Drop bar diameter vs. Stem diameter
11-04-18, 01:54 PM
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Drop bar diameter vs. Stem diameter
I have a set of drop bars that are 24.8 mm and a couple of aluminum stems that are 25.4 mm. I tried one and was able to get it to tighten up, but it took a little force-- not excessive though. I saw a couple of 24.8 mm stems on eBay, but they looked like death stems-- which I don't want.
Is there anything I should be concerned about safety wise with the mismatch in stem to bar diameter and having to close the clamp on the 25.4 stem down to 24.8? I figured that's only .6mm or .023 inches, but I'd rather be sure that I'm not over stressing the stem and creating a possible safety issue.
Is there anything I should be concerned about safety wise with the mismatch in stem to bar diameter and having to close the clamp on the 25.4 stem down to 24.8? I figured that's only .6mm or .023 inches, but I'd rather be sure that I'm not over stressing the stem and creating a possible safety issue.
11-04-18, 01:58 PM
#2
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Diameter difference is 0.6mm, as you say,
can you find 0.3mm thick, shim stock to get the fit spot on?
Or bars that are not undersized..?
...
can you find 0.3mm thick, shim stock to get the fit spot on?
Or bars that are not undersized..?
...
11-04-18, 03:55 PM
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11-04-18, 04:53 PM
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Sounds French. A lot of French bars and stems were 25.0.
11-04-18, 05:00 PM
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Is there anything I should be concerned about safety wise with the mismatch in stem to bar diameter and having to close the clamp on the 25.4 stem down to 24.8? I figured that's only .6mm or .023 inches, but I'd rather be sure that I'm not over stressing the stem and creating a possible safety issue.
It's not guaranteed it will fail, but you're much better off shimming the bar as you've mentioned. MOst of the old bars in that diameter are better off replaced with something more durable anyway. The bar itself can fail after it starts to sag.
11-04-18, 06:05 PM
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Yep. It's a French bike and the bars are French -- Belleri (BF).
Thanks -- I'm glad I asked. I hope I didn't stress the stem by tightening it down to 24.8. I've had these bars for a long time-- they are in good shape and I wanted to put them to use.
Maybe I should play it safe, toss them both and get new bars and a new stem...
...yeah, there is. Even if you can get it to work, it's a bad idea and can lead to failure at the clamping end. Even 26.0 to 26.4 mismatches can fail sometimes.
It's not guaranteed it will fail, but you're much better off shimming the bar as you've mentioned. Most of the old bars in that diameter are better off replaced with something more durable anyway. The bar itself can fail after it starts to sag.
It's not guaranteed it will fail, but you're much better off shimming the bar as you've mentioned. Most of the old bars in that diameter are better off replaced with something more durable anyway. The bar itself can fail after it starts to sag.
Maybe I should play it safe, toss them both and get new bars and a new stem...
11-04-18, 06:07 PM
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This happened to me with a 26.0 stem that, unbeknownst to me, was clamped down onto a 25.4 bar. After many years, I noticed a crack, figured out the cause, and took the stem out of service.
11-04-18, 07:33 PM
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DO NOT clamp a too-small thing with a too-big clamp. It creates concentrated stresses that can lead to part failure.
Use compatible parts or an appropriate shim.
Use compatible parts or an appropriate shim.
11-05-18, 02:38 AM
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Hey watch this!
Cinelli 1A 30+ years 26.4mm stem on 25.0mm bars then PING!
3TTT Record
verktyg
3TTT Record
verktyg
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Don't believe everything you think! History is written by those who weren't there....
Chas. ;-)
Don't believe everything you think! History is written by those who weren't there....
Chas. ;-)
Last edited by verktyg; 11-05-18 at 02:45 AM.
11-05-18, 05:10 AM
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11-05-18, 09:00 AM
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