Do Truck Conversions ever have tag axles like MCI busses?

[BravestDog]

Wondering if truck conversions ever have a tag axle either in front of or behind the main drive axle like the tag axle on MCI busses?

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...?

Comments?

Thanks.

[fastlap]

I am considering a single wheel air tag on my next conversion
they ride much more quiet then tandem drivers but still give many of the same benefits without the danger in slippery conditions !

[Doug]

I have thought about it, and will have serious discussions with the dealer and manufacturer when it comes time; a tag out back helps with weight capacity (a single RA is likely to be too light in capacity), but can be lifted for tight spots and to put more weight on the drive axle when in the slop.

[Gary Atsma]

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?

[QRTRHRS]

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.

[Gary Atsma]

Originally posted by QRTRHRS:
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".

Not true. There is a differential between the two axles that is housed in the "front" tandem axle that divides the power just like the differential divides power between the wheels. Both axles get power, but the one with the least traction will spin just like the spinning wheel on either side of a single axle. This is why there is usually an "inter-axle differential lock" to lock this differential so that the axle with the most traction will then pull the truck out of trouble.
Check an exploded drawing of a splitter axle or check out an actual axle and you will see that this is true.

[fastlap]

A single axel air tag can be rated as high as half a tandem dual set up ( when using super singles )
they are very good for high cg applications and in a coach the lack of all that gear noise and vibration is a nice plus !
as far as having extra traction with tandem drivers??? maybe, but probably not in most real world situations ! most of the time single axels have more traction while opperating with realitively light loads !(especially if you have a air diff lock s/a )
an air tag can increase available traction (drive ) if lifted
I am probably going this way cause sometimes we dont pull our race trailer, we just use the coach as a camper alone !

[Gary Atsma]

Very true, Fastlap! You hit it on the head with the capacity issue when you mentioned the "super-single". With regular single tires, the tag axle capacity is far less than with "super singles". All of this is a non-issue with me as the rig I plan to use will be short and light enough to warrant a single axle; tandems would be a total waste of weight and space, and just make things too complicated in general. I'm a firm believer in the KISS principle; Keep It Simple Stupid (referring to me, of course!). Have a terrific Christmas and New Year!
Gary