Tyre size for wets?

[ttonks993]

Currently running 225/45/19 on the front and 255/40/19 on the rear on my BMW F30 track car. I’m thinking about buying some F80 competition wheels and fitting some semi slicks to them, widening the track and contact patch by 40mm on the front and 30mm on the rear.

I then plan on using my OEM wheels for wets only.

Should I keep the standard 225/45/19 and 255/40/19 tyre size for wets?

Thanks

[brillomaster]

Narrow tyres are better at cutting through standing water, so are at less risk of aquaplaning. Very wide tyres would float over the top. So yeah, id get a really good wet tyre at the standard widths if its due to rain.

However, if a trackday gets so wet that there is standing water around, im probably waiting it out in the garage.

[sabid]

ttonks993 said:

Currently running 225/45/19 on the front and 255/40/19 on the rear on my BMW F30 track car. I m thinking about buying some F80 competition wheels and fitting some semi slicks to them, widening the track and contact patch by 40mm on the front and 30mm on the rear.

I then plan on using my OEM wheels for wets only.

Should I keep the standard 225/45/19 and 255/40/19 tyre size for wets?

Thanks

Forgive me jumping in a bit late on this.

I’d keep the standard sizes on the OEM wheels for the wets. As you'll appreciate, once you’re into standing water, a narrower tyre is usually happier because it puts more pressure through a smaller patch and cuts through rather than floating.

In my experience the thing that makes a hugh difference to grip in the wet is tyre pressure. I'm not sure if you check or actively set these but I recommend you do. For the wet I’d start your pressures at what you’d want them hot in the dry (or a touch more).

Low pressure in the wet can see the middle of the tread lift up - due to the water - and you lose the quite a bit of contact patch that way.

There’s a picture of that tread-in-water effect here if it’s useful: https://www.yourdatadriven.com/wet-tyre-pressure-g...

In the meantime, hope the semi slicks generate the smile intended!