A 25 inch gear on a road bike? Unthinkable even a year ago
How times have changed! And how quickly! If you’re familiar with chainsets, cassettes and other gear-related issues, please skip the rest of this paragraph and read on to the nitty gritty below…. But if you don’t care about the technicalities, then actually it’s quite simple: just tell your bike shop (or friendly technically-minded club member) that you want low gears – at least 27 inch (that’s the small front ring the same size as the largest rear ring on a standard 700c wheel) and preferably a bit lower than that. No problem of course if you have a triple (3 rings at the front), but far from straight forward if you have the now standard 2 ring setup. Read on for the detail…

Now for the nitty-gritty
Just a few years ago the biggest ring (lowest gear) on an Ultegra cassette had 27 teeth. In recent years, road cassettes began appearing with lower gears (larger rings). It has taken the industry some time to catch up with the needs of the recreational rider, but last spring (2018), the Ultegra road groupset included a cassette with 34 teeth.

If your road bike has the standard 34-50 chainset, you can now have a 1:1 gear ratio. This gear ratio (or lower) is recommended by Cycling UK as a minimum for recreational riding.

It’s all about “spinning”
Question: What do I mean by a low gear?
Answer: low enough to be able to spin at 80+ rpm (rather than having to “grind”) up a 12-15% climb.

Why “spin”?
The consensus is that spinning is the most efficient way to climb for most people (if you’ve been watching the Tour, you won’t need reminding). Tour riders don’t need a very low gear because they can maintain enough power (350+ watts) to spin up the whole of a 10k climb (+ most Alpine climbs are not that steep. The iconic Alpe d’Huez has an average gradient of 8% with nothing steeper than 11%). By contrast, recreational riders typically produce less than half that power and face much steeper climbs (even if they are also much shorter).

The good news for those of us with “road bikes” is that the industry at last understands all this and in the spring of 2018 Shimano added a 11-34 cassette to its Ultegra groupset. Not all shops are selling it yet, but you can find it here.

Click here for a review of the new Ultegra 11-34 cassette. I’ve already bought and fitted mine.

Together with my new “sub-compact” chainset, I now have a 25 inch gear on a road bike. That’s a proper low gear! I think I can cope with the extra 57 grams 🙂