Bike Advice
 

I'm a roadbike rider and am looking to purchase an entry level mountain bike. My road bikes are both 54cm. I have the opportunity to purchase a GT MTB in medium size,18". I am 5'10" with 29-30 inseam and wonder if this bike would work for my first .

I think it would be close to the small side for you, if you can see it in person that would be great. Riding a bike
that is to small is NO fun at all.. Richard

I'd guess its fine. I'm 5'11" with a 32" inseam and I've got an 18" GT that fits fine (I'm probably a 56cm in road bikes). It may be on the smaller side of things (I have a lot of seatpost showing on mine), but shouldn't be any issues.

Definitely ride it if at all possible, but I'd err smaller rather than larger for an MTB. Smaller bikes are a little easier to control IMO.