Frame size Help for MTB-do size really matter
 

Hi,
I am 53, was a road rider for many years until kids, but now I want to get back into it. We have paved rail trails, some dirt roads. I have someone that has a 2005 Rockhopper comp, frame is XL.

I am 6', inseam 31-32,,,would that size be ok. I am going to be more site seeing MTB more than comp. I am thinking the XL frame might be more comfortable.

Would appreciate any advise or opinions,

Thanks

Borrow the bike and ride it.

Seems a good idea.

I went the other way 4 years ago and in general for aggressive Offroading it is the norm to go smaller on frame size than you would on a road bike. Couple of reasons- one of which is standover height. You do need more clearance on the top tube on a mountain bike and 4 " is the usual figure quoted. Never had that clearance on any of my MTB's and the Tandem definitely has negative clearance. The other reason is for maneuverability. It is easier to throw the bike around if the bars are closer to you rather than the normal Road stretched out ride position.

But if the bike fits- feels comfortable and you are not going to be doing "Aggressive" offroad- start negotiating the price.

I'm 6' and have ridden 22" and 20". The 22" is a bit more comfortable for riding distances and the 20" is easier on single track plus the extra clearance is quite comforting when it gets rough.

It's not the inseam. It's the virtual top-tube length. Once you set the seat height and the seat fore-aft position for the knee position relative to the pedal spindle (cranks horizontal, plum bob; I like about 3/4" back), you should have something like a 45 to 50 degree back angle to the horizontal with the elbows slightly bent for shock with an 80 to 100 mm stem length. Inseam length is some what irrelevant unless one has very short legs. It's upper-body length that matters.

My wife is 5'7 and I'm 5'11, but we have roughly the same inseam length. She takes a small frame (Superlight) and I take a large (Blur XC) in the Santa Cruz bike line. I have my grips 1.5" below the seat and I get 45 deg with the arms slightly bent with an 80 mm stem. And that's not just for youngsters as I'm 70 and she is 68.


Al

I've found a lot of mtb frames to have long top tubes and short head tubes so I end up with the bars too low even on the x-large frames. My legs are a little long for my height, however.

thank you for all the info..I am going to go meet the guy and take it for a test ride,,thanks again!!

Remember...........on a road bike, standover clearance doesn't matter as much as the top tube length for comfort on long rides. On an MTB however, standover clearance takes precidence during short stops. Translation..........unexpected sudden dismounts require room.

Most modern MTB's are disigned with a sloping top tube (many with a great deal of slope). This provides some extra clearance. In general, go with the same length virtual top tube as your road bike fit and you will be fine. If the bike is too big, you will have difficulty shifting your weight around on the saddle (and behind it) for off road control.

The virtual top tube length on a MTB should be a little longer than on a road bike because the handlebars don't have the forward reach of drop bars. At 6' with 34.5" cycling inseam, I ride a 19" or Large MTB frame. Is 31-32 your real inseam length or your pants inseam?

That used to be a serious problem. Now they seem to be selling ATB's with extra long steering tubes with spacers to allow customizing. I started building/assembling our own bikes so I could cut the steering tube where we wanted them. If not sure, I leave a half inch or more protruding above the stem. And then there are always riser bars which can be cut in length to the that of the flat bars.

I have this KHS and I have a lot of spacers on the steer tube to get the bars up there. Kinda scary.

http://i171.photobucket.com/albums/u...S2010009-1.jpg