Mountain Biking - MTB sizing

I purchased a Giant Rainier hardtail MTB about a year ago. I am 5' 9.5" tall. I rode both the 17" and the 19" frame and bought the 19" because I just felt too cramped on the 17". Since then everything I read and hear about MTB sizing leads me to believe that this bike is too big for me. If that's the case what kind of disadvantage am I under when trying to ride, at times, some fairly technical terrain on a bike that's too big for me? Obviously, I'm somewhat of an off-road novice.

I purchased a Giant Rainier hardtail MTB about a year ago. I am 5' 9.5" tall. I rode both the 17" and the 19" frame and bought the 19" because I just felt too cramped on the 17". Since then everything I read and hear about MTB sizing leads me to believe that this bike is too big for me. If that's the case what kind of disadvantage am I under when trying to ride, at times, some fairly technical terrain on a bike that's too big for me? Obviously, I'm somewhat of an off-road novice.

A 19" might be a bit tall for you for off-road riding. You won't have too much room for bailing off before the dangly bits hit the top tube. As you've probably already learned, hitting the dangly bits is bad;) If you have less than an inch on level ground between the bike and your dangly bits, the bike is to tall. 2 to 3" is better.

The other issue is going to be reach. If you are too far forward when you are reaching for the bars, it can throw your balance off and make technical riding more challenging. It won't be impossible to ride but you will be biased more towards the front which can effect the up hill and downhill handling.

All this said, you might be a spider man for all I know. If your legs and arms are abnormally long, then a 19" might fit. Go try it and see what happens. If you have the possibility to rent or borrow the next size down, try the same trail. The good news is that you probably didn't put too much money into the Giant and most people, after they get bitten by the bug, want a better bike anyway;) Mountain bikes are an awful lot like computers...last years model is ancient:D

if you think it fits you why not?

My balls have about a 1/2 clearance from the top-tube... The geometry is great for long, less-technical trails. I can ride for hours on end without any pain, but it can get scary on technical parts. There is the fear of falling off and smashing your balls, but it's also a bit harder to control due to the extra length. I will add a shorter stem though, that should help out with balancing.

I purchased a Giant Rainier hardtail MTB about a year ago. I am 5' 9.5" tall. I rode both the 17" and the 19" frame and bought the 19" because I just felt too cramped on the 17". Since then everything I read and hear about MTB sizing leads me to believe that this bike is too big for me. If that's the case what kind of disadvantage am I under when trying to ride, at times, some fairly technical terrain on a bike that's too big for me? Obviously, I'm somewhat of an off-road novice.

You won't know until you ride it enough. Chances are though, if you felt too cramped on the 17" ... it was too small.

i'm 5-10 and ride a 20"...my brother is the same height as you and he rides an 18"...it all depends on the rider and how they want to feel on the bike. if the bike is to big it will be hard to handle and will take a while to get used to it, and in that time you will fall a lot (i did!)

Thanks, GR. I do fall alot, but that's lack o' skilz vs. mis-sizing, me thinks. One of my mates snapped a pic of me on the Rainier on a recent ride, and it "looks like" the bike fits me. I'm stickin' with it.