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Old 01-20-07, 10:33 PM   #1
kmart
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26mm bars in a 25mm stem?

I have a 26mm stem that looks kind of like this:


Could I securely fit 25mm handlebars to this type of stem? It seems like It could just tighten the screw more...
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Old 01-20-07, 10:56 PM   #2
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Quote:
Originally Posted by kmart
I have a 26mm stem that looks kind of like this:


Could I securely fit 25mm handlebars to this type of stem? It seems like It could just tighten the screw more...
25 mm is the ancient French size, I don't think that they have made these in the last 25 years, and most of the older bars that used that size were of marginal safety even when new.

However if you're set on doing this, the right way to do it would be with a shim, typically a strip of 0.5 mm aluminum sheet (or equivalent thickness made up of multiple layers, if you don't have 0.5 mm aluminum sheet on hand.)

If you try to mount a 25 mm bar in that stem, the clamp would have to close up pi mm, which would probably cause the clamp to clamp onto itself. In addition, there's a risk of cracking an aluminum stem by bending it too much. Aluminum really doesn't like to be bent.

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Old 01-20-07, 11:12 PM   #3
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Gah! I just realized I mixed things up in the my post but not in the thread title. I meant to say 26mm bars in a 25mm stem, not the other way around.
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Old 01-20-07, 11:40 PM   #4
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are you sure they aren't 25.4mm bars and if they are you can get a stem shim for cheaps yo
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Old 01-21-07, 06:27 AM   #5
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Quote:
Originally Posted by kmart
Gah! I just realized I mixed things up in the my post but not in the thread title. I meant to say 26mm bars in a 25mm stem, not the other way around.
No a 26 mm bar will not fit in a single bolt quill stem sized for 25.4 mm. If it was an open face stem (removeable faceplate, 2 or 4 bolt) then it would with care but not in a quill stem. You can still get Nitto drop handlebars that fit 25.4 mm clamps.

Regards, Anthony
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Old 01-22-07, 12:54 PM   #6
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I've heard of people TRYING to put their 26 mm into a 25.4 mm with little success and lots of broken stems....
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Old 01-22-07, 01:10 PM   #7
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An example of 26mm bars in a 25.4mm clamp. It was actually fairly easy on this bike. I tapped a slotted screwdriver into the clamp from the side and the bar slid right in.

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Old 01-22-07, 01:29 PM   #8
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Quote:
Originally Posted by kmart
I have a 26mm stem that looks kind of like this:


Could I securely fit 25mm handlebars to this type of stem? It seems like It could just tighten the screw more...
I had a 26.4mm older Cinelli stem very similar to that with a 26.0mm newer Cinelli bar and it seemed OK on the floor but when I rode it the bars rotated - Not realizing that they didn't match, I kept tightening the bolt until it finally broke. 25.8 with 26.0 seems OK though so that must be about the limit in size difference.
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Old 01-22-07, 02:49 PM   #9
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It can be done. Before spreading the clamp apart, I would use a circular-file to grind away the corner and sharp-edges of the slot. These areas will not spread and enlarge like the circular parts of the clamp and will end up biting into your bars and causing stress-risers.
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Old 01-22-07, 11:27 PM   #10
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Either buy a new stem, or buy new bars!

Search for Nitto B-105's or B-115's on eBay, they're made for 25.4 stems.

Good 25.4 stems are harder to come by, though I think the Nitto Technomic is designed for this smaller diameter... You can also find older SR/Sakae stems in this size.

e. Technomics are available in both 25.4 and 26.0

Last edited by AGuinness; 01-22-07 at 11:43 PM.
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Old 03-31-11, 11:17 PM   #11
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Did this problem ever get sorted out? I myself have a French stem with Italian bars
My thought was to get some kind of 26mm drill bit (step drill bit perhaps?) or even a grinder, or milling machine, to grind off the excess 1mm diameter. Only problem I could conceive was that it would catch the open part of the clamp and possibly destroy the thing... =/
Any input?
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Old 04-01-11, 01:21 AM   #12
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26.4 is a Cinelli only bar diameter , so you need to find a cinelli Bar of the same era.

Nitto makes a lovely 26.0 to 25.4 shim. 1" road bars are Rare
straight bare are common.
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Old 04-01-11, 08:59 AM   #13
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Not Cinelli... 3ttt
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Old 04-01-11, 11:07 AM   #14
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Why go to such lengths when a proper fitting stem/bar set can be purchased with relative ease and will work properly without the danger of failure.

Believe me you do not want to be riding when either a stem or bar fails.
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Old 04-01-11, 07:47 PM   #15
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With the cinelli bar, 26,4 i would advice you to ream the stem to the size you need, why? two reasons, the stem in the long term would crack and secondly you will scratch the handlebar big time. Some stems are so cheap that inside are not even that rounded to go 26.4, u have to ream them.
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Old 04-01-11, 08:37 PM   #16
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25.4mm bars in a 25mm stem with extreme care, minor sanding of the stem clamp, and limiting weight on those bars to less than 180lbs = Probably not going to kill you, that's .2mm off the radius. I've done it and lived, but I also weigh ~150lbs. Edit: .4 millimeters = 0.0157480315 inches or ~1/64" of an inch off the diameter or 1/128th off the radius.

I wouldn't go .5mm off the radius of a stem clamp, that would be REALLY cutting into the safety factor. I figure stems probably had a safety factor designed for roughly 200lbs. Every little bit removed from the clamp area is cutting into that safety factor by an undetermined amount. I guessed 10lbs per .1mm in my case, but I don't recommend it.

Your life, severe injury, or disfigurement isn't worth saving money on a stem because you took an entire millimeter out of the diameter.

Last edited by Fenway; 04-02-11 at 08:22 AM. Reason: Added fractional inches to post
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Old 01-25-12, 09:54 AM   #17
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hi all!
Does anyone know if a 26mm handlebar will fit well in a 25.4mm stem? Just want to use my road bike for urban use. I'm not sure about it.

However, I don't understand why brands are still producing stems and handlebars with those 2 sizes: 25.4mm (1'') and 26mm (1 1/8'' ?) instead of use the most common: 26mm.

Thanks!
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Old 01-25-12, 10:17 AM   #18
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You can fit a small peg into a big hole using a shim to fill the gap. But you cannot shim a big peg smaller to fit a small hole. Same with bars and stems 25.4 in 26.0, OK with a shim. 26.0 in 25.4 not possible.

Some people say you can stretch the stem open, or make a removable faceplate stem work with some force, but this is a recipe for disaster since the curvatures won't match and either the bar or stem will be over stressed with a high likelihood of failure.

There is one way to do this job right. If there's enough meat on the stem you can ream the 25.4 bore out to 26mm. You'll need an adjustable blade reamer (or fixed 26mm reamer) of the type shops use for seat tubes, and a bit of skill to do a workmanlike job. Any decent bike shop mechanic should be able to do it, or you can mail me the stem and I'll do it for $10.00 including return postage.
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Old 01-25-12, 10:25 AM   #19
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Originally Posted by FBinNY View Post
There is one way to do this job right. If there's enough meat on the stem you can ream the 25.4 bore out to 26mm. You'll need an adjustable blade reamer (or fixed 26mm reamer) of the type shops use for seat tubes, and a bit of skill to do a workmanlike job. Any decent bike shop mechanic should be able to do it, or you can mail me the stem and I'll do it for $10.00 including return postage.
Yup:

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Old 01-25-12, 11:52 AM   #20
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However, I don't understand why brands are still producing stems and handlebars with those 2 sizes: 25.4mm (1'') and 26mm (1 1/8'' ?) instead of use the most common: 26mm.
no 1 1/8"? is not 26mm, it is larger 28.6, the new oversize is like 1.25"

1" center, bars are 7/8" for the rest of your Bar.

Roadie brakes are different, because,a 26mm center bar is 15/16"
for the rest of its tube.
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