Good Sam Club Open Roads Forum: Tow Vehicles: SRW vs DRW
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 > SRW vs DRW

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BenK

SF BayArea

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Posted: 05/16/21 01:05pm Link  |  Quote  |  Print  |  Notify Moderator

Double sigh...

There are many other variables that come into play that this discussion hasn't even touched on.

Like the crevices of asphalt pavement comes into play. when tire compound gets mushed into them...coefficient of friction is not in play. As it is now interference & potential tearing of the compound off of the tire...or pulling out that gravel/stone from asphalt.

There is also a temperature component and not what one might think. It has to do with the boiling of tire compound during a skid or extremely high rate of change between pavement and tire compound...it can and does boil the tire compound for an instant to lay down those black marks that only come off over time via wear.

How's about the braking system components...like the brake's friction material ?

And etc, etc...

Not all of these kinds of tests are with EVERYTHING the same.

philh wrote:

{sigh}

This is not a simple friction equation. In general, given the same weight, frictional forces do not change with contact area.

Turn off traction control and I can guarantee the brakes will lock up the wheels, no matter if it's DRW or SRW

Where it really gets complicated, unloaded DRW, vertical load on contact area is less than SRW. Loaded, the weight increase means DRW will stop faster... but even that gets confused with trailer brakes entering the picture. I most certainly wouldn't to do a panic brake stop without trailer brakes, jack knife comes to mind.

This is best seen on snowy surfaces, wider tires have lighter vertical load and subsequently less traction.

Bottom line, while towing, DRW has the capacity to stop in a shorter distance on dry roads. While not towing, SRW might stop faster.


Plus there are FMVSS MINIMUM stopping distance spec's for all automotive

So splitting hairs, as all OEM vehicles has to meet DOT/FMVSS guidelines.


This image from their site years and years ago and assume the distances listed have changed
[image]
[image]Click For Full-Size Image.

* This post was edited 05/16/21 01:14pm by BenK *


-Ben Picture of my rig
1996 GMC SLT Suburban 3/4 ton K3500/7.4L/4:1/+150Kmiles orig owner...
1980 Chevy Silverado C10/long bed/"BUILT" 5.7L/3:73/1 ton helper springs/+329Kmiles, bought it from dad...
1998 Mazda B2500 (1/2 ton) pickup, 2nd owner...
Praise Dyno Brake equiped and all have "nose bleed" braking!
Previous trucks/offroaders: 40's Jeep restored in mid 60's / 69 DuneBuggy (approx +1K lb: VW pan/200hpCorvair: eng, cam, dual carb'w velocity stacks'n 18" runners, 4spd transaxle) made myself from ground up / 1970 Toyota FJ40 / 1973 K5 Blazer (2dr Tahoe, 1 ton axles front/rear, +255K miles when sold it)...
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fj12ryder

Platte City, MO

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Posted: 05/16/21 02:39pm Link  |  Quote  |  Print  |  Notify Moderator

I believe the basic premise is, all things being equal: tires, surface, brakes, etc., a DRW will stop shorter than a SRW. Yes, there are tons of different parameters, but ignore them and consider everything is the same for both trucks.

Heck, pull two of the rear duals, check the sopping distance, put the duals back on and recheck the stopping distance over the same surface. That should give a decent answer?


Howard and Peggy

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Mike134

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Posted: 05/16/21 02:48pm Link  |  Quote  |  Print  |  Notify Moderator

fj12ryder wrote:

I believe the basic premise is, all things being equal: tires, surface, brakes, etc., a DRW will stop shorter than a SRW. Yes, there are tons of different parameters, but ignore them and consider everything is the same for both trucks.

Heck, pull two of the rear duals, check the sopping distance, put the duals back on and recheck the stopping distance over the same surface. That should give a decent answer?


Best answer so far.


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Lantley

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Posted: 05/16/21 03:01pm Link  |  Quote  |  Print  |  Notify Moderator

Boy we can get off track. Will a SRW make a better Mars Rover? What happens if the streets are full of molten Lava?.....We don't need to examine kinds of "What if's"
The discussion doesn't have to be so complicated.
Remember this is the towing forum. The DRW will brake better than a SRW while towing a heavy load under similar conditions.


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fj12ryder

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Posted: 05/16/21 04:31pm Link  |  Quote  |  Print  |  Notify Moderator

Lantley wrote:

...
The discussion doesn't have to be so complicated.
Remember this is the towing forum. The DRW will brake better than a SRW while towing a heavy load under similar conditions.
It gets complicated because not everyone believes as you do. Lots of different opinions. Yours is just one...which I happen to agree with.

blt2ski

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Posted: 05/16/21 05:46pm Link  |  Quote  |  Print  |  Notify Moderator

Assuming we are disCUSSing DOT class three trucks,a DW will stop and carry more than a single wheel setup.

If you want to disCUSS class 8 trucks DW vs super singles. The singles win!

So assuming both rear axles have the same braking, springs, tire capacities, same sq inches of tire on the road, singles are better generally speaking

Marty


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blofgren

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Posted: 05/17/21 08:49pm Link  |  Quote  |  Print  |  Notify Moderator

Sagebrush wrote:

Your also not pushing the rear tire's load ratings of a DRW like a SRW. Even with a 4k or 5K pin weight. Using the tire load charts or even the truck's door sticker for max payload I've never needed to air up my DRW to the tire's 80 psi max. My max payload rating needs 65 psi in the tires. Its nice to have those rear tires well within their load capacity.


Yep, and the lower pressure in the rear tires makes for a better riding truck.


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pressure_welder

brandon

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Posted: 05/23/21 09:24am Link  |  Quote  |  Print  |  Notify Moderator

You know guys... not sure why iam so concerned with going to a srw... on a pipe job today figured id check payload capacity of my 07 5.9, yep! 4705lb payload and 15,750 max tow so iam already pushing the hell out of this dually. When were pulling camper/boat we MIGHT be within that max tow number as boat is rolling resistance. But as for payload.... lol. I have my tool boxes with maybe 250lbs of tools, 60 gallons in slip tank, oxy/acet bottles, 900lb welder, andersen hitch if that even counts at 30lb, and of course a 1000lb welding bed. I have air bags so she sits level, and truck still handles rig perfectly fine. But 2017 and up srws certainly “as a rule” have more payload and towing capacity than i currently have, and garunteed better braking. Only thing they wouldnt have is stability lf dually

In reality ive towed alot more than our camper/boat on our 40ft gooseneck.

* This post was edited 05/23/21 10:15am by pressure_welder *


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