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Tires (the weakest link)

AH_AK
Explorer
Explorer
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?
45 REPLIES 45

JimK-NY
Explorer II
Explorer II
I started here in 2010 and learned a lot. Nine months later we took off as full timers in a truck camper we had never even tried out for a night. We had no major issues and the minor fixes were largely due to knowledge gained here.

AH_AK
Explorer
Explorer
I am extremely appreciative of all the feedback I have gotten from this site. It is a great resource for newbies like me.

JimK-NY
Explorer II
Explorer II
As with every other issue when you solicit advice, you need to do your own research and look for a consensus. You will always find some divergent opinions.

AH_AK
Explorer
Explorer
I would think the supersprings or any progressive spring pack upgrade would be less โ€œbouncyโ€ than airbags due to the more linear stiffness profile over the range of travel. What I experienced felt like underdamped oscillations. The downside of increasing damping (shocks) is that it will make the ride more harsh. Coming from the mountain bike world, I am used to the more you pay, the more adjustments you get, and the more you can dial it in. Keep in mind that I have no real experience in the TC world. I understand fundamentals pretty well, but fundamentals without practical experience can get you into trouble (and waste a lot of money)...thus, asking this community.

jimh406
Explorer III
Explorer III
JimK-NY wrote:
At least for me, shocks did not work and added to a harsh, jolting ride. They are also pretty expensive. I would go with the Supersprings first. They are very inexpensive.


Iโ€™m not sure where you priced shocks or what setting you used the Rancho 9000s on. Looking online, the shocks and Supersprings are approximately the same cost. However, springs do something totally different than shocks. Supersprings are more comparable to air bags or timbrens.

One companies comparison of each type of spring is in the link below.

https://www.generalspringkc.com/blog/best-truck-suspension-upgrades

'10 Ford F-450, 6.4, 4.30, 4x4, 14,500 GVWR, '06 Host Rainer 950 DS, Torklift Talon tiedowns, Glow Steps, and Fastguns. Bilstein 4600s, Firestone Bags, Toyo M655 Gs, Curt front hitch, Energy Suspension bump stops.

NRA Life Member, CCA Life Member

JimK-NY
Explorer II
Explorer II
AH_AK wrote:

...Supersprings seem easy enough to install and they are not super expensive. I might see if better shocks help first. It is good to know that I have a reasonable option if he ride is too harsh.


At least for me, shocks did not work and added to a harsh, jolting ride. They are also pretty expensive. I would go with the Supersprings first. They are very inexpensive. They bolt on quickly and the only minor issue is adjusting the tension by changing the positions of the shackles. A dealer put mine on for a small fee but I would not hesitate to do it myself. Another good choice are Timbrens. I am using them on my 3500 but my 2500 needed something more.

AH_AK
Explorer
Explorer
JimK-NY wrote:
I tried airbags and immediately had an issue with bounce and sway. I lowered the pressure to the point where the bags hardly helped leveling the rig but at least the bounce and sway were decreased.

I had Rancho shocks and to help with the bounce and sway I had the rear shocks set on high. The ride was poor with lots of jolts when driving over highway tar strips, etc. It took a couple of years before I finally got rid of the airbags, added Supersprings and was then able to dial back on the shocks. The Supersprings made all the difference! I will never mess with airbags again.


It makes sense that the airbags would be bouncy, especially with the limited damping capacity of OE shocks. I honestly feel dumb for blindly installing airbags. They work for leveling but naturally take load off the leafs and disengage the overloads. Supersprings seem easy enough to install and they are not super expensive. I might see if better shocks help first. It is good to know that I have a reasonable option if he ride is too harsh.

JimK-NY
Explorer II
Explorer II
I tried airbags and immediately had an issue with bounce and sway. I lowered the pressure to the point where the bags hardly helped leveling the rig but at least the bounce and sway were decreased.

I had Rancho shocks and to help with the bounce and sway I had the rear shocks set on high. The ride was poor with lots of jolts when driving over highway tar strips, etc. It took a couple of years before I finally got rid of the airbags, added Supersprings and was then able to dial back on the shocks. The Supersprings made all the difference! I will never mess with airbags again.

jimh406
Explorer III
Explorer III
I ran Rancho 9000s on my SRW with Visions and 19.5s on my F350.. I used 6 front and 9 rear with the same TC I have now, and 3 front and 1 rear empty.

'10 Ford F-450, 6.4, 4.30, 4x4, 14,500 GVWR, '06 Host Rainer 950 DS, Torklift Talon tiedowns, Glow Steps, and Fastguns. Bilstein 4600s, Firestone Bags, Toyo M655 Gs, Curt front hitch, Energy Suspension bump stops.

NRA Life Member, CCA Life Member

AH_AK
Explorer
Explorer
My 19.5 Visions are on their way. Those of you running 19.5 on SRW trucks, do you run aftermarket shocks? I noticed I have some underdamped bounce when I hit bumps with a 3600lb camper on the back. Nothing scary, but I am thinking 19.5โ€™s are going to make it worse. I am running OE shocks right now. I havenโ€™t had a chance to mess with my airbag pressure. I set at 40 psi. Lower overloads engaged, uppers not. Looked level, so I left it. I gather that airbags contribute to bounciness. I am thinking a shock with better damping might help with the bounce. I can live with it, but i am worried that itโ€™ll get worse once the 19.5โ€™s go on. Also, I would hate to โ€œdeal with itโ€ if there was a relatively easy solution.

ticki2
Explorer
Explorer
I would also like to know where you found a weight rating stamped on a GM wheel .
'68 Avion C-11
'02 GMC DRW D/A flatbed

AH_AK
Explorer
Explorer
Where is this stamp located on OEM steelies?

Supercharged111
Explorer
Explorer
The factory rims are stamped with their no shjt weight rating and it won't correspond with the axle weight rating. It will be higher. Did you check for that and I missed it?
2007 Lance 1131
1997 GMC K3500 crew cab supercharged dually

Bedlam
Moderator
Moderator
The 19.5 can be regrooved, but I have not heard of anyone running this size in recap.

Host Mammoth 11.5 on Ram 5500 HD