Just posted this up on the Fiat forum website in answer to somebody asking if its possible to fit disk brakes under 10" wheels. I thought it may interest the folks on here as well:
It is indeed possible to do a disk brake conversion with 10" wheels, i've just done a conversion myself. There are two ways of doing it, the first is to buy a kit off the shelf,Nanni's do a kit but its expensive:
http://www.fiat500sport.com/brakes/fiat-500-10-12-wheels-brembo-front-brake-rotor-conversion-kit-0182.htmlThe other way is to make your own kit which is what I've just done. I think I have spent about £300 doing mine but its not an easy job. There is very little room inside a 10" wheel so first you need a very small disk. I used Citroën GS rear disk. The calipers are from a Ducati Paso 903 and the hub was custom made by the same guys who made the wheels for me. The mounting plate is custom made by me.
It all only just fits into the wheel with about 3mm to spare! The other thing that needs doing, if you want a decent inset on the wheels, is the arms in the kingpins that the track rods fix to need shortening so that they sit inside the wheel, I have seen some racers in Italy cut and weld them at 90 degrees but that would change the Ackermann angle.
There is not a massive difference in diameter (17mm) between a 10" wheels with a 165 70 10 tyre and a 12" stock wheel but the choice in tyre compounds is much more extensive as its the same size as a classic mini.
Some people like the chunky look of the 10" wheel others prefer 13" wheels with lower profile tyres, its a matter of personal taste...
Hope that helps a little
Nigel