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Old 01-11-2019, 05:11 PM   #1
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80 to 85 series trailer tire switch?

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.

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Nancy & Phil
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Old 01-11-2019, 06:14 PM   #2
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I found by accident years ago that the extre inch made a huge difference in handling for positive effects!
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Old 01-12-2019, 12:42 AM   #3
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"psokora"......The 235 is basically the height and the 80 is a percentage of width. If you go to a 235/85, the tire will get taller, but also more narrow. If looking for height, look at a 245/80. You'll be taller, but keep the width.
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Old 01-12-2019, 05:11 AM   #4
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Quote:
Originally Posted by Dutch Star Don View Post
"psokora"......The 235 is basically the height and the 80 is a percentage of width. If you go to a 235/85, the tire will get taller, but also more narrow. If looking for height, look at a 245/80. You'll be taller, but keep the width.
Thanks but they don't make a 245. They do make a 255. But I wasn't necessarily looking for more width. Besides, a 235 is 235 no matter what the aspect ratio. I should look up the dimensions of the 255 and what hubs it will fit, and what widths my hub will accept.
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Old 01-12-2019, 05:17 AM   #5
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That extra inch in diameter is really only adding a half inch in height. It's the radius that counts. Handling - if you are moving from a 'China Bomb' tire to a Goodyear Endurance, you will probably see better handling/less tail wag. Added capacity - up to a point, more is better plus they may run cooler. Distance between tires is where you may see a problem if they are already pretty close already and where that half inch radius/tire may make a difference. It may affect a BAL X-Chock and how it fits between tires, especially one of their heavier duty versions.

Downside - may add a harsher ride to your trailer with added wear and tear but probably insignificant with the added safety of a better tire
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Old 01-12-2019, 05:40 AM   #6
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That extra inch in diameter is really only adding a half inch in height. It's the radius that counts. Handling - if you are moving from a 'China Bomb' tire to a Goodyear Endurance, you will probably see better handling/less tail wag. Added capacity - up to a point, more is better plus they may run cooler. Distance between tires is where you may see a problem if they are already pretty close already and where that half inch radius/tire may make a difference. It may affect a BAL X-Chock and how it fits between tires, especially one of their heavier duty versions.

Downside - may add a harsher ride to your trailer with added wear and tear but probably insignificant with the added safety of a better tire
Thanks, IC2. I have an X-Chock but not sure/didn't know there were different models. I do have to crack it down to fit them in sometimes. Will go out and compress them all the way and see if that extra inch between them can be accommodated. Of course it had to go down to 19 last night to make this more fun.

I was thinking it would be a less harsh ride as the aspect ratio increases.
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Old 01-12-2019, 07:49 AM   #7
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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, it decreases 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.
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Old 01-12-2019, 08:30 AM   #8
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Originally Posted by FastEagle View Post
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, it decreases 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, FastEagle. You're adding to my admittedly limited understanding here.

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.
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Old 01-12-2019, 11:44 AM   #9
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"Do manufacturers try to meet the minimum standard as opposed to trying to achieve the next level up?" Simple answer--NO. Most just put on cheapest tires that can carry the rated weight on the axles.
I would always be in favor of more load capacity to enhance tire life. Probably wouldn't want a 125psi/6000/J tire on a 12000 fiver, but more capacity usually will lead to longer tire life/fewer blowouts.
What tires were on the trailer that blew out? Size? Rating? Age?
Just changing to GY Endurance will probably be a great improvement over the OEMs.
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Old 01-12-2019, 12:28 PM   #10
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"Do manufacturers try to meet the minimum standard as opposed to trying to achieve the next level up?" Simple answer--NO. Most just put on cheapest tires that can carry the rated weight on the axles.
I would always be in favor of more load capacity to enhance tire life. Probably wouldn't want a 125psi/6000/J tire on a 12000 fiver, but more capacity usually will lead to longer tire life/fewer blowouts.
What tires were on the trailer that blew out? Size? Rating? Age?
Just changing to GY Endurance will probably be a great improvement over the OEMs.
Hey wingnut60,
They are the ubiquitous Towmax STR Power King of size ST235/80 R16 of speed rating N and three years old at the time. It's possible that we hit something near the edge of the road, since it was on the right, but more likely it was that we were driving too fast (70mph) for a few hours and it was plenty hot as was the road surface.
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Old 01-12-2019, 12:44 PM   #11
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Quote:
Originally Posted by Dutch Star Don View Post
"psokora"......The 235 is basically the height and the 80 is a percentage of width. If you go to a 235/85, the tire will get taller, but also more narrow. If looking for height, look at a 245/80. You'll be taller, but keep the width.
235 is the tread width in mm not the height. The 80 or 85 number is the height percentage so tire width will be identical just a bit taller.

245 would be a wider tire than the 235 by 10 mm.

Rob
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Old 01-12-2019, 12:53 PM   #12
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TowMax says it all...
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Old 01-12-2019, 01:03 PM   #13
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The extra inch won't be a big deal.
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Old 01-12-2019, 03:41 PM   #14
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I, along with many on the Montana Owners forum have gone to the Sailuns which come in both 80 and 85 series. I went with the 85s with no problems. Research the Sailun tires, as they have a stellar reputation and cost significantly less than the Goodyear G rated tire. The difference in weight between the Sailuns and the OEM tires was noticeable.
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