Upgraded tires

Spletbr · 03-22-2021, 01:02 PM

Just invested in new tires for our Montana, 14,300# gvwr (although we don’t tend to go that high). Moved up from F rated OEM to G rated Sailuns. Originals called for 95 psi and that is what is on the side placard. New ones can handle 110 psi and the rims are stamped for such. My question is...do I need to go 110? Will it make the ride too rough? Should I keep them at 95 or 100 even? I want the safety of the better tires but don’t need to overdue it if the ride sucks. Thanks!!

**sourdough** · 03-22-2021, 02:30 PM

I have a similar weight trailer and run mine at 105-110 psi (just depends on weather etc.). This trailer rides more rough than my last TT (seat of the pants watching/feeling) but I blame that on the Road Armor suspension vs MorRyde that I had. The steel cased tires have something to do with it I'm sure but in 6k miles or so we've not had any issues inside from "stiff" tires/suspension.

**flybouy** · 03-22-2021, 02:45 PM

If the reason for the higher rated replacements was to increase the safety cushion of reserve capacity then you will not achieve that without increasing the air pressure. The air pressure is the load capacity, not the sidewall or tread.

Ken / Claudia · 03-23-2021, 07:44 AM

When I went from D tires at 65psi to Es at 80psi. I made the same trip of about 900 miles within about 1 week and never noted a change in anything regarding towing performance or trailer handling. I will admit I never rode in the trailer ever, it may or may not caused a rougher ride inside of it. Nothing inside indicated it was shaken any more.
As last post I upgraded for the safety and will use the higher psi rated tires at their recommended inflation.

ChuckS · 03-23-2021, 07:57 AM

My original OEM tires were E rated ten ply at 80 psi.. the next year model of my exact same unit came with G rated 14 ply tires.. same 7K axles

I upgraded to 14 ply G rated tires 3 months after towing with the E rated tires.. my wheels are stamped 110 psi

I also had all metal high pressure valve stems installed.. Ive been running these tires for 6 years now at 105 psi.. no issues with rough riding fifth wheel at this pressure.. I initially ran at 110 psi for 3 years and just decided to drop to 105 psi just because....

CWtheMan · 03-23-2021, 10:23 AM

Quote:

Originally Posted by Spletbr

Just invested in new tires for our Montana, 14,300# gvwr (although we don’t tend to go that high). Moved up from F rated OEM to G rated Sailuns. Originals called for 95 psi and that is what is on the side placard. New ones can handle 110 psi and the rims are stamped for such. My question is...do I need to go 110? Will it make the ride too rough? Should I keep them at 95 or 100 even? I want the safety of the better tires but don’t need to overdue it if the ride sucks. Thanks!!

Okay, I have to get a little technical here. Are the replacement tires the same designated size as The OE tires?

Example: ST235/85R16 LRF to ST235/85R16 LRG. In the example both tires are the same designated size. Both tires will provide identical load capacities at 95 PSI. So what happened with the example is an option to increase tire load capacity with more inflation pressure. The certification is still valid because there was not a designated size change and the 95 PSI is still the minimum value for that trailer.

I suspect the OE tires were ST235/80R16 LRF. The same method applies as stated above with an increase load range to letter G.

If you have opted for the ST235/85R16 size to replace the ST235/80R16 it requires a completely different procedure; because the new tires are considered plus sized.

Spletbr · 03-23-2021, 01:24 PM

Quote:

Originally Posted by CWtheMan

Okay, I have to get a little technical here. Are the replacement tires the same designated size as The OE tires?

Example: ST235/85R16 LRF to ST235/85R16 LRG. In the example both tires are the same designated size. Both tires will provide identical load capacities at 95 PSI. So what happened with the example is an option to increase tire load capacity with more inflation pressure. The certification is still valid because there was not a designated size change and the 95 PSI is still the minimum value for that trailer.

I suspect the OE tires were ST235/80R16 LRF. The same method applies as stated above with an increase load range to letter G.

If you have opted for the ST235/85R16 size to replace the ST235/80R16 it requires a completely different procedure; because the new tires are considered plus sized.

Thanks Man. Both sets are ST235/80R16. Just went from F to G (and up in overall quality I hope). Looking to make it saker for a long trip out west and up north this summer.

CWtheMan · 03-23-2021, 02:06 PM

Quote:

Originally Posted by Spletbr

Thanks Man. Both sets are ST235/80R16. Just went from F to G (and up in overall quality I hope). Looking to make it saker for a long trip out west and up north this summer.

You can increase the PSI to 100 and gain another 110# in load capacity reserves per tire.

https://fifthwheelst.com/documents/C...T-Modified.pdf

rhagfo · 03-24-2021, 04:20 PM

Quote:

Originally Posted by Spletbr

Just invested in new tires for our Montana, 14,300# gvwr (although we don’t tend to go that high). Moved up from F rated OEM to G rated Sailuns. Originals called for 95 psi and that is what is on the side placard. New ones can handle 110 psi and the rims are stamped for such. My question is...do I need to go 110? Will it make the ride too rough? Should I keep them at 95 or 100 even? I want the safety of the better tires but don’t need to overdue it if the ride sucks. Thanks!!

Well lets see you have a 5er with a 14,300# GVWR, assume a low pin of 20% 2,860# leaves 11,440# on the four tires. 11,440# divided by the four tires equals 2,860# per tire, what are your G rated tires rated at? my guess is around 4,000# +/-, that is a heck of a reserve capacity.

Your 2020 F350 what is the axle rating, and what is the OEM tire rating? Not a weight police question, a question on capacity reserve.

You can get to the point of being Fred Flintstone, and your trailer is riding on rocks.

ChuckS · 03-24-2021, 06:19 PM

OP.. with the MHC you made a wise choice in going up in load capacity. Period..

Your RV will ride just fine and you will be packing and hauling more than the load you posted in your first post... period

RickV · 03-30-2021, 06:31 AM

I put Saliun 637 ST235/80R16's on my old 13K+ 5th Wheel. I contacted Saliun and their tech told me to run 75lbs in em. He asked me how much weight was on the axles and I told him under 12k he said 75lbs would give me the best ride and wear on the tires. I suggest you contact Saliun directly.

ChuckS · 03-30-2021, 07:49 AM

There is NO WAY I would run 75 psi in a G rated 14 ply tire... What was the point of buying them if you are gonna run such an under inflated tire pressure for the load carried?

**JRTJH** · 03-30-2021, 08:08 AM

Maybe someone else might have a different opinion, but here's mine:

First, tire load carrying capability is directly impacted by the tire pressure. It's the air that carries the load, not the rubber sidewalls. With that in mind:

1. Sidewall flex is the main reason for heat buildup in trailer tires. Reduced tire pressure is the main reason for sidewall flex....

2. The reason for buying "oversized tires for an RV" is to increase the tire capacity to prevent "running on the bare minimum capacity" thus avoiding a blowout.

3. To buy G rated tires that are capable of carrying 4000 pounds and then "airing them down" so they can only support 3000 pounds (like the tires they replaced) is an "exercise in futility"...

Running a G rated tire at (or below) E rated pressures makes it an E rated tire. You've negated all of the potential increased safety margin and reliability from the better tire.

If you're going to "only use half the new tire capacity" then why not just reinstall the same tire as what was on the trailer? There's no improvement in safety or in carrying capacity and no increased safety margin if you don't take advantage of the new tire's capability.....

YMMV

travelin texans · 03-30-2021, 08:15 AM

I would absolutely agree with both these guys.
Why bother with the upgrade???
If concerned with a possible rough ride (doubt you'll notice) don't ride back there.

RickV · 03-30-2021, 09:45 AM

All I know is I was having tires separating all the time. I read all the so called experts recommendations and tried different G rated tires same result, separation. Changed to the 637s ran em at the pressure the tech told me to run em at went from Florida to Kalispell, Mt and back two years in a row never had any issues. I am trading in that 5ver tomorrow for a Alpine 3790FK and the tires still look like new. I only hope that the HiSpec tires that are on it are anywhere near reliable as the 637s.. Supposedly they are warranted for 6 years. Can' find any info on em anywhere.

**JRTJH** · 03-30-2021, 10:43 AM

Quote:

Originally Posted by RickV

All I know is I was having tires separating all the time. I read all the so called experts recommendations and tried different G rated tires same result, separation. Changed to the 637s ran em at the pressure the tech told me to run em at went from Florida to Kalispell, Mt and back two years in a row never had any issues. I am trading in that 5ver tomorrow for a Alpine 3790FK and the tires still look like new. I only hope that the HiSpec tires that are on it are anywhere near reliable as the 637s.. Supposedly they are warranted for 6 years. Can' find any info on em anywhere.

All the info you "really need" is basic tire maintenance/upkeep and the pressure requirement that's on the tire decal on the front left of the trailer sidewall. I'd bet that if they are "G" rated tires, that decal will state, "Minimum operating pressure: 110 PSI COLD"... If they are "F" rated tires, that decal will state, "Minimum operating pressure: 95 PSI COLD"....

I haven't seen a tire decal on a Keystone trailer that recommends any "operating pressure" lower than the maximum PSI rating for that size/ply rated tire. It's always inflate to the same pressure as the maximum pressure reflected on the tire sidewall.

Spletbr · 03-30-2021, 10:47 AM

I originally had F rated tires so the decal shows 95 PSI. Now I have the same size tire, but G rated.

CWtheMan · 03-30-2021, 11:01 AM

Quote:

Originally Posted by RickV

All I know is I was having tires separating all the time. I read all the so called experts recommendations and tried different G rated tires same result, separation. Changed to the 637s ran em at the pressure the tech told me to run em at went from Florida to Kalispell, Mt and back two years in a row never had any issues. I am trading in that 5ver tomorrow for a Alpine 3790FK and the tires still look like new. I only hope that the HiSpec tires that are on it are anywhere near reliable as the 637s.. Supposedly they are warranted for 6 years. Can' find any info on em anywhere.

Are you reading the wheel information? HiSpec wheels are primarily OEM for many trailer applications. To my knowledge they do not make tires.

CWtheMan · 03-30-2021, 11:10 AM

Quote:

Originally Posted by RickV

I put Saliun 637 ST235/80R16's on my old 13K+ 5th Wheel. I contacted Saliun and their tech told me to run 75lbs in em. He asked me how much weight was on the axles and I told him under 12k he said 75lbs would give me the best ride and wear on the tires. I suggest you contact Saliun directly.

For future reference, ask the tech for a reference. They can guess in phonecons but when the signature goes on a verification document, industry standards must be met.

rhagfo · 03-30-2021, 11:32 AM

Quote:

Originally Posted by travelin texans

I would absolutely agree with both these guys.
Why bother with the upgrade???
If concerned with a possible rough ride (doubt you'll notice) don't ride back there.

Well to you and John, I think G rated tires on a 14,300# 5er are over kill! Second running a tire inflated to cover the load make a lot sense to me. The 235/75-16 on our Ram DRW only call for 65 psi for full axle rating weight of 9,750#. Putting G rated tires on the OP’s 5er means the are overinflated for load carried, rougher ride, and less tread contact with the road, poor wet weather braking.
I had a neighbor who ran log trucks, he only aired his tires up to 90 psi, tires rated to 110 psi. I don’t remember him ever throwing a cap, the only blowout was on an almost new tire on his tag axle. Dropping the inflation greatly reduced the tread cuts from the logging roads. Which resulted in near zero tire failures.
I run the LT tires on our 5er at about 75 psi as I only have about 10,000# on tires rated at 3,042# each or 12,168# total.
In reality the OP
Should have gotten good quality F rated tires and inflated accordingly.

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