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  • stevecowles

Bike Tyre Sizes - Confused?

I need to start thinking about some tyres for a bike project I'm working on so have been wondering what to fit.

The bike in question is an old hybrid frame and will be for 'general purpose' use but it is possible that it may get converted to a commuting ebike at some point in the future, depending on where my next job is, as I fancy trying a bit of bike commuting at some point.

This means that I'm going to want something fairly robust and puncture resistant but easy rolling and hard-wearing (surely this combination is the holy grail of tyres). Tyre weight is not really an important consideration for me in this instance. I don't want something too narrow but they will need to fit my existing frame.

I'm considering Schwalbe Marathon Plus tyres but as this will be an investment of almost £100 I want to get it right. I could put two tyres on my car for less!!

Tyre sizes can be very confusing with some measured in inches (e.g. 27 x 1 1/2) and some in a cycling-specific range of sizes (e.g. 700c x 38 or 650b). Add into this a range of compounds, sidewalls, tread patterns and protection systems and it is all fairly bewildering. On top of that, they may be supplied as wired or foldable.

So this is my understanding of how it works….. Fortunately, there are some standards to assist. Pretty much all tyres made in recent years will have a strange marking on the sidewall which consists of two sets of numbers separated by a hyphen. This is the definitive size of that tyre identified in line with international standards. An example would be 37-622 which is a 37mm wide tyre to for a rim with a diameter of 622mm. Although these sizes are in metric, they also cover imperial sizes and the list of options is huge.

The key thing is to make sure that the rim size on the new tyres is the same as those they are replacing, if not you will be unable to fit them on. The maximum width you can use is limited by your frame, forks, brake callipers and mudguards and there is not a lot of room to play with so measure carefully.

When buying tyres check this carefully, the details will almost always be in the advert somewhere even it if it not in the headline.

Let's hope I get it right as they won't be returnable.

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