Convex wheels keep on turnin'!

May 22, 2008 9:03 AM

Why do most large trucks and other heavy vehicles have wheels with hubs that protrude outward in front?
posted by Mr. Anthropomorphism to Travel & Transportation (6 answers total)

I always assumed it was because the same wheel could be used on the front or the back. If you look at the back, you'll usually see a doubled-up wheel on each side. That protrusion is turned towards the inside on the back outer wheel, and toward the outside on the back inner wheel. The protrusion allows spacing between the tires when the wheels are mounted to the tub.
posted by rhys at 9:14 AM on May 22, 2008

uh, hub, not tub.
posted by rhys at 9:15 AM on May 22, 2008

I have seen the drivers use them as steps to get into the driving position.
posted by JtJ at 9:15 AM on May 22, 2008

Thanks rhys, I knew there had to be a logical answer. Seems obvious now!
posted by Mr. Anthropomorphism at 9:21 AM on May 22, 2008

I'd always assumed they were configured that way because of a slight improvement in aerodynamics.
posted by le morte de bea arthur at 9:23 AM on May 22, 2008

Nope, not aerodynamics, duallies. Even on the super-heavy-duty railroad trucks, if they're not dually (double wheels on each side of the rear axle(s)), they won't have this.

Basically, the setup is such that on the back, the offset in, and the offset out, from the hub is the same, so you can mount two wheels on one set of studs. So as to be able to only have one type of spare, there's an artificially long hub on the front. That's it.
posted by notsnot at 9:35 AM on May 22, 2008