I have a mountain bike w/ 26 wheels. My question is what's the biggest difference between aluminum vs. steel? If most of my riding is off-road, wouldn't the steel wheels be stronger/more durable?
You would think that is the case, right? Well, it isn't. Steel rims are necessarily made of very thin sheet. This sheet, when formed into a rim tends to dent very easily. On top of that, because the material is so thin it can and does flex- a lot. Aluminum rims on the other hand are formed by a process called extrusion... basically, a big block of material is shoved through a die (think PlayDoh shape maker) and then formed into rims. This forming process along with the stiffer nature of aluminum (in this instance) makes an aluminum rim far stronger and far lighter than a steel counterpart.
Aluminum is by far the better choice for wheels, mirageguitarwork is right on the money with his description. One other thing that detracts from steel wheels is that they rust. Wheel builders used to chrome plate them, but all this did was add weight. The wheels would eventually still rust, and this weakens them even more.
Go with Aluminum. Mirageguitarworks could not put it any better.
Short answer: Aluminum is lighter and stiffer than steel. Steel is stronger but flexier. However, the technology used to make mountainbike wheels has become very advanced that it is possible to make very strong and reliable aluminum wheels that are at the same time light. Mavic and Sun Ringle make strong and light wheels. You may want to check your local bike shop for their recommendations for your style of riding.
