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Tyres, Wheels and Inner tubes - (almost) all you ever wanted to know.
There seems to be a never ending queue of questions on Tyres, tubes and wheels, so here goes......
Clinchers and Tubulars.
Bike wheels come in two types – Clinchers and tubulars.
The vast majority of wheels in use today are clinchers, i.e. the wheel has a lipped side-wall which engages with a wire or Kevlar “bead” running along the outside edge of the tyre; pressure from the air in the inner tube holds the tyre in place.
Tubular wheels lack the bead seat, and the tyre is glued in place directly onto the rim. These are used almost exclusively for racing/time trials and are not covered in this article.
Wheel Sizes.
Wheels come in several sizes, however unless you have a very old bike, or are riding something odd – like a BMX, folder or a recumbent then it’s likely that your wheels are one of two standards.
Now bikes being what they are, there are several ways of describing the same thing….
The traditional method of measuring the wheel size was to use the notional diameter of the wheel and tyre. This could be described in millimetres or inches. There is also a newer international standard ISO (also given as ETRTO) size which measures the wheel at the point the tyre bead seats on the rim. This ISO standard sizing should appear on all rims and tyres.
The larger wheel in common use is an ISO-622 (traditionally described as 700C). This type of wheel is usually fitted to road bikes and road-bike derived hybrids.
The smaller wheel is traditionally known as a 26” wheel; commonly fitted to mountain bikes and MTB derived hybrids – again this has a standardised method of describing the size – ISO-559.
The newer 29” mountain bikes actually use an ISO-622 wheel; however the rim width is likely to be wider than a road bike rim.
Besides the wheel diameter, the other important measurement is the width of the rim. Not surprisingly wider rims allow wider tyres to be mounted. This measurement is included in the ISO standard, so a wheel may be described as ISO-15-622.
This would indicate a road style wheel with a rim width of 15mm. A mountain bike style wheel may have a measurement of ISO-23-559 indicating the smaller diameter (559) and wider width (23mm).
Tyre Sizing.
Tyres sizes are generally given in the same way as wheel measurements. A typical road tyre would be an ISO-23-622… but is more likely to be described as a 700Cx23
In this case a 23mm wide tyre designed to fit a 622 (700C) road wheel.
Just to confuse matters however, 26” Tyres (and 29” off-road tyres) tend to be described in decimal inches – so a typical mountain bike tyre may be a 26”x 1.9 which equates to a 26” diameter by 1.9 inches width (The ISO standard is almost never used for 26” tyres).
Rim width should be considered when increasing or decreasing the width of tyre fitted. For example the road rim described earlier (ISO-15-622) could safely cope with a range of tyre widths from 23mm to 30mm, however attempting to fit a very narrow (18mm) or very wide (34mm) tyre would be dangerous as the tyre would not seat correctly on the rim.
Generally it is fine to increase or decrease tyre width by a couple of sizes either way, however if you are considering an extreme size change please check that the rim is OK for the proposed tyre width.
Inner Tubes – Sizes & Valve Styles.
Most tyres will use an inner tube to contain the air. There are “tubeless” tyres and wheels which allow a seal without the tube – but these are not yet in common use.
The inner-tube is sized in the same manner as tyres and wheels (are we seeing a pattern here?) but generally tubes will have a wider range of widths. A mountain bike inner tube may be described as 26x2.00 and may comfortably be used for any 26” wheel with a tyre width of 1.8” – 2.2”.
Each tube will be fitted with a valve to allow the air to be pumped in or let out. There are 2 common valve types – Presta and Schrader 2 have different valve diameters, and a wheel rim is likely to be drilled to accept one or the other – ensure you get the correct type when buying replacement inner-tubes.
The Schrader valve is more commonly fitted to 26” wheels. It’s the same type of valve as is fitted to car tyres. A central spring loaded “pin” inside the valve opens and closes the air-way. In order to deflate a Schrader valve the pin can be depressed with a small screwdriver or Allen key.
The Presta valve is thinner, and has a screw down crown which must be unscrewed before the tube can be inflated or deflated. Once the locking crown has been unscrewed the valve can be opened by simply pressing the end of the valve. NB – One of the common problems when inflating a tube fitted with a Presta valve is that the valve can “stick” when the crown is unscrewed. This can be avoided by simply pressing the end of the valve to release a tiny bit of pressure before attempting to fit the pump.
Folding or Rigid Tyres?
Tyres may be described as either folding or rigid tyres. Some models will come in both versions; usually the folding model will have a price premium.
Rigid tyres use a steel cable as the bead. These tyres hold their shape even when not fastened to the wheel.
Folding tyres (as the name suggests) can be folded. Instead of steel a Kevlar fibre is used to form the tyre bead. Folding tyres tend to be lighter but this is pretty much the only distinction – However if you are considering a long tour, or are riding where carrying a spare tyre may be wise, then a folding tyre will be considerably easier to pack.
Tread Patterns & Rubber Compounds
Everyone knows cars have to have tyres with a decent tread, as this makes them safer in the wet; surely this must be the same for bikes, and those super slick road tyres must be deadly in the rain? Err no.
Car tyres have a tread pattern in order to allow water to be squeezed out from under the tyre. Without tread there’s a danger the tyre will ride up on a film of water and all traction will be lost – a condition known as hydroplaning.
Bikes Cannot Hydroplane. The comparatively narrow, rounded profile of a bike tyre is very effective at forcing water from underneath the tyre; no tread pattern is needed to help with this. Irrespective of the wetness of the road the safest form of road bike tyre, is the one that puts the most rubber in contact with the tarmac – this will often be a slick tyre. Furthermore tyres with large knobbly treads can deform badly when ridden on tarmac, leading to “squirmy” handling when cornering at speed. Many “commuter” tyres have a cosmetic tread pattern, for example a herring bone design, or thin wavy grooves; this type of tread has no practical use, as the tyre will deform around the road surface more than the tread anyway.
Off-road however things are more complicated. The tyre pattern here is used to provide mechanical grip. Knobbly tyres can deform around outcroppings and help to dig through soft surfaces providing increased traction. Some tyre patterns are designed to help shed mud and prevent the tyre clogging up and slipping in loose wet conditions.
Mountain bike tyres come in a myriad of patterns, each manufacturer will design and market tyres for a range of conditions from dry rocks to thick wet mud. Actual individual tyre choice largely comes down to personal preference as there is no “best” tyre for every condition.
The actual formulation of the “rubber” compounds used to manufacture the tyre can have a great impact on the handling characteristics of the tyre. Manufacturers develop a range of different compounds in an attempt to balance grip with lifespan.
Generally a softer/stickier tyre compound will provide more grip, but will have a shorter lifespan than a harder compound. Some manufacturers produce the same design tyre in a number of differing compounds
For example Maxis produce the popular Minion downhill tyre in 3 versions:
MaxxPro hard compound (60a) to give you the grip you need on hardpacked surfaces
Super Tacky- compound (42a) to address the wet, muddy courses.
Slow Reezay- compound (40a) which allows the tyre to rebound much slower than a conventional tire, offering maximum grip and is the softest compound available.
Other tyres may mix compounds on the same tyre, typically a road tyre may have a harder wearing compound in the central band, and softer stickier rubber along the shoulders for increased grip during hard cornering.
Cheap, low quality tyres such as those supplied with lower end bikes, tend to use a hard “plasticky” compound which provides little grip – especially in wet weather.
Winter Tyres.
There are specific winter tyres marketed for use in snow and icy conditions. Generally however any off-road style mud tyre will work reasonably well in loose snow or slush – as long as it’s not too deep.
On ice, no tyre irrespective of its tread pattern is going to help. The exception to this being studded tyres specifically designed for ice riding. These have carbide/metal studs embedded at regular intervals and offer the only solution for properly icy conditions. They are however expensive, very heavy and prone to shed studs if used on normal un-iced roads.
Tyre Pressure.
Each tyre will normally have a pressure range or maximum inflation pressure embossed on the side wall. This will differ depending on the type of tyre; for example a typical mountain bike tyre may have a range of 20-80 psi, whilst a 23mm road tyre will be 80-120psi.
The actual pressure you need to inflate to will depend on several factors. For example a heavier rider will generally require a higher pressure, whilst severe off-roading where the requirement for mechanical grip is increased may dictate a very low pressure is best.
Generally increasing the pressure will decrease the rolling resistance on smooth surfaces, although once a certain point (dependant on load) is reached further increases in pressure may serve to increase resistance as the tyre “bounces” over minute surface imperfections rather then rolling over them. The same increase in pressure will however harden the ride, reducing rider comfort.
Lower pressure will increase mechanical grip, and soften the ride increasing comfort. The risk of pinch flats is increased however, and on smooth hard surfaces the resistance will be increased.
Punctures – Protection from the Fairy.
The only type of puncture proof tyre is one without air. These do exist; they’re used on shopping trolleys, cheap wheelchairs and kids toys. They’re also bloody horrible and have no place on a bicycle.
Proper tyres, with air get punctures. There are things you can do to minimise the occurrence, but rest assured at some point (probably when you’re late and it’s raining) you will get a visit from the puncture fairy.
The easiest way to prevent punctures is to keep your tyres inflated to the correct pressure (see above). This will eliminate the majority of impact punctures caused when the inner-tube is crushed between a deforming tyre and the rim – these are commonly called “snakebites” because of the twin puncture holes commonly left in the tube.
This just leaves the day-to-day punctures caused by glass, thorns, flints and other assorted sharp road debris. Again, a properly inflated tyre will help reduce these, as will a quick inspection of the tread after every ride, and the removal of any debris from the surface of the tyre before it has chance to work its way into the carcase.
Many manufactures produce a “puncture resistant” line of tyres. These typically have either thicker/harder wearing tread rubber, a Kevlar or similar “band” beneath the tread or both. These tyres will normally be heavier than a similar non-protected tyre and are often sold as commuter or winter training tyres. Probably the most well known of this type of tyres is the Shwalbe Marathon and Marathon+ range of tyres, which have an almost legendary level of protection (and an equally “impressive” weight). These tyres are often recommended when a “puncture proof” tyre is requested. The Michelin Krylion Carbon/Pro Race Endurance, the Schwalbe Durano + and Bontrager Hardcase are also well respected tyres with increased protection.
There are several products designed to be injected into tubes to prevent punctures. These are generally a chemical “slime” that oozes through a puncture and congeals, sealing the hole. These generally add weight to the tyre, have a limited number of uses and make a traditional repair difficult or impossible. The high pressures used in road tyres also make the slime less effective. Such products can help with punctures in lower pressure tyres – especially the smaller holes caused by thorns.
Another common cause of punctures comes from the inside of the wheel itself. Traditional rims have numerous holes to allow the fitting of spokes. These holes must be covered by a layer of rim-tape. Otherwise the pressure of the inflated tube causes it to rub on the sharp edge of the spoke hole and eventually puncture. If the rim tape is worn or badly fitting, or the ends of spokes intrudes into the wheel rim then punctures will occur. Electrical insulation tape can be pressed into service for an emergency rim tape but this is not recommended long term. The usual preference is to employ a specifically designed fabric tape such as that produced by Velox.
Tyres wear out, and as they do the frequency of punctures will usually increase; especially on the rear tyre, as this bears the majority of the riders weight. Replace a tyre that has become too thin. Resist the temptation to swap a worn rear tyre to the front - a high speed blowout on a front tyre is not something you want to risk.
Repairing a Flat Tyre.
Punctured tubes can be reliably repaired using either the traditional patch and glue, or the more convenient self adhesive patch. Either of these methods is suitable for both low pressure MTB and higher pressure road tubes.
In some cases the puncture will be too large, or in an inaccessible place (such as up against the valve stem) in these cases it will be necessary to replace the entire tube.
When a puncture is repaired it is wise to try and identify the cause; a piece of glass embedded in the tyre will continue to cause further punctures until removed.
A severe puncture may damage the tyre itself. Small holes are OK, however if the carcase of the tyre is showing or a large tear is present causing the inner tube to balloon out then the tyre should be replaced as soon as practical. An emergency tyre “boot” can be carried to allow a limited amount of riding on such a tyre. These can be purchased, or made from a strip of an old tyre with the bead removed. This can then be placed between tube and tyre to provide a temporary patch. Smaller tears can even be patched in dire emergencies using empty crisp packets or £5 notes!
Final Note.
The tyres fitted to your bike are (ideally anyway) the only point of contact between bike and ground. The size of this contact patch on a road bike tyre is approximately the size of your thumb, and not much larger even on a MTB fitted with super wide tyres. It’s probably a good idea to ensure that these thumb sized bits of rubber are in as good a condition as possible before descending that mountain pass in the rain, or throwing yourself down a black run.
This doesn’t mean you necessarily need to spend a fortune on the latest whiz bang super-tyre. Decent tyres are available from many reputable manufacturers for a fraction of the price of the top end race-rubber. Make sure that whatever tyres you have are in good condition, and that you understand their (and your) limits.
There seems to be a never ending queue of questions on Tyres, tubes and wheels, so here goes......
Clinchers and Tubulars.
Bike wheels come in two types – Clinchers and tubulars.
The vast majority of wheels in use today are clinchers, i.e. the wheel has a lipped side-wall which engages with a wire or Kevlar “bead” running along the outside edge of the tyre; pressure from the air in the inner tube holds the tyre in place.
Tubular wheels lack the bead seat, and the tyre is glued in place directly onto the rim. These are used almost exclusively for racing/time trials and are not covered in this article.
Wheel Sizes.
Wheels come in several sizes, however unless you have a very old bike, or are riding something odd – like a BMX, folder or a recumbent then it’s likely that your wheels are one of two standards.
Now bikes being what they are, there are several ways of describing the same thing….
The traditional method of measuring the wheel size was to use the notional diameter of the wheel and tyre. This could be described in millimetres or inches. There is also a newer international standard ISO (also given as ETRTO) size which measures the wheel at the point the tyre bead seats on the rim. This ISO standard sizing should appear on all rims and tyres.
The larger wheel in common use is an ISO-622 (traditionally described as 700C). This type of wheel is usually fitted to road bikes and road-bike derived hybrids.
The smaller wheel is traditionally known as a 26” wheel; commonly fitted to mountain bikes and MTB derived hybrids – again this has a standardised method of describing the size – ISO-559.
The newer 29” mountain bikes actually use an ISO-622 wheel; however the rim width is likely to be wider than a road bike rim.
Besides the wheel diameter, the other important measurement is the width of the rim. Not surprisingly wider rims allow wider tyres to be mounted. This measurement is included in the ISO standard, so a wheel may be described as ISO-15-622.
This would indicate a road style wheel with a rim width of 15mm. A mountain bike style wheel may have a measurement of ISO-23-559 indicating the smaller diameter (559) and wider width (23mm).
Tyre Sizing.
Tyres sizes are generally given in the same way as wheel measurements. A typical road tyre would be an ISO-23-622… but is more likely to be described as a 700Cx23
In this case a 23mm wide tyre designed to fit a 622 (700C) road wheel.
Just to confuse matters however, 26” Tyres (and 29” off-road tyres) tend to be described in decimal inches – so a typical mountain bike tyre may be a 26”x 1.9 which equates to a 26” diameter by 1.9 inches width (The ISO standard is almost never used for 26” tyres).
Rim width should be considered when increasing or decreasing the width of tyre fitted. For example the road rim described earlier (ISO-15-622) could safely cope with a range of tyre widths from 23mm to 30mm, however attempting to fit a very narrow (18mm) or very wide (34mm) tyre would be dangerous as the tyre would not seat correctly on the rim.
Generally it is fine to increase or decrease tyre width by a couple of sizes either way, however if you are considering an extreme size change please check that the rim is OK for the proposed tyre width.
Inner Tubes – Sizes & Valve Styles.
Most tyres will use an inner tube to contain the air. There are “tubeless” tyres and wheels which allow a seal without the tube – but these are not yet in common use.
The inner-tube is sized in the same manner as tyres and wheels (are we seeing a pattern here?) but generally tubes will have a wider range of widths. A mountain bike inner tube may be described as 26x2.00 and may comfortably be used for any 26” wheel with a tyre width of 1.8” – 2.2”.
Each tube will be fitted with a valve to allow the air to be pumped in or let out. There are 2 common valve types – Presta and Schrader 2 have different valve diameters, and a wheel rim is likely to be drilled to accept one or the other – ensure you get the correct type when buying replacement inner-tubes.
The Schrader valve is more commonly fitted to 26” wheels. It’s the same type of valve as is fitted to car tyres. A central spring loaded “pin” inside the valve opens and closes the air-way. In order to deflate a Schrader valve the pin can be depressed with a small screwdriver or Allen key.
The Presta valve is thinner, and has a screw down crown which must be unscrewed before the tube can be inflated or deflated. Once the locking crown has been unscrewed the valve can be opened by simply pressing the end of the valve. NB – One of the common problems when inflating a tube fitted with a Presta valve is that the valve can “stick” when the crown is unscrewed. This can be avoided by simply pressing the end of the valve to release a tiny bit of pressure before attempting to fit the pump.
Folding or Rigid Tyres?
Tyres may be described as either folding or rigid tyres. Some models will come in both versions; usually the folding model will have a price premium.
Rigid tyres use a steel cable as the bead. These tyres hold their shape even when not fastened to the wheel.
Folding tyres (as the name suggests) can be folded. Instead of steel a Kevlar fibre is used to form the tyre bead. Folding tyres tend to be lighter but this is pretty much the only distinction – However if you are considering a long tour, or are riding where carrying a spare tyre may be wise, then a folding tyre will be considerably easier to pack.
Tread Patterns & Rubber Compounds
Everyone knows cars have to have tyres with a decent tread, as this makes them safer in the wet; surely this must be the same for bikes, and those super slick road tyres must be deadly in the rain? Err no.
Car tyres have a tread pattern in order to allow water to be squeezed out from under the tyre. Without tread there’s a danger the tyre will ride up on a film of water and all traction will be lost – a condition known as hydroplaning.
Bikes Cannot Hydroplane. The comparatively narrow, rounded profile of a bike tyre is very effective at forcing water from underneath the tyre; no tread pattern is needed to help with this. Irrespective of the wetness of the road the safest form of road bike tyre, is the one that puts the most rubber in contact with the tarmac – this will often be a slick tyre. Furthermore tyres with large knobbly treads can deform badly when ridden on tarmac, leading to “squirmy” handling when cornering at speed. Many “commuter” tyres have a cosmetic tread pattern, for example a herring bone design, or thin wavy grooves; this type of tread has no practical use, as the tyre will deform around the road surface more than the tread anyway.
Off-road however things are more complicated. The tyre pattern here is used to provide mechanical grip. Knobbly tyres can deform around outcroppings and help to dig through soft surfaces providing increased traction. Some tyre patterns are designed to help shed mud and prevent the tyre clogging up and slipping in loose wet conditions.
Mountain bike tyres come in a myriad of patterns, each manufacturer will design and market tyres for a range of conditions from dry rocks to thick wet mud. Actual individual tyre choice largely comes down to personal preference as there is no “best” tyre for every condition.
The actual formulation of the “rubber” compounds used to manufacture the tyre can have a great impact on the handling characteristics of the tyre. Manufacturers develop a range of different compounds in an attempt to balance grip with lifespan.
Generally a softer/stickier tyre compound will provide more grip, but will have a shorter lifespan than a harder compound. Some manufacturers produce the same design tyre in a number of differing compounds
For example Maxis produce the popular Minion downhill tyre in 3 versions:
MaxxPro hard compound (60a) to give you the grip you need on hardpacked surfaces
Super Tacky- compound (42a) to address the wet, muddy courses.
Slow Reezay- compound (40a) which allows the tyre to rebound much slower than a conventional tire, offering maximum grip and is the softest compound available.
Other tyres may mix compounds on the same tyre, typically a road tyre may have a harder wearing compound in the central band, and softer stickier rubber along the shoulders for increased grip during hard cornering.
Cheap, low quality tyres such as those supplied with lower end bikes, tend to use a hard “plasticky” compound which provides little grip – especially in wet weather.
Winter Tyres.
There are specific winter tyres marketed for use in snow and icy conditions. Generally however any off-road style mud tyre will work reasonably well in loose snow or slush – as long as it’s not too deep.
On ice, no tyre irrespective of its tread pattern is going to help. The exception to this being studded tyres specifically designed for ice riding. These have carbide/metal studs embedded at regular intervals and offer the only solution for properly icy conditions. They are however expensive, very heavy and prone to shed studs if used on normal un-iced roads.
Tyre Pressure.
Each tyre will normally have a pressure range or maximum inflation pressure embossed on the side wall. This will differ depending on the type of tyre; for example a typical mountain bike tyre may have a range of 20-80 psi, whilst a 23mm road tyre will be 80-120psi.
The actual pressure you need to inflate to will depend on several factors. For example a heavier rider will generally require a higher pressure, whilst severe off-roading where the requirement for mechanical grip is increased may dictate a very low pressure is best.
Generally increasing the pressure will decrease the rolling resistance on smooth surfaces, although once a certain point (dependant on load) is reached further increases in pressure may serve to increase resistance as the tyre “bounces” over minute surface imperfections rather then rolling over them. The same increase in pressure will however harden the ride, reducing rider comfort.
Lower pressure will increase mechanical grip, and soften the ride increasing comfort. The risk of pinch flats is increased however, and on smooth hard surfaces the resistance will be increased.
Punctures – Protection from the Fairy.
The only type of puncture proof tyre is one without air. These do exist; they’re used on shopping trolleys, cheap wheelchairs and kids toys. They’re also bloody horrible and have no place on a bicycle.
Proper tyres, with air get punctures. There are things you can do to minimise the occurrence, but rest assured at some point (probably when you’re late and it’s raining) you will get a visit from the puncture fairy.
The easiest way to prevent punctures is to keep your tyres inflated to the correct pressure (see above). This will eliminate the majority of impact punctures caused when the inner-tube is crushed between a deforming tyre and the rim – these are commonly called “snakebites” because of the twin puncture holes commonly left in the tube.
This just leaves the day-to-day punctures caused by glass, thorns, flints and other assorted sharp road debris. Again, a properly inflated tyre will help reduce these, as will a quick inspection of the tread after every ride, and the removal of any debris from the surface of the tyre before it has chance to work its way into the carcase.
Many manufactures produce a “puncture resistant” line of tyres. These typically have either thicker/harder wearing tread rubber, a Kevlar or similar “band” beneath the tread or both. These tyres will normally be heavier than a similar non-protected tyre and are often sold as commuter or winter training tyres. Probably the most well known of this type of tyres is the Shwalbe Marathon and Marathon+ range of tyres, which have an almost legendary level of protection (and an equally “impressive” weight). These tyres are often recommended when a “puncture proof” tyre is requested. The Michelin Krylion Carbon/Pro Race Endurance, the Schwalbe Durano + and Bontrager Hardcase are also well respected tyres with increased protection.
There are several products designed to be injected into tubes to prevent punctures. These are generally a chemical “slime” that oozes through a puncture and congeals, sealing the hole. These generally add weight to the tyre, have a limited number of uses and make a traditional repair difficult or impossible. The high pressures used in road tyres also make the slime less effective. Such products can help with punctures in lower pressure tyres – especially the smaller holes caused by thorns.
Another common cause of punctures comes from the inside of the wheel itself. Traditional rims have numerous holes to allow the fitting of spokes. These holes must be covered by a layer of rim-tape. Otherwise the pressure of the inflated tube causes it to rub on the sharp edge of the spoke hole and eventually puncture. If the rim tape is worn or badly fitting, or the ends of spokes intrudes into the wheel rim then punctures will occur. Electrical insulation tape can be pressed into service for an emergency rim tape but this is not recommended long term. The usual preference is to employ a specifically designed fabric tape such as that produced by Velox.
Tyres wear out, and as they do the frequency of punctures will usually increase; especially on the rear tyre, as this bears the majority of the riders weight. Replace a tyre that has become too thin. Resist the temptation to swap a worn rear tyre to the front - a high speed blowout on a front tyre is not something you want to risk.
Repairing a Flat Tyre.
Punctured tubes can be reliably repaired using either the traditional patch and glue, or the more convenient self adhesive patch. Either of these methods is suitable for both low pressure MTB and higher pressure road tubes.
In some cases the puncture will be too large, or in an inaccessible place (such as up against the valve stem) in these cases it will be necessary to replace the entire tube.
When a puncture is repaired it is wise to try and identify the cause; a piece of glass embedded in the tyre will continue to cause further punctures until removed.
A severe puncture may damage the tyre itself. Small holes are OK, however if the carcase of the tyre is showing or a large tear is present causing the inner tube to balloon out then the tyre should be replaced as soon as practical. An emergency tyre “boot” can be carried to allow a limited amount of riding on such a tyre. These can be purchased, or made from a strip of an old tyre with the bead removed. This can then be placed between tube and tyre to provide a temporary patch. Smaller tears can even be patched in dire emergencies using empty crisp packets or £5 notes!
Final Note.
The tyres fitted to your bike are (ideally anyway) the only point of contact between bike and ground. The size of this contact patch on a road bike tyre is approximately the size of your thumb, and not much larger even on a MTB fitted with super wide tyres. It’s probably a good idea to ensure that these thumb sized bits of rubber are in as good a condition as possible before descending that mountain pass in the rain, or throwing yourself down a black run.
This doesn’t mean you necessarily need to spend a fortune on the latest whiz bang super-tyre. Decent tyres are available from many reputable manufacturers for a fraction of the price of the top end race-rubber. Make sure that whatever tyres you have are in good condition, and that you understand their (and your) limits.
