mtn bike size chart
 

is there a size chart on the web somewhere?
How are MTN bikes sized, I see s, m, l, xl...how does that equate to 16 inches 18 inches 19 inches etc. Where is the bike size measured from?
Thanks for answering a noobs q's

I've never seen a chart although that seems a reasonable request. What I can tell you is the letters S, M, L, XL do not equate to an exact size frame. As an example, I'm a 'M' in Specialized bikes, which equates to 17 inches, but my son's Trek is an M at 18 inches. I tried another brand that called 16.5 inches a Medium. So while the sizes are close, they are not always equal. If you post your height and inseem, maybe we can provide some additional help.

okay, height 72" inseam from ground to crotch is 32...I did find a sizing program it said 17 or 18

I'm 5' 8.5" with a 30 inch inseam. I ride a 17 inch Specialized frame. I tried a 19", it was a little too large. I tried an 18 inch Gary Fisher, it was just a little uncomfortable, but not bad. In my opinion, the chart you found is wrong. I think you need at least an 18 inch, or preferably a 19 inch frame, maybe even 20". Unless you've ridden a 17" or 18" and find the fit to work for you, I recommend you try a larger bike.

Remember standover is not the only important measurement - with mountain bikes "reach" is actually more important. Most manufacturers post bike specifications. A good fitting will help you understand what top tube length best suits you. You also have to consider the size of the fork, and frame geometry. Some frames are built "very large" compared to others. For example the Santa Cruz Blur LC/XT. If you are somewhat inbetween consider a bike built like the Specialized FSR or SC Superlight.