Just to follow up on this thread for the archives.....for anybody wondering if the stock 300E rims will fit a 400E, the answer is yes, but they will definately scrape your calipers in the back and especially in the front. I know this because I just tried it. I suppose you could grind down the calipers a bit and they would fit but I didn't want to take a chance. The stock 400E rims are just a bit more concave than the 300E.

Jerry