tires overloaded?

[aruba5er]

recently bought a new TC and fully loaded, ready for travel, weighed it at a CAT scale. left me just a few #'s under what the tires are rated for. It rides good, no sway, no sag but being so close to max on the rear tires bothers me. last thing I need to do is blow a tire. Is this thing that bothers me worth looking into larger tires, wheels? As is, tires are new Michlean's and capable of 50/70 #'s more.
Thanks for your opinions.

[JimK-NY]

^^^ Lot of conjecture there. Instead of jumping to conclusions it might be best to find out some specifics: age of tires, how maintained, if the pressure was set, inspected for damage, etc. Getting a higher load rated tire is not going to fix or compensate for low tire pressure, damage, or dry rot.

[dustytires]

My co-worker just returned from a trip to Big Pine CA for some early season trout fishing. Lost a tire on the SRW Superduty with camper on it. Luckily he felt it as soon as it started to de-laminate, and before the tread started flapping he had it off the road.

Truck campers are much higher off the axle than a motorhome, and usually very heavy in the rear so unless a you have a DRW truck, more tire on a SRW is better than trying to cheap out or play the % of safety margin game. An engineered margin is only as good as the manufacturer was that day. Tolerance is always noted, but on a heavy truck with highly mounted mass like a camper pitching, yawing and rolling down the road I don't want to be wondering if my tires were at the bottom of tolerances or the top! Go big as you can or go DRW.

[Marcela]

Bradymydog wrote:
I recently purchased a new 2018 GMC 3500 HD SRW CC 4x4 Gas with 10800 GVWR. GRAWR is 7050. Stock 265/70/18 tires were rated 3525 lb ea. My fully loaded Bigfoot 25c9.4 with wife, dog and I with full fuel, ready to travel was 180lbs (90lbs/tire) under the max tire rating at 80psi. I was not comfortable with the safety margin. I opted to purchase (5) Cooper Discoverer AT3 XLT's size 295/70/18 rated at 4080lb/tire at 80 psi with 60K mile warranty. No mods were done to the truck to fit the larger tires, although my speedo now reads 3.5 mph slow at 60 mph. I recently completed a nearly 4000 mile round trip from MA to FL. I cannot say enough good things about the truck and tire combo. Both preformed great -the tires very very quiet with a nice aggressive tread. .

Interesting I have the same truck though regular cab and switched out the tires for michelin with the 4080# rating. My new 10.4 imo was still too much for the SRW so bought an older DRW, which I feel better about driving. Kind of wish I had a smaller/lighter camper for pulling a bigger trailer to contain goodies. My GMC has the tpms btw which is nice. It was downrated on the door tag for commercial use I believe.

[Bradymydog]

I recently purchased a new 2018 GMC 3500 HD SRW CC 4x4 Gas with 10800 GVWR. GRAWR is 7050. Stock 265/70/18 tires were rated 3525 lb ea. My fully loaded Bigfoot 25c9.4 with wife, dog and I with full fuel, ready to travel was 180lbs (90lbs/tire) under the max tire rating at 80psi. I was not comfortable with the safety margin. I opted to purchase (5) Cooper Discoverer AT3 XLT's size 295/70/18 rated at 4080lb/tire at 80 psi with 60K mile warranty. No mods were done to the truck to fit the larger tires, although my speedo now reads 3.5 mph slow at 60 mph. I recently completed a nearly 4000 mile round trip from MA to FL. I cannot say enough good things about the truck and tire combo. Both preformed great -the tires very very quiet with a nice aggressive tread.

Additionally, I fabricated a front spare tire mount using my existing snow plow mount. This had the added benefit of reducing the rear axle load by approx. 75 lb. and allows for quick access to the spare tire.

Also as the truck's GVWR is over 10K, no TPMS were installed at the factory. In order to monitor my tire pressure "real time", I installed an ORO TPMS with internal sensors as I did not want external valve stem sensors. The ORO not only measures tire pressure but allow the user to set min and max tire pressure warning, measures tire temp and voltage output. It is extremely accurate within +/- 1 lb. When I first installed the ORO, I thought it was defective, it was not, 2 out of 4 of my pressure gauges were. I verified the accuracy with a brand new gauge as well as a new Viair dial gauge which came with my portable compressor. This isn't a cheap solution but the peace of mind was worth it to me on my SRW truck.

[dustytires]

If you smoke an rear end bearng you stop. If you blow a tire with a 3-5k camper on the truck..... More tire will never hurt.

[JimK-NY]

bighatnohorse wrote:
Opinion: Tire ratings are good to the very last drop.
In other words - when the tire is old and worn, it should still have near the same capacity.
2) Manufacturers build in a safely margin.
3) What road conditions will it see?
Personally, I think you're rig is good. Just consider the above and inspect the tires regularly.

That is supposed to be the case at least for LT tires. They are rated for max load use for the life of the tire. They are not rated for misuse or abuse. The big, big factor is proper tire pressure especially when at load. They are not rated for high speed. On my last truck, I upgraded to Rickson 19.5 wheels and tires. I had plenty of excess load capacity, BUT reading the fine print, the tires were only rated to 70 mph. I see a great many RVs traveling at very high speed and cannot help but wonder how many users are driving way over the tire speed ratings.

If that was not enough, the other big factor is use and age. Many RV tires are have low mileage but are not replaced soon enough. Seven years is a rule of thumb maximum but that can be way, way over what is acceptable. Tires need to be flexed, built up heat and be used frequently. If not, they dry rot! That happened to me with a spare tire that was stored under the truck out of light for only 4 years.

Running a tire at 80 per cent or less load capacity is not a solution for low tire pressure or dry rot due to age, excess speed, and/or infrequent use.

[bighatnohorse]

Opinion: Tire ratings are good to the very last drop.
In other words - when the tire is old and worn, it should still have near the same capacity.
2) Manufacturers build in a safely margin.
3) What road conditions will it see?
Personally, I think you're rig is good. Just consider the above and inspect the tires regularly.

[Marcela]

Here is some information that might be useful but who knows.

http://www.trucktrend.com/how-to/towing/1407-understanding-tire-load-ratings/

[ticki2]

DRW almost always have more tire capacity in rear than axle rating . 3525## x2 = 7050 x95 per cent = 6697.5# , and that is with 18"wheels . So which truck is using the 80 per cent ?

[Marcela]

My 2001 F350 DRW with factory 235/85-16 tires rated at 2778# show 8250# on the door sticker.

My 2017 GMC 3500 SRW with 265/70-18 factory tires rated at 3525# show 6700# on the door sticker.

[ticki2]

CapriRacer wrote:

Marcela wrote:
Why do OEM rate capacity at 80% of tire rating?

Actually, it's the other way around: They select the tire capacity such that it meets the vehicle capacity at 80% of the tire's rated load. That's just good engineering practice. They do the same thing for nuts and bolts, but no one notices those.

Not sure where you are getting that info . I know on GM 2500hd for many years the grawr has been exactly what the oem tire rating is Times two .

[Grit_dog]

The 80% number may be in some cases, but in our context here it's not always true. Plenty of trucks running around with "7000lb rated" rear axles with 7200 lbs of "rated" tire capacity.

[jimh406]

I don’t usually keep OEM tires on my vehicles very long since I find them lacking. For trucks, it’s usually traction and toughness they are lacking. In any case, I’ve noticed huge load rating differences for tires even for SUVs. Sure, it costs money, but you can almost always find a better tire than stock. For sedans, it’s ride quality and noise. For sports cars, back to traction and ride quality. Of course, you can also find worse tires than OEM.

What’s the reference source for the 80% number?

[CapriRacer]

Marcela wrote:
Why do OEM rate capacity at 80% of tire rating?

Actually, it's the other way around: They select the tire capacity such that it meets the vehicle capacity at 80% of the tire's rated load. That's just good engineering practice. They do the same thing for nuts and bolts, but no one notices those.