5er Tire Issue

[rcg270]

This discussion has become too mundane.

[FastEagle]

Originally Posted by JIMNLIN

Calvin there is no different set of stds for choosing tires for a commercial truck/trailer vs a rv truck/trailer vs a non commercial truck/trailer. Light'n up with your bull shitz and offer something for the OP question for a change.

Sure is a difference. Commercial tire selections are basically selected for the maximum load carried and have no recommended cold inflation pressure standards other than the fact they must be inflated to carry the current load.

Automotive - including RV trailer tires - tires are selected by the vehicle manufacturer and provide a load capacity via vehicle manufacturer recommendation inflation pressures appropriate for that particular vehicle. Replacements are selected in accordance with vehicle manufacturer recommendations found in the vehicle owner's manual and may include options. The industry wide standard calls for the replacements to be of a size equal to the OE tires size and to provide a load capacity equal to or greater than the OE tires provided at vehicle manufacturer inflation recommendations.

Now days, size includes the prefix, ST, LT, P etc.. The industry uses the phrase, "Size Designation".

[JIMNLIN]

Sure is a difference. Commercial tire selections are basically selected for the maximum load carried and have no recommended cold inflation pressure standards other than the fact they must be inflated to carry the current load.

More gibberish....
In selecting a tire for a commercial or non commercial trailer we use the same selection process dictated from experience or the dealer.....just like its always been.

[FastEagle]

Originally Posted by JIMNLIN

More gibberish....
In selecting a tire for a commercial or non commercial trailer we use the same selection process dictated from experience or the dealer.....just like its always been.

Original Equipment or replacements.

When the Federal Motor Vehicle Safety Standards are the governing body, the vehicle manufacturer has the sole responsibility for OE tire selections and fitments. PERIOD.

Their minimum size designation must provide a load capacity equal to the vehicle GAWRs. There is a couple of caveats. Probably the most important is the OE tire's load capacity. The standard says the vehicle manufacturer must set a recommended cold inflation pressure that is appropriate for that fitment on that vehicle. Then the vehicle manufacturer certifies that inflation pressure for that vehicle and posts the information on the federal certification label, on the tire & load placard and, as mandated by NHTSA, in the vehicle owner's manual. The tire industry now enters the discussion. They unanimously support the vehicle manufacturer's decision and will not knowingly install replacement tires that do not have the load capacity the OE tires provide.

Examples:

Goodyear: Never fit tires to a vehicle that have less load carrying capacity than required by the Original Equipment Manufacturer.

Michelin: Never choose a tire that is smaller in size or has less load-carrying capacity than the tire that came with the vehicle.

Cooper: The new tires must have a load carrying capacity equal to or greater than the maximum load carrying capacity specified on the tire placard on the vehicle.

Toyo: Any replacement tire must be of a size and load range that will offer equal or higher load carrying capacity compared to the original equipment (OE) tire on the vehicle.

When you say it's from your experience or IYO, I can't argue with that. Owners can do what the consider safe, in their opinion. They are the ones that have to pay the piper. I just like to post what is supposed to be done from the governing bodies, tire industry safety standards or tire industry Standards of Procedures.

[racer4]

I got this Sailun S637 Load Inflation chart from one of the RV forum members who got it from Sailun and posted it. You can probably get one direct from Sailun by calling them.

When opening the .pdf file click "Cancel" if you see a Print window. Keep clicking cancel until you see the .pdf file.

iRV2 Forums - Files - Sailun S637 Load Inflation Chart

[grindstone01]

Originally Posted by racer4

I got this Sailun S637 Load Inflation chart from one of the RV forum members who got it from Sailun and posted it. You can probably get one direct from Sailun by calling them.

When opening the .pdf file click "Cancel" if you see a Print window. Keep clicking cancel until you see the .pdf file.

iRV2 Forums - Files - Sailun S637 Load Inflation Chart

Thank You, the chart shows I should be running 95 PSI for my load, I always like to run 5 PIS over for better MPG, so 100 PSI works for me!

[dskyward]

Originally Posted by grindstone01

Thank You, the chart shows I should be running 95 PSI for my load, I always like to run 5 PIS over for better MPG, so 100 PSI works for me!

Just curious, what psi have you been running, what size R? Your sig shows 34’ 5er, how do you figure 95 psi? I wouldn’t think you’re running anywhere near 13,220 lbs on your trailer axles, given the lowest 80R 3305x4? My 42’ 5er is 12300 (no water) and the chart says I should use <65 psi on my 85R set of S637s. However, I been using 85 psi instead.

[grindstone01]

Originally Posted by dskyward

Just curious, what psi have you been running, what size R? Your sig shows 34’ 5er, how do you figure 95 psi? I wouldn’t think you’re running anywhere near 13,220 lbs on your trailer axles, given the lowest 80R 3305x4? My 42’ 5er is 12300 (no water) and the chart says I should use <65 psi on my 85R set of S637s. However, I been using 85 psi instead.

My last axle scale weight was at 14360 lbs or 3640 lbs/tire. The S637 G tires are rated for 4050 lbs at 110 psi cold. I did a guessestimate that I should be running 95 psi for my loads and then just bumped up 5 psi for a better MPG. That's how I got to 100 PSI which the chart now confirms. When I am driving, my TMPS shows tire pressure between 115/120 PSI. I did try 110 PSI one trip and saw PSI readings up to 134, which was concerning for me. My rims and tires are rated for 110 PSI and the 134 PSI I had was 20% over design load. As a retired engineer, I'm not comfortable running anything 20% over design load. (my opinion)

[jacknife]

As an engineer you should know that outside surface road temp , rolling resistance and tire pressure are all directly related to how much how much pressure will build when going down the road. The Engineers at the tire manufacturer dial all this in to tire design. Very smart people . Why do people that have zero to do with tire design and manufacture keep second guessing them.

[jacknife]

I forgot speed is also a big factor

[grindstone01]

Originally Posted by jacknife

As an engineer you should know that outside surface road temp , rolling resistance and tire pressure are all directly related to how much how much pressure will build when going down the road. The Engineers at the tire manufacturer dial all this in to tire design. Very smart people . Why do people that have zero to do with tire design and manufacture keep second guessing them.

\
I'm not a tire engineer! I do know that 160F is the critical temp for rubber and I never approach that or exceed 60 mph on 75 MPH rated tires. Other than that you are right in that I really don't care to know any more about tires!

[dskyward]

Originally Posted by grindstone01

My last axle scale weight was at 14360 lbs or 3640 lbs/tire. The S637 G tires are rated for 4050 lbs at 110 psi cold. I did a guessestimate that I should be running 95 psi for my loads and then just bumped up 5 psi for a better MPG. That's how I got to 100 PSI which the chart now confirms. When I am driving, my TMPS shows tire pressure between 115/120 PSI. I did try 110 PSI one trip and saw PSI readings up to 134, which was concerning for me. My rims and tires are rated for 110 PSI and the 134 PSI I had was 20% over design load. As a retired engineer, I'm not comfortable running anything 20% over design load. (my opinion)

Thanks for the reply grindstone. You sure that’s trailer axle only and not your total 5er weight? You’re Cameo is only 34’ or 8.5’ shorter than mine and 2k more on the trailer axles sounds way too much. That sounds more like total axle and pin wt. Otherwise you’d have a 4000+ pin weight and would need 8k axles as you’re over on 7k axles. Just looked up a 37’ Cameo with a 16k GVWR. Just wanting to verify.

[grindstone01]

Originally Posted by dskyward

Thanks for the reply grindstone. You sure that’s trailer axle only and not your total 5er weight? You’re Cameo is only 34’ or 8.5’ shorter than mine and 2k more on the trailer axles sounds way too much. That sounds more like total axle and pin wt. Otherwise you’d have a 4000+ pin weight and would need 8k axles as you’re over on 7k axles. Just looked up a 37’ Cameo with a 16k GVWR. Just wanting to verify.

My cameo axle weight is actually 14360 lbs carried by 5 tires. To understand the whole picture, I do have a swivel trailer with a Goldwing (at time of weighing) hanging off the rear bumper which weighs in at 1500 lbs with the trailer/bike and that is included in the Cameo axle weight. The swivel tire carries about 750 lbs (leaving Cameo axles w/13610 lbs) and the rear bumper/frame is carrying the other 750 lbs which would then be subtracted from the front pin weight. I guesstimate my pin weight is around 2000 lbs which I know is light so it's another reason to keep my speed down.

[dskyward]

Aha, a big bike on the rear...and an actual 5th wheel, ha...that clarifies it some more. You really had me going.[emoji16] I was going to mention you must then be hauling a ton of bricks to get that kind of weight to show up on a 34 footer’s axles. Its interesting to note on Cameo’s website, the 34’ CK3 dry axle weight is listed at 9830 lbs. You picked excellent tires to do the job nonetheless.

As a side note, I went against the Sailun logic chart yesterday and inflated my Sailuns to 100 psi (from 79 psi cold@60deg) and traveled 340 miles thru 57 degree, level w/headwind MI today...and with 4000 lb pin wt, dually pressure was upped to 60 from 50 (had ‘em 55 in warmer temps 2 mos earlier) and the rig towed somewhat effortlessly today. I might add the coolant avg 200 deg(215 norm), and tranny fluid avg 140 deg(175 norm). Lie-o-meter said 11.0 avg mpg, I estimate 9-9.5 mpg. Even in 57 deg, the TireMinder TPMS read 110-112 psi max on the Sailuns while towing @ 64 mph.

I’ve only seen a swivel setup once in our 2.5 years fulltiming. Might have been you. Ha.