Just one in each corner, change them when then they wear out…right?

Nothing could be further from the truth. You only have to look to the pantomime of F1 each fortnight to see just how important they are. If a team has “the wrong tyres” they are nowhere. A wrong tyre choice by a team, bad luck with the weather (wets/inters/slicks) or even a better compound by the opposing manufacturer, means that the driver has a mountain to climb as this can mean half a second advantage when 10ths are huge. A poor wet/dry tyre choice can be worse, loosing several seconds per lap! So, it is obvious that tyres make all the difference; so what can they do for your tvr?

On the road they can turn your smooth running sportscar in to a tram-lining pain in the butt, and push the grip way down, yet they can also improve grip and high-speed stability. But how?

 Well the essential ingredients to consider are construction, compound and pressure. As cars grow in quality, gizmos and safety they become more and more lardy. You may have seen the 80s-2000 comparisons on “Top Gear”, where the Mk1 Golf belted away from the Mk5, which had a 50+ bhp advantage. This was mainly due to the addition weight it was carrying…this in turn, must be supported by the tyres. The stronger construction means stiffer sidewalls and this means less compliance in the sidewalls of your tvr and that can lead to a harsher ride and tram-lining. This was the problem with the Bridgestone’s originally spec’d for the Griffith. These particular tyres were also used on the BMW 3 series and there are quite a lot of them, so they had to get stronger and harder to cope with the newer heavier model.

The compounds were also changed to achieve this. The Bridgey S03 had a twin compound construction with a stronger and harder compound in bands round the tyre on each edge (to reduce wear from PAS) and in the centre third of the tyre (for longevity) and with a slightly softer couple of bands in between to maintain grip levels. I have to say that I didn’t have a big problem with them as combination road/track tyres but many did causing them to move to the new TOYO tyres. And guess what, they had a much softer wall construction and compound!

Pressures are obviously also critical. Running pressures aside there are a couple of golden rules for the track. You need to run “a couple of psi” over normal road pressures on the track, to help reduce distortion during high-speed cornering yet not over-inflating. THIS MUST BE SET WHEN THE TYRES ARE HOT! After a session, when you return to the pits, check the pressures immediately and maintain the +2psi rule. As the tyres warm during vigorous use on the track, you will gain temperature and therefore pressure. As the tyre distorts with the pressure, you will gain more heat and so the cycle continues, and off you go…possibly literally! So keep your eyes on your pressures especially after lunch, as your tyres will be stone cold and LOW!

This, tragically, was how the great Ayrton Senna lost his life. While dicing at Imola, the safety car came out due to a crash and the cars followed for many laps while the incident was cleared. This took sometime and though constantly weaving, the field’s tyres cooled dramatically and so grip and ride height dropped. The Williams that Ayrton was driving was a ground-effect car, which grounded when being pushed too hard after the safety car came in. The Legend lost his life due to cold tyres and low pressures. So be warned.
The same goes for the drive home. After a long day on the track…remember to
Re-inflate!

So now we’ve dealt with the basics for the road, but what about the track?
Well put simply, a full set of road legal track tyres will give you THE most improvement in your track times possible in one hit. It’s not unusual for a set to give -1 second on a 1-minute lap. To do the same in power terms would cost you several thousand pounds and around 50 bhp! How can it achieve this? There are three areas to improve your times. Accelerating, cornering, braking; and improved grip will help with every one of these.

We recently did a back-to-back test at Spa in the Monster Griff. Nothing was altered on the car, and we built on the initial times achieving a 3m: 11s lap by lunchtime on TOYO Proxie TS1 road tyre (see pic). Not bad, but after changing them for R888s over lunch, we put in a 3m:03 lap in the first session…and the car still had more left in it. Not bad for a mod costing a few hundred pounds and you have to buy them anyway.
The R888 (photo) is my weapon of choice, but the Dunlop R01 is also used by many and seems to do well too. Dunlop know quite a bit about tyres and are the control tyre for the tvr Challenge, so they are definitely worth considering. The most important thing is that they are “E” marked just like your car windows and lights are. This means that they are road legal and if stopped by Plod you can easily point to the mark on the tyre and smile. So, improved grip and handling with reasonable wear? There must be a downside right? Yes there is. As with “proper” race tyres, when it starts raining grip levels fall. No problem to racing cars that can pop in the pits and stick on another set, but what about you? I’ve used the R888s for a couple of years and around 10,000 mainly track miles all over Europe. Grip in the dry, damp is excellent and wet conditions are similar to road tyres so still the R888s have it, but in standing water it’s another story. They aquaplane a lot more than a road-tyre, as they are unable to eject the water quickly due to the lack of grooves and consequently lift onto the surface of the water. The more water there is, the worse the problem.

So can you use them safely on the road? Of course, otherwise they couldn’t get an “E” mark but make allowances for the reduced, standing water performance. I have several sets of rims and tyres, and when on the “monster” trips to Europe I can swap between them, but if not with us then all you have to do is stop at the services or at a café and have a coffee, allowing the standing water to clear. How many times do you actually travel in your tvr in very wet conditions anyway? If it’s teeming down, you will probably stop anyway as the wipers/demister aren’t exactly in the BMW class. So the tyres won’t make much difference anyway…but you have been warned!

Finally, what of “block-shift, “feathering”, “graining” and slip angles? What are they and what do they mean to the handling? Well, block shift is what happens to a tyre under heavy side loads. If you think of the individual “blocks” of tread in your road tyre as a kids jelly, stay with me here, and then push the top over to one side. That’s and exaggeration of what happens to the blocks of tread in your tyre under cornering.

This shape distortion leads to uneven wear and it is this shape of wear that is called “feathering” (see photo). The softer the compound and the taller (newer) your tyre is, the greater the effects of block shift. This effect will destroy a new set of tyres in only one Trackday, so always bed in your tyres well before tracking, if not for the handling then purely to save costs!
Heavy cornering loads also cause “Graining”. But in this case, instead of the tyre being miss-shaped by the moving of sections of rubber as in feathering, the rubber is removed from the tyre and is rolled across its surface, which it tries to stick to. This is by far the worst form of tyre degradation to have, as it gives the impression of driving on marbles. There is no cure as such; you just have to drive through the condition. Mercifully, this is mainly confined to full race rubber and not track/road tyres.
Finally “slip angles”. This is a fact of pure physics and is unavoidable. However, being aware of the effect gives a greater understanding of what happens when cornering, therefore improving speed and confidence. When driving at speed, the wheel and tyre rotate together as one, maintaining your course. However, should you turn the steering wheel suddenly, the front wheels will turn shortly after controlled by the steering rack. The car and the tyres however (controlled by the tarmac under it and gyroscopic forces) will still be travelling straight ahead. The tyres will then react due to the sidewall being pulled by the rims and be pulled round to follow the wheel. Hopefully the car will then start to follow and the turn begins. The difference between the angle of the front wheels and the course that the tyres are following is called the “slip angle” and will always exist, but minimising this improves steering control and can only improve times. Stickier tyres mean greater slip angles requiring greater construction. But that’s another issue.

Hopefully, this out line of tyres an terminology will help you to get the most from your own tyres and car. It is not meant as a bible, just a guide to help you pick the right tyres for you and your requirements and to get more from the rubber you use. Your tyres are a fluid and changeable entity. They are also the only thing that secure your car to the road via a total contact patch roughly the size of a piece of A4 paper!
Ignore them at your peril!