Originally posted by Gary Atsma:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Why does a tag axle on an MCI bus only have two tires total while a dual rear axle conversion has 4 tires per axle...?
Because the tag axle on a bus is NOT driven, where the twin axles on most conversions are BOTH driven. Also, the tag on a bus is not rated for as much weight as the drive axle, hence the single wheels, but both driven axles on most trucks are rated for the same weight per axle, hence duallies all around.
Does this help clarify things a little? </div></BLOCKQUOTE>Note that on a tandem only one axle is being powered under normal conditions. The other axle just free wheels along saving fuel unless switched "on". Some dual drive axles are set up so you can throw the "power divider" while in motion while others must be at a stop.
The reason for a "tag axle" is to save money and/or weight. If I was in the market for a tandem axle motorhome, I would want both axles to be driven rather than just one. My feeling is the added traction in a bind is worth the slight savings in fuel mileage.