I left my bike in our boiler room over the winter, and now the back tire is rubbing heavily on both chain stays. Before it was a very tight clearance, but it worked without a problem. Now, it heavily rubs on both sides at all times, so it is neither a centering nor a trueness issue. My only theory a is that it has to do with the fact that the boiler room was pretty hot ~96 degrees, and over the winter either the aluminum tubes or the tire expanded. Is this plausible? do you guys have any other solutions? The bike is a '95 Cannondale road bike, works perfectly otherwise.
Well, the aluminum would not expand, for all intents and purposes, so that leaves the tire as the cause. If it were exposed to high temperatures for an extended length of time then the tire could start to deteriorate (rubber, tire cords) to cause it to not contain the air pressure within the same volume, i.e., enlarging the tire. An extreme example of this can be seen when a bike is carried on a rear rack on a vehicle, where the bike tire is in line with the exhaust pipe on the vehicle. Over time, the bike tire will swell and eventually burst due to the heat.
Other things to consider: are there any other chemicals or fumes that are in the boiler room? If there are any caustic or acidic fumes (even minor ones) in a hot environment they could have a deteriorating effect on rubber or other compounds.