road to mountain sizing
 

quick question. what size mountain bike frame should i generally look for if i ride a 52-54cm road frame? I'm 5'8".

Mountain bike sizing has less hard and fast rules than road sizing. Some people like their bikes on the smaller side, others like theirs larger. Medium-ish frames are probably a good place to start, but really, try a bunch of bikes out in different sizes, because differences in geometry plus personal preference will make a big difference.

I start with inseam, what is yours. Sounds like a 17 to start with, but this link might be the most helpful

http://www.competitivecyclist.com/za...LCULATOR_INTRO

It helped me.

I agree with both posters above, I'm 5'8" or just a tad taller. I've been told by bike shops to ride a 17" frame and those that don't have a 17" go for a 18" frame. My first two MTBs were both 17" frames.
However, I now ride a 15.5" hardtail and a 16-16.5" dual suspension frames that have slightly longer top tubes. When I brought the hardtail into two different bike shops, they both said that I had a problem because the frame is too small for me. But I find I like it better. It's a personal preference to ride the smaller frame.
If you're new to MTBs, I'd play it safe and go with a 17" "medium" frame. Most of my freinds that are around 5'8" ride medium frames.