Words by Chris | Images by Flow

“Is it two seven five?” the question came down the phone line. My brain went blank. What is he asking me? Two seven five…? The mountain bike Enigma machine began grinding away, deciphering this combination of numbers and suddenly realised that I was being asked about wheel size. “Oh shit! Right! Yes, it is 27.5, sorry.”

I’ve never been any good with figures, but increasingly my conversations about mountain biking feel like I’m reading a barometric pressure chart – my poor brain sometimes struggles to attribute meaning to numbers being flung my way. And every year the mountain bike numerical soup gets thicker, swimming with new component or frame standards that sound like an international dialling code.

"You know what moments like this really need, mate?" "No, what?" "A discussion about wheel sizes."

“You know what moments like this really need, mate?” “No, what?” “A discussion about wheel sizes.” “Dickhead…”

The thirst for evolution and incremental improvements is the driver, and don’t get me wrong, I love the way bikes are always progressing. I just wish there weren’t so many numbers that went along with it!

Go back fifteen or so years and it wasn’t so. The only numbers thrown about were frame size and travel – you certainly didn’t need to specify wheel size because wheels had one size. Now you can’t talk about wheels without sounding like you’re rattling off the dimensions of package you’re shipping.

Definitely not thinking about bottom bracket measurements.

Definitely not thinking about bottom bracket measurements.

The times-table of axle sizes and hub widths was much simpler too: 90% of mountain bikes had the same axle and hub widths, with downhill bikes the only exception. Admittedly most riders’ wheels were being held in by ridiculous little chopsticks, never may they return, but that’s not the point. Now we’ve Boosted the issue to include 100×12, 100×15, 110×15, 142×12, 148×12 and 157×12 too, plus good old 110×20, 150×12, 100×9 and 135×10. The answer is 15,964 by the way.



A handlebar was just a handlebar. It had the diameter of a handlebar and was about one handlebar wide. Yet now we agonise over just how much to trim (or not) off our 808mm bars and debate the merits of 31.8 and 35mm clamps.

Dare we get started on bottom brackets? Once 68mm or 73mm (both threaded), the bottom bracket options now read like the Australian Standards sticker inside your helmet: 68mm, 73mm, BB92, BB98, BB30, PF30, BB386 and about a dozen other variants on the theme too. Or drivetrains? 3×9 has become 1×10, 1×11, 1×12, 2×10, 2×11 and 3×10…phew.

Not concerned about hub widths.

Not concerned about hub widths.

While I’m not sure if my improved numeracy can be called an upside, in some ways the onslaught of number has made actually getting out on the bike even more of an escape. Once you’re on the trail, you can forget about the fact your bike’s running 27.5, 2×11, 148×12 with BB92, you’re just riding, and hopefully that never changes!

The important numbers: how far and how long you rode this week.

The important numbers: how far and how long you rode this week.