Cycling UK Forum

Earlier today I was puzzled by - of all things - cable ferrules (now sorted…). Here’s another: my bar stem, dating from the eighties, has a clamp dia of 25.5mm. The old bars clamp dia is exactly the same. The newish bars I thought I would use measure at 26mm - are these 2 different standards? Have things changed since 1987? If so, why on earth are they different by 0.5 of a mil? The upshot appears to be that the new bars won't readily fit in to the old stem…
(I tried a couple of searches but nothing helpful was revealed.)

25.4mm is an inch, that's why it's been a standard. Of course those foreigners who refused to use our sensible measuring system came up with their own.

My go to for all cycle confusion is Sheldon’s pages so I’d already seen that crib sheet - but I’m none the wiser. I said 26mm but its actually less than that - just.

25.8 and 26.0mm bars were commonplace back in the day. One size made by ITM the other by 3T. "Bloody Italians" Some manufacturers stated there stems were suitable for both sizes. This link sheds some light on the topic. Some riders squeezed their 25.8mm bars into 25.4 stems.
viewtopic.php?t=25426#p201264
Oh and i squeezed my Cinelli LA84 bars (26.0mm) into a 25.4 clamp on the tandem for the stoker. I had to spread the stem clamp with a wedge to get the bars in.

That was a helpful read, rjb I'll make life easy for myself and just stick with the older bars. There's actually very little difference between them and the newer bars I was complaining about!

simonineaston wrote: ↑21 Apr 2024, 8:58pm That was a helpful read, rjb I'll make life easy for myself and just stick with the older bars. There's actually very little difference between them and the newer bars I was complaining about!

Lots of brand new bars in 25.4mm, bars sourced from Nitto or Soma.

25.4mm is ISO. 26.0mm is really common for replacement road bars. 25.8mm was supposed to fit either, and doesn't, but you can get 25.8mm bars and stems which do fit each other. Cinelli used 26.4mm for years and Ambrosio dabbled in it too.

31.8mm is pretty standard on better new bikes.