DRW vs SRW safety, tire blowout

Lwiddis wrote:
Any advantage of DRW trucks regarding blowouts can’t be discussed in a vacuum IMO. The extra cost, lower MPG, width inconvenience etc. need to be factored into the discussion. But if you need the weight carrying availability, discussion over.

As one who has converted a SRW Truck to a DRW through running gear/axle changes, here's my own personal experiences and thoughts regarding this:

1.) Extra Cost
Additional Options when purchasing new always cost more, same goes for Diesel vs Gas engines, Regular Cab vs Extended Cab and so on, so on that front its more of a moot point since its simply an option cost, a DRW axle is generally a stronger piece of equipment in terms of Bearings, load bearing capability braking capacity, etc.... than a SRW, so it costing more as an option is entirely logical.

In terms of Maintenance costs, that comes down to having two more tires to replace at serving time. Other consumable parts, like brake pads/shoes brake drums are generally not immensely different in terms of after market replacement parts, usually a little more, but not drastically more.

2.) MPG

Fuel economy is somewhat negligible, as the actual larger MPG differences are more likely visible from different axle gear ratios (usually 4.10s, 4.11s, 4.56s are more common on DRW trucks vs SRW trucks off the lot) vs the rolling resistance of the extra two tires.

From my own real life experience where the same truck with an axle swap done, but the gear ratios remained the same and having gone from SRW to DRW, the total change in normal MPGs was around 0.2-0.4 mpg from the extra mass spinning.

This is with a pre-Multi-port modern Fuel injection system and on an older style TBI gasoline engine. If the truck had the diesel engine, the recordable difference between the two would likely be even smaller as the diesel power plant from the same era was vastly more fuel efficient than its small block V8 counter part.

3.) Width inconvenience
This one is highly subjective, and comes down more to the personal driving skills of the operator and less down to the extra tire width.

I've actually found length to be more of a challenge with my own truck, as its a Extended Cab truck, and the 4x4 package of the era made the turning radius very wide.

The only thing I had to relearn was to accomodate slightly for the rear wheels in very tight driveways and that was simply altering my turning rate slightly, but you can have the same issue going between different sized vehicles in general, even without the extra rear tires of a DRW truck.

In terms of parking, the DRWs are usually not the limiting factor but length of the space and width of the driveway between spots. Alot of businesses that are new have very narrow pathed parking lots, meant for small cars, and even when my truck was still SRW, the same problem was present due to the parking lot design.


4.) Blowouts
The original subject of the thread :), if one has a blow out on the front tire, the experience SRW or DRW will likely be the same.

On a rear tire, with a blowout, the experience will be different, as a SRW will pull much harder to one side in this scenario than the DRW will, as the DRW still has a tire on the failed side bearing the load and keeping even contact with the road way. That is not to say that the vehicle will not still potentially pull to that side some due to the additional resistance of the blown tire, but the immediate impact will be less.

As another poster note before me, on medium duty/heavy duty gear its easy to miss a duals blow out and why they normally check for low tires by "pinging" them with a hammer or other object to listen for the telltale sounds of a low inflation or flat tire.

I adopted the same practice when hauling my camper, especially on longer trips to use the "hickory stick" I keep in the truck to thunk the inner and outer duals and listen for pitch changes to discover if one is losing air.