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What is the diameter of the handle bar on a mid 1980s Trek 520?

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What is the diameter of the handle bar on a mid 1980s Trek 520?

Old 10-15-17, 07:30 AM
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Abandoscious
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What is the diameter of the handle bar on a mid 1980s Trek 520?

What is the diameter of the handle bar on a mid 1980s Trek 520?
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Old 10-15-17, 07:39 AM
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Assuming you have original aluminum drop bars, then odds are it's 26.0mm which was the standard for road bars until fairly recently.

However, there's a small possibility that it 25.4mm (1").

The difference is big enough that you can make a gauge by carefully cutting a 1" slot into a piece of card stock, then seeing if it will slip over the fat section near the stem.
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Old 10-16-17, 02:03 AM
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Originally Posted by FBinNY View Post
Assuming you have original aluminum drop bars, then odds are it's 26.0mm which was the standard for road bars until fairly recently.

However, there's a small possibility that it 25.4mm (1").

The difference is big enough that you can make a gauge by carefully cutting a 1" slot into a piece of card stock, then seeing if it will slip over the fat section near the stem.
Or a piece of string to measure the circumference and use C = π * d (C= circumference, π = pi, d = diameter). Works well also with OD of plumbing pipes.
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Old 10-16-17, 04:04 AM
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25.4 is most likely. 26.0 is common on European bikes esp. Italian bikes.


https://www.sheldonbrown.com/cribsheet-handlebars.html
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Old 10-16-17, 06:06 AM
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The Belleri on this one is 25.4

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Old 10-16-17, 10:02 AM
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The clamp, as discussed above, is either 25.4 or 26.0.

The handlebar itself is probably 23.8 mm assuming it's an aluminum drop bar. If it's a steel bar, the diameter may be 22.2 mm.
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Old 10-16-17, 01:15 PM
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Note how #5 is doing it right, rather than asking online strangers, Measure It Yourself.
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Old 10-16-17, 01:22 PM
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Originally Posted by FBinNY View Post
Assuming you have original aluminum drop bars, then odds are it's 26.0mm which was the standard for road bars until fairly recently.

However, there's a small possibility that it 25.4mm (1").

The difference is big enough that you can make a gauge by carefully cutting a 1" slot into a piece of card stock, then seeing if it will slip over the fat section near the stem.
For a 26mm stem and a 25.4mm bar, would a shim from an aluminum can work?
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Old 10-16-17, 01:29 PM
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If it's 0.3mm thick. I believe that's more than the bypical can, so no.

OTOH - I once bailed out a friend with a paper shim made by winding paper coated with glue around the bar to reach the right diameter. I assembled and clamped it wet for good adhesion between the layers, and my friend rode it for much longer than we had originally planned, no problems.

FWIW, I'm a big fan of paper laminate shims and have enjoyed great success using them in all sorts of applications. I greatly prefer them to reliance on beer cans.
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Old 10-16-17, 01:44 PM
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My dad as a hobby makes recurve bows out of laminate pre-paper. (Only one or two have assploded in people's hands)
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