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Thread: Stem Question: 25.4 vs. 31.8?

  1. #1

    Default Stem Question: 25.4 vs. 31.8?

    What is the difference (besides size) between a 25.4 and 31.8 stem/handlebar?

    Is there an advantage of one over another? Standard size vs. harder to find parts for? I'm confused.

  2. #2


    Oversize is marginally stiffer due to the larger tube but also slightly heavier. Today nearly all reputable carbon bars are 31.8, whereas most jumping/DH riser bars have a one inch clamp. I ride a Black market 3" rise and feel some flex but it's not enough to fatigue the material. So if you are tall and want a bar that is higher that a 1.5" rise go 25.4

  3. #3
    A little Shaggy Bryguy17's Avatar
    Dec 2007
    Fullerton, CA


    both will be easy to find parts for, it's just a difference in attributes.

    31.8 OS will be a stiffer bar, but will also be a little stronger. In some cases, (not all mind you) you might end up with a slightly lighter stem as well, but not usually. OS seems to be the trend for most new bikes. I personally like the extra stiffness, as it adds control and tactile feedback.

    25.4 will be a flexier bar, but not necessarily weaker. the bar will take up more of the vibrations from the trail, so your hands dont feel them. pretty much every bar has a 25.4 size, so finding one wont be a problem. These will also be much cheaper, as they are technically out of vogue. you can find a good carbon bar/stem combo for a comparable price to a nice OS stem.

    Another thing to consider: should you want to run a titanium bar, you will want to go 25.4. As far as I know they only come in that size due to the difficulty in making a ti OS bar. it's a bling option though, so not really a big deal

  4. #4


    Almost every single bike coming out now that isnt entry line has 31.8 bars. we have 4 out of 50 bars in teh shop that are 25.4 Seems 31.8 is the new standard. Anything you gain weight wize on teh bar, your going to make up on the stem. Stronger, stiffer. the 31.8 is the way to go. Even the road bikes are that way too

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