In a previous question, I have been told that the grip diameter of a MTB riser bar is 22.2mm. From research I did, the grip diameter of BMX handlebars is also 22.2mm. In fact, it's possible to use BMX grips on MTB handlebars. I thought this would allow to use also BMX bar plugs on MTB riser bars. As I experienced first hand, this is not the case, see picture below.

Is that because the internal diameter of MTB bars is smaller than in BMX bars?

see picture

  • If they're too big, shave them down or cut slots lengthwise through the shaft. If they're too small and rattling around then use plumbers tape, or some silicon mastic to cure and hold it in place. Or shove a wine cork in the end instead of the blue plug.
    – Criggie
    Oct 7, 2017 at 4:20
  • @Criggie any suggestion on how I can shave them down? Oct 7, 2017 at 9:10
  • Is there a hole under your index finger? I'd mount it on a drill press or lathe using some threadded rod and nuts, spin it, and thin it using a file or a chisel. You could take layers off the mushroom part too, to make it flush with the bars. A sharp knife like a carpet knife would cut it too. Depends on overall thickness.
    – Criggie
    Oct 7, 2017 at 20:22

2 Answers 2


The outer diameter of bars is the same. Internal diameter can vary a bit between manufacturers, but you're going to have an ID of around 20 mm for road bars and 17 mm for mountain bars (source). A BMX bar is somewhere in between -- if you get the right MTB bar and the right BMX plugs, they'll probably work.

That being said, if you can't get those in with a bit of twisting and turning, you could probably shave them off. Or, go for an expander style plug.

  • Thanks for the answer! If the ID varies, I wonder why the plugs manifacturers don't specify it. Can you please post an example of expander style plugs? Oct 7, 2017 at 9:07
  • They do in the expander models ("fits bars 18 mm - 20 mm ID " or something) sometimes. You can see this example.
    – Batman
    Oct 7, 2017 at 14:17
  • It would make more sense to specify it in non-expander ones, wouldn't it? Anyway, thanks for your answer, upvoted! Oct 7, 2017 at 15:26
  • @AlessandroCosentino - Lots of things would make more sense. The simple fact is that bar inner diameters are not standardized, so you gotta try products and see if they work. Most of the time for most people, everything is OK. You're unfortunately one of the few that aren't.
    – Batman
    Oct 7, 2017 at 15:50

Recently I fitted some cheap aluminium bars to my bike, but trimmed 120mm off each side for Reasons.

Upshot - the ID of the bars was much smaller, despite the OD being relatively consistent.

To get my barend mirror fitted I had to nip a small amount of rubber off it, and I also had to use a round file to clean up the inside of the cut, much more than a simple deburring. Then I used a gentle hone in a hand drill to get a bit of additional space, but I only needed a half-millimetre so it wasn't bad.

Another option is to use a lubricant, but NOT an oil. Something like spray-on hairspray or spray glue will work as a lube and when it sets will act as an adhesive. Dishwash liquid can help, but that tends to go back to slippery when it gets re-wetted by rain.

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