I had a ASE test the other day and I was brushing up on powertrain stuff when I ran across the usage of different styles of bearings.

This is what I found: tapered roller bearings are for High load aplications and require a preload. (this makes sense for a high HP build).

However if Im not mistaken, the timkin mod only dose one side...right? if so, then the crank is not preloaded because the roller bearing on the other side is unable to preload the crank.

how could the mod work? can the crank be preloaded with two different styles of bearings?

 

There is no preload on the Timkens like what you described. Even in earlier applications the bearings were always set with some clearance [.001-.002]. The timkens control side to side movement as well as carrying the load put on them by the drivetrain. In a different setup [wheel for ex.] you would set the bearing up with a specified preload usually with a torque wrench. On a car it might be 10 ftlbs. but on a semi it could be 75 ftlbs. If you didn't do this the bearings & races would wear out quickly.