Wheel size performance advantages?

[Nictrix]

Reducing tyre flex improves steering response but loses grip. Grip comes from maximising contact patch and keeping it in contact with the tarmac and tyres with more give in them do that better. That’s the main reason non run flats are so much better than run flats.

At last, someone who understands that tyre/suspension systems NEED controlled compliance to maintain grip, beyond a certain point bigger wheels, lower profiles and lower/stiffer suspension will do squat for performance on real UK roads

I would think that is why formula 1 cars dont have low profile tyres either.

[Lazza]

Reducing tyre flex improves steering response but loses grip. Grip comes from maximising contact patch and keeping it in contact with the tarmac and tyres with more give in them do that better. That’s the main reason non run flats are so much better than run flats.

At last, someone who understands that tyre/suspension systems NEED controlled compliance to maintain grip, beyond a certain point bigger wheels, lower profiles and lower/stiffer suspension will do squat for performance on real UK roads

Of course! It's why the road tyres on my MX5 are 205/40/17 but the track tyres are 195/50/15, Which also gives the big advantage of lighter wheels. The deeper sidewalls also help to make the handling more predictable, allowing the tyres to slide in a more controllable way rather than all or nothing. If big wheels with rubber-band tyres were the way forward, F1 would have them.

[Mister T]

Of course! It's why the road tyres on my MX5 are 205/40/17 but the track tyres are 195/50/15, Which also gives the big advantage of lighter wheels. The deeper sidewalls also help to make the handling more predictable, allowing the tyres to slide in a more controllable way rather than all or nothing. If big wheels with rubber-band tyres were the way forward, F1 would have them.

Rubbish. Porsche 919, faster than an F1 car, 18" wheels. Regulations dictate wheel and tyre size in F1, they're aren't chosen for optimal performance.

[Lazza]

Porsche 919 tyres look pretty chunky to me.

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[Ewazix]

Please lets nail this one, tyres and suspension work together to provide the best grip and handling i.e keeping a big sticky patch of tyre actually in contact with the road. A 919 or go-cart race on a predicable relativity smooth surface so can afford to reduce compliance in the tyre/suspension. A rally car is at the opposite end of the spectrum and needs a very different set-up to provide travel and compliance to keep the contact patch on the road. A road car needs to be somewhere in between, if like me you spend a lot of time on s4ite UK A/B roads with potholes, mid-corner camber wobbles and ruts, then ultra-low profiles, big wheels and lowered suspension will not effectively keep the tyre stuck to the road.

If you track your car or just like the look of big wheels and lowered stance that's fine. If you want the car to perform in a controlled way then set your car up to suit your roads.