80 to 85 series trailer tire switch?

[psikora]

When I switch to the Goodyear Endurance tires for my 5th wheel, I'm wondering about things to consider about changing from an ST235/80 R16 to a /85 series tire. I'm thinking the extra inch in diameter will not be a big deal.

Why even do it? It looks like you get an extra 200 pounds in load.

What I haven't done is weigh the trailer. Can you do that per axle and per side? Will do that on our next long trip in a few weeks when we're fully loaded.

Even if I'm within the limits, how could the extra capacity be a problem?

I'm not considering an LT tire so those responses will be superfluous.

TIA,
Nancy & Phil

[ependydad]

The only way to get per wheel weights is to find an outfit the does individual wheel weights like Escapee’s SmartWeigh.

You can get per axle weights at a CAT scale by pulling forward on the scale and splitting the axles on 2 of the scales. Using the “Weigh My Truck” app makes it easy to get positioned and then to capture the weight.m

As for the extra diameter- check to see the space between the tires. On my last trailer, I didn’t have room to space for anything with a larger diameter.

As for extra capacity not being bad- within reason, it’s a good thing. What you say is the increase seems fine.

[Airdale]

When changing tire size from ST235/80R16 LRE to ST235/85R16 LRE you’re actually doing what the tire industry calls “Plus Sizing”. Because the tires have different designated sizes they do not conform to the same load inflation chart. That makes the tire information placards on your trailer invalid.

What you gain is a little more height or decreased clearances in your wheelwells and between dual tire assemblies. Would your trailer’s manufacturer approve the size change?

In today’s market there is no real reason for changing designated tire sizes. Both of those tire size designations are manufactured in load ranges E, F & G. Being a brand shopper could lessen the options.

[psikora]

Originally Posted by Airdale

When changing tire size from ST235/80R16 LRE to ST235/85R16 LRE you’re actually doing what the tire industry calls “Plus Sizing”. Because the tires have different designated sizes they do not conform to the same load inflation chart. That makes the tire information placards on your trailer invalid.

What you gain is a little more height or decreased clearances in your wheelwells and between dual tire assemblies. Would your trailer’s manufacturer approve the size change?

In today’s market there is no real reason for changing designated tire sizes. Both of those tire size designations are manufactured in load ranges E, F & G. Being a brand shopper could lessen the options.

Thanks, Airdale. I saw your response on the other forum and will add my further questions here for completeness.

Just to tweak it a little more, please help me understand this. On the Goodyear site, the load range for the 235/80 tire is 3,420 pounds. The /85 is listed as 3,640. Without having weighed each tire for load, this becomes a bit of an esoteric discussion but could more load capacity be a positive enhancement just because the existing load is further away from the rating? As someone said, would it run cooler? Do manufacturers try to meet the minimum standard as opposed to trying to achieve the next level up?

On our first long trip to FL (from NY), we were on Alligator Alley on an 80+ degree day, at speed, driving a few hours, when we got two blowouts on the same side. If running cooler might be a possibility, I'm all for that. I've since installed a TPMS and intend on driving slower, especially when ambient and road temps are higher.

Thanks.

[Airdale]

Originally Posted by psikora

Thanks, Airdale. I saw your response on the other forum and will add my further questions here for completeness.

Just to tweak it a little more, please help me understand this. On the Goodyear site, the load range for the 235/80 tire is 3,420 pounds. The /85 is listed as 3,640. Without having weighed each tire for load, this becomes a bit of an esoteric discussion but could more load capacity be a positive enhancement just because the existing load is further away from the rating? As someone said, would it run cooler? Do manufacturers try to meet the minimum standard as opposed to trying to achieve the next level up?

On our first long trip to FL (from NY), we were on Alligator Alley on an 80+ degree day, at speed, driving a few hours, when we got two blowouts on the same side. If running cooler might be a possibility, I'm all for that. I've since installed a TPMS and intend on driving slower, especially when ambient and road temps are higher.

Thanks.

We don't know what your certified axle ratings are (GAWR). Reserve load capacity above the axles ratings is a good thing. The new minimum recommendation from RVIA is 10%. I've always used 15%+ with my replacements but not to the point of over kill. Normally, going up a load range- if available - will do the trick.


This is the acceptable standard the tire industry uses and publishes. Never use a replacement tires with less load capacity than the original tires provide.


It's a slippery slope and often misunderstood. The government regulations and tire industry standards folks are fixated on the description; designated tire size. It's more precise with an emphasis on tire design. Here are examples, ST235/85R16 is a complete designated size. So is LT235/85R16. See the difference? You pull your trailer into a Discount Tire retailer and tell them you want some good LT tire put on it. The tire installer is trained to look at the tire placard on the trailer. When they see the ST on that placard they are not going to put LT tires on that trailer. It would be considered a misapplication. A word often used in tire warranty packages.

[psikora]

Thanks!!! All great info for me and any others contemplating a similar move or just wanting to increase their understanding.

[jtesta1]

Just do what you want. Im sure you know more than the people that designed your trailer.

[NMWildcat]

Originally Posted by jtesta1

Just do what you want. Im sure you know more than the people that designed your trailer.

So I'm guessing you just blindly do what you are told without doing any thinking for yourself?

For the OP Psikora: Most everyone in my group goes to a taller tire and upgrades their load range by one, if they can. With today's taller trucks, any gain in trailer height helps with pulling level. As previously advised, just ensure your new tire is not rated lower than your original.

As far as the PSI indicated on the yellow placard, I honestly don't know anyone with a towable who pays much attention to it. In our RV group we air up our tires to the max cold PSI on the tire, or at least close to it.

What you want to do seems perfectly plausible, given you have the room for a taller tire.

[Airdale]

Originally Posted by NMWildcat

So I'm guessing you just blindly do what you are told without doing any thinking for yourself?

For the OP Psikora: Most everyone in my group goes to a taller tire and upgrades their load range by one, if they can. With today's taller trucks, any gain in trailer height helps with pulling level. As previously advised, just ensure your new tire is not rated lower than your original.

As far as the PSI indicated on the yellow placard, I honestly don't know anyone with a towable who pays much attention to it. In our RV group we air up our tires to the max cold PSI on the tire, or at least close to it.

What you want to do seems perfectly plausible, given you have the room for a taller tire.

Isn’t your group a sort of do-it-yourselfer group? Do-it-yourselfers have to pay for their own mistakes.

There are safety standards that are mandated to be in every vehicle owner’s manual. Here is one of those safety standards from a RV trailer manufacturer’s owners manual. “To maintain tire safety, purchase new tires that are the same size as the vehicle’s original tires or another size recommended by the manufacturer.” When an owner bypasses that safety standard they take all the responsibility for their decision to do otherwise.

[NMWildcat]

Originally Posted by Airdale

Isn’t your group a sort of do-it-yourselfer group? Do-it-yourselfers have to pay for their own mistakes.

There are safety standards that are mandated to be in every vehicle owner’s manual. Here is one of those safety standards from a RV trailer manufacturer’s owners manual. “To maintain tire safety, purchase new tires that are the same size as the vehicle’s original tires or another size recommended by the manufacturer.” When an owner bypasses that safety standard they take all the responsibility for their decision to do otherwise.

I don't disagree with any of your comments. I also don't always agree with every CYA manufacturer's statement. And all of us are always responsible for our own actions.

I don't see anything wrong with going with a bigger tire, with better load ratings, as long as you have room to do it.

[MR.M]

this would all mean something if the manufactures really knew what they were doing . they put tires on based on gvwr of the trailer less 10 to 15% since of course the TW carries some [so they say] leaving the owner with tires that are not suitable for the load from the get go . it's no wonder people go from the D rated to E rated right off the bat . My unit came with the d rated and they were not enough for my loaded TH . so up to e rated once i got it home . Going with a taller tires is fine as can be as long as you have the clearance . now show me the studies FR did on TT tires and loads .

[KFX450RXC]

I did what I wanted. When putting on my G614s, I went to a 235-85-16. Everything has worked perfectly for almost three years, 23 trips, and close to 7000 miles.

I like the little added clearance. The only negative (if you want to call it that) is the 6 pt. leveling sometimes won't hit ground on one side if I'm on a bad slope. I made wooden blocks and I also have Snap Pads on the landing gear so that's rarely an issue anymore.

I'd do it if you want to. Not a big deal in my opinion.

[Airdale]

Originally Posted by MR.M

this would all mean something if the manufactures really knew what they were doing . they put tires on based on gvwr of the trailer less 10 to 15% since of course the TW carries some [so they say] leaving the owner with tires that are not suitable for the load from the get go. (NHTSA will recall tires in a flash if it's discovered minimum standards are not met.) it's no wonder people go from the D rated to E rated right off the bat . My unit came with the d rated and they were not enough for my loaded TH . so up to e rated once i got it home . Going with a taller tires is fine as can be as long as you have the clearance . now show me the studies FR did on TT tires and loads .(The tire manufacturer is responsible for tire testing to standards. The vehicle manufacturer is responsible for appropriate fitmants.) Some kind of uncle requires the vehicle manufacturer to certify their tire fitments.

Going up a load range with the same designated tire size does not change the physical size of the tire. It just adds more available load capacity via the ability to add more PSI.


All tires are fitted to, at the very minimum, support a vehicle's GAWRs. Automotive fitments will provide a percentage of load capacity reserves. That is not a requirement for RV trailer tire fitments.


Vehicle manufacturers set specifications for their needs. Tire manufacturers build to those needs.

[MR.M]

Originally Posted by Airdale

Going up a load range with the same designated tire size does not change the physical size of the tire. It just adds more available load capacity via the ability to add more PSI.


All tires are fitted to, at the very minimum, support a vehicle's GAWRs. Automotive fitments will provide a percentage of load capacity reserves. That is not a requirement for RV trailer tire fitments.




Vehicle manufacturers set specifications for their needs. Tire manufacturers build to those needs.

If the tires are fitted to the minimum of the GAWR then the tires that came with my camper were off a 1000 lbs , fully loaded it would not carry the weight per the tire manufacture . what Vehicle manufactures do and what rv manufactures do are to different things . Sometimes i think they just grab whats on the shelf , though i'm sure they base their tire picks on the trailer max weights and they miss the mark all the time . no wonder so many have to up grade load ratings on new Trailers usually after a few blow outs . the facts are in all the threads posted about just this . now the OP was talking about going up in tire DIA which is fine if he has the clearance . FR may post a tire size on their trailers based on bear minimum load ratings . It's not effecting operation nor would it effect warranty If one was to go to a higher load rated tire or a larger DIA tire .

[Tall frog]

The only problem I see is clearance as stated above and with the taller side wall you will have more side to side movement. That's wjy all sports cars have very short tires even if they have 22" wheels. Most semis have a shorter side wall and bigger wheels

[CaptnJohn]

I have the clearance so went with the 235/85/16. My wheels are rated for 110 PSI so I went with the tire with the best proven reputation, Sailun. The 320# per tire, difference is 4400 vs 4080. If my wheels were only rated 80 PSI I'd have gone with the Sailun 235/80/16 and ran them at 80 psi as approved by Sailun is OK.