Mountain bike sizing?

Question

I would like a 19" mountain bike, but found a nice one that's a 17 for a good deal. Any reason I shouldn't get and just jack up the seat to fit me? I plan on doing mostly mountain bike trails and some xc.

Answer 1

Well there is a reason - if it doesn't fit you. I honestly don't know if a 19" is the right size for you or not. So is a 17" OK? - I can't say. Mountain bike sizing is more forgiving than road bikes for certain. I'm 5' 8" and ride a 16" Giant HT that fits me perfectly. I could ride a 17" as well I'm sure. A 17" for you may be fine but you didn't provide enough info to even make a guess. How tall are you, what's you inseam and what kind of riding will you be doing. Are we talking HT or dual sus?



OK, thanks for the extra info: 17" is too small for sure - do NOT buy it. A 19" will be about right IMO. If you've already tried the 19" and you're cool with it then you're good to go. Like I said, I ride a smallesh frame at 16" for my size and I'm 5'8". 17" on you would be tiny.



EDIT: As you see a lot of what I wrote in reply to your email, Ride! wrote below as well. I'd ride a little too small of a bike any day than one that is too big. Hope you make a descision you're happy with in the end is all I can say.

Answer 2

I'm thinking that with your extra-long inseam, a 17" frame might just do ok for you. I'm 6' with a 34" inseam and the 19"-20" frames usually fit me ok. Your body proportions may be a little different, but there's a good chance that you'd appreciate the shorter top tube of the 17" frame. You could adjust your stem length a little, but you don't want to ride with too long a stem if you'll ever be doing any rough downhill sections of a trail.



One disadvantage to the smaller frame is that they will *usually* (but not always) have a shorter head tube. This, coupled with the way many manufacturers set up the bikes with short steerer tubes and minimal spacers, could mean that your bars will be lower than optimal. Combine that with a high seat to match your leg length, and it could really cause you to ride hunched over a bit much. Not comfortable for most people, certainly not a good idea for rooty and rocky trails. You might be able to get around this with a riser stem and high-rise handlebars, though...just depends on how you like your bike to feel. Another (expensive) option would be to get a fork with 1" more travel than what is spec'd for the frame....this is usually ok to do, but you don't want to put more legs on a frame design than that. For instance, a 6" fork on a frame designed around 4" is a bad idea....for both fork and frame (and you, if it causes the head tube or fork to crack!).



A lot of this really depends on the geometry and sizing methods of the frame itself....if you can post what you're considering buying, we might be able to help a little better. Offhand, though, I'd say you'd be ok with the 17".



EDIT: Sizing on hardtails and f/s is essentially the same. The geometries may be different, though. Most f/s bikes have a higher bottom bracket to help give clearance when the shock compresses...but not always. There are lots of bikes designed for lots of purposes, so you can't really give a straight answer about this. As far as choosing size, for an xc bike there isn't anything extra to think about when comparing hardtail to squish.

Answer 3

well just make sure it rides comfortably, so i recommend taking it for a test ride. If you do need a19'' you should be able to tell right away, you will just feel like your a bear on a unicycle. Also when going down in size of the frame the rider tends to ride more like they are sitting straight up, you want to be at a comfortable arch because its easer to take that next peddle stroke if your pushing your limits, helps you breath better, and it doesn't make your head a target for low tree branches.

good luck

Answer 4

I'm gonna pull out the cut and paste again!



http://sheldonbrown.com/frames/index.html



A cut and paste is worth 1000 words. Don't be skeered it's just his weird beard.