Quote:
Originally Posted by Spuds
Aluminum
-is 3lb lighter
-can be designed to be as strong and stiff as a steel part, usually with less total mass (though slightly greater volume) as seen above
-has no fatigue limit, meaning the part will become less strong/stiff over time and eventually fail, regardless of design.
-is weaker than steel at key interface points.
-costs more
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Should point out that manufacturers will design aluminum components to survive multiple lifetimes of the most harsh usage. So even though theoretically with enough load cycles parts will begin to fatigue and crack, in most cases you'd have to drive over rough roads for 250k+ miles to get to that number of cycles. Tons o testing to validate designs and analysis as well. When I was in the two-wheeled world, a company specializing in vehicle testing rode our vehicles day and night for weeks. The guy who rode at night was known as "The Night Rider"
So typically aluminum components will actually be a bit stiffer due to being bulkier (higher sectional moments of inertia) while also being lighter-weight, while being sufficiently stout to withstand multiple lifetimes of load cycles without loss of stiffness due to fatigue/cracking.