Carry a spare in your dually?

[Far Raider]

I've got an ambulance body 4x4 F350 dually that I am building up and when I bought it this summer it did not have a spare, so I bought one. Since then I have spent way too much time thinking about the best place to put it and how to secure it. Lamenting this in a conversation with a friend he asked why I needed one since I've got six wheels and can run one in the rear until I get to a shop if I can't plug it. After thinking about it, I started to doubt my "need" for a spare and thought I would posit the question to the vastly more experienced dually owners on this site. Is this a crap idea or a brilliant way to save weight and space?
Thanks,
FR

 

[Joe917]

The reason for dual rear wheels is tire load. Design axle weight exceeds the maximum load capacity of a single tire so duallies are required. What happens when you lose one? The remaining tire is overloaded as much as double its capacity. Leading causes of tire failure are overloading and under inflation. How far do you want to limp like that?
Best option, go to single rear wheels in a tire size that can take the build weight and get a spare.
Worst option, stay with the duallies no spare.
Probable choice, stay with duallies get a spare.

 

[2025 deleted member]

Unless your pulling a heavy trailer I would skip the spare. If you have good tires, it should carry the load fine with 3 across the back axle. I would weigh the truck and look at the tire ratings.

I've ran on a single on a dually around town for a day with a heavy bed and it was fine.

 

[Happykamper]

Ahhhh one time I disagree with planejane lol . I always have a spare on dually 4x4 chinook motor home . And on my ford ! Never can tell. The ford I rack two on a custom rack in the back.
Where it isn't fine is when that ambulance or in my case the chinook is off-road . Or for that matter anywhere . As mentioned they are built with four in the rear for a reason. Overkill , maybe.....but for the price of a spare or two . Your going to be glad you did if anything goes awry !

 

[dlh62c]

Look into installing a receiver hitch on the front and carrying it up there. You'll need a bottle jack and a torque multiplier to break the nuts loose.

 

[nick disjunkt]

I've had a rock wedged between the twin tyres at the back which ruined both tyres on that side. Something to bare in mind.

 

[2025 deleted member]

Also something to think about. A new tire and someone to install it is just 250 bucks for a generic tire and a 1 hour wait usually for roadside service in most of the USA. Doesn't apply offroad obviously.

 

[IdaSHO]

I see zero reason to not carry a spare.

If you get a flat, even on a diesel, you still have to remove the wheel/tire to continue driving, so you might as well replace it with a good spare when you are there.

 

[Far Raider]

OK, I'm convinced, especially since I do plan on roaming about south of the border. It is getting bolted down, under the bed. Sigh.

 

[2025 deleted member]

I see zero reason to not carry a spare.

If you get a flat, even on a diesel, you still have to remove the wheel/tire to continue driving, so you might as well replace it with a good spare when you are there.

I've driven 10o miles at speeds up to 75mph with one flat on a dually and it had zero issues on truck or tire. This was a nail hole flat, I wouldn't do it with a separated tread or something that would destroy a fender.

 

[dlh62c]

Getting a rock stuck between the rear duals can happen.

https://youtu.be/DFs7fiYXSzQ

In a muddy track, the duals will load up with mud.

 

[Bikersmurf]

I ran for a spare for almost 2 years... I'm glad to now have one pulled up under the rear with a hand winch. Yes you can run on 5, but if you're going out of the city limits I wouldn't.

 

[pappawheely]

I have singles and plan to carry two spares. I hit a huge pothole one time in my lowered street truck that took out both wheels on one side. I just so happened to be in bfe with no cell coverage. Two is one and one is none. The guys who rescued me hit the same hole, it was dark, but they had a prerunner and 39" bfg project tires. If they felt it in that, you know it was bad.