General Cycling Discussion - ~ Roadie to MTB sizing? ~

I am about 5' 9 1/2" tall and am currently riding a 57cm roadie. I'm thinking about getting a cheap MTB so I can play on same rail trails in the area. Can you all give me an educated guess as to what size MTB I should be looking for. My inseam is right at 34" if I remember right from when I bought my roadie. I know, I know..... just go to my LBS and let them fit me....blah, blah, blah. Just trying to do a little research before I go, so please just give me some opinions here. Thanks! :D

Have you checked out wrenchscience.com you can type in you're measurements and it will tell you a frame size.. at 5'9" and 34 inch inseam.. I would guess at around a 18-19 inch frame.. but I could be wrong :)

Yes Kev I have done that wrenchscience.com deal before. Also gone thru the one on coloradocyclist.com. I just don't have a way to get all my measurments right now so I was just hoping to get a few opinions from folks here that ride both. Thanks!!

yeah ... around 18" sounds about right

oh i just noticed... DANG you have long legs! maybe a 20" would fit you???

I screwed this up on a Road bike sizing question the last time I relied on my memory but I'm pretty confident that the magic formula for "getting it in the ballpark" is 59% of your inseam. In fact, I think Colorado Cyclist even uses this factor on their Web site fitting guides.

So, if you were "proportional" 20" would be a reference. But, at 69.5" with a 34" inseam as d5 pointed out -- you got some long sticks dude. So, go ride some of the LBS' bikes and see what combination of top tube height/reach gives you a nice neutral riding position. A 20" might be the sweet spot if your arms are as long as your legs are relative to your body's trunk.

Road Bike to MTB up 1 frame size.

MTB to Road Bike down 1 frame size.

Ok thanks a lot dudes. Yeah I have pretty long legs but I don't think the rest of me is quite in proportion. When I ordered my Litespeed from coloradocyclist I went thru their fitting deal and it came out to about a 58cm. Since they make a 57 and 59, I went with the 57. After I got it, I had to change the stem because it was WAY more stretched out than my old junk bike I had been riding. The dude at my LBS said the Litespeed's have a little longer top tube than some bikes. It feels great now after going to a 90mm stem but if I were doing it again I'd prolly order a 55cm instead of the 57. So anyhow, I think I might want to go a little smaller on the MTB if/when I get one. Some of you say a 20" might be about right for me so I'm thinking maybe a 17-18 would be a better fit. I'll just have to "try on" a few and see I guess. Thanks again!!!

Go on the small side for a MTB. You will be much more agile on it.