advantages and disadvantages of running different size tyres

[2204]

went from 16x8 +20 offset with 205/45/16 tyres to

15x6 +38 offset with 195/50/15 tyres

what are the advantages and disadvantages?

[SuperDave]

Isn't this something that should be considered prior to the purchase?

The track width will be about 87mm narrower, ignoring tyre size as the tyre 'size' rarely matches it's dimensions.

The 15x6 has the potential to be lighter, reducing unsprung mass. But it depends on the actual weight as it's possible that the 16x8 could be the same weight depending on the design and materials. Less track width will reduce lateral grip; but it's more dependant on the tyre compound, but assuming the same compound it will be reduced.Do some reading up on scrub radius to learn about the effects on the suspension geometry, but as I'm guessing it's a road car, it'll be fine.

[4ABHGE]

Basically you'll find the car is twitchier and will have better feel to the limit of grip of the tyres but will lack heaps of grip (if its the same compound)