difference tyre size makes

[player.777]

On the monty2s, I have 205/55 R16s.  I reckon the car would look a lot better if the tyre wall was smaller- 50, or 45.  If I put 205/45/R16s on, what difference would that make to anything- The rolling radius would be smaller so would that mean the speedo would be out?  The car would sit nearer the ground too?  what else?  Has anyone else changed the wall size- notice any difference? how does the car look?

[Steve_PD]

it would lower your car by about 20mm, your speedo will be out and you'll accelerate quicker  possible tyres will be more expensive due to not being common 
I wouldn't do it purely because of the speedo

[player.777]

yes thats what I'm thinking too mate.

[Ivor Mk4 Turbo]

I wouldn't do it (well maybe if 50 profiles weren't so expensive, I might??).  Have a play with this:-

http://www.miata.net/garage/tirecalc.html

[Ivor Mk4 Turbo]

ps  You don't really want to be straying from +/- 3%.

[player.777]

Thanks mate- good little toy that. Ok, think I'll stick to the normal size then. thanks