Tread Patterns and Profiles

Most people don't realise it but tyres are fashion accessories. No, you won't get away with giving your wife or girlfriend a pair of 255/35R16 as a set of earrings, but, when a car is designed, an integral element in the designing of a car is to include the tyre width, profile, diameter and pattern as a core factor in the design.

Whilst the tyre will always be required to do its job, of providing grip, traction, adhesion and being an element of the car's suspension, it nowadays also has to look good. It has to look good on the car and in the showroom. That makes the car tyre a fashion item.

It is impossible to tell from looking at one tyre tread whether it works better than another tyre of a similar style. It used to be pretty simple, a question of bars and lugs, and blocks. Now we have a different approach to tyres and how they work, and that means that things can get very confusing for the tyre buyer: Though they need not be.

Back to Basics

Very early on it was realised that tyres worked better if they had a tread pattern. Designs were arbitrary and Dunlop actually produced a tread pattern that left an imprint of the brand name Dunlop as it ran over soft surfaces.

There is a history of tread design that can be followed through the years. But essentially, there was the bar or lug type tread with solid lugs across the tyre tread traction. Then there was the circumferential channel pattern that gave lateral grip. A combination of the two basic patterns led to the block type tread pattern that survives in many tyre patterns today.

Interestingly, all three early type patterns are still available for specific uses today. However, modern motoring's focus has changed slightly, and whilst grip and traction are still core values, today we are more focussed on wet and dry handling and braking ability.

The best tyre on dry, level road surfaces is a slick. However, road surfaces are rarely dry, and the roads that we drive on every day - even the smoothest of them, are a far cry from racetrack surfaces, and as a consequence the road tyre needs to be harder wearing, so it has a firmer compound (generally), it has to have grip and traction, and it also needs to resist aquaplaning.

The tread on a modern car tyre is considered to be a water pump, designed to express water from between the contact patch and the road surface. How it manages to do that is the subject of many millions of pounds of investment for each of the leading tyre manufacturers.

For the tyre buyer, generally speaking, the greater the number of channels in your tyre's tread the greater its ability to pump water away. However, the design of those channels may make the tyre more or less efficient. A wide tyre may require a different approach to water dispersal than a narrow tyre. So that trendy looking tread you find on a Porsche tyre, may not be suitable on a narrow tyre fitted to the family saloon - and vice versa.

A recent trend has been the development of high performance tyres with circumferential grooves and tread bands that offer different characteristics across the tread of a tyre - these tend to be asymmetric and directional. Another trend is for the "single tread" where the tread pattern is such that the "land" area of the tyre never breaks contact with the road and the "sea" area (the troughs) channel water away from under the tyre. Both these tyre patterns are claimed to be quieter than block type tread patterns.

Noise Travels

Tyre noise is a big issue nowadays. Cars have become so quiet that often the loudest bypass noise comes from the induction system and the tyres. Tyre pattern can make a great deal of impact on the noise a tyre makes. The noise actually comes from the leading edge of the tyre block making contact with the road surface, and the trailing edge snapping back as it breaks contact with the road. So, the more blocky a tyre is, the noisier it will be: Perhaps something to consider if road noise is intrusive in your car. Winter tyres are always going to be louder than their all season counterparts because they are blockier and have many more sipes (thin slices in the tread block) to give better grip and pump more water away.

Noise is a comfort issue and comfort is a big issue for vehicle manufacturers and tyre makers. The tyre is an integral part of your vehicle's suspension. It absorbs the first and all minor impacts with variations in the road surface. It softens the ride and suspension settings at the point of vehicle design and manufacture take into account the Original Equipment (OE) tyre design. So, when replacing your car's tyres it is always a good idea to buy, at least with the first replacement, the same tyre as is fitted OE. By the time your car needs its second or third change of tyres the original specification of the suspension will have been diminished by wear and tear and it becomes feasible to fit non-OE tyres without any real impact on the car's feel since it will rarely feel like new by that stage anyway.

Comfort Profile

Comfort is also impacted by profile. Now this is where we are all becoming fashion victims. Cars are coming with ever larger wheels and lower profile tyres. The technical reason is that the larger wheels allow the manufacturers to fit larger brakes, and therefore make the braking of the car more efficient. In utilising larger wheels the car requires thinner, lower profile tyres to stay within the style and design characteristics of the vehicle, and also within the ability of the tyre industry to produce suitable tyres, and the aftermarket to deal with them. A vehicle that leaves the factory with 18 inch rims and 20 profile tyres will have had its suspension designed to deal with the harsher ride created by the low profile tyres. However, if a car comes with 70 series on a 15 inch rim and the owner changes to 18 inch and 20 profile (as an example), he will definitely have a harsher riding car as the lower profile tyre has a stiffer, less supple sidewall and will absorb far less of the surface undulations than the car fitted with the 70 profile.

So, unless you drive on excellent road surfaces for most of the time the low profile tyre is potentially harsher. If you fit low profiles to a car not designed for them, you will gain in looks (perhaps) but suffer in the ride. Your handling on smooth roads will improve, but on poor roads and potholed surfaces your handling will only be of use to you as you dodge the rim smashing voids in the asphalt.