I have four wheels on my rear axle -- is that just as good as 4-wheel drive?

Dear Car Talk

Dear Car Talk | May 01, 1995

Dear Tom and Ray:

Please settle an argument in which I am embroiled. My Dodge-chassis motorhome has dual rear wheels (side by side). I maintain that I thus have a four wheel drive vehicle, in effect, with as much traction as any garden-variety 4WD. I realize that ordinary 4WDs can out-perform my rig in an instance where their front wheels are not mired, but in other circumstances, my machine is just as good. Do I win the bet?

RAY: I?om afraid not, Bob. Not unless you?ore applying a very liberal definition to four wheel drive.

TOM: You do have better traction than the same motorhome without dual rear wheels. Your main advantage over, say, a ?"74 Chevy Caprice is that with four rear wheels--and four rear tires--your driven wheels have twice as much rubber touching the road.

RAY: Plus, you have far more weight than the average car, which also improves traction.

TOM: But just like that ?"74 Chevy, if your rear wheels happen to be on ice or in mud you?ore completely out of luck.

RAY: Whereas if you had a true four wheel drive vehicle with a locking differential, you could actually send power to all four corners at the same time, which would double your chances of getting unstuck.

TOM: So you lose, Bob. I just hope the bet wasn?ot for anything too embarrassing, like that the loser has to go into Midas and say "I?om not going to pay a lot for this muffler" wearing a pink tutu and pumps.

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