[JimD]

I've read the 135i brake thread (it has a sticky) but it doesn't seem like the issue is totally sorted. The ceramic topped pistons are a good bit of the issue but it also seems like the relatively thin rotor is part of the problem. The component you want to cool is the rotor. You don't want the caliper getting hot - that is where the fluid is - you want the rotor cooling off so the caliper doesn't get too hot. Bigger rotors with larger air passages with slots or holes and brake ducts are all ways of cooling off the rotor (I like slots more than holes because holes are also stress risers).

I would expect a little difference in stopping from larger rotors because they will get hot more slowly. One panic stop doesn't heat the brakes a ton but still they should be slightly better - a few feet (maybe less). The primary advantage is clearly with hard frequent use - like on a race track. That is where the heat builds up and the cooling advantage would be experienced.

Pads have different characteristics. Racing pads are made to function better hot. On everyday driving, they may actually not stop you as quickly and may require more force.

135i and 128i brakes are quite different. 135 brakes have a bolted in position caliper with pistons to push the pads against the rotor on both sides. 128i brakes are the more typical sliding variety where a piston on the inside pushes and the caliper moves to pinch the outside pad against the rotor. 135i design seems more elegant but there are also a lot of pistons and seals. 128i type is undoubtedly lower in cost but works quite well.

Anybody try 330i rotors and calipers? Is the rotor larger?

It isn't high "bling" but I painted my stock 128i calipers. The bling factor is consistent with the cost (about $20, I used a brush on duplicolor kit).