Mountain Biking - need help sizing

I'm buying a mountain bike for my wife for Christmas. Never bought one online before. She is 5'7" with a 32" inseam. The local bike store suggested a large. The online store suggested a medium. Any suggestions would be greatly appreciated.
Thanks!

That's a tall request (no pun intended) on that sparse of information. In general terms, though, it sounds like your wife has a very long legs/short torso thing going there that will make sizing even trickier. For a 32" inseam, yeah, I can see where the shop may suggest a large; but cockpit length will likely be oversize for her - - and so long that it can't be compensated for with a shorter stem, etc. It's my guess (only a guess mind you) that you will end up with a medium and maybe a high-quality, long seatpost that can withstand minimum-insertion depth.

That's tough because there are several factors involved. Differing manufacturers label sizing differently, so that she may fit well on Brand A's Medium, while she may need a large in Brand B. Also, there are major geometry differences between Men's and Women's frames, so that she may be comfortable on a Men's Medium but cramped on a Women's medium.

My best reccomendation is to have her test ride the bikes in different sizes at the local shop and get their professional opinion (hopefully they have one, and aren't just trying to get a bike out the door). Also, most shops offer a professional fitting, where they can take measurements and size her to a frame.

If you are looking to purchase a bike online, it is probably a good idea to get the bike fitting at a local shop (most shops will charge for this service), and get the specifications from them. Use the specifications and check the frame geometery of the manufacturer to make sure you are getting the correct size. If this is too much of a hassle, just by locally and pay a little extra to get a bike that fits her. If it fits, she'll want to ride it more!

Thanks guys that's a huge help. The bike I'm looking at is online at Performance Bicycle. It's a GTw Avalanche Expert. It is women's specific bike/frame. The tech guy told me definitely a medium. The bike I was looking at in the bike shop was a Specialized Myka HT Elite 29er. It's the only one they had in the store and it was a large. And they suggested without a doubt that she would need a large.

I'd say at least a medium...possibly small. Large is way to big.

The bike I was looking at in the bike shop was a Specialized Myka HT Elite 29er. It's the only one they had in the store and it was a large. And they suggested without a doubt that she would need a large.

Yikes. Pushing a large 29er? I'd stay away from that shop.

For a WSD bike, large; for a non-WSD bike, medium.

Thanks guys that's a huge help. The bike I'm looking at is online at Performance Bicycle. It's a GTw Avalanche Expert. It is women's specific bike/frame. The tech guy told me definitely a medium. The bike I was looking at in the bike shop was a Specialized Myka HT Elite 29er. It's the only one they had in the store and it was a large. And they suggested without a doubt that she would need a large.

Only one in the store and they said it was the right size? Shocker.

Well if it helps, I'm 5'8" with a 32" inseam. I have both a large and a medium MB. I can ride either but the medium feels so much more natural.

Thanks for the tips guys. She's gonna love this bike!