Frame sizes - MTB vs. Hybrid vs. Road

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Permalink Reply by Gecko on February 27, 2009 at 11:36am

What part of the MTB is too small? Where is the measurement taken? Fit is measured from the center of the bottom bracket to the center of the top tube (usually), but some brands take the measurement from the center of the bb to the top of the top tube. If the 22" is from center to center on the hybrid and center to top on the MTB, the hybrid will be larger because the measurement isn't taking into account the other half of the top tube. Also, top tube and stem length, and also saddle position, can have a noticeable effect on bike sizing. If the MTB has a shorter top tube and stem than the hybrid and its seat is moved forward farther, it will feel smaller because you're not as stretched out over the bike.

Road bikes are a slightly different animal because of the geometries and riding positions, but most people can ride larger-frame road bikes than mtb's because of the increased standover clearance needed for mountain biking (you want to be able to stand completely flat-footed on the ground with at least a few inches clearance on a mtb for safety's sake). For example, I ride a 54cm (21.5") road bike and an 18.5" mtb.

In your case, I would say measure each of your tubes (seat tube & top tube) center to center, and also measure stem length from the center of the steer tube to the center of the handlebar, and length from the center of the saddle to the center of the handlebar. Record each of the measurements for each bike, and note differences between them. This will allow you to adjust your current setups for the most comfort. You may just have to swap stems on your mtb and slide the seat back on the rails rather than buying a whole new frame.

Also, I know Trek makes 24" mountain bikes. You have to ask about them and special order them because a local bike shop won't stock a frame that large for fear of not being able to sell it. We ordered one for a very tall customer at the shop I used to work at. Other brands might make larger frames as well, if you ask around someone will probably have something.

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Permalink Reply by Todd on February 27, 2009 at 12:33pm

Thanks so much for responding and being so detailed.

My issue is that I put the darn seat so high because I wasn't getting good extension but now my arms get so fatigued, I'm assuming because the seat is too high. I think this is the issue with buying used off of CL and not going to my LBS.

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Permalink Reply by Gecko on February 27, 2009 at 12:48pm

Well that could have more to do with your seat angle and stem height than frame size. I've found that angling the nose of the seat slightly upwards (somewhere between totally horizontal and parallel to the top tube) on a mtb gives more of a relaxed ride.

Combined with a taller stem, you can really create a nice relaxed position, similar to a hybrid. You can also swap your handlebars out for some with more rise to them, which gives you a little finer range of adjustment without testing out different length/rise stems. I prefer the stem method because I like flat handlebars, but that's just personal preference. You can even combine a tall stem with higher rise handlebars to get a REALLY relaxed ride.

CL is not a bad way to get a good deal, but your LBS will know a heck of a lot more about proper fit than someone selling their old bike. Hopefully you'll learn some good information about your sizing as you get this bike set up, and when you upgrade again, you'll know what to look for.

And FYI, just because a bike doesn't fit right the first time doesn't mean you can't MAKE it fit. I bought a 21.5" mtb once because it was brand new and a ridiculously super cheap deal. Like I said before, I ride an 18.5" normally, so this frame was HUGE to me. After a quick stem swap and seat adjustment, I was able to ride it comfortably (even offroad) for 8 months before I sold it.

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