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Handlebar fitment concerns, diameter

Old 01-12-22, 03:43 PM
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tiger1964 
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Handlebar fitment concerns, diameter

As I was musing in another topic, on my 1974 Zeus track bike project, “It has been 45 years but I am pretty sure the bar and stem came to me together; I knew someone with a Favorit bike and was upgrading one component at a time and I bought these from him. I like the combination of steel and aluminum on the stem, to me it “looks right” on a track bike. Oddly, there is no raised center section on the bars and the stem really does not want to tighten down snug.” Well, between them appearing a bit bent and the clamp-down issue, perhaps I should replace the bars and keep the stem; I suspect I’ll have to hacksaw the bars to get them off. The micrometer reads the bar diameter at 23.7mm, and I’ve only found a couple of websites selling classically-shaped bars (I could use advice on sources) and not much below a center diameter of 25.4mm. Are there other sizes out there? If this is some odd Czech-only size perhaps the bar and stem both have to go… sad.
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Old 01-12-22, 04:21 PM
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Maybe the bars are supposed to be 23.8 and it's just a tight fit (or corroded together?). Sheldon's crib sheet says in row 2 that obsolete British steel drop bars would have been sized at 23.8mm at the clamp: https://www.sheldonbrown.com/cribsheet-handlebars.html
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Old 01-13-22, 01:09 PM
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Originally Posted by noobinsf View Post
Maybe the bars are supposed to be 23.8 and it's just a tight fit (or corroded together?). Sheldon's crib sheet says in row 2 that obsolete British steel drop bars would have been sized at 23.8mm at the clamp: https://www.sheldonbrown.com/cribsheet-handlebars.html
Not a tight fit at the center, indeed I cannot get the stem to tighten on the bars. Hard for me to remember what I was doing 47.5 years ago or where I sourced stuff; there's some nasty scarring on the first bend on one side like I once tried to separate the bars/stem and failed (why would they design bars with no raised center section???) And that crib sheet does not show much anywhere near what I am measuring. I smell deep dark trouble...

So I am inclined to locate some nicer bars; perhaps start with a WTB here at C&V/BF? Not tied to a particular brand, maybe GB, or TTT or, hmm, what other brands should I be considering? And I'm right that the only diameter to worry about is at the clamp, no? With all 1'" steerers, the insertion diameter is a constant? That does not sound right, there's no universal diameter for anything.
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Old 01-13-22, 03:25 PM
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Is it possible that bar was supposed to be used with a shim?

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Old 01-14-22, 10:14 AM
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Originally Posted by Miele Man View Post
Is it possible that bar was supposed to be used with a shim?
Hmm, I do have a package of assorted-size brass shim stock I had used for automotive purposes -- if I could being myself to trust such a connection to hold and not slip and the worst moment.
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Old 01-14-22, 10:19 AM
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Originally Posted by tiger1964 View Post
Hmm, I do have a package of assorted-size brass shim stock I had used for automotive purposes -- if I could being myself to trust such a connection to hold and not slip and the worst moment.
People have used shims and bars for eons without issues. Use enough shim that allows the binder bolt to tighten adequately and you'll be fine.
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Old 01-14-22, 01:32 PM
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Originally Posted by TugaDude View Post
People have used shims and bars for eons without issues. Use enough shim that allows the binder bolt to tighten adequately and you'll be fine.
To get the inside diameter of the stem to determine thickness of shim needed, and likely to mount the bars in a vise to correct what seems to be slightly bent bars, imperative to separate bars and stem. Just spent a lot of time and no matter how much I try to pry the stem open further, won't got past the bends in the bars. Next stop: WTB. Sad because I think the stem is really cool.

Originally Posted by tiger1964 View Post
And I'm right that the only diameter to worry about is at the clamp, no? With all 1'" steerers, the insertion diameter is a constant? That does not sound right, there's no universal diameter for anything.
Micrometer says about 22mm for insertion into the steerer... common size?
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Old 01-14-22, 04:57 PM
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How did they get the bars in in the first place? Something isn’t adding up here.
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Old 01-14-22, 05:59 PM
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I would say, you NEED to have the ID of the stem handlbar mounting bore and the center of the handlebar OD match. If the bar is too big, the stam clamp should fraccture as you tighten the clap bolt. the bar is too smal for the stem, you will over tighten the clamp screw and possibly never achieve tension. And due to the over tightening, it could still fracture the stem.

When the stem fractures, if you are riding, you will most likely crash and hit the ground, possibly with your face.

There are many sizes for the parts in question, and if they are now distorted, they are already over stressed and hence dangerous. Aluminum does not like to be cold-set.
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Old 01-14-22, 06:05 PM
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I have dated 1951 Reynolds drop bars that are 23.8 and require a shim to fit old GB Hidminium bars. I suspect this was always a thing.

Brass shim stock will work in most any application as will aluminum. I make sure to have any gap or overlap centred in the opening in the stem to prevent stress risers

Last edited by clubman; 01-14-22 at 06:14 PM.
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Old 01-15-22, 12:19 AM
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Bent handlebar? Deep scoring at one of the bends? In retrospect I'd ditch that handlebar and get something else that I could be sure wouldn't fail in use.

Prying alloy stems very much isn't a good idea either as you can easily introduce stress risers.

You really don't want a handlebar or stem failing on a fast ride or in traffic.

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Old 01-15-22, 08:44 AM
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Originally Posted by clubman View Post
I have dated 1951 Reynolds drop bars that are 23.8 and require a shim to fit old GB Hidminium bars. I suspect this was always a thing.

Brass shim stock will work in most any application as will aluminum. I make sure to have any gap or overlap centred in the opening in the stem to prevent stress risers
Yes, that was a pretty common English handlebar standard, as 23.8mm is the metric equivalentt of 15/16". I've seen lots of English bars that used a shim to accommodate the stem. My only shim advice is to to not build up the shim with several pieces of stock. Use a single piece of the correct thickness. The more layers between the bar and stem, the greater the chance of slippage.
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Old 01-15-22, 10:20 AM
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Yes, I meant Hidminium stems.
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Old 01-15-22, 12:16 PM
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Originally Posted by TugaDude View Post
How did they get the bars in in the first place? Something isn’t adding up here.
You got that right! Maybe they bent the bars to shape from straight stock after passing through the stem?

Originally Posted by Road Fan View Post
I would say, you NEED to have the ID of the stem handlbar mounting bore and the center of the handlebar OD match.
Micrometer says about 24.7mm inside diameter. How do I know? Because...

Originally Posted by Miele Man View Post
Bent handlebar? Deep scoring at one of the bends? In retrospect I'd ditch that handlebar and get something else that I could be sure wouldn't fail in use.
Upon reflection, I decided that's correct. So, to possibly save the stem, I hacksawed the bars to release the stem. So, my WTB 1.0 is to find bars to fit, my WTB 2.0 would be bars and a stem. Unsure what bars fit a 24.7mm hole.

Originally Posted by T-Mar View Post
Yes, that was a pretty common English handlebar standard, as 23.8mm is the metric equivalentt of 15/16". I've seen lots of English bars that used a shim to accommodate the stem. My only shim advice is to to not build up the shim with several pieces of stock. Use a single piece of the correct thickness. The more layers between the bar and stem, the greater the chance of slippage.
Presuming I found some 23.8's, to fit a 24.7mm stem means 0.45mm shim. AM i calculating that right at 17.72 1000th's of an inch thick? Less any desired clearance, if indeed any is desired (I'm going through a "clearance crisis" on a seat post now at the same time).
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Old 01-15-22, 02:52 PM
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Originally Posted by tiger1964 View Post
You got that right! Maybe they bent the bars to shape from straight stock after passing through the stem?



Micrometer says about 24.7mm inside diameter. How do I know? Because...



Upon reflection, I decided that's correct. So, to possibly save the stem, I hacksawed the bars to release the stem. So, my WTB 1.0 is to find bars to fit, my WTB 2.0 would be bars and a stem. Unsure what bars fit a 24.7mm hole.



Presuming I found some 23.8's, to fit a 24.7mm stem means 0.45mm shim. AM i calculating that right at 17.72 1000th's of an inch thick? Less any desired clearance, if indeed any is desired (I'm going through a "clearance crisis" on a seat post now at the same time).
I think I should not say anything more than "Godspeed!" It sounds like you're on the path.

Anything I can try to help with, HMU.
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