Event date: 7 July 2020
Tyres. They’re the black bits which stop the wheels clattering on the road right? Well, Yes, but they do a lot more than that!
Tyres are the last and possibly most important link between you, the driver, and the road. Ultimately the tyres determine how well the car rides, how noisy it is, how well it brakes and turns, how much fuel the car uses and how safe you, your passengers and other road users around you are.
So, they are worth a bit of attention and understanding.
And who better to de-mystify some aspects of the art of tyres than Andrew McCathie from Traction Tyres who kindly hosted our virtual members meeting on Tuesday, July 7.
As a quick aside, whilst virtual meetings are not as friendly as physical ones, everyone gets a ringside seat, which is great.
Andrew explained that there are 3 critical parts of a tyre: tread compound (the mix of rubbers, carbon and other secret ingredients but no herbs or spices), the tyre carcass or structure (what the casing of the tyre is made of and its construction), and tread pattern (which is the bit most people look at and choose more on its artistic merit than function).
It was fascinating to hear that tread design, the most easily observed part of all this, has pretty well gone full circle (no pun intended) from the 1960’s and 70’s when little slits running out to the side of the tyre were all the go. These “sipes” are designed to carry water away from under the tyre.
I fondly remember the adverts for Dunlop’s 1968 AquaJets which claimed to use the squish of the tyre as it meet the road to actually pump water out of the side. Up to 30 litres per second.
But Andrew pointed out that these slits separate the tread blocks from each other and allow them to move about, creating noise and wear and reducing performance.
We have probably all seen the slick, treadless tyres used on race cars such as F1. These are great for grip but no good in even mildly wet conditions.
And herein lies the eternal quest for the perfect compromise between performance and practicality.
So the slits went out of fashion to a degree but have returned, with the subtle twist of not actually joining up to the main grooves and thus helping to stabilise the tread and reducing wear.
Only he made it sound more interesting.
The other critical thing I picked up on was he mentioned a tyre’s “flex point”, the sort of hinge between the sidewall (the vertical bit) and the tread (the horizontal bit), which profoundly influences how a tyre reacts to grooves and ridges along the road, such as the tendency to follow tram lines, hence the term “tram lining”.
Whilst excessive tram lining can be due to a steering alignment issue (which Traction Tyres can also help you with) it is often due to the wrong tyre for the car’s design.
If I learnt nothing else form Andrew’s expert explanations, I learnt that it takes an expert to guide you through the process of choosing the right tyre for your car and needs and that is all the more critical when selecting tyres for track use, or even deciding whether to go for a tyre which will do road and track if that is your intent.
On the track having the wrong tyre may cost you several seconds per lap. On the road it may cost you extra metres in stopping distance even with ABS and the difference between hitting something hard, or not.
Lawrence Glynn | Member #3
BMW Drivers Club Melbourne