DRW vs SRW safety, tire blowout

[AH_AK]

Every time the DRW vs SRW debate starts up, dually owners always point to the safety of having 4 rear wheels in case of a blowout while driving. What I am wondering is has anyone actually experienced (or have first hand knowledge of) a SRW blowout that ended in a catastrophic outcome (e.g. crash)?
Obviously, the DRW is going to have better lateral stability
in cornering/cross winds compared to the SRW, but I am only considering the blowout safety aspect. While the redundant tire safety argument is logical, I am wondering how likely such blowout situations are.
To be clear, I am talking about SRW that are not exceeding the maximum tire load, are correctly inflated, and being driven within the tire speed limit. I am running 19.5’s with Firestone AT3’s so I am in this category. I realize most SRW truck camper owners are over their max tire load and yet, there is little to no documentation of blowout failures despite the obvious overloading. It makes me think the DRW blowout safety argument is essentially moot, even though it is totally logical.

[Bedlam]

So after almost 11 months of posts, the information is beginning to repeat because people do not read the entire thread. Time to close this out.

[AH_AK]

I am with you Mark. I don’t think the blowout probability on my SRW with commercial 19.5’s is high enough to worry about.

For brakes, I find my stock 1T brakes to be good as long as I don’t forget to downshift in the mountains and not ride the brakes. If I change my mind, I will buy a big brake kit.

Some of the handling characteristics are subjective. A truck that a more experienced driver would be fine in, a less experienced driver might be white knuckling. I drew out a free-body diagram for the rear axle and the rear track width and tire stiffness COULD affect rotational (body roll) stiffness, but with the addition of an anti-sway bar, you have three “springs” acting in parallel, so the question becomes, is the added stiffness of moving the tire “spring” point outboard negligible compared to the other springs. That depends on the stiffness of the other springs. I am not surprised that some people report an “outrigger effect” while others (especially those moving from heavily modded srw) do not. Depends on your specific rig/tire. Throw the dynamic aspect in there and now shocks are in play. At the end of the day, if you find you are white knuckling and thinking “oh sh*t” as the camper rocks laterally, probably time to “stiffen your springs” and or get better shocks to dampen the rocking more effectively. If cost isn’t a big factor, a 1T stock DRW seems to be a great plug-and-play option. I completely understand why so many people opt for this. If you aren’t comfortable modding your srw, then the stock drw is an even better choice.

[Grit_dog]

^Absolutely. The primary/main/#1 advantage of a dually is more tire and wheel weight capacity. And consequently less tire deflection than same load on a srw. Not static, but dynamic deflection.
#2 is usually duallies have a heavier OE suspension.

Both contribute to stability in the context of Truck campers.
It’s mostly what folks “think” make a dually more stable that is false.

Same reason when I get a new milquetoast half ton company truck with P or XL factory tires and need to load it heavy, I increase the air pressure to basically whatever makes the tires “round” in a static configuration. If that’s 10-20 psi over the max “rated” pressure, so be it.
If the tire is gonna pop from overloading it will pop whether it’s round or squishy. But it won’t generally just “pop” from over inflation or load but it will heat up and blow out more readily at the “right” pressure for the tire and the “wrong” pressure for the load.

[mbloof]

AH_AK wrote:

Photomike wrote:
If I bought a truck for a camper I would go with a DRW just to be safe.

Problem that I have is that a DRW would not go down many of the trails / roads that I like to drive on. That was the reason I got rid of my little class C. Was just to wide.

This thread has jumped all over, but the original question had to do with safety. Are DRW safer in terms of maintaining stability in a blowout situation? The answer…probably. The thing is that if the probability of a blowout is low (with quality tires) to begin with and then the DRW advantage in terms of avoiding a subsequent loss-of-control accident is relatively small, then do you care enough to upgrade your truck on these grounds? I was simply trying to get a better feel for how often accidents (loss-of-control) result from a blowout on a truck with a camper and to see if there were more SRW accidents than DRW accidents. Right now, not enough data to say. If fact, no firsthand data of an accident and only one secondhand account. The lack of data tells a story.

Maybe all the SRW folks that had accidents died in the resulting rollover, but it is starting to feel like the actual risk associated with a SRW blowout-induced accident is pretty darn low. In my case, probably low enough that I won’t consider the safety advantage in my decision to upgrade to DRW or stay with my built out SRW. There are other, non safety-related aspects that I will still consider though. Of course, to each their own.

With a bit of "googling" one might find the #1 reason that tires "blow out" is because of sidewall overheating. A bit more will indicate this is caused by ether or both under inflation and overloading.

So outside of manufactured defects and sidewall damage from running into something (#2 & #3) if you use proper PSI inflation AND pay attention to (and don't exceed) the weight rating on the side of the tire a "blowout" is rather unlikely to happen.

Would a DRW be "safer" if it actually DID happen? IMHO sure why not?

While it could be said that ANYTHING is possible personally I don't worry about stuff that is not very probable.



- Mark0.

[Grit_dog]

Nah, I looked up tire and wheel weights real quick. It’s close but depends on exact size/model etc. and someone on this forum is bound to nit pick the lack of absolute proof…lol.
Yes spring pack may be a bit heavier too. But it’s not the sprung weight that adds “much”. It’s the unsprung weight. Which the truck can handle just fine and minimal effect on braking distance either.
But when that weight becomes rotational, our little friend inertia shows up and poops all over some folks’s uninformed “theories”. (Or all those classes I paid a lot of money for to become an engineer were a farce….but I doubt it)
The 7lbs per lb is a rough rule of thumb but the point is, is rotational mass has a FAR greater effect than static mass.

[mkirsch]

If you leave it people aren't going to disregard it.

Depends on what you consider "way heavier." I'd have to get out a scale but I'd estimate a wheel-n-tire from my DRW truck to weigh about 75lbs. 16" steelies for the record. That's 150lbs. Couple of spring leafs... let's get wild and say the additional suspension adds 200lbs. That's 350lbs, which is maybe 12-13% of what an empty SRW weighs. Is that "way heavier?" Not to me.

[Grit_dog]

Disregard the last post as someone will pickup on the approximate and slightly incorrect math.
The takeaway is 4 OE tires and wheels on the back of a dually, best case, is way heavier than a typical OE srw tire/wheel combo.
And the fronts are lighter but not near as much lighter as the rear is heavier.
Period.

[Grit_dog]

jimh406 wrote:

Grit dog wrote:
the ONLY time a comparable dually is putting more rear braking force into the pavement is once a srw would lose traction, assuming the dually wont.

Of course, there is no SRW that is comparable to a DRW. You can try to cherry pick some spec to make them seem the same.

If you want to play the rotational mass game, go find the actual numbers. The front tires/wheels of typical F350 DRW that are small 17s are much lighter than the typical F350 SRW running stock 35s and 18s or 20s. I think it's likely that there is little difference in the entire rotational mass, but wouldn't be surprised if the 6 DRW stock tires don't weigh less than SRW.

You have to ignore every person who's driven both SRWs and DRWs with the same TC to believe DRW/SRWs are equivalent with the exception of two less wheels and tires. You can do that, but don't kid a kidder.

Well, taking a typical 20” OE srw alloy wheel and OE tire and drw OE outer alloys x 4 and steelies x 2.
Tires are about 10lbs less/ea x 2 = -20lbs + 2 more tires @ about 45lbs /ea so about 80lbs more rear tire.
Rims, inner drw steelies and 20” alloys are about the same plus add 2 more drw alloys at 30 lbs/ea, so about +60 lbs in rims.
All in, about 140lbs more rotating mass on the rear axle with a drw.
Front is about 20lbs lighter per wheel alloy to alloy. So -40lbs up front to the Dooley.

All in, not kidding, since I did look it up even before you suggested I do that while speculating, yourself, drw is about 100lbs more total rotating mass between both axles.
And over 100lbs more on the axle in question.
Thanks for playing….

And I never said they were equivalent. The lengths some of y’all go to to put words in people’s mouths is amazing.
He11, I’d have a dually for anything much heavier than our old AF 860 campers. Never disputed that. Just disputing the false claims. Like a dually has better brakes and stops faster …

[rhagfo]

AH_AK wrote:

mbloof wrote:

Lantley wrote:


There is always friction between road and tire.
One of the reason cars cannot stop on ice is there is no friction between tire and ice.
Sure the brake pads stop the wheel but on ice the wheel does not stop the vehicle.
Eliminate the ice and the vehicle is able to stop.

Forgetting for the moment that it is the friction between pads+rotor that ought to be slowing/stopping rather then the tires themselves here's what I had exception with:

"My dually also has more braking power, it certainly stops my trailer much faster the my SRW trucks. Again this is determined from the drivers seat not from the text book."

I'm simply pointing out that for 1T trucks the SRW and DRW have the same pads and rotors IE: SAME BREAKS.

Any implied or imagined extra stopping "power" is NOT from the breaks.



- Mark0.

Calipers and master cylinder.

Well not sure who BROKE your Brakes, but my DRW has Brakes, not Breaks. 🙂

Got to love the English language!!

[jimh406]

Grit dog wrote:
the ONLY time a comparable dually is putting more rear braking force into the pavement is once a srw would lose traction, assuming the dually wont.

Of course, there is no SRW that is comparable to a DRW. You can try to cherry pick some spec to make them seem the same.

If you want to play the rotational mass game, go find the actual numbers. The front tires/wheels of typical F350 DRW that are small 17s are much lighter than the typical F350 SRW running stock 35s and 18s or 20s. I think it's likely that there is little difference in the entire rotational mass, but wouldn't be surprised if the 6 DRW stock tires don't weigh less than SRW.

You have to ignore every person who's driven both SRWs and DRWs with the same TC to believe DRW/SRWs are equivalent with the exception of two less wheels and tires. You can do that, but don't kid a kidder.

[JRscooby]

Lantley wrote:

mbloof wrote:

Lantley wrote:


There is always friction between road and tire.
One of the reason cars cannot stop on ice is there is no friction between tire and ice.
Sure the brake pads stop the wheel but on ice the wheel does not stop the vehicle.
Eliminate the ice and the vehicle is able to stop.

Forgetting for the moment that it is the friction between pads+rotor that ought to be slowing/stopping rather then the tires themselves here's what I had exception with:

"My dually also has more braking power, it certainly stops my trailer much faster the my SRW trucks. Again this is determined from the drivers seat not from the text book."

I'm simply pointing out that for 1T trucks the SRW and DRW have the same pads and rotors IE: SAME BREAKS.

Any implied or imagined extra stopping "power" is NOT from the breaks.



- Mark0.

Your catching on. I never said it was due to the brakes. As you claim the brakes are the same.
It's do to the fact it is a DRW truck that has 2 extra wheels that gives it additional tire surface that contacts the ground!

I'm not real smart, but think without changing what surface is made of, the way to increase friction was increase area, or increase pressure. If you double the surface area, but the weight doesn't also increase, is there more friction? Next when you double the spinning mass, brakes need to absorb more energy to stop the spin.

As to the blow-out safety, can we agree the safest one is the 1 that does not happen? A issue I have not seen discussed often is something like this; Loaded heavy enough to need duals, and 1 blows out. (Even worse, slow leak) You safely get it stopped. All is good, right? Might even drive someplace to get new tire put on. But from the time the bad tire starts to loose pressure, the good tire is overloaded. (Slow leak, it can be many miles of leaky tire heating the good tire) Now that good tire may not fail today, but the damage is just like a note at the bank, it will come due. So the odds of the 2nd blow-out increase.
Then the tire wear problem; Blow-out 1 of pair that has 75% of life left in it, replace that tire. By the time the new wears down to 95%, that 75% will be gone.

[Lantley]

mbloof wrote:

Lantley wrote:


There is always friction between road and tire.
One of the reason cars cannot stop on ice is there is no friction between tire and ice.
Sure the brake pads stop the wheel but on ice the wheel does not stop the vehicle.
Eliminate the ice and the vehicle is able to stop.

Forgetting for the moment that it is the friction between pads+rotor that ought to be slowing/stopping rather then the tires themselves here's what I had exception with:

"My dually also has more braking power, it certainly stops my trailer much faster the my SRW trucks. Again this is determined from the drivers seat not from the text book."

I'm simply pointing out that for 1T trucks the SRW and DRW have the same pads and rotors IE: SAME BREAKS.

Any implied or imagined extra stopping "power" is NOT from the breaks.



- Mark0.

Your catching on. I never said it was due to the brakes. As you claim the brakes are the same.
It's do to the fact it is a DRW truck that has 2 extra wheels that gives it additional tire surface that contacts the ground!

[AH_AK]

Photomike wrote:
If I bought a truck for a camper I would go with a DRW just to be safe.

Problem that I have is that a DRW would not go down many of the trails / roads that I like to drive on. That was the reason I got rid of my little class C. Was just to wide.

This thread has jumped all over, but the original question had to do with safety. Are DRW safer in terms of maintaining stability in a blowout situation? The answer…probably. The thing is that if the probability of a blowout is low (with quality tires) to begin with and then the DRW advantage in terms of avoiding a subsequent loss-of-control accident is relatively small, then do you care enough to upgrade your truck on these grounds? I was simply trying to get a better feel for how often accidents (loss-of-control) result from a blowout on a truck with a camper and to see if there were more SRW accidents than DRW accidents. Right now, not enough data to say. If fact, no firsthand data of an accident and only one secondhand account. The lack of data tells a story.

Maybe all the SRW folks that had accidents died in the resulting rollover, but it is starting to feel like the actual risk associated with a SRW blowout-induced accident is pretty darn low. In my case, probably low enough that I won’t consider the safety advantage in my decision to upgrade to DRW or stay with my built out SRW. There are other, non safety-related aspects that I will still consider though. Of course, to each their own.

[KKELLER14K]

Whew!, this thread went all over the place, I'm back to check in. Well let me reiterate. This is about tire failure on two types of trucks right? I have had 14 Toyo tires on a DRW over a span of time. Two were recalls, which did not fail. I have had (4) tire tread separations with this particular type of Toyo tire, (3) of which I had to replace at my own cost. I gave it a chance. The marriage is over. I love good tires when they are safe and having four under the load is safer in my opinion... I already said I do not bash brands. Why do you think I had Toyo tires in the first place? It is like saying Ford makes great trucks but look back in time, they made the Pinto. I consider this many fails in my situation a safety issue and me as a consumer have gone elsewhere. I hope that clears up my opinion on tires. Now, what those tires are on is also your choice. If you cannot afford a DRW, that is understandable. I personally have had 4 trucks that have carried a TC, 3 which were SRW. I worked my way up and now have the DRW I currently have. I don't regret it, not one bit and I asked myself what took me so long to make the jump up? I'm pretty sure anyone who has or had a DRW truck wants a BIGGER DRW....LOL! Thanks everyone for the info...always love the education, that is what keeps me coming back!