January 15, 2021

tyre

Updated: 01/04/2020.

In this post I’ll explain when to replace bicycle tyres, how to tell they are due for replacement and what to look out for related to tyre wear and replacement. A separate post explains how to mount (and dismount) a bicycle tyre.

Contents:

  1. Introduction
  2. Tyre aging
    2.1. What is tyre aging?
    2.2. What affects tyre aging?
    2.3. Aged tyre examples – how to tell?
    2.4. Consequences (risks) of tyre aging
  3. Tyre wear
    3.1. What is tyre wear?
    3.2. What affects the tyre wear?
    3.3. How to tell a tyre is worn?
    3.4. Consequences of tyre wear
  4. Common mistakes – like swapping front and rear tyres
  5. When to replace a bicycle tyre?
  6. Conclusion

1. Introduction

When reading some tyre manufacturer instructions, it seems as though we should cover the Earth with (un)worn tyres, and as though we are all millionaires, throwing away tyres as soon as we get a flat. OK, I am exaggerating, but not too much – the recommendations are rather “strict”, probably in order to prevent anyone from suing the companies in case of any problems. On those terms, I must say that all the info and advice given here is based on my knowledge and experience, but you are following them at your own risk. It has served me well for decades, I’m as convinced as I can be that it is a safe way to do it, but can’t guarantee anything to anyone, of course.

For start, before explaining the tyre wear, I will explain tyre aging.

2. Tyre aging

2.1. What is tyre aging?

Tyres have certain properties: elasticity, grip (as opposed to being “plastic”), shape etc. Tyre aging is the loss of these properties’ quality over a period of time – due to time, not (just) because of wear.

In appropriate storage conditions (temperature, humidity etc.) tyres can last for a decade, without any notable aging. Aging, as an important factor, starts once a tyre is mounted.

2.2. What affects tyre aging?

When discussing factors that affect tyre aging, I will mention the perfect conditions. Of course, tyres should serve you, not the other way round, so compromise is often necessary. However, knowing the perfect conditions is good as an ideal to strive for, in situations when it is possible and convenient to choose – so that you can choose what’s better for the tyres. I’ll numerate all the factors, for easier reference:

1. Pressure
As soon as a tyre is mounted and inflated, the air pressure tries to tear the tyre’s carcass (for more details, see tyre sidewall and rubber compound quality). The higher the pressure, the more tyre’s carcass is put under stress and the faster a tyre ages. This is one of the reasons for inflating tyres to the optimal pressure (not too high, and not too low).

If a bicycle is stored for a longer period, it’s not a bad idea to have the pressure lower than optimal, just make sure the tyres are not

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