Pusher Axle Question

[Marc1107]

I broke down about a month ago and a Peterbilt wrecker towed me I asked the driver why do they put a pusher axle on the truck instead of making it a regular ten wheeler. The driver couldn't give me a straight answer. Keep in mind the truck was NOT a tri-axle, that I understand. The truck was a six wheeler with a pusher. Can anybody tell me the purpose of the puser axle on a heavy duty wrecker?

Edited December 20, 2008 by Marc1107

[Terry T]

Several years ago, Century re-badged there 5030 (25,000 boom/30,000 under reach) to 5130 for single drive application and 5230 for tandem drive application. The dealers pushed the 5130 as they would sell them for a s/a application, thereby avoiding the additon FET (Federal Excise Tax) then when they were ready to install on the truck, the dealer cut out the area ahead of the axle cut out for the 2nd drive axle. With only one drive axle you are suppose to get better fuel mileage and purchasing a used single axle is typically cheaper than a used tandem. For simple traveling and for a lot of the towing that is done, you can be legal with a single axle, but if you find yourself in need of a tandem you have one with the lift axle. One thing I always believed, and a few tow operators are now trying is a tag axle (behind the drives). The thought here is that adding air to the tag can push more weight to the steer axle which typically lightens up when towing refuse trucks, dump trucks, and other vocational trucks.

The above might have gotten a little involved, I guess I could have just said that many times a s/a is sufficent, but sometimes the weight of the casualty requires a tandem. With the lift axle you should see better fuel mileage, less maintainance, less tire & brake wear, and your wrecker is a bit lighter as well.

I posted the pic of my Ford, struggling with the concrete pumper chassis, the steer axle was actually bouncing off the ground on rougher streets. My Mack had no trouble with that broke down Peterbilt.

[RowdyRebel]

I broke down about a month ago and a Peterbilt wrecker towed me I asked the driver why do they put a pusher axle on the truck instead of making it a regular ten wheeler. The driver couldn't give me a straight answer. Keep in mind the truck was NOT a tri-axle, that I understand. The truck was a six wheeler with a pusher. Can anybody tell me the purpose of the puser axle on a heavy duty wrecker?

Depending on where that wrecker operates, it could be like that for any number of reasons. If near a tollway, by lifting that axle and running as a 2-axle truck, it saves money over time. Also, all of the empty miles the truck runs there are 4 tires that aren't on the ground wearing out...unless you've got a vehicle on the hook that makes the drive axle weigh more than 20K, the tag ain't gotta be on the ground wearin' out them tires. Also, less parts to fail...no need for a power divider or short driveshaft between the drive axles. Better traction too in adverse weather with all of the weight on the back of the truck concentrated on 4 tires instead of 8. Plus the whole tax thing being only a 2-axle truck...

I'm sure I missed more than a few others...

[Dlock13]

A single axle tow truck can pick more weight without transferring as much weight from your front axle. The difference is your overhang is measured from the center of the rear axle to the underlift/towbar on a single axle whereas a tandem is measured from the center of your tandems your basically adding half the measurement of your axle spread. The single axle runs into problems with being overweight(DOT) on the rear axle and the lack of braking unless you run an auxiliary braking devise. The truth of the matter is you need enough wheelbase to allow you to safely keep 50% of your front axle weight. The formula used to determine the safe towing capacity of your truck is as follows:

(1/2 FAW multiplied by your wheelbase) divided by the overhang

For example if you have a single axle truck that has 12K lbs on the front axle and the wb is 260" and the overhang is 90" the tow capacity is 17334 lbs

Now a tandem axle with the same weights and wheelbase but now the overhang is increased to 116"(half the typical 52" spread is added to the overhang) it drops to 13448 lbs

A tow truck is just a big lever and depending on how you set it up whether counter weighting the front end or changing the suspension setup like adding Timbren load boosters or running the air leveling valves on the rear axle allows you to cheat a little bit, but numbers don't lie.

The pusher axle allows you to cover your butt at the scale house and gives you some extra braking when needed. Some disadvantages are they can hang you up off road sometimes. It really depends on what you are trying to accomplish with the truck and what your needs are.