No experience with your specifics. However, any tire shop will know of any spacing issues with the 255s. They must also be aware of the turning angle in the front. It is possible the 255 may hit the fenders in a tight turn. Not likely with only 20mm difference, but possible. Perhaps why the coach mfg says 235. I would be more concerned with load range, but would also go with the 255 if there were no clearence problems.
John & Clare - Buck & Zeus - Jack & Husky
2008 Fleetwood Bounder 38P
Towd: 2 HD Streetglides