Don't be afraid of 215s. They'll keep the sidewalls pulled tighter, and won't roll around on the rim as much, for the same tyre-pressure as the 225s.
Skinnier tyres on wide rims also break sideways earlier, gentler, with more warning etc. than fats on skinny rims. Fat tyres on little rims tend to hang on, rolling over until they're almost on the sidewall, then WHAMM!!! - They just let go completely. Nasty!!