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.

[Photomike]

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.

[AH_AK]

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.

[Grit_dog]

^Bingo.
Unless you’re intentionally trying to compare a class 4 or 5 truck to a srw 3/4 or 1 ton like someone here did, a page or 2 ago….lol.
But by his logic, a semi truck ought to stop faster than a Lamborghini since it has bigger brakes and so many more tires! Lol.

One thing that hasn’t been mentioned this far in this brain trust of Defenders of the Dually is rotational mass.
First, how much more rotational mass is typically present with a pair of rear duals vs a pair of single wheels. The difference is very noticeable. Example, the heavier 37s with 20x12 rims on the ole brodozer affects braking noticeably compared to the same truck wearing little OE wheels and tires.
And second, the fact that adding 1 lb of rotational mass to a vehicle is roughly equivalent to adding 7lbs of static mass.

The fact remains, 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.

[mbloof]

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.

[Grit_dog]

^Not even sure what point you’re trying to make with that last statement but it makes sense (even though it seems obvious).
What is hard for people to wrap their head around is the friction thing. Surface area (srw vs drw) is only a small part of the equation and it’s insignificant until a srw tire reaches its limit. (The proverbial “ice.”)
For the same reasons that apples to apples, a srw get better traction in the snow, it also doesn’t get worse traction braking until it’s limit has been reached. And again the surface area of rubber on the road is both an advantage or a disadvantage depending on conditions.

Take a loaded truck lots of weight on the rear axle. One would be hard pressed to overcome the available braking force (and lock a wheel of kick in abs) in normal to hard braking.
Now move to hard braking/ panic stops.
What happens to the vehicle? A significant amount of weight/ force is transferred forward to the front axle, unloading the rear axle to whatever extent. (Like on a bike you can do a stoppie, picking up the rear axle).
This is the one condition where duals may out-brake a srw. You’re on the brink of or have lost traction and the additional rubber on the road will help.
But at that point, the advantage may be of diminished return. Or in the case of a TC, you’d still be hard pressed to exceed the available braking force of the srw due to sheer weight. Maybe wet pavement? However if that much weight is transferred, the rear wheels aren’t doing much of the braking at that point anyway.
There are many other factors. But the fact is, the primary reason for dual rear wheels on a pickup is for greater tire/wheel load carrying capacity. The tires and wheels in and of themselves don’t provide more stability (except by default due to much less tire flex) or braking force.

[Lantley]

mbloof wrote:

StirCrazy wrote:

mbloof wrote:

Lantley wrote:
No dog in this fight but actual experience always supersedes text book theories
My dually is more stable than my SRW trucks.
Is it the out rigger effect or is it stiffer sidewalls? Does it matter? From the drivers seat I can feel a noticeable difference.
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.

Funny as if you look at the actual part numbers for the DRW and SRW breaks guess what?

They are the same.

So much for "seat of the pants" theories... 🙂

Enjoy your DRW, for whatever reasons you have.



- Mark0.

your forgetting a few things, there is twice as much rubber touching the ground in the back so twice as much friction against the road.

in your previous post about spring mounts being narrower vs side walls if that was all that was inolved you would be right but DRW also have a heavier spring pack so theres that also you forgot about..

I have a SRW myself but there are times I wish I bought a DRW just for the higher load carring capacity.

Your forgetting that the width of the tire(s) has no bearing on the breaking distance - until they begin skidding - THEN the increased friction of the wider tire patch comes into play.

You also failed to read my prior post. I mentioned having the SAME springset (and assumed same mounting position as there is no difference between SRW and DRW trucks when it comes to spring pack location).

Yes SOME (not all) DRW's have heavier spring packs. Keeping in mind that almost ALL camper owners modify their suspensions regardless if they have a DRW or SRW AND most would not buy a DRW simply for the stiffer springs IMHO your point is moot.



- Mark0.

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.

[Buzzcut1]

having had a rear tire blow out ( full disintegration not a slow loss of air) on both a F350 SRW and and F350 DRW at freeway speed with a 4600 pound Lance 1055 in the bed. I can honestly say that controlling the vehicle an bringing it to a full stop in the DRW was a piece of cake. The SRW was a white knuckle affair to keep from rolling and I am a trained Emergency Vehicle operator (fire engines and ambulances). I will stick with DRWs

[Grit_dog]

jimh406 wrote:
Warning .... some satire follows.

SRWs are just as stable as DRWs and brake just as well. Springs are the same as well. That's why the DRWs have more payload. You could get the same payload by doing a second tire on each side with a kit. You can ignore everything but the tires/wheels.

There are no brake differences. Brakes are just discs and pads. It doesn't matter that DRWs don't usually have the same calipers as SRWs. Calipers don't matter. DRWs also are rated to tow more even though the brakes are identical.

The disc diameter is different on F450s and up compared to SRWs. Doesn't make any difference. They might use the same brake pads.

No satire follows ...

There could be a conspiracy to convince people to buy DRWs. Or, there may be something to the differences since so many people can tell the difference and note it.

Finally, buy what you want, but don't make things up to try to justify your reasoning. There are good reasons to buy a SRW just like there are good reasons to buy a DRW. YMMV.

That was a lot of words to say “I don’t know what I’m talking about.”

[jimh406]

Warning .... some satire follows.

SRWs are just as stable as DRWs and brake just as well. Springs are the same as well. That's why the DRWs have more payload. You could get the same payload by doing a second tire on each side with a kit. You can ignore everything but the tires/wheels.

There are no brake differences. Brakes are just discs and pads. It doesn't matter that DRWs don't usually have the same calipers as SRWs. Calipers don't matter. DRWs also are rated to tow more even though the brakes are identical.

The disc diameter is different on F450s and up compared to SRWs. Doesn't make any difference. They might use the same brake pads.

No satire follows ...

There could be a conspiracy to convince people to buy DRWs. Or, there may be something to the differences since so many people can tell the difference and note it.

Finally, buy what you want, but don't make things up to try to justify your reasoning. There are good reasons to buy a SRW just like there are good reasons to buy a DRW. YMMV.

[mbloof]

StirCrazy wrote:

mbloof wrote:

Lantley wrote:
No dog in this fight but actual experience always supersedes text book theories
My dually is more stable than my SRW trucks.
Is it the out rigger effect or is it stiffer sidewalls? Does it matter? From the drivers seat I can feel a noticeable difference.
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.

Funny as if you look at the actual part numbers for the DRW and SRW breaks guess what?

They are the same.

So much for "seat of the pants" theories... 🙂

Enjoy your DRW, for whatever reasons you have.



- Mark0.

your forgetting a few things, there is twice as much rubber touching the ground in the back so twice as much friction against the road.

in your previous post about spring mounts being narrower vs side walls if that was all that was inolved you would be right but DRW also have a heavier spring pack so theres that also you forgot about..

I have a SRW myself but there are times I wish I bought a DRW just for the higher load carring capacity.

Your forgetting that the width of the tire(s) has no bearing on the breaking distance - until they begin skidding - THEN the increased friction of the wider tire patch comes into play.

You also failed to read my prior post. I mentioned having the SAME springset (and assumed same mounting position as there is no difference between SRW and DRW trucks when it comes to spring pack location).

Yes SOME (not all) DRW's have heavier spring packs. Keeping in mind that almost ALL camper owners modify their suspensions regardless if they have a DRW or SRW AND most would not buy a DRW simply for the stiffer springs IMHO your point is moot.



- Mark0.

[Grit_dog]

This thread needs to DIE!

[StirCrazy]

mbloof wrote:

Lantley wrote:
No dog in this fight but actual experience always supersedes text book theories
My dually is more stable than my SRW trucks.
Is it the out rigger effect or is it stiffer sidewalls? Does it matter? From the drivers seat I can feel a noticeable difference.
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.

Funny as if you look at the actual part numbers for the DRW and SRW breaks guess what?

They are the same.

So much for "seat of the pants" theories... 🙂

Enjoy your DRW, for whatever reasons you have.



- Mark0.

your forgetting a few things, there is twice as much rubber touching the ground in the back so twice as much friction against the road.

in your previous post about spring mounts being narrower vs side walls if that was all that was inolved you would be right but DRW also have a heavier spring pack so theres that also you forgot about..

I have a SRW myself but there are times I wish I bought a DRW just for the higher load carring capacity.

[Grit_dog]

SoonDockin wrote:
I feel more tires is better, also bigger is better. Its why I went from a F350 Single to a F450 Dually and now a 5500. F450 was super stable, 5500 takes it to a whole new level.

And a bit of new-truckitis I suspect. Although financially the last few years has been unusual so I suspect there was a bit of incentive with the ridiculously high values of your previous trucks?

[Grit_dog]

Lantley wrote:

Lantley wrote:
No dog in this fight but actual experience always supersedes text book theories
My dually is more stable than my SRW trucks.
Is it the out rigger effect or is it stiffer sidewalls? Does it matter? From the drivers seat I can feel a noticeable difference.
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.

Yes but I have 2 extra tires transferring that braking force to the ground.
For the same reason I believe SRW trucks perform better in snow because they have less ground contact and dig/sink into the snow for better traction. DRW trucks have more ground contact and brake better. All my comments are from real encounters from the drivers seat not from trying to match part numbers or derived from what I think might happen.
Once you have experienced the performance first hand from the driver's seat, you no longer have to imagine what will happen.

You’re still being credulous here, imo. I too have driven and towed with countless duallies and srw trucks. And I don’t recall that general behavior. If thinking apples to apples for comparisons.

But it’s fine. We all have our own views and opinions. Cheers!

[Grit_dog]

greenno wrote:
Gdog I have a hard time believing that I should be running 35psi in my rear tires.
I could probably drop the front a bit more but I'm thinking not 15psi.
I have pretty even wear across the tire tread so I know I'm close to having a flat surface on the road.
Side treads as well as the centers were about the same so it's not crowning.

Have you ever viewed a load vs pressure chart for your size tires? If you had, you would not have a hard time believing what I told you.
Min safe pressures for all conditions (not talking aired down for off road traction) for a truck your size (unloaded) with that size tire is actually 40F/25R. But that’s a little squishy. It’s a good pressure to run for the best traction on snowy roads.
When you have the camper on, different story due to weight on the rear axle and even though the front axle weight does not change appreciably (generally), bumping the front pressure up some from what is necessary helps with minimizing tire flex due to body roll with the camper.

Good to hear your tires aren’t wearing prematurely due to being over pressure when empty.
I’d surmise that most of your miles are loaded and not empty highway miles though. As that is enough pressure to balloon the tires a bit. Especially the rear.