jmac wrote:

believe it or not, tread width isn't the big deal here. It's friction co-efficient of the tyre tread compound (apart from chassis/suspension tweaks to maximise downforce/grip)

Here's the deal - IF (and it's a big if) the tread compound is identical - then a 235 will provide exactly the same grip as a 195 width tyre. The reason is simple enough. Grip is a result of teh combination of 2 things - downforce and friction co-efficient. If you have the same tread compound, but halve the width, then there is double the 'load' on each square cm of tread, so it basically has the same grip.

Obviously you can get to a thin enough tyre where it'll just overheat too quickly. And it'll also wear out quicker (since at half the width, it'll have half as much tread area to wear down). Since thinner tyres will experience that, very generally, the tyre makers run harder compounds in thinner tyres, and can 'get away with' softer compounds on wider tyres and still have acceptable tyre life.

So in general, wider tyres 'might' grip more, but it's only because they were made with softer grippier tread, not just due ot the width all by itself.

The reason I mention this is pretty simple - it is probably now obvious - it's not so much a matter of finding 'a' tyre in 225 or 195 or whatever the widest width is, the REAL trick is to look at each individual tyre in the sizes that will fit, and find the ones with the stickiest tread compound.

Now, even people who compete in short sprint races can overcook their tyres, so you have to try and find a balance between tyre life, the traction you need, and how long they will be good for 'thrashing' around before they start to go off a little due to overheating. As a good example - this is why the smaller cars (relatively speaking) tend to do so well compared to the big ones in Improved Production - the tyre sizes are too narrow (relatively) for the bigger cars and they overheat after a couple of laps, so the drivers have to nurse them a lot more. They can't 'really' use grippier compounds, because the tyres/compound are a regulated item.

But on a streeter, you can find a happy medium (if you are willing to go through tyres perhaps every 5-10,000km)

jmac wrote:


so as bad as it sounds, often the loss of traction is just as much to do with a car being 'too low' and ending up with undesirable suspension geometry as a result.