The first of the 2CV had 125-400 tyres on millimetric wheels. They then moved onto 125 R380 tyres. (380mm being the same as 15” and a 125 R15 tyre). Although people do fit 135 R15 tyres on 2CV, but that is only because there are some cheap tyres available in this size. The 2CV had 125 section tyres as an important part of the design of this car. The Michelin X carcass and tread profile are also an important part of the 2CVs design. 135 R15 should not be fitted to a road going 2CV.