Tires (the weakest link)

[AH_AK]

Like every other truck camper owner, I am looking to increase the safe load carrying capacity of my truck (2012 Chevy 3500HD SRW). I get that you can't increase the payload, but I also know that 90% of TC's on the road are overloaded (some egregiously) and you don't hear a lot about catastrophic failures. I imagine this is likely thanks to the healthy factor of safety that auto- and tire-makers build into their designs. Perhaps the nature of heavy haul driving (slow, cautious) helps to provide an additional buffer.

When I looked into the limiting factor for the payload, it appears to be the tires. The wheels, axles, suspension, and brakes all seem capable of handling a larger GVWR/GAWRR. Handling (sway, squat, etc.) is a different beast, but can be addressed with upgrades. So here is the rub (pun intended), my truck is very limited in terms of upsizing the tires ( with the intention of bumping the load index). I considered Rickson 19.5x6.75 wheels with 225/70r19.5 G or H tires, but Rickson is sort of MIA in terms of communications...also $$$. Vision wheels would be great, but the 19.5x7.5's can only run 245/70r19.5 and I am told they will rub...also $$$.

So I start looking for load range F tires in the stock size (265/70r18) and I find that one company makes them https://www.prioritytire.com/kanati-armor-hog-atx-lt-265-70r18-127-124q-f-12-ply-at-a-t-all-terrain-.... Now these get me to a load index of 127, which I am satisfied with, but they have a speed rating of Q (99mph). No worries, I am not planning on racing around with my TC. Looking at S-rated (112 mph) tires, the absolute largest I can fit without lifting the truck is 275/70r18, and the load index is only 125 on these.

This gets me thinking about the basis for the load index and I find this http://www.trucktrend.com/how-to/towing/1407-understanding-tire-load-ratings. Apparently, it is based on temperature, which is a function of load, speed, materials/mass, pressure, and ambient conditions. So hypothetically, if I commit to never driving faster than 60 mph, would I actually have a greater factor of safety on the 125 index, S-rated tires due to the additional speed margin? I wonder if these calculations are done by tire makers using models, or, if they physically test every model.

Now before you all light me up: YES, I know I could buy a dually. YES, I know I could buy a smaller camper. YES, I know I can reduce the driving weight by emptying tanks and lightening my gear load. YES, I know that I can just relax and the extra 200-300 lb per tire probably won't kill me and my family. I am genuinely curious as to what these tires can handle practically speaking. I also believe that the more you know about the likely cause of failure (e.g. overheating) the better you can manage you operations to mitigate risks (e.g. drive slow/empty tanks when it is hot).

The tread on those Kanati's is probably going to wear fast, but the steel construction and the increased load index are awfully tempting. Plus, I don't need to solve the Rickson puzzle to actually buy them. What say ye?

[JimK-NY]

AH_AK wrote:
......
Alas, I am slowly caving to the idea of 19.5's. The more I think about it, committing to using a very niche tire (Kanati) is probably a bad idea long term. While I may not end up being a fan of the stiff ride or the cost of the 19.5's, the tire options are numerous.

I think I just needed some time to marinate on the investment......

While you are marinating this idea, do not forget that 19.5 tires are likely to greatly outlast OEM sized tires. If feasible in your area, they are also made to be recapped. In addition to the added safety, long term they might actually be lower cost.

[AH_AK]

Bedlam wrote:
It comes down to where you use your truck (do you need flotation) and how heavy you will be loaded. I was putting 8000 lbs on the SRW rear axle which stopped me from using LT or even the smaller 225/70r19.5 tires.

Practically speaking, if I have a 4000lb truck camper on my SRW, I am not going to be taking my truck anywhere too extreme.

I was really just looking for a solution that would let me keep my current wheels while increasing my safety factor on my tires, and avoiding the learning curve associated with commercial tires.

Alas, I am slowly caving to the idea of 19.5's. The more I think about it, committing to using a very niche tire (Kanati) is probably a bad idea long term. While I may not end up being a fan of the stiff ride or the cost of the 19.5's, the tire options are numerous.

I think I just needed some time to marinate on the investment. It helps that I found a freight forwarder that can get the wheel to AK for $350 (rather than $1200 FedEx).

I am still curious about the practical load limitations of OEM steel wheels. I would just hate to "experiment" with my family in the truck with me.

[Bedlam]

It comes down to where you use your truck (do you need flotation) and how heavy you will be loaded. I was putting 8000 lbs on the SRW rear axle which stopped me from using LT or even the smaller 225/70r19.5 tires.

[AH_AK]

Bedlam wrote:
I have destroyed off road vehicle rims pushing a vehicle over rocks and logs, but have not broken a rim on the road. This is not to say it does not happen - I have seen a cast rim fail in front of me when a truck turned to pull into a parking spot and considered him lucky that it was not at speed. There also pictures posted here of steel rims separating from the vertical center, so don't think that steel gives you more reserve capacity. Method rim models like the 305 NV HD or 701 HD are rated at 4500lbs.

If you need the ability to air down for flotation, These 4k lb rated LT tires with upgraded rims may be for you. If you need a high capacity tire that is more puncture resistant and longer wearing, the move up to 19.5's is worth it and about the same cost.

Right you are. The HD rims have a higher rating. I still think the OE steelies will handle a few hundred extra pounds each. The nice thing with sticking to 18s is I can buy the tires put them on OE wheels and upgrade to Methods later. The switch to 19.5 is committing and requires the full investment up front.

[Grit_dog]

Bedlam wrote:
I have destroyed off road vehicle rims pushing a vehicle over rocks and logs, but have not broken a rim on the road. This is not to say it does not happen - I have seen a cast rim fail in front of me when a truck turned to pull into a parking spot and considered him lucky that it was not at speed. There also pictures posted here of steel rims separating from the vertical center, so don't think that steel gives you more reserve capacity. Method rim models like the 305 NV HD or 701 HD are rated at 4500lbs.

If you need the ability to air down for flotation, These 4k lb rated LT tires with upgraded rims may be for you. If you need a high capacity tire that is more puncture resistant and longer wearing, the move up to 19.5's is worth it and about the same cost.

^ What he said. Have seen the odd failure or 2 of OEM light truck rims and have also worked in an industry that uses HD pickups as (often abused) tools for 25 years, including personally hauling things that I would never recommend as prudent to anyone.


To the OP's point of...
" To be clear, I am talking about their real capacity, not the rated capacity. I could never find an official rating above 3600lb, which makes sense since the GAWRR is 7050 lb. Seems like most components on these trucks are overbuilt to account for the inevitable abuse and dynamic loading that owners throw at them."
...I fully believe this to be a true statement and believe that large mfgs (like auto mfgs) carry ALOT of liability (obviously) and with that will and do design critical components with a high liability if they fail (like rims) to withstand a certain degree of stupid human tricks above and beyond their rated capacities.
Right wrong or indifferent, I am comfortable dipping into that "factor of safety" a little bit, not totally out of ignorance, but somewhat out of understanding of engineering principle and somewhat out of practical experience and others' experiences.

Again, not a recommendation, but rather sharing an opinion.

If going for dual duty, daily driver and heavy hauler and fully rated 4000lb or more tires and wheels that could double as something comfortable to drive on empty and the ability to air down for different conditions, I would 100% get Method HD wheels and any number of 3900-4000lb rated light truck tires.

[Bedlam]

I have destroyed off road vehicle rims pushing a vehicle over rocks and logs, but have not broken a rim on the road. This is not to say it does not happen - I have seen a cast rim fail in front of me when a truck turned to pull into a parking spot and considered him lucky that it was not at speed. There also pictures posted here of steel rims separating from the vertical center, so don't think that steel gives you more reserve capacity. Method rim models like the 305 NV HD or 701 HD are rated at 4500lbs.

If you need the ability to air down for flotation, These 4k lb rated LT tires with upgraded rims may be for you. If you need a high capacity tire that is more puncture resistant and longer wearing, the move up to 19.5's is worth it and about the same cost.

[AH_AK]

Bedlam wrote:

AH_AK wrote:

Bedlam wrote:
Method makes some higher rated rims in LT tire sizes. 245/70r19.5 will fit the GM, but you may need tie back the fender liner up front or use a leveling kit to prevent rub at full lock. My Vision rims worked well, but I did not have a GM. American Force also makes high weight rated 19.5" rims - they have many patterns but a price that rivals or exceeds Rickson.

I would be fine with modifying the fender, but I'd rather not mess with the suspension/steering geometry (if I can help it). I wonder how often rub at full lock will actually be an issue anyway. I suppose it'd just be annoying when I forget and try a K turn. I am only seeing wheels on Method's site not tires. I looked at American Force, but they only seem to have 19.5x7.5 and looks like they have the same offset as Visions, so they might rub. I could likely trim the fender and get rid of the rub, but I'd almost certainly save some $$ and go with the visions if I am ready to trim.

I pointed to Method to get higher rated rims in 16-20" to go with some of the LT tires rated over 4000 lbs. The GM OEM rim ratings are typically less, so going to tires that exceed the rim capacity may help with ride, but will not give you more capacity than the lowest rated component.

In my case, I was running a SRW with 8000 lbs or rear axle weight which is why I went the 4500 lb rated Vision rims but then I went 245 H-rated tires that were over 5000 lbs to get the handling and tire strength I wanted.

You do not need to trim the metal fenders on the GM to fit 245/70r19.5 tires, but the plastic fender liner may interfere unless worked back a little.

Ahh I see. I was under the impression that the OE steelies had a significant safety factor. To be clear, I am talking about their real capacity, not the rated capacity. I could never find an official rating above 3600lb, which makes sense since the GAWRR is 7050 lb. Seems like most components on these trucks are overbuilt to account for the inevitable abuse and dynamic loading that owners throw at them.

When I started poking around unofficial sources, the consensus was that GAWRR was limited by the tires rather than the wheels and that the steel OE wheels could handle more. These were not engineers making this assessment but people that had towed heavy and not experienced yield or cracking of the wheels. Obviously, this is a pretty bootleg justification, but if I go with my stock tire size and the kanati armor hogs, then I will only be at 3860 lb per wheel. I would be amazed if those OE steelies can’t handle that. All this is assuming that the beads can also take the 95psi pressure that these tires will require. Again, the internet consensus is yes. Do you have specific info on OE failure that suggest that my assumptions and unofficial info are wrong? If so, I would love it of you’d share your source.

If I were planning to go up to 4500 I might be more concerned about the wheel capacity. Looks like all the methods with 8x180 r18 are rated at 3600 lb.

Thank you for confirming that the 245/70r19.5 will fit. Looking at it and measuring, I was thinking the same thing about having to pin back the plastic. Looks like the outboard metal part of the fender will clear. TBH, it is not a super nice truck, so if I pay $$$ for 19.5 and get them to AK, I will find a way to make them fit. I may end up going the vision route when all is said and done.

[Bedlam]

AH_AK wrote:

Bedlam wrote:
Method makes some higher rated rims in LT tire sizes. 245/70r19.5 will fit the GM, but you may need tie back the fender liner up front or use a leveling kit to prevent rub at full lock. My Vision rims worked well, but I did not have a GM. American Force also makes high weight rated 19.5" rims - they have many patterns but a price that rivals or exceeds Rickson.

I would be fine with modifying the fender, but I'd rather not mess with the suspension/steering geometry (if I can help it). I wonder how often rub at full lock will actually be an issue anyway. I suppose it'd just be annoying when I forget and try a K turn. I am only seeing wheels on Method's site not tires. I looked at American Force, but they only seem to have 19.5x7.5 and looks like they have the same offset as Visions, so they might rub. I could likely trim the fender and get rid of the rub, but I'd almost certainly save some $$ and go with the visions if I am ready to trim.

I pointed to Method to get higher rated rims in 16-20" to go with some of the LT tires rated over 4000 lbs. The GM OEM rim ratings are typically less, so going to tires that exceed the rim capacity may help with ride, but will not give you more capacity than the lowest rated component.

In my case, I was running a SRW with 8000 lbs or rear axle weight which is why I went the 4500 lb rated Vision rims but then I went 245 H-rated tires that were over 5000 lbs to get the handling and tire strength I wanted.

You do not need to trim the metal fenders on the GM to fit 245/70r19.5 tires, but the plastic fender liner may interfere unless worked back a little.

[mbloof]

I ran into this issue years ago with my 1997 Ford. (16-17" rims, I forget which)

As I recall the 19.5" Visions cost ~$250-300ea and the tires were ~$350ea. (there were options that cost way more and way less) Add it all up it was not cheap. (but worth it)

Rims and tires are no longer the "weakest link" on my rig. 🙂


- Mark0.

[AH_AK]

BurbMan wrote:

AH_AK wrote:
Sorry, I probably wasn’t clear. I am going off the load index. I am only looking at the F-range because they get me to a higher load index.

That's exactly the point I was trying to make, you can't just go off the load index, because tires with the same load index will have different actual load ratings based on the size.

As far as I know the load index dictates the the max load of the tire. The chart you posted supports this. Both the 127 index tires on the list have the same max load.

[BurbMan]

AH_AK wrote:
Sorry, I probably wasn’t clear. I am going off the load index. I am only looking at the F-range because they get me to a higher load index.

That's exactly the point I was trying to make, you can't just go off the load index, because tires with the same load index will have different actual load ratings based on the size.

[AH_AK]

jimh425 wrote:
If your Chevrolet can’t handle the Vision offset, you could always trade for a Ford. Another option is to buy new wheels that can give you a better offset for 4080 capacity tires.

That being said, it’s probably going to cost you about the same to switch to a DRW if a DRW will work for you. In that case, your load problems will simply disappear.

For sure, 19.5 tires are tougher tires, but you pay for it in a rougher ride. Btw, it’s one of the reasons that I bought a F450 of the year range I bought. Maybe or maybe not a good idea, but I haven’t had a flat or even slow leak in 15 years of 19.5s.

I got this truck at auction for a good deal (government vehicle). It is tough to find dually gassers. Diesels seem like fun when they are under warranty and potentially $$$ when you buy an old one (which I would have to with my budget). I am also in AK, so handling in the snow is important. That said, if a dually had come up first in my price range, I would have probably bought it. Alas, here I am playing the "how to make my SRW into a dually-lite with mods" game.

[AH_AK]

Bedlam wrote:
The 275/70r18 was same height as my 245/70r19.5 and I used it as spare tire.

If I could get 19.5's with the correct offset, I think they would fit without any trimming/rubbing, but that is proving somewhat difficult to find. Got a good deal on the GM, but I am starting to regret my brand decision a little. I might just have to commit to trimming the fender well.

[AH_AK]

Bedlam wrote:
Method makes some higher rated rims in LT tire sizes. 245/70r19.5 will fit the GM, but you may need tie back the fender liner up front or use a leveling kit to prevent rub at full lock. My Vision rims worked well, but I did not have a GM. American Force also makes high weight rated 19.5" rims - they have many patterns but a price that rivals or exceeds Rickson.

I would be fine with modifying the fender, but I'd rather not mess with the suspension/steering geometry (if I can help it). I wonder how often rub at full lock will actually be an issue anyway. I suppose it'd just be annoying when I forget and try a K turn. I am only seeing wheels on Method's site not tires. I looked at American Force, but they only seem to have 19.5x7.5 and looks like they have the same offset as Visions, so they might rub. I could likely trim the fender and get rid of the rub, but I'd almost certainly save some $$ and go with the visions if I am ready to trim.

[Bedlam]

The 275/70r18 was same height as my 245/70r19.5 and I used it as spare tire.