26.0 and 25.4 stems interchangeable?

[jmeloy]

Had a good shop owner tell me today that I could go with a 25.4 stem for my 26.0 bar with no issues. Is that a fact or was he trying to make a sale when he did not have a 26.0 in stock?
Thanks!!

[wildboar]

From Peter White's website:

You must not use a stem and handlebar which are not perfectly matching in the clamp size! Don't try to match a 26mm stem with a 25.4mm bar, or a 25.4mm stem with a 26mm bar! And don't use either with the old Cinelli spec 26.4mm stem or bar!

[Likes2ridefar]

I've used them that way with no issues in the past on mountain bikes. I know others who have too.

[myette10]

ok but not the best for the mtn. never try it for road (rotational forces)

[jpw]

Would there be a problem with Deda 31.7mm and the oversize industry standard of 31.8mm? Would it be ok to mix the two sizes?

[dekindy]

This probably works since Rivendell sells it. Anybody have any experience? I definitely would not try it without a shim.

http://www.rivbike.com/products/list/handlebars_stems_and_tape?a=1&page=all#product=16-095

[PacNW2Ford]

Would there be a problem with Deda 31.7mm and the oversize industry standard of 31.8mm? Would it be ok to mix the two sizes?

This would be okay since the quoted metric standard is likely a hard conversion of the English 1.125" diameter and also within the manufacturing tolerance of the bars. So size-wise at least they're compatible.

The old 3ttt bars ran small, nominally 25.8 mm and worked in most 26.0 stems, but could slip in some stems. I'd use a shim to go from a 25.4 bar to a 26.0 stem. I don't think I'd try a 26 bar in a 25.4 stem.

[RPS]

This probably works since Rivendell sells it. Anybody have any experience? I definitely would not try it without a shim.

http://www.rivbike.com/products/list/handlebars_stems_and_tape?a=1&page=all#product=16-095
You can shim down to a smaller bar, but not up. As I understand the question the bars are already larger than the stem; hence a shim will not work in this case.

[RPS]

Had a good shop owner tell me today that I could go with a 25.4 stem for my 26.0 bar with no issues. Is that a fact or was he trying to make a sale when he did not have a 26.0 in stock?
Thanks!!
It's not a good idea and if you haven't bought it yet then why not get the right size in the first place?

Although it may have worked in some cases, it doesn't mean that bending the face plate and flattening the bars doesn't place additional stresses in that area. It may or may not break, but why take the chance of riding with something that has a lower margin of safety than the engineers who designed it intended?

I'd buy the right size stem even if it means spending a few extra pesos. And I'd buy quality too.

[11.4]

Deda wanted to patent the 31.8 mm bar size but didn't pull it off well. Since 31.8 mm is simply a conversion from English measurement, rounded up to the next tenth millimeter, and 31.7 mm is the same conversion rounded down, Deda didn't protect the 31.7. Various manufacturers want to make you stick with their own equipment plus they want to ensure no undue liability issues, so they lined up on specific dimensions. But we have put a micrometer on plenty of stems and bars and see much more than a 0.1 mm variance from one sample to the next. At that point, I don't really think the 31.8/31.7 difference has any relevance.

On the 25.4/26.0/26.4 debate, I generally try to respect the different dimensions. But especially with older 26.4 mm equipment and much of the 26.0 mm, the clamping areas on the bars are anything but round -- I just re-measured some 26.4 mm Cinelli Criterium bars and the diameter on a single bar varies from 25.8 to 26.8 depending on the cross-section you are measuring (all at the same clamping point on the same bar). Old bottom-pinch-bolt stems (like the Cinelli 1-A) are anything but round and their clamping method actually deforms the bar clamping areas. As for Cinelli 1-R's, don't even ask.

I mostly race track and have a handful of Nitto steel bars, nominally 25.4 mm. All are out-of-round, varying in the best case at the clamp from 25.2 to 25.9, and there are a couple little ridges on two of the bars that increase the variance quite a bit farther. When I mount Nitto steel track bars, I typically measure various cross-sections and sometimes have to file down such ridges and stuff to make them fit well.

So ... It isn't just a matter of reading the diameter off the bar, although that will at least get you close. I'd borrow a micrometer or vernier caliper from the shop where you get your bar or stem and make sure things actually are round and fit together.