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The Cyclist guide to buying the right inner tube

Joseph Delves
24 Jul 2018

How to find the right size inner tube for your bike

How to find the right size inner tube...

There’s no quicker way to invoke the wrath of your local bike shop employee than by asking for a regular size tube. With a baffling array of different widths, diameters, and valve types - you’d hope there’d be a standard way of describing them. There isn’t.

Read on and we’ll help you find the right one.

First things first

If you’re reading this and you have a drop handlebar road bike you can probably just go in and ask for a standard 'road' tube. This will normally fit 700c tyres from 18 to 28mm wide and come with a Presta valve.

If you’ve deep section rims you’ll need a longer value. If you’ve got really deep section rims you’ll need a really long valve. If you’ve got silly deep rims you’ll need a valve extender.

But what about your kids' bike, that old Raleigh 3-speed in the shed, of the vintage racer you picked up at the bike jumble? Here’s where things get tricky...

What do the numbers on my tyre mean?

700 x 35c = common description, 35-622 = Etrto number 

Either measured in inches or millimetres most tyres are described by their nominal external diameter. However, as tyre sizes have changed over the decades these numbers have lost any direct relation to the exact measurement of the tyre or rim.

Further complicating this is the fact that decimal and fractional descriptions are not interchangeable. Not only is 26 x 1.75 not the same width as 26 x 1 ¾, it also represents a different internal circumference.

Then there’s marketing. Road wheels are normally described as 700c, on mountain bikes this same size is called 29 inches.

On-road, smaller tyres are 650b, whereas when they come with knobbly off-road treads they’re known as 27.5 inches.

Etrto to the rescue

If you’re unsure which tube to buy the best thing to do is default to the Etrto (European Tyre and Rim Technical Organisation) number.

This is an international standard designed to make tyre sizing consistent and clear. Printed somewhere on every tyre this will be two digits and a dash followed by three digits.

The first number is the width of the inflated tyre, while the second is its inner diameter. For instance, 700c x 23 becomes 23-622.

Know these two numbers along with your valve type and any decent bike shop will get you the right tube.

Valve type

There are three main types of valve. Presta is the most common and found on all road bikes and most quality modern bikes.

They require the smallest hole in the rim to fit through and need to have the valve unscrewed before they can be inflated.

Schrader valves are the same as found on most cars and motorbikes. Larger in diameter they require a bigger opening in rim than Presta valves.

Dunlop or Woods valves have the same diameter valve as Schrader types but use a removable flange to secure the valve in place. They can be replaced by Schrader valves without modifying the rim.

You’ll need a pump with the right fitting, although many will fit all three.

Valve length

If you’ve got aerodynamic deep section rims you’ll need a longer than average valve to make it up and through the rim.

There’s no standard as to how much longer a long valve tube is, but most are around 60-80mm. For comparison, a standard length tends to be around 40mm.

If your rims are really, really deep you’ll need to get a valve extender. These little widgets add length to the valve stem.

Some screw over the top and others require you to remove the valve before fitting. If you buy posh wheels they usually come with them included.

What about lightweight and latex tubes?

Most tubes are made of butyl rubber. Many brands producing standard tubes will also make a lightweight version that costs a little more and can save a few grams of crucial rotating weight.

These make you go a little bit faster but are more puncture prone. Even more expensive are latex tubes. They’re delicate, hard to repair, don’t like being left inflated between rides, and leak air more rapidly than rubber alternatives.

However, they roll faster and weigh less. Worth investing in if you already own racing tyres and want the quickest roll possible.

Can’t I just bung any old tube in?

As any poor bike maker who’s received a battered test bike back from me will vouch, yes you can. Up to a point. In an emergency a road tube will normally just about inflate to fit a cyclocross or hybrid tyre. It might even work in a mountain bike tyre if you’re lucky.

However, tubes don’t like being stretched too far and are more likely to bust or puncture if you push them beyond their intended usage rage.

Conversely fitting a tube wider than necessary can be tricky and might cause the tyre not to seat properly. Consider yourself warned.

Some common diameters, their uses, and descriptions

Etro 630 mm

Obsolete size for most vintage pre-1980s road bikes

Roadie: 27” x anything
Mountain Bike: n/a

Etrto 622

Roadie: 700c
Mountain Bike: 29”, 29er

A standard size for racing bikes, tourers, hybrids and many modern mountain bikes

Etrto 584

Roadie: 650b
Mountain Bike: 27”, 27.5”, 650b

Smaller size for diminutive road bikes, gnarly gravel bikes, and manoeuvrable mountain bikes

Etrto 559

Roadie: n/a
Mountain Bike: 26”

Formerly the standard mountain bike size. Now less common. Increasingly used on kids' bikes

Etrto 507 mm

Roadie: n/a
Mountain Bike/BMX: 24”

Smaller size for kids' bikes, mountain bike jump bikes, and BMX cruisers

Etrto 406 mm

Roadie: n/a
Mountain Bike/BMX/Folding: 20”

Standard size on BMX bikes. Used on folding and kids' bikes.

Etrto 349

Roadie: n/a
Vintage and Folding: 16 x 1 ⅜”

Small wheeled vintage bikes and Bromptons.

Etrto 305 mm

Roadie: n/a
Mountain Bike/Kids/Folding: 16”

Kids' bikes and folding bikes (not Bromptons)

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