I have a road bike from Circa 2003 and it currently boasts an ITM Millenium stem. The stem is a bit long for my liking at around 130mm and I was thinking of replacing it with a shorter one for a slightly more upright riding position.

I have a feeling my bars however are of clamping diameter 25.4 mm, although they may be 26mm as it is an Italian bike (ITM bars too). Shopping around I notice that pretty much all new stems are of the oversize 31.8 mm clamping diameter so I assume they won't fit my bars.

How would I get around this problem? I heard one could get shims to thicken the bars at the clamping point but sourcing them seems to be tricky.

  • Probably a silly question but if are going for upright then is then is the stem in the highest position and angled up? Is the seat forward. Understand you may still want shorter stem. But have you used up all your adjustments?
    – paparazzo
    Jun 5, 2014 at 19:54
  • I'm happy with the handlebar height, I just feel the reach is a bit far. Saddle has been adjusted forward too.
    – harryg
    Jun 6, 2014 at 12:59

1 Answer 1


25.4 ( or one inch ) is almost always an MTB handlebar diameter or a very old cheap bike. From 2003 and of good quality, it is almost certainly a 26mm handlebar.

There are parts of the bike you can bodge without much concern and parts you can't. Anything in the fork/headset/handlebar area is not something you should try and "make work". If it goes wrong, you'll crash hard.

You should still be able to find 26mm stems if you look hard enough. Here is a good source.


They also sell the appropriate shims to use your bar with a 31.8 stem, but if it were my bike, I'd just pony up for a new 31.8 handlebar.

  • 1
    To expand: if those shims slip, most likely your handlebars will rotate down when you're on the hoods and you're going to struggle to control the bike. Also, downvoter can you explain why?
    – Móż
    Jun 6, 2014 at 1:22
  • 1
    yeah the shims look like what I'm after, just a shame VO is in the US as I'm in the UK. Bit was top range when new so I doubt it'll have cheap parts (Full Ultegra De Rosa). I might visit a LBS and see what they recommend, if not I'll just stick with the current stem - it's not too bad but I feel I could improve comfort a bit.
    – harryg
    Jun 6, 2014 at 13:02
  • I actually think I meant 25.8mm. After some googling for ITM Millenium bars there are plenty of sources citing that dimension. e.g. cyclingforums.com/t/320249/…
    – harryg
    Jun 6, 2014 at 13:28

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