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Using a 26.0mm stem clamp with a 25.4mm bar okay?

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Using a 26.0mm stem clamp with a 25.4mm bar okay?

Old 07-18-17, 04:45 PM
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Using a 26.0mm stem clamp with a 25.4mm bar okay?

Hi! I have a lovely Velo Orange stem (70mm, 26.0, 1-1/8", 6deg) with which I'm trying out 25.4mm bars and wanted to know if it's safe to ride with this combo. I got the stem years ago to use with a 26.0 Nitto Noodle bar, which I'm now selling, and I'd rather not have to buy another stem.

I know VO sells shims, but each bar has felt totally secure, and I do recreational riding at best (back on a bike after decades off), so no crazy jumps or rock hopping for me. Does 0.6mm make that much of a difference? I'm hoping you experienced folks can help. Thanks for your input!

(Hope this is in the right forum; please let me know if not!)
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Old 07-18-17, 04:54 PM
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I'd use a shim. This is one place where you obviously don't want a failure.
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Old 07-18-17, 05:08 PM
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Shim or the correct size bar. When you hit a bump and your bars end up near your wheel you could lose control and die.
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Old 07-18-17, 05:13 PM
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You can cut a shim from a tin can. A steel can should be better than aluminum.
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Old 07-18-17, 05:26 PM
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Shim. They make shims for exactly this reason and they work.
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Old 07-18-17, 06:01 PM
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.
...sadly, if you've already cranked it down tight on the smaller bar, prying it out again to fit the bar size it was designed for is often the cause of a tiny crack, fatigue, and eventual failure. They make and sell these things in certain sizes for a reason. Cast, or even forged aluminum is not very amenable to this sort of abuse. Steel, OTOH, does nicely.

But at this point it's pretty much your call on riding as is or prying it back open and shimming it. Sorry.

Edit: I did an image search for VO stems, and most of them look like they would work with either size, so I'm puzzled as to what you have. You should always post a photo of what you're asking about here to get sound advice.



^^^is made from steel and will work fine on a variety of bar sizes.



^^^also works well with a wide range of bar diameters.

Last edited by 3alarmer; 07-18-17 at 06:09 PM.
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Old 07-18-17, 08:58 PM
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Originally Posted by 3alarmer
.
...sadly, if you've already cranked it down tight on the smaller bar, prying it out again to fit the bar size it was designed for is often the cause of a tiny crack, fatigue, and eventual failure. They make and sell these things in certain sizes for a reason. Cast, or even forged aluminum is not very amenable to this sort of abuse. Steel, OTOH, does nicely.

But at this point it's pretty much your call on riding as is or prying it back open and shimming it. Sorry.

Edit: I did an image search for VO stems, and most of them look like they would work with either size, so I'm puzzled as to what you have. You should always post a photo of what you're asking about here to get sound advice.



^^^is made from steel and will work fine on a variety of bar sizes.



^^^also works well with a wide range of bar diameters.
Many thanks to everyone for your feedback...I appreciate all the quick responses.

And sorry for not posting a pic. My VO stem is exactly the last (threadless) one you posted, 3alarmer. Polished silver aluminum alloy.

So do you mean that my 26mm stem can work with a range of bars, including 25.4mm? I got worried after reading the responses above and want to make sure I'm safe before I go out again. Thanks!!

Last edited by Cyclist759; 07-18-17 at 09:04 PM.
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Old 07-18-17, 09:04 PM
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Originally Posted by velocipedia
Thanks to everyone for your feedback...I appreciate all the quick responses.

And sorry for not posting a pic. My VO stem is exactly the last (threadless) one you posted, 3alarmer. Polished silver aluminum alloy.

So do you mean that my 26mm stem can work with a range of bars, including 25.4mm?
...if it clamps down on the bar tightly enough that there's no rotation when you put your weight on the brake hoods, you ought to be golden. I've used similar stems with a variety of bar sizes with no issues. If it's not rock solid in there in terms of rotation under weight, buy a shim. they're pretty cheap, and VO sells them, as do others.
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Old 07-18-17, 09:19 PM
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Originally Posted by 3alarmer
...if it clamps down on the bar tightly enough that there's no rotation when you put your weight on the brake hoods, you ought to be golden. I've used similar stems with a variety of bar sizes with no issues. If it's not rock solid in there in terms of rotation under weight, buy a shim. they're pretty cheap, and VO sells them, as do others.
Okay, thank you! I'm trying different North Road type bars now (possibly the VO Tourist bar) to replace my Nitto Noodle, and they have scores, or threading, in the clamp area, which should also help the bar stay in place, I assume?
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Old 07-18-17, 09:19 PM
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Originally Posted by 3alarmer
...if it clamps down on the bar tightly enough that there's no rotation when you put your weight on the brake hoods, you ought to be golden. I've used similar stems with a variety of bar sizes with no issues. If it's not rock solid in there in terms of rotation under weight, buy a shim. they're pretty cheap, and VO sells them, as do others.
...just so you know, the shim solution is the "proper"way to do this. It's what I would do if I were doing it for someone else. The stem portions at the bar have a curve that best fits 26 mm, so without the shim, you're losing some contact surface at the top and bottom of the curve.

But I've done it in the absence of the proper shim, and it works fine if it's solid in terms of rotation.
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Old 07-18-17, 09:32 PM
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As long as you can get it tight enough that it doesn't spin you should be fine. .6 mm is not much difference.
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Old 07-18-17, 11:49 PM
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Originally Posted by 3alarmer
...if it clamps down on the bar tightly enough that there's no rotation when you put your weight on the brake hoods, you ought to be golden. I've used similar stems with a variety of bar sizes with no issues. If it's not rock solid in there in terms of rotation under weight, buy a shim. they're pretty cheap, and VO sells them, as do others.
The real test is that the face plate still has a small gap. If there's a gap, the bar is being firmly clamped and there is no issue.

Also I feel like standard tolerance on a bar is probably +-0.3mm so as long as both parts aren't at the opposite ends of their tolerances you're fine.
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Old 07-19-17, 08:32 AM
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Originally Posted by gsa103
The real test is that the face plate still has a small gap. If there's a gap, the bar is being firmly clamped and there is no issue.

Also I feel like standard tolerance on a bar is probably +-0.3mm so as long as both parts aren't at the opposite ends of their tolerances you're fine.
Thanks again to all who replied! Here are a few pix of my stem...good to go or not?
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Old 07-19-17, 08:38 AM
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I say no. It will not and does not work. I have tried with exact same alloy 26mm stem and 25.4mm bars. I even put gaffer tape to act as shim. It will slip. Good luck with your testing.
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Old 07-19-17, 09:21 AM
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Originally Posted by velocipedia
Thanks again to all who replied! Here are a few pix of my stem...good to go or not?
Looks fine. I would loosen the top bolt and tighten the lowers to even out the gaps. But there's plenty of gap, which means the stem is clamping directly on the bars, so it's clamping exactly the same as it would with 26mm bars..
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Old 07-19-17, 10:06 AM
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Originally Posted by trailangel
I say no. It will not and does not work. I have tried with exact same alloy 26mm stem and 25.4mm bars. I even put gaffer tape to act as shim. It will slip. Good luck with your testing.
...gaffer tape is not an especially good material for this use. Just sayin'. You want something that is more resistant to compression, like metal. Aluminum works, but almost any metal sheet stock of the proper thickness works well.
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Old 07-19-17, 11:35 AM
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You are almost there. You just need to tighten it so your top and bottom gaps are equal. Make sure there is a gap on both top and bottom, if not you'll need a shim.
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Old 07-19-17, 12:57 PM
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THINK about a seat post for a minute. .2mm difference means it will either be impossible to shove it into the tube, literally, or that it will fall in and be so sloppy that you have to over tighten and damage the tube/clamp in hopes of having it hold. And it usually won't hold.

You are asking your stem and bars to mate properly and be safe with triple that amount mismatched sizing.

You have an "Egg in a circle" interface there. Not 100% uniform contact. I suspect the flaceplate will devlop cracks in time.

I would never do that.

Keep an eye on it frequently.

Shims are dirt cheap.

Face plants suck.
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Old 07-19-17, 01:26 PM
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I had an old Cinelli stem with 26.4mm diameter and tried to make it work with a 26.0 bar... only 0.4mm difference vs OP's 0.6mm difference.

Could not get it tight enough to not rotate, and then I broke the stem binder bolt.
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Old 07-19-17, 01:34 PM
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Originally Posted by DiabloScott
I had an old Cinelli stem with 26.4mm diameter and tried to make it work with a 26.0 bar... only 0.4mm difference vs OP's 0.6mm difference.

Could not get it tight enough to not rotate, and then I broke the stem binder bolt.
...I agree that bar diameter and clamp diameter is a much more critical match in an older, cast aluminum quill stem. Other than that, I've not much more to say.
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Old 07-19-17, 01:35 PM
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You might get away with it, he wrote doubtfully, if the tolerances are large and in your favor. With the threadless stem, it'd be better to put a shim in. It's not so much a question of whether the bar will rotate when you push gently on it, as will the bar rotate when you hit a pothole, the bar gets loaded to 3 times your upper body weight, you lose your grip on the bar, and end up holding yourself off the ground with your teeth against the stem.
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Old 07-19-17, 01:45 PM
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Originally Posted by Peter White Cycles
Q: My friend said he heard that his other friend's cousin used a 26.0 stem with a 26.4 bar and that it didn't break for 72 years, three months, six days, four hours and twelve minutes. Given this undeniable fact, don't you think your recommendations are a bit too conservative?

A: Well, I guess maybe perhaps if you put it that way, uh...
Stems, Peter White Cycles
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Old 07-19-17, 01:55 PM
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Originally Posted by velocipedia
Thanks again to all who replied! Here are a few pix of my stem...good to go or not?
No.

The clamp is not evenly tightened against the bar and more importantly, the part does not fit.

You are asking for trouble. Get a proper shim or a bar/stem combination designed to work together.

Beer cans and duct tape are not the right shims. They may work but this isn't a combat situation or Apollo 13.

Get the right parts.


-Tim-
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Old 07-19-17, 03:09 PM
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Originally Posted by TimothyH

Beer cans and duct tape are not the right shims. They may work but this isn't a combat situation ...
...every time I ride my bike in city traffic it's a combat situation, man.
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Old 07-19-17, 04:33 PM
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Hi, all...so the majority of you strongly suggest shims or a new stem, though a handful of you think it's fine if there's a gap and it's secure. I've been doing very short runs (4 miles apiece) on flat-ish smooth roads to test out different bars and, thankfully, I have only one left to test.

After reading all your replies, I don't think I'll feel safe unless I have the correct stem. I'll try to sell mine on eBay and get a new one. It's not worth taking chances, and I'm a worrier, so there's that.

Thanks very much, everyone, for lending your thoughts and time to this discussion...I really appreciate it and hope it helps others, too.
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