Higher fuel consumption. Lower performance (acceleration, top speed suffers). Handling can be improved (less walking of the tyre), or worsened (if the suspension can't cope anymore and the wheel is in the air there is simply no grip at all). Also say goodbye to comfort, since yes, higher unsprung weight can upset the suspension setup, and also the tyre itself is a suspension when you use a reasonable size. The bigger the rim, the less the tyre absorbs, and that makes a big difference on the comfort (I've experienced it on a Touran with 15 or 16" steel rims vs Touran with 17" alloys... the smaller one was much more comfortable).

Wider tyres should result in better grip while driving in the dry, though FC is yet again higher. Steering becomes a bit harder too, especially at low speeds/stand still. In the wet a wide tyre is more likely to swim, though there are obviously good ones that can take a lot of water, and bad slim ones that can't.

Lower performance and higher FC can be countered with with very lightweight rims, but those are even more costly.

To me the disadvantages easily outweight the advantages, so I'm happy with 14".

Watch that TG video someone linked to earlier. More than 3 seconds faster on a short race track, just by using smaller rims. And look at F1 tyres. They use 13". IndyCars, which are less regulated, use 15". That seems to be a good size.


This post has been edited by kadajawi: Jan 12 2013, 01:18 PM