The German motor federal motor vehicle agency regulation is a maximum of 30 mph/50 kmph, which will certainly feel fast when driving on roads were snow chains are required! Different manufacturers of snow chains have different speed limits but the majority state 30 mph. In reality if conditions require snow chains you won't be travelling this fast. You will need to remove snow chains where conditions allow for various reasons, e.g. to avoid damage to your chains and the road and also using snow chains on a normal road surface is fairly noisy.