Trailer tires, what to buy?

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Chris Behm

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May 8, 2022, 1:30:43 PMMay 8
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Looks like the plane I intend to buy will need new trailer tires.
It's a Cobra trailer and the tires are size 175/80R13.
What are the latest trends and suggestions?

Light truck tires vs trailer tires, pro's and con's?

Going up a width or two in size, pro's and con's?

Thanks.

Target

2G

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May 8, 2022, 2:06:09 PMMay 8
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Good luck on finding a light truck tire that will fit a Cobra. I got a trailer tire from Les Schwab after the wife blew out one of the tires driving the trailer over a curb (it is now the spare).

Tom

Dave Nadler

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May 8, 2022, 3:05:27 PMMay 8
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On 5/8/2022 2:06 PM, 2G wrote:
> ...I got a trailer tire from Les Schwab after the wife blew out one of the tires
> driving the trailer over a curb (it is now the spare).

Has she now trained you not to ask her to drive the trailer?
Or further lessons required???

Mark Mocho

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May 8, 2022, 3:06:07 PMMay 8
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I suggest etrailer.com for the best selection, price and delivery. Can't give any advice on what to buy, as far as size and composition. My trailer probably hasn't moved five miles in the last five years, but the tires are two years old just in case I get wanderlust.

Bob Carlton, who used to tow his Salto or other airshow gliders upwards of 40,000 miles per year insisted on using properly sized radial car tires as opposed to S/T "trailer" tires.

Anders Black

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May 8, 2022, 3:45:40 PMMay 8
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Apparently, trailer tires are pretty different from car or truck tires - FWIW.

https://trailervalet.com/what-is-the-difference-between-trailer-tires-vs-regular-car-tires/

Andy Blackburn
9B

AS

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May 8, 2022, 6:55:53 PMMay 8
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I posted the same question with my friends in Germany and their resounding response was to stick with the OEM-type tires. The OEM tires on my Cobra trailer had no indication that they were anything but regular car tires.
I had a blow-out last year after hitting one too many potholes in the Memphis, TN area. Fortunately, this was a non-event because my trailer has twin-axles. I replaced all tires with the same size and type but I picked the ones with a highest load rating I could find, which gives one a little extra margin. If memory serves me right, the OEM tires had a Load Index of 81 (1,019#) and I picked one with 88 (1,235#).

Uli
'AS'

Guy Acheson

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May 8, 2022, 10:57:24 PMMay 8
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America's Tire and Discount Tire have trailer tires for your rig.
For 13 inch wheels it may take a couple of days to get them in the store.
I find "trailer tires" have stiffer sidewalls and don't sway as much as automobile tires.
I also buy new tires every five years. Tires rot.
Learn to read the manufacturing date that is on every tire.

Eric Greenwell

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May 9, 2022, 9:53:12 AMMay 9
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This article contains substantial misstatements.

"Bias ply trailer tires have a shorter tread life, but are built with a different
construction method intended for heavier loads." Wrong: The tire rating tells you how much
load a tire is intended to handle, NOT the construction.

"While LT tires may have thicker sidewalls and seem to make sense as an option, they still
are not designed to respond to trailer specific issues." Wrong: LT tires have a much
higher speed rating than ST tires (20 to 30 mph higher), and can easily handle trailering
side and braking loads.

"The load bearing capacity listed on an LT tire is designed based on the frame of a truck
– not the frame of a trailer. Wrong: the ratings are not based on the frame design, which
is not standardized for trailers or trucks. Trailers and light trucks do often have the
same solid axle design, which seems more relevant than the frame to which the axle springs
are attached. Also, Cobra trailers have an independent axle for each wheel, yet there is
no requirement to use a different tire.

Not mentioned in the article:

- ST tires generally have a 65-70 mph speed limit with the standard inflation pressures,
but can go a bit higher with higher pressures

- Bias ply ST tires have only one advantage over radial ST tires: they are cheaper.

--
Eric Greenwell - USA
- "A Guide to Self-launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications

2G

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May 9, 2022, 11:11:38 AMMay 9
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I taught her how to pull a trailer, but she forgot most of it. Basically, a trailer tracks inside of the vehicle's track while turning and there was a curb that she pulled the trailer over too fast. We had another driving lesson after this.

BTW, we caravan pulling two trailers; I pull the travel trailer.

Tom

Papa3

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May 9, 2022, 11:44:54 AMMay 9
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Just did this last weekend with my 2013 Cobra. Mine had OEM tires from Cobra which were Dunlop auto tires 175/70/R14. My tire guy couldn't get the exact same Dunlops (they were one of their middle-of-the-range Sport models) and we replaced with the same spec tires from General. Drove them back to the gliderport at 65-70 mph and couldn't tell any difference from the originals.

P3

On Sunday, May 8, 2022 at 1:30:43 PM UTC-4, Chris Behm wrote:

Dan

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May 9, 2022, 11:57:17 AMMay 9
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I recently bought these tires for my Cobra Trailer-
Goodyear Endurance st205/75r14
These are made for trailers and I noticed that the trailer tows much better than the original tires installed by Cobra
There is a lot of info on them on the internet- Google them

Dan Rihn

2G

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May 9, 2022, 8:38:31 PMMay 9
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You never mentioned where you can buy LT tires that will fit a Cobra trailer.

Tom

Charlie M. (UH & 002 owner/pilot)

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May 9, 2022, 9:19:43 PMMay 9
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A tire can't be sold as new if it was molded more than 3 years ago.
Most trailer tires rot before wearing out. It seems like 5-7 years is about it for a "safe tire" before rot/cracks.
The date code is on one sidewall, it's molded in a oval about 1" long by 1/2" tall and close to the rim. It's 4 digits....the first 2 digits are the week of the year, the second 2 digits are last 2 digits of the year. So a code of "2321" is 23rd week of 2021.

Just a tidbit. ;-)

Guy Acheson

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May 9, 2022, 9:46:52 PMMay 9
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See my post of 8 May.
America's Tire and Discount Tire can get you trailer tires for 13/14/15 inch wheels.

Eric Greenwell

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May 9, 2022, 10:54:29 PMMay 9
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Eric Greenwell

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May 9, 2022, 10:59:53 PMMay 9
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I've always wondered what "tire rot" was. Is that a technical term? If so, what is the
specific meaning?

Michelin recommends 10 years as a replacement age limit on their tires. I don't know what
other manufacturers recommend.

https://www.michelinman.com/auto/auto-tips-and-advice/tire-buying-guide/when-do-i-need-new-tires

2G

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May 10, 2022, 12:18:27 AMMay 10
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Tire rot is the oxidation of the rubber while exposed to air. Since the air in the tire is compressed oxidation occurs faster from the inside than the outside.

Mike the Strike

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May 10, 2022, 1:43:21 AMMay 10
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I have had the best success with tires designed for trailer use - I believe this is due to the sidewall construction, since trailer tires aren't typically steered or driven like car or truck tires. Discount tire has always found me something suitable.

Some years ago, a tire on my Cobra trailer disintegrated on my way from Tucson to Moriarty. Apparently, 200 miles at 75 mph proved too much for the cheap Chinese tire, and it flew apart spectacularly! In Arizona, you are lucky to get 5 years out of tires, due to heat and UV exposure - even if they look fine.

Mike

Eric Greenwell

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May 10, 2022, 8:48:42 AMMay 10
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I stumbled upon this page by Goodyear, which says "Tire Dry Rot, aka Sidewall Weathering,
is visible cracking in a tire’s tread or sidewall caused when a tire’s rubber compounds
break down."

https://www.goodyear.com/en-US/learn/tire-care-maintenance/dry-rot-tires

It doesn't comment about the air inside the tire, or using nitrogen to reduce the rot,
even on the page that discusses using nitrogen.

https://www.goodyear.com/en-US/learn/tire-care-maintenance/nitrogen-in-tires

Dee

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May 10, 2022, 11:24:15 AMMay 10
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This is an expansive article on the wear issue. Even explains why tire aging is worse if they sit idle vs. road use. Google search is an amazing tool; this one took about 8 seconds.\

https://www.liveabout.com/the-science-of-tire-aging-3234377#

Phyllis

SF

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May 10, 2022, 5:04:45 PMMay 10
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Eric,
John Murray did a very scientific study based on his sales of replacement Cobra trailer fenders, and asking questions as to how old the tires responsible were at the time of the incident. And if I remember correctly his data indicated that tires less than 5 years old did not tend to destroy trailer fenders on their way to wherever dead tires go when they die. There might be some sarcasm in the scientific claim in my first sentence, however that bar has been lowered significantly as of late, so maybe not. Replace every 4-5 years, car radials are fine is what I remember. Load and speed ratings Mo is Betta, considering how I drive. Other studies on truck fleet tires indicate Nitrogen fill significantly increases tire life. But sadly the nitrogen fill station is never where you need it to be, when the tires look a little slack. Given the price of the tires, and the price of the problems they could cause whilst trailering in the nether regions of bumfuckistan where the flying is good, and the repair shops are 2-weeks distant, a 4-5 year replacement schedule seems cheap.
SF

2G

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May 10, 2022, 9:20:32 PMMay 10
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Atmospheric pressure is about 14 psi, your tires are inflated to 40 psi or more (3x). It makes sense that there are a lot more oxygen atoms available to oxidize the rubber from inside the tire than outside. UV from the Sun is also a factor, which can be mitigated with tire covers. Filling with nitrogen solves this problem, as well as not changing in pressure much as the tire heats, but finding tire shops with nitrogen is problematic.
Tom

Kevin Finke

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May 10, 2022, 10:52:52 PMMay 10
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I've never understood the claim that nitrogen filled tires won't change the pressures with temperature as much as Air filled tires. Ideal gas law states that the relationship between Delta P, pressure change, is wholly a function of delta T, temperature change. There's no constant multiplier for different types of gas. Air, pure Oxygen, pure Nitrogen all behave like ideal gasses.

2G

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May 10, 2022, 11:11:00 PMMay 10
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On Tuesday, May 10, 2022 at 7:52:52 PM UTC-7, Kevin Finke wrote:
> I've never understood the claim that nitrogen filled tires won't change the pressures with temperature as much as Air filled tires. Ideal gas law states that the relationship between Delta P, pressure change, is wholly a function of delta T, temperature change. There's no constant multiplier for different types of gas. Air, pure Oxygen, pure Nitrogen all behave like ideal gasses.

You are right. This explains the benefits of nitrogen fill (not the least of which is the absence of internal oxidation):
https://www.tirerack.com/tires/tiretech/techpage.jsp?gclid=Cj0KCQjwmuiTBhDoARIsAPiv6L_S9-Dgqc4r41PHU3ZmgXYZBkDe8fvwb3lWB_sYPrT9IdSGyu9vA0MaApNIEALw_wcB&techid=191&ef_id=Cj0KCQjwmuiTBhDoARIsAPiv6L_S9-Dgqc4r41PHU3ZmgXYZBkDe8fvwb3lWB_sYPrT9IdSGyu9vA0MaApNIEALw_wcB:G:s&s_kwcid=AL!3756!3!354820920608!p!!g!!air%20vs%20nitrogen&gclsrc=aw.ds

Tom

Eric Greenwell

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May 11, 2022, 8:54:08 AMMay 11
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On 5/10/2022 7:52 PM, Kevin Finke wrote:
> I've never understood the claim that nitrogen filled tires won't change the pressures with temperature as much as Air filled tires. Ideal gas law states that the relationship between Delta P, pressure change, is wholly a function of delta T, temperature change. There's no constant multiplier for different types of gas. Air, pure Oxygen, pure Nitrogen all behave like ideal gasses.
I've not seen it explained very well, but what they might be talking about is
condensation. Most tires are filled with compressed ambient air, which has some water
vapor in it, and a lot of vapor in humid areas. If the tire cools below the dew point, the
air in the tire is no longer an ideal gas, as some of the gas (water vapor) condenses. On
a SkewT diagram, it's where you switch from the dry adiabat to the wet adiabat - very
different curves.

Guy Acheson

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May 11, 2022, 10:02:48 AMMay 11
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In car racing the subject of using nitrogen or carbon dioxide or argon to fill tires has been around for some time.
The physics of gas expansion with heat is the same for any gas.
Turns out that it is the moisture in the gas used to fill the tires that is the reason for variable increases in tires pressure with heat.
It does not matter what gas you use to fill the tires.
The value of using something like nitrogen/carbon dioxide/argon to fill tires is the lack of water vapor.
Now, making this change is not as simple as just letting the air out of your tires and refilling them with a compressed gas.
To get the benefit of using any of these gases you have to purge the tire of all air first, otherwise you still have moisture inside the tire.
This is why the people who just refill their tires with nitrogen are disappointed by the results and then speak loudly about the whole idea being fiction.

Honestly, unless you are driving a formula one or Indy car there is no benefit to using something other than air.

Herbert Kilian

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May 16, 2022, 1:09:37 PMMay 16
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Tsk, tsk, tsk Tom! Knocking your retrieve crew/wife is never a good idea.

Nicholas Kennedy

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May 16, 2022, 8:09:24 PMMay 16
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I like my trailer tires like I like my GF's:
Round
Black
Hot
Nick
T

2G

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May 16, 2022, 11:14:32 PMMay 16
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No, she knows she screwed up - I relived this in the hopes that a little instruction to other crew can circumvent a similar experience. It could have been worse: she could have cut a corner at a gas station!

Tom

Mark Mocho

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May 16, 2022, 11:35:27 PMMay 16
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Nick- And how does Betsy feel about your preference? I assume she doesn't check RAS. At least you better hope she doesn't.

Ron Gleason

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May 17, 2022, 12:10:24 AMMay 17
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On Monday, 16 May 2022 at 21:35:27 UTC-6, Mark Mocho wrote:
> Nick- And how does Betsy feel about your preference? I assume she doesn't check RAS. At least you better hope she doesn't.
When I read Nick's post my first thought 'Mocho highjacked Nick's identification'
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