About the only way I've found is from the bike manufactures website. Hard to tell from just looking at it. The other problem is even with knowing the measurements of the chainstays, I doubt you'd find the measurements of the tire height. If you had that though, you'd be good to go. The width of the stays usually isn't the problem, but rather the length of the stays as you found out.
__________________
Demented internet tail wagging imbicile.