the magic circle

Personally I find punctures one of the many entertaining things about riding a bike. Their random character, the chance to stop where you hadn’t planned to, to demonstrate your competence and efficiency, your progress towards the distant – probably impossible – goal of ‘becoming a cyclist’. A puncture is a special message from God – or John Boyd Dunlop – “Go home and back-up your hard-drive my child. For surely if it spins and was made by men, one day it will fail.’

Personally I find punctures one of the many entertaining things about riding a bike. Their random character, the chance to stop where you hadn’t planned to, to demonstrate your competence and efficiency, your progress towards the distant – probably impossible – goal of ‘becoming a cyclist’. A puncture is a special message from God – or John Boyd Dunlop – “Go home and back-up your hard-drive my child. For surely if it spins and was made by men, one day it will fail.’
Let me make a bold prediction. There will be pneumatic tyres on suitcases within ten years.

Think about it? Wheels on luggage used to be quite a novelty now they’re everywhere. Baby carriages – once sedate appliances with leaf springs –  are now available with puncture possibility. Where will it end?

also seen in Stoke Newington Church Street

We can divide the World’s population into two categories, those who understand how to fit pneumatic tyres and those who do not. Key information is in the three digit element of the ISO number etched on your tyres ‘622’, ‘559’, ‘406’ or whatever.

These numbers are not much used in England, where ignorance of technical matters is often worn as a badge of honour. Here people prefer to use the historic designations – ‘700c’, ’26 inches’, etc. – of a tyre’s diameter. The problem with these is they aren’t definitive. According to the late, great Sheldon Brown who – as usual – provides the most comprehensive explanation of the subject, there are seven(SEVEN) unique, non-interchangeable tyre sizes that may be marked with the diameter ’26’.

Once – in a specialist bike shop to make a distress purchase – I asked the tattooed man at the counter for “two 406 tubes please?”

“Sorry we only do BMX.” He replied.

In his defence when I explained – gently I hope – that 406 is BMX, he took it on the chin saying: “Oh yeah, I’ve seen those numbers on the boxes” and thanked me for the clarification as he took my cash and handed over the rubber.

This three digit element – ‘630’, ‘590’ ‘349’, or whatever –  is known as the BSD – a TLA* standing for  ‘bead seat diameter’. The ‘beads’ are the wires around the inside edges of the tyre. BSD is the inside diameter of the tyre and also the diameter of the circle on the rim where the tyre beads sit when in use.

The centre of the rim – the ‘well’ of the rim – will always be nearer the centre of the wheel, and a smaller circle than the bead seat.

life changing information

In order to fit a tyre on a rim you have to control the bead with tension so it stays along the shorter circle of the rim well. This generates enough slack to flip the last section of tyre bead over the rim wall.

People who think fitting tyres is hard don’t know how to do it. There’s no shame in this. Nobody is born knowing how to mount a tyre on a rim. The problem has lately been exacerbated by ‘puncture proof tyres’. Some of these are so rigid that – as well as giving a slow and uncomfortable ride – they are harder to fit.

A pneumatic tyre is already a  Faustian bargain. You get to ride on air, but will also suffer random punctures. Nasty armoured tyres raise the stakes of this gamble. They mean you are less likely to get a flat, but when you do it will be harder to get the tyre off to change the tube and more of a challenge to get it back on.

If you understood the above – and didn’t know it before – you are now on the way to joining the minority group, the people who know how to fit tyres without hurting their fingers or losing their sang-froid. This minority divides into those who can fit tyres but don’t have the conscious competence to explain to others how it’s done, those who know how they do it but want to keep that knowledge secret. If you can charge others £17.50 to undertake a simple task on their behalf, and you’re not able to do much else, why would you want to give them the secret of doing it for themselves? Others among the cognoscent are so desperate to drag the innocent down to their own tragic level of bicycle-dependence that they give the secret away freely.

Readers of the Guardian online may have noticed this item on Monday’s front page, a link to free content, moving pictures with audio commentary and written notes, from MadeGood.org.

more important than cancer but  less significant than hungry hippos

I’m proud to be a collaborator on this project to spread knowledge of, and confidence in, the simple – not rocket-science – subject of keeping push-bikes running sweetly. This directory of instructional films will soon be enlarged. The plan is to make the library comprehensive and keep it updated.

Off course some people – especially young men with old men’s beards – will find plenty of weak spots in this work-in-progress. But hey, it’s free, and you have to start somewhere. Punctures are part of riding a bike, and the first twenty are the worst.

*TLA = three letter abbreviation.

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