Running 19.5" wheels; what about the spare?

[Ski_Pro_3]

I've got a set of Rickson 19.5" wheels recently and currently shopping for tires. In the meantime, I've been reading up about the 19.5" option and it would seem Rickson's website does not find having a spare as necessary.

Rickson wrote:
Getting a spare is not necessary, however, if the spare is worked into the rotation pattern, then the set will last that much longer. It's not a good idea to leave the spare under the truck and never run it, as the rubber will dry rot and the spare may not be any good when you need it. In most cases, the 225/70R19.5 is the only size that will fit in the factory spare location, although some 245s will fit. We recommend getting a spare if it will give you peace of mind, or if you plan on traveling to Alaska or Mexico.

So I'm wondering what other 19.5" wheel owners are doing about their spare tire? Do you carry one? If so, is it rotated or changed regularly to avoid a dry rot and worthless tire?

From my research, 19.5" tires are fairly available while out on the road. My insurance covers roadside service. There are several commercial tire dealers that are capable of dispatching and installing new tire in the field.

If I had a flat, I wouldn't attempt to change it anyways, that's why I got roadside assistance with my policy. Whether I'm towed in, a tire replaced on the spot, my spare installed or any other options I'm not thinking of, I do not think it's a safe option to try and fix a roadside flat without assistance.

Follow-up question;
How many 19.5" tire owners on their truck camper have had a flat while on the road? How did you handle the situation?

[BigToe]

Just a quick reminder that 19.5" truck tires are not invincible. I've had 4 tire blowouts in my lifetime, and 3 of them were with properly inflated 19.5" tires. If you don't have dual rear wheels, then making provisions for a spare seems like a good idea to me, even with roadside service. That way, you'll have a tire handy for them to change for you.

[Ski_Pro_3]

Kayteg1 wrote:

skipro3 wrote:
Best method is to take the tire, mark a spot and roll it one revolution, then compare to the other tire's distance it rolls in one revolution. For better accuracy, roll for several revolutions, then divide by that number for the average.

Why invent the wheel again and do it with errors?
Low speed rpm are different than rpm at 60 mph.
That is why manufacturers list rpm at set speed.

Of course RPM's are different low speed than at 60mph. That is the definition of RPMs; More and you are going faster, less and you are going slower.

Perhaps you mean distance covered per revolution? Depending on the wear of the tire and the spare, the factory specs may not be accurate. Check the actual distance covered on one revolution and compare with the other tire for accuracy and accounting for tire wear, inflation pressure.

[Kayteg1]

skipro3 wrote:
Best method is to take the tire, mark a spot and roll it one revolution, then compare to the other tire's distance it rolls in one revolution. For better accuracy, roll for several revolutions, then divide by that number for the average.

Why invent the wheel again and do it with errors?
Low speed rpm are different than rpm at 60 mph.
That is why manufacturers list rpm at set speed.

[Ski_Pro_3]

Best method is to take the tire, mark a spot and roll it one revolution, then compare to the other tire's distance it rolls in one revolution. For better accuracy, roll for several revolutions, then divide by that number for the average.

[Kayteg1]

Bedlam wrote:
Both tire sizes were the same physical diameter between my 18" Michelin LTX A/T2 and 19.5" DynaTrac PD890.

Unfortunately putting tape measure or slide caliper on tires doesn't work too well.
Rubber in tires is subject to sag under the load, change with inflation pressure and then be exposed to centrifugal forces.
That is why manufacturers list rpm for each tire model.
I have seen 2 tires with the same nominal sizes, coming from the same manufacturer and having 6% different rpm

[COboondocker]

jeffreyduncan wrote:
Also, do you think that 245/70/19.5 will fit without rubbing? I'd like to stick with the 245 because of the H load rating. Using the 225 G rated I only gain 840 pounds vs the 1,980 in the 245. Not that I will be close to that, but I'd be close to the 840 - enough that if I am spending that kind of cash I'd want to go with the extra load.

They fit just fine on our 2015 Sierra 3500.

Also here is a site that gives a great visual comparison on tire sizes. Put in your current vs desired size.

[Bedlam]

jeffreyduncan wrote:
Also, do you think that 245/70/19.5 will fit without rubbing? I'd like to stick with the 245 because of the H load rating. Using the 225 G rated I only gain 840 pounds vs the 1,980 in the 245. Not that I will be close to that, but I'd be close to the 840 - enough that if I am spending that kind of cash I'd want to go with the extra load.

You can run drive or steer on the front or rear. Open shoulder tread will make more noise up front than a closed shoulder design.

245/70R19.5 easily fit Ford and Dodge/Ram. GM trucks will require some front liner trimming or increasing the tension the on the front torsion bars to clear the fronts.

[Bedlam]

Kayteg1 wrote:

Bedlam wrote:
My 275/70R18 spare was the same height as my 245/70R19.5 primary tires. I never had to use it, but it was like insurance you hope you don't need but still carry.

Your generic rpm difference calculates to 3.8% what is below 5% that seems magic border.
go to tire size comparison. )
To make 100% comparison you should go to tire manufacturer site and pull the actual rpm numbers to compare.

Both tire sizes were the same physical diameter between my 18" Michelin LTX A/T2 and 19.5" DynaTrac PD890.

[jimh406]

On my previous truck, a SRW, my 18s and 19.5s were the the same diameter. I always planned to put the 18 on if it was ever required. My new to me truck has 19.5s all around, so the spare difference isn't an issue related to load difference although the spare could be slightly different in diameter.

[jeffreyduncan]

Also, do you think that 245/70/19.5 will fit without rubbing? I'd like to stick with the 245 because of the H load rating. Using the 225 G rated I only gain 840 pounds vs the 1,980 in the 245. Not that I will be close to that, but I'd be close to the 840 - enough that if I am spending that kind of cash I'd want to go with the extra load.

[jeffreyduncan]

Got it. Is it okay to use a drive tire up front, such as the Toyo M-608?

[Bedlam]

Actual height verses the .15" marked difference was almost identical between tires. My plan was the same to use the spare only on the front and rotate a 19.5 to rear if required.

[Kayteg1]

Bedlam wrote:
My 275/70R18 spare was the same height as my 245/70R19.5 primary tires. I never had to use it, but it was like insurance you hope you don't need but still carry.

Your generic rpm difference calculates to 3.8% what is below 5% that seems magic border.
go to tire size comparison. )
To make 100% comparison you should go to tire manufacturer site and pull the actual rpm numbers to compare.

[Bedlam]

My 275/70R18 spare was the same height as my 245/70R19.5 primary tires. I never had to use it, but it was like insurance you hope you don't need but still carry.

[Kayteg1]

Just want to make sure guys with modern trucks, having ABS and traction understand that spare with RPM (diameter) different by 5% can create some mess with the systems.