knees or hips, groin, or wrist and hand pain, then its time to shuffle things around. cycling should never hurt. if you feel excessively cramped or stretched out, shift your seat forward and backwards first before you spend money replacing stuff.

    especially on a mountain bike, you dont always want your seat at the optimum pedaling position.

    put your heel on the pedals and stand up. raise your seat until it just touches your crotch. go down maybe 10mm and this is your optimum most efficient pedal position. get a feel for that, its good for long sustained climbs.. and sucks for going down. use a quick release seat post clamp and adjust as you see fit during your ride. on the fly adjustable seat posts are so popular for a reason! not that you *need* one, but peoples desire to frequently change seat post lengths during a ride is justified.

  6. #6
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    same answer applies (now with less variables), what kind of terrain will you be riding?
    the steeper/more technical/rougher the terrain, the more upright you'll want to be. (by steep I mean downhills)
    if the terrain's medium to easy-ish (less rocks/roots/trail detritus, more uphills) then you would be better off more stretched out, because the easier trail conditions will allow you to ride faster and you want your body position to reflect that ability.

    again, it's up to you.
    we've got guys on MTBR with short legs but orangutan arms, running 16" frames with 135mm stems... and guys with long legs and short torsos running 70mm stems on 19" frames.
    ride what you've got for a bit on the trails you're expecting to be on the most, and if you find yourself wanting to sit upright every now and then, shorten the stem.
    if you find you need to stand and lean far forward, lengthen the stem.

    I'm not touching bar angle preferences with a ten foot pole!
    If steel is real then aluminium is supercallafragiliniun!

  7. #7
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    Thanks for all the advice!

  8. #8
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    Quote Originally Posted by byknuts
    ride what you've got for a bit on the trails you're expecting to be on the most, and if you find yourself wanting to sit upright every now and then, shorten the stem.
    if you find you need to stand and lean far forward, lengthen the stem.
    This.

    I mean, for all you know, that Motobecane might have the perfect cockpit for you. The only way you're gonna know is to get out there and ride it for a while.

  9. #9
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    Simple answer:

    1. Standover height (roughly equivalent to frame size). Standing flat-footed over the frame, there should be about a 1 to 2" gap between the top tube and your crotch for a road bike, ~ 2 to 4" for a mountain bike.

    2. Saddle height/leg extension. Seated on the saddle and feet on the pedals, when the pedal is at its lowest point, there should be ~ a 30-degree bend at your knee. Watch someone from behind as they're pedaling... if their hips are rocking from side-to-side, the seat's too high. That being said, I usually drop the seat on my trail bike just a smidgen from the ideal height so as to give myself a little more clearance... I tend to be off the saddle a lot more with the MTB than with my road bikes...

    3. Reach (distance to the handlebars). You don't want to be too stretched out with your butt on the saddle and your hands on the grips, and likewise you don't want to be too scrunched up, either. You want it to be just right, so you can be seated and just put your hands to the bars and it all feels natural...

    Lots of other little measurements (there are whole books on bike fit); but these are the three key things you want to check when setting up any bike.
    Ride a mountain bike... you will not regret it if you live.
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  10. #10
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    Byknuts posts are right on.
    You have to account for rider preference, bike type and size, terrain, and riding style. Forget about rules of thumb and conventional wisdom because there's just too many variables.
    If you want to find what works best for you, you need to experiment. You can always find good deals on cheap stems and they're easy to swap out, so I recommend getting an assortment. Try the classic XC race setup (longer stem, seat above the bars) and see how nice it climbs and handls the flats, then try a more downhill/tech riding setup with a shorter stem, possibly wider bars (risers), and the seat lowered a bit. You'll feel how much more confidence inspiring it is going downill and over obstacles. Then try variations to find what works best for you.
    Warning: may contain sarcasm and/or crap made up in an attempt to feel important.

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