Mountain Biking - Roadie to MTB guy.... fit question

Alrighty boys... I'm a roadie that is going to be getting a MTB to mikx things up a little over the summer... and do some XC races this fall. I'm pretty much narrowed my bike choies down to a Specialized Rockhopper comp or a Stumpy hardtail. I'm leaning more to the Stumpy at this point from a bike weight and component quality standpoint (even though it is quite a bit more $$) I just don't want something that I 'm going to outgrow in 4 months, like I did with my first road bike. Plus I don't want the thing falling apart after the first couple runs either. Anyhow.... I'm curious about bike fit. What kind of position should I be in for riding. I felt so upright when I was testriding the bikes.... like I was tooling around town on a beach cruzer ;) or something! I'm a road racer... and ride in a pretty aggressive position on my road bike. I imagine I don't want to be quite that aggressive on the MTB, but it feels so different I'm not sure what to expect. I'm 6' 1.5" and ride a 58cm effective top tube road bike, with a 120mm stem. So it seems that a 17" Stumpy would be the size to get, based off ETT... but the stem is obviously much shorter at 90mm than my road bike. Any suggestions about position and how it should look/feel when I'm on the bike? Just trying to get a little more informed so I can talk to the guys at the LBS in a more effective manner. Thanks for your time!

You probably want a large sized frame or maybe around 19". 17" might be a little small. Just test ride and see what you like. If you plan on racing, skip the rockhopper.

A 21" will probably feel a little more natural to you given your roadie background, but you should stick to a size large or 19". I'm your size and that's what I ride.

I would DEFINATELY go with a stumpy, but a 19"-19.5". (whatever specialized has) You want to be upright enough that you can hop logs and do technical descents, but still be able to climb like a MO-FO. Specialized usually has their bike setup pretty right-on if you get a size that fit's your height appropriately. I wouldn't worry too much 'bout that 90mm stem.

I used to run a 20 degree stem with riser bars. The more I rode, the more I saw a necessity for lower bars. I am finally running a low rise bar with a 6 degree 105mm stem on a 19" GF. If I go too low, I have a more difficult time in the air and getting over obstacles.

Ride how your comfortable.

You probably want a large sized frame or maybe around 19". 17" might be a little small. Just test ride and see what you like. If you plan on racing, skip the rockhopper.

Yeah, 17" sounds too small...it's probably why you felt more upright, the cockpit is shorter. See how you feel on a 19" or bigger...just make sure you have the inseam clearance. I'm 6'1" and for XC, I generally ride 20"/21" bikes...I have enough inseam clearance and I like to feel more stretched out with a longer TT.

I'd also say go for the Stumpy, just ride a few different sizes and see what fits you the best. On the test ride, ride over obstacles so you can get a feel for how you can control the different sized bikes under you.

I ride both road and MTB, and I'm about your hieght, so I'll toss in my 2 cents. First off, fit on a MTB is not nearly as sensitive or critical as it is on a road bike, as you are moving around on the bike a lot more. That said, I think a 17 is too small. I think you need something more like a 19 or 20. Test ride to find out for sure, and shop around a lot before you buy.

As for the upright riding position, you are absolutely right, it is like a beach cruiser. That kind of position works well for aggressive terrain-but not as well for pedalling efficiently. You can easily play with your position on the bike by swapping out the bar or stem, or both. I would try it for at least a few rides the way it is before trying to move to moving around-upright works really well for a lot of trails. Smoother XC type race courses may favour a more aggressive stance.

+1 for the 19 inch size....I ride a 58cm road bike and a 19.5 MTB...I'm 6'2" with 34" inseam

Briscoelab,

As a roadie you most likely know that "fit" considers much more than standover. Rather than blindly suggesting numbers over the web, I'll suggest this instead: Go out and buy Ned Overend's book "Mountain Bike Like a Champion."

It's got a section that does a great job of covering all the proper body angles and measurements. More than that, though, is the advice it gives on riding techniques, equipment choices, etc.

I was more of a roadie, too, before I started mountain biking a couple years ago. I'm not even finished reading Overend's book yet, but my skills and techniques are already so much better than they were before I bought it.

It's a must-have.

Looks like Specialized has a 18"... that has a total reach that is within a half a cm of my road setup... 600mm TT and 105mm stem vs my roadie of 585mm TT + 120mm stem. My roadie has a -8* stem... the Stumpy obviously has a riser stem. I think that seems just about right. Now, I'm gonna go over to the LBS and see if they have one in that size. Last time, they only had a 17" and a 21". I really felt the 17" was too small... and the 21" was way too big. Thanks for the input guys!

Anyone have experience using a MTB in a cyclocross race? I'm going to have to use mine in a few this fall before I get a cross bike built up. Conti makes some wicked looking 1.5" cyclocross tires that I think would work well enough. I'll prolly pick up a set to try out at least. Looks like they'd work pretty well for gravel races as well. At least until I get another bike built up... any thoughts?

I've got a stumpy 18" but I'm only just under 6'. However, I would have gone for a 17" if it wasn't for the fact that I bought it off eBay and it was too good a deal to turn down. When I was about 18 I bought myself my second mtb and was instructed by lbs to get a 19" frame. It was way too big and luckily it got stolen a while later and I got a 17.5" instead (different brand). I know I'm waffeling here, so I'll say what I was going to say: Ride 18" AND 19" AND 20" and think about how they will handle off road where agilty matters. Position can be messed with by changing seats & stem etc. so in my book handling/agility is more important. My preference (because that's all it is: preference!) is a smaller frame.