completely random tyre question

[retrorigg]

very random and i apologise but saw a newish astra today , well new in my eyes bout a 52 reg and ive noticed it before on other astras and a few other modern plaggy euroboxes but they have real high profile tyres on, and it got me thinking how does a manufacturer decide on what size tyres and profile to use, most cars all have diffrent profile/width tyres on some low some high some medium, how do they know what size to use when they develop/make a car

[Copey]

i bet they say its all kinds of stuff to do with brakes and suspension

 

when in reality its probably they have a deal with a certain company and can get half decent tyres for cheap

[sambo]

Its to do with what the car is marketed for too. You wont find 45 series tyres on a rep car, they would have bigger profile tyres for comfort.

My girlfriend has a sport ka and the tyres are very low profile for the 'sporty' feel i guess.

[you'll get 10s on that]

Primerily cost...but also the handling characteristic required of the car .

In a few cases manufacturers have downsized on diameter to compensate for mechanical integrity of parts/bodyshell and fitted a higher sidewalled tyre to afford greater cushioning.

On performance cars the wheels are often dictated by the desired brake components plus the customer appeal of large diameter wheels in such a market

[antz]

my mate had a suzuki swift sport and the tyre size was only made by one tyre company (pirelli i think) as they had a contract with them to supply that tyre in that size to them only for the swift.