TYRE TECHNOLOGY

Regardless if it’s a truck, race car or bicycle tyre, grip is created by two key things;

1. Contact patch – i.e. the amount of rubber touching the ground. This is also related to the pressure (weight) pressing on the ground
2. Composition/Compound – i.e. how ‘grippy’ the rubber is

CONTACT PATCH 

TREAD

Basically the larger the area of rubber touching the ground the greater the resulting grip. This is why racing cars have the widest/largest tyres they can legally have in their class.

Tread does NOT give grip and is counter productive in dry conditions as it reduces the contact patch area. In adverse conditions tread allows water and sand etc to be squeezed out of the way so that the rubber can touch the ground and therefore grip the road surface. Because tread effectively reduces the amount of rubber on the road it also has the effect of increasing the pressure (weight – weight is not technically correct but helps explain it) that the remaining rubber places on the road. Therefore in wet and/or sandy conditions tread is excellent on cars, trucks, and mountain bikes etc all of which have relatively wide tyres for their weight. However racing bicycles have very narrow tyres that already have a very high ground contact pressure (that’s why we need 100psi pressure in racing bike tyres compared to around 30psi in cars) so they will ‘slice’ through water and sand without the assistance of the tiny tread patterns that can fit on the tyres.

Summary – Tread does NOT significantly increase grip on road racing bicycles

TYRE WEAR

Most bicycle tyres that are ridden on the road wear such that they wear the crown of the tyre down and end up having a flat surface. This happens mostly on the rear tyre. Tyre life can be improved slightly by rotating tyres front to back several times during their life.

Worn tyres lead to two things; more punctures from the thinner rubber and, potentially, a decrease in contact patch area when cornering. Visualise the contact area when a bike is leaning while cornering. A new tyre has a rounded shape that has approximately the same contact patch area on the ground while cornering as it does when going straight. A tyre that has worn flat will have a reduced contact patch area and, therefore, reduced grip.

Summary – Tyres that are worn flat will have less grip while cornering.

COMPOSITION/COMPOUND

Not all tyres are created equal. Some compounds are great in both wet and dry conditions. Some are great in the dry but poor in wet conditions and vice versa. Some are poor in all conditions (usually the cheap ones fitted to your expensive bike when you purchased it).

Tyres can be very slippery when brand new because they have ‘packaging’ sealants on them. Tyres also get harder with age. Don’t use old tyres.

Tyre pressure also effects contact patch area i.e., lower tyre pressures result in increased contact patch areas. Some elite riders use lower tyre pressures (say 10psi lower than usual) for criterium racing where high cornering speeds are important.

Summary: Only buy high quality tyres with excellent grip levels both wet and dry. The internet has sites that rate grip levels both wet and dry of the better quality tyres. For example a Continental GP4000 is an excellent all round tyre. A Continental GP4000S will wear slightly faster but has higher grip levels (These could be a good choice if you want a safety margin). Michelin Pro Race 3 offer similar grip levels and have better cut and puncture resistance than Continentals so are possibly the pick of the tyres at this time.

OTHER ITEMS

Camber of the road. If the road slopes toward the outside of the corner; grip will be less

Braking – A tyre only has a specific amount of grip. During cornering the available grip is used to counter the cornering forces. During braking the available grip is used to counter the braking forces. If you corner and brake at the same time the available grip must be shared between countering the cornering and braking forces at the same time. Therefore braking in a corner will increase the likelihood of losing grip and crashing. If possible brake before the corner. 

Oil slick line and painted road surfaces – Both these things lower the effective grip level of any rubber compound. DO NOT ride in the centre of the lane where cars have leaked oil. Be particularly careful where cars and trucks have stopped at traffic lights. Also be careful staying off the slick line when turning at traffic lights because oil and fuel spills out of vehicles racing the lights. Where possible make it a habit to avoid riding on painted road surfaces including cross walks and lane marking lines, particularly when it’s wet. 

Fresh rain – Oil floats on water. Therefore when it rains the oil floats to the surface and you’ve got a fresh oil slick. Be careful!

Light weight tyres – Some manufacturers and retailers promote tyres that are low in weight because they make the whole bike lighter. These tyres are not suitable for general riding because they will generally get more punctures than a good quality tyre

 SUMMARY

Buy good quality tyres and change them before they are too worn. You won’t care how much money you saved on bargain tyres if you crash.

Take corners carefully particularly during rain following a dry spell. Remember it takes a long time to get better from a big impact.

Happy cycling

Peter Trench