That’s really helpful thanks for the info from everyone.
Is it possible to fit a wider tyre, say a 205? Or would this be no benefit?
It largely depends on what you want to achieve. On a race track, you're on a predictable, smooth track with no unexpected events (hopefully). you are prepared to sacrifice a great deal for speed and you want maximum ultimate grip so wider tyres will help that.
But on the road, you need to deal with a more complex set of factors, not the least of which is steering feel and agility. You also have to accept that you can't dodge the laws of physics. If a tyre loses grip, then the car will start sliding and you'll slide until you stop or slow down enough to regain grip or hit something. On a racetrack, you'll see the first two, but on the road it'll be the last almost every time.
So: do you want to drive around on a tyre that gives loads of feedback, starts squealing under modest pressure, and lets go gracefully at comparatively low speed, or do you want a tyre that hangs on like grim death at high speed, but when it does let go you're going very fast indeed?
Personally, I'd rather be going backwards into a hedge at 50mph that 70mph so I go with the narrower tyres because I prefer the light and agile feeling and not fussed about ultimate grip. My 4/4 gives 165bhp and runs on 165 section tyres perfectly happily.
