I have a spare hardtrail frame which is too big (20.5") for me (5'7") for riding trails. Would it make sense to build a commuter bike for me as road/touring bike frames are generally larger than MTB? Could it be comfortable to ride this frame on road? I like to lean forward on a bike and I'm a fast type of commuter.

  • If the frame will fit a 26x2.3" knobbly tyre, a 700x28c tyre will definitely fit. (Disc brakes would make this an easy conversion.)
    – Emyr
    Commented Sep 16, 2014 at 7:53
  • If its not disc braked, chances are you can't get the rim brakes to line up. In any case, there are lots of good 26" commuter tires these days.
    – Batman
    Commented Sep 17, 2014 at 3:33

3 Answers 3


It's a good, cheap way to build a first commuter. Throw on a pair of road slicks and lights and go to work. It will give you a chance to decide what you really want in a commuter bike. It will be able to handle bad roads and pot holes better than a road racing bike. But, it will still be heavier and slower than a bike based on a cyclocross/utility/road frame with 700c wheels.

  • 1
    A rigid fork is also a good idea to add. Fenders are also a good idea n a lot of climates.
    – Batman
    Commented Sep 15, 2014 at 23:16

You've got it the wrong way around. Road frames, in terms of horizontal toptube length, are significantly shorter than mountain bike frames. If it's a hardtail frame and it's too big for you with a flat bar, it's going to be way too big for you with a drop bar.

On the other hand, you might be able to put a bar with significant sweep on the frame and have it fit you a bit better. However, this would effectively shorten the stem, which may make the handling a bit twitchy.

  • I'm guessing the "too big" part isn't length but height - you need more than 2 inches of clearance to your genitals when riding off road.
    – Batman
    Commented Sep 15, 2014 at 23:58
  • Also, where does the OP say anything about drop bars? I wouldn't commute on drop bars if it can be avoided. I have tt bars on my commuter which I find way more comfortable.
    – arne
    Commented Sep 16, 2014 at 5:20
  • Jeeze, bicyycles.stackexchange got a little standoffish while I was gone.
    – joelmdev
    Commented Sep 16, 2014 at 12:45
  • @Batman a 20.5", which basically an XL, is 2-3 sizes too big for someone 5'7". At that point it's more than just a matter of standover.
    – joelmdev
    Commented Sep 16, 2014 at 13:59
  • @arne should I not mention the use of a drop bar since it wasn't specifically mentioned? Drop bar bikes are pretty common commuters and most people don't understand geometry that well, so I thought it best to cover all the bases from longest to shortest cockpit. Also, suggesting TT bars keeps all the problems with drop bars and adds some more. TT bars are designed for breaking, sprinting, and climbing, not holding onto for long distances, so for many they cause nerve impingement. They also have the same reach problems as drop bars for this situation. But you do get hip points, so there's that.
    – joelmdev
    Commented Sep 16, 2014 at 14:06

Unless you have the spare parts laying around build-outs are expensive and always labor intensive.

It is not worth spending money on a frame the does not fit you. Road versus trail the fit is not that different. The frame fits you or not.

I had mountain bike that the shock wore out and bought a better mountain bike. I put a fixed fork and tires on it to use it as a city bike and still had to think about it. I am good with that decision but the frame fit me and the conversion was $200.

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