2mtr

i need to get new handlebars. i was shopping online, and saw all these confusing numbers and such. I checked out sheldon brown, and i've got the theory down. but how do i put it into practice? how do i figure out my particular handlebar's diamater so that i may get a new one which will work for my present stem?

i don't see any real information on either the bar or the stem.

G'ak

There aren't really many options about that...

Your handlebar can be only a regular (25.4) or an oversized one (31.8). I am talking in mm's... if you are american or something similar wich works with inches i guess you will have to convert.

To found wich one is yours, with the help of a ruler measure it's diameter at the border of the stem clamp. Or to be more accurate, disassemble the handlebar and measure the stem's clamp.

It can't go wrong. It's a difference of 6 cm wich is well noticeable.

If there's a better way, well i don't know.

Little Darwin

There are also 26.0 mm clamp diameters... Depending on who you ask, and what risks you are willing to take, some use 25.4 and 26.0 without regard to the details. Personally I would opt for not confusing 25.4 and 26.0 for safety.

G'ak

Always learning... I've never saw a 26mm handlebar and/or stem...

Old Hammer Boy

It's not cm, it's mm (only 10X different). There are 25.4mm in one inch, or 2.54cm. Find someone with a caliper and measure at the stem to determine your stem's handlebar requirements. Many calipers have both inch and mm scales. Heck, you can buy a digital one at Harbor Freight for about $20. If you plan to live a few more years, it's a great tool to own. I don't use mine often, but it sure does come in handy for lots of measurements. OHB

Don Cook

Maybe I'm missing something on this? How to measure the diameter? There's "rocket science" and then there's things as simple as getting out a caliper and taking a measurement. Someone explain to me why this is "rocket science" to anyone. If you don't have a caliper in the tool chest, wrap a piece of cellophane tape around the circumference of the bar, mark the point where the tape makes one complete "wrap". Remove the tape and measure the distance (in millimeters) from the end of the tape to the mark you made. Divide this number by pi (3.1415). If you're after the inside diameter, go buy a caliper.

juicemouse

If your bike is fairly modern and it has straight handlebars (like a mountain bike), G'ak's advice is spot on.

But as you've discovered, there have been many "standards" over the years. To be sure, you can measure the bar more accurately than just holding a ruler up to it and eyeballing it. All you need is a piece of scrap paper that's at least 5 inches long and a ruler. Remove the handlebar from your stem. Take the piece of paper and wrap it around the bar right where the stem would clamp it. Mark the paper where it overlaps itself, at one of the edges of the paper. Once you unwrap the paper from the bar, you'll then have a fairly accurate measurement of the circumference of the bar. Take that measurement with your ruler. To get the diameter, just divide that number by pi (3.14). Your number probably won't match any of the "standards" exactly, but should be close enough to one of them to put your mind at ease.

Of course let us know if that doesn't work out for some reason or if you have any other questions.

San Rensho 

You can also get a regular vernier that measures to .1 mm for less than $10. Or, put a piece of tape around the bar, mark it, remove, measure and divied by 3.14159..... to get diameter.

juicemouse

Someone explain to me why this guy needs to insult people because he knows something they don't. Turn it down, Mr. Cook.

TallRider

Cinelli used to make handlebars and stems with 26.4mm clamp diameter. But just for road bikes. And it sounds as if you've got a flat-bar bike, or you'd have run acrost the 26.0, at least, while looking on the internet. I think it's very easy to eyeball the diff between 25.4 and 31.8, but that's partly because I'm used to seeing them. 31.8 has a much larger bulge between the "regular" part of the bar (which is 22.2mm on a flat handlebar) and the clamp part of the bar. You could be able to tell just by ratios.

However, most handlebars and stems have their clamp diameter printed on them.
And if they don't, then on flat-bar stuff it's extremely likely that it's 25.4mm, b/c cheaper stuff.

DannoXYZ 

There's also 26.6mm bars & stems as well... Modolo I believe. Best way is to pull out some calipers and measure. Mismatched clamp sizes will lead to all sorts of trouble due to the uneven seating which causes pressure-points. You'll end up with creaking, loose bars that'll slip when you hit a bump, and overtightening to compensate will lead to quicker failure of the bar... imagine snapping your bar in half during a sprint... not fun...

masiman

If you have an adustable wrench, cinch it down on your bar (doesn't need to be supertight, just snug it up), slide the wrench off, measure the distance between the jaws with any old measuring device, convert as necessary to mm.

Measure where the bar is the same diameter as where the stem clamps the bar. Some bars taper smaller after the clamping section. While you're at it, measure and remember your seatpost diameter. Alot more variations there.

Sheldon Brown

My site has over 2000 pages...didja check out my Handlebars/Stems Cribsheet?

https://sheldonbrown.com/cribsheet-handlebars.html

By the way, the best way to find stuff on my site is to either start at the Bicycle Glossary (links to all of the articles) or to use the Google search engine window.

Sheldon "Numbers" Brown