put my 19.5s on today

pjay9 wrote:
don't they use the same axel on different models...cost economy of manufacturing sort of thing!

Yep, but not on trucks that come with 19.5s from the factory. As far as I know, ALL of them come with larger rear axles than 1 tons do.

AH64ID wrote:

Aside from tires do you the know the only difference between my SRW and a DRW of the same year? The main leaf pack of the DRW is rated 7% higher, that's it! Everything else you listed is identical. Ford and GM do similar things.

But they're not identical. Because they are located on a truck that has a different stance. A truck is not merely the sum of its parts.

Why do is everything a DRW and not a super single SRW? There is a minor benefit to the width, but one is generally above GVWR at that point.

Over what GVWR? No doubt the DRW GVWR has its most significant connection to the two additional wheels and tires, but once again, a truck is not merely the sum of its parts

There is also public perception, same reason the all new powerstroke was made a V-8 when OTR trucks have shown us an I6 is better.

Engineering does not depend on public perception. Marketing might.

A V8 diesel has advantages in a pickup that don't exist in an OTR rig. The first is weight. A V8 has a shorter block with fewer main bearings and other heavy components. I don't have the numbers off the top of my head, but it seems intuitive that an engine that is smaller will weigh less.

The second is displacement, and more specifically, stroke. V8 diesels have wider powerbands than I6s when used in this application. That's one thing I noticed immediately when comparing the trucks when I was shopping--the Cummins has a far narrower powerband than the Ford or Chevy.

Which is "better" for a particular application is complex and not a simple answer. An I6 is probably better for OTR because there is plenty of room, the weight doesn't really matter, and the increased number of bearings makes for less stress over the long life of an OTR truck. Many of these factors are different in a pickup, which has a much shorter useful life and can benefit much more from a lighter weight engine.

As with all engineering problems, cylinder configuration is a tradeoff, not a slam dunk.

Tire cost is another, as well as ride. My 19.5's ride petty good compared to my LRE's, in fact I prefer the ride in most conditions, but they are not what most people want from a ride. They also carry a 75 mph speed rating, lower than the rural interstate speed limit out here.

And with 3.55, 3.73, or 4.30 gears, that could be an issue. On a Class 4 or 5 truck that comes with 4.88s, it isn't as much of an issue. Either way, a non-commercial truck with a 75 mph speed rating probably isn't something that the NHTSA would be too fond of.

...

You can see there isn't a lot of difference, and certainly nothing a pair of airbags can't handle for a SRW.

By that logic, there would be no meaningful difference between my own truck with 19.5s on it and a DRW truck with E rated tires. The comparison is also apples to oranges, because no DRW 1 ton--nor any 1 ton for that matter--comes with 19.5" tires.

I have not argued that airbags and heavier duty tires don't make a difference--they clearly do and I have them on my own truck. But to suggest that even if the frames, springs, overloads, etc. were identical, that a DRW isn't safer with a heavier load than an SRW--even an SRW with tires that aren't overloaded--is to once again miss a key point: a truck is not merely the sum of its parts.

It should not go unnoticed that NO light truck comes with 19.5s, and the trucks that do come with 19.5s use heavier rear axles than a 1 ton truck.

Perhaps ideally, the manufacturers would start making Class 4 and 5 trucks with 3.55 or 3.73 gears so that they were capable of carrying a heavy load but yet not designed for pulling so much. A Ram 5500 loaded at 15k lbs GVW doesn't need 4.88 gears. Along with the heavier duty wheels and tires, you'd get the suspension and rear axle designed for the GVWR necessary for the heaviest campers.

Me personally, I'd still rather have a 1 ton for my use, for ground clearance and for traction since E rated tires are softer and grippier in general than that which is available in 19.5 sizes. But the reason I say that is that my camper is light enough that I can stay within a 1 ton's GVWR if absolutely necessary.

Those of you with campers that are technically too heavy for any light duty truck have no choice but to either band-aid a pickup into handling the load or buy a Class 4 or 5 truck. I don't blame you for putting 19.5s on a 1 ton and rolling on, since that gets you the gearing for the highway, components that are probably capable of handling the load anyway, and tires and wheels that will certainly handle the load. But don't make the mistake of believing that installing Class 4 or 5 tires makes a pickup into a Class 4 or 5 truck. It doesn't. It just makes an overloaded pickup minus its weakest components.