Trailer tires

[paulfredricks]

We have a dual axle travel trailer with 13" wheels. On our last trip blew one of tires. I started doing some research and found that these are ST rated tires which I think means they are rated to 65 MPH.

Now, I know, I should keep my speed down and just enjoy the trip, but I do occasionally find the need to speed up a bit. I do like to keep up with the flow of traffic. I'd like tires with a better speed rating.

Now I did see an ST175/80R13 that says it has an "M" rating, which is 81MPH. But from what I've read ST means 65 MPH.

I'm confused.

Anyone have any insight?

[Atlee]

RE: #2) I have always aired my tires to the max on the side wall. I have yet to experience any slippage of the trailer due to not gripping the road very well. I have also yet to have the center of the tire wear out pre-maturely.

Re: #1) I don't ever plan on going to a scale and weighing each trailer tire in order to know how much air to put in it. You can't take the overall weight of the trailer and divide by 4 to determine the tire inflation amount. Weight for each tire may vary.

rbpru wrote:
Tire inflation 101:
1. Tires are inflated to match the load being hauled.
2. Over inflated tires do not grip the road as well and will wear out the center of the tire.
3. Under inflated tires will overheat and tend to show cupping on the edges.
4. The correct tire inflation pressure to match the load comes from the tire maker, not someone opinion on an RV bulletin board.

[gmw_photos]

Again, at the risk of sounding repetitive, I'll say it again: I have four tandem axle trailers. I run all of these trailer tires at max sidewall pressure ( 65 psi on my D rated tires and 80 psi on my E tires ).
All of my trailers have far more tire load capacity vs what I am actually carrying. None of them are wearing tires "in the center, in a classic over inflation wear pattern". None of them. That's 16 tires. All wearing normal.

I base my inflation on three things:

1. the trailer manufacturers recco
2. the recco of a retired tire engineer, with a background in failed tire forensics
3. personal experience

....as always, YMMV. Your money, your tires, do what you think will work for you.

[mileshuff]

rbpru wrote:
Tire inflation 101:
1. Tires are inflated to match the load being hauled.
2. Over inflated tires do not grip the road as well and will wear out the center of the tire.
3. Under inflated tires will overheat and tend to show cupping on the edges.
4. The correct tire inflation pressure to match the load comes from the tire maker, not someone opinion on an RV bulletin board.

^^^^This!

[rbpru]

Tire inflation 101:
1. Tires are inflated to match the load being hauled.
2. Over inflated tires do not grip the road as well and will wear out the center of the tire.
3. Under inflated tires will overheat and tend to show cupping on the edges.
4. The correct tire inflation pressure to match the load comes from the tire maker, not someone opinion on an RV bulletin board.

[mike-s]

mileshuff wrote:
That isn't what Maxxis stated.

Actually, that's exactly what they said.

mileshuff wrote:
They state at max cold PSI at max rated load the tire is rated to 65mph. But if you run well under max load the speed rating goes up. Tire is rated to 99mph (Q rating) if under loaded sufficiently. Take a look at typical car tire specs. Manufactures will usually provide a table showing load vs speed vs PSI.

That's not at all what they said. Let's take a look, quoting from here, the entire response from Maxxis:

Maxxis wrote:
To ensure your reply reaches the proper destination, do not modify or remove the subject line of this email.
Nick,
"High Speed" is used to differentiate the M8008 ST Radial from other products we offer that are intended for industrial and/or commercial use, in slow speed applications. The Maxxis M8008 ST Radial carries a "Q" speed rating. However, according to the Tire and Rim Association, the U.S. tire industry specification authority, inflation pressures and load specifications in general for any ST Radial trailer tires without a service description, regardless of the manufacturer, are designed and rated at 65 MPH. However, if the speed is higher than 65 MPH, the pressure and load need to be adjusted according to the following guidelines:
From 66 to 75 MPH – the tire inflation pressure needs to increase 10 PSI (not to exceed the maximum PSI the tire is rated for) but requires no load adjustment.
From 76 to 85 MPH – the tire inflation pressure needs to increase 10 PSI (not to exceed the maximum PSI the tire is rated for) and load should be reduced by 10%.
We hope this information is helpful. Thanks for your inquiry and interest in Maxxis Tires.
Best Regards,
Your Maxxis Support Team
--
Maxxis International – USA
Email: MaxxisSupport@maxxis.com | Web: maxxis.com
--


09/07/2015 20:00

Submission from: Nick

Name::
Nick

Unequivocally, they state that the M8008 carries a Q (99 mph) service description. Then, they go on to cover other tires, which they qualify with the phrase "in general for any ST Radial trailer tires without a service description..." What follows is not meant to apply to the M8008, which they already gave a specific service description for, but to other ST tires in general. It would make no sense for them to give a 99 mph rating, then describe how to inflation and load can be adjusted to get to only 85 mph.

Edit: Maxxis says the inflation/load/speed adjustments apply to all ST tires, not just Maxxis, and I suspect that comes from the Tire and Rim Association yearbook. But, I'm not spending $119 to be sure.

[mileshuff]

RinconVTR wrote:
Why in the world would anyone study the load inflation charts for ST tires and adjust to the lowest PSI possible? That sounds insane to me!

True but the same can be said about simply running max cold PSI regardless of applied load. That said it is better to be over needed PSI than under as the latter is the prime culprit in over heating tires. I prefer to find the optimum for both load carrying/speed abilities as well as tire longevity and handling.

[mileshuff]

RinconVTR wrote:
Oh, so you believe if the Maxis ST in question is at max cold PSI their tire is rated for 99mph? Good luck with that!

That isn't what Maxxis stated. They state at max cold PSI at max rated load the tire is rated to 65mph. But if you run well under max load the speed rating goes up. Tire is rated to 99mph (Q rating) if under loaded sufficiently. Take a look at typical car tire specs. Manufactures will usually provide a table showing load vs speed vs PSI.

[mileshuff]

time2roll wrote:
Unless you go way up in size and load rating most all trailers are so close to the max that is where you run it.

Not the same as the oversize tires put on your vehicle so lower pressure and softer ride can be obtained.

You put tires on 2x the GVWR and you can start looking at tire pressure charts.

Thats true with stock tires TT manufactures install. Often they are right at the load limit. Manufactures trying to save a few $'s. When replacing with new tires I'd ALWAYS get a higher load rated tire. Not a place to skimp.

On both my popups I replaced the stock C tires with D's and ran them at 60PSI (Rated to 65). On my TT and 5th wheel I changed out the ultra cheap chinabomb D tires with E's. They are rated to 80PSI. I run them at 75 and find they wear quite a bit better while still having enough cushion room for load rating.

[mike-s]

RinconVTR wrote:
Oh, so you believe if the Maxis ST in question is at max cold PSI their tire is rated for 99mph?

I have no reason not to believe what Maxxis says in writing. In fact, since it's the manufacturer which does the rating, believing otherwise would be foolish. I do trust that nevadanick was truthfully quoting what Maxxis wrote.

RinconVTR wrote:
Most TT's and trailers in general have PSI recommendations of max cold. I've yet to personally see one stating less. Look at the sticker on your trailer, prove it to yourself.

Many trailers are near their limits - max PSI is on the sticker because that's what's required to support the GAWR rating with the minimal tires they spec. Put a bigger tire on, or a higher load range, or run at an actual weight significantly less than the GAWR, and there's no need to run at the max pressure, which will only help shake your TT apart.

[RinconVTR]

time2roll wrote:

mileshuff wrote:

RinconVTR wrote:
Question is, who in their right mind is running their ST tire at less than max cold PSI on their TT? Gotta be crazy not to.

Not sure why you would insist on running max cold PSI regardless of trailers weight and tire load capacity. Most tire manufactures list specs for their tires showing recommended PSI for a given load and speed for proper handling and tire wear. The max cold PSI rating is just that, the MAX it can handle, not what you should ALWAYS run them at regardless of load or speed.

Unless you go way up in size and load rating most all trailers are so close to the max that is where you run it.

Not the same as the oversize tires put on your vehicle so lower pressure and softer ride can be obtained.

You put tires on 2x the GVWR and you can start looking at tire pressure charts.

Precisely.

[RinconVTR]

mike-s wrote:

RinconVTR wrote:
Question is, who in their right mind is running their ST tire at less than max cold PSI on their TT?

That's meaningless for this discussion. The statements like "From 66 to 75 MPH – the tire inflation pressure needs to increase 10 PSI (not to exceed the maximum PSI the tire is rated for) but requires no load adjustment." apply whether you overinflate your tires or not. If you're already 10 psi over the load/pressure table, you're already good to run at higher speed.

Oh, so you believe if the Maxis ST in question is at max cold PSI their tire is rated for 99mph? Good luck with that!

Why in the world would anyone study the load inflation charts for ST tires and adjust to the lowest PSI possible? That sounds insane to me! (And keep in mind we're talking RV's that are always loaded, not empty haulers and such..but even then!)

Most TT's and trailers in general have PSI recommendations of max cold. I've yet to personally see one stating less. Look at the sticker on your trailer, prove it to yourself.

[mike-s]

RinconVTR wrote:
Question is, who in their right mind is running their ST tire at less than max cold PSI on their TT?

That's meaningless for this discussion. The statements like "From 66 to 75 MPH – the tire inflation pressure needs to increase 10 PSI (not to exceed the maximum PSI the tire is rated for) but requires no load adjustment." apply whether you overinflate your tires or not. If you're already 10 psi over the load/pressure table, you're already good to run at higher speed.

[Adam_H]

You don't need to increase rim size to get what you need. A 185/80/13 LR D tire is rated for 1710 lbs each, that's 3400 lbs per axle. Your camper maxes out at 5K?, it's a tandem axle.... So you can keep your 13" rims, install 185/13 tires and have 1800 lbs of capacity in reserve, not counting tongue weight which further increases this reserve. I think you'll be just fine, most trailers max out their tires / axles have little or no reserve. You could even keep the 175/13 tires and still have a comfortable reserve. Don't over think this.

Adam

[time2roll]

mileshuff wrote:

RinconVTR wrote:
Question is, who in their right mind is running their ST tire at less than max cold PSI on their TT? Gotta be crazy not to.

Not sure why you would insist on running max cold PSI regardless of trailers weight and tire load capacity. Most tire manufactures list specs for their tires showing recommended PSI for a given load and speed for proper handling and tire wear. The max cold PSI rating is just that, the MAX it can handle, not what you should ALWAYS run them at regardless of load or speed.

Unless you go way up in size and load rating most all trailers are so close to the max that is where you run it.

Not the same as the oversize tires put on your vehicle so lower pressure and softer ride can be obtained.

You put tires on 2x the GVWR and you can start looking at tire pressure charts.

[mileshuff]

Most on these forums seem to favor the Maxxis 8008 over the Carlisle HD. Main reason is history. The Maxxis have a long history of being one of the few decent ST tires. Carlisle had a long history of rather poor tires with frequent blow outs. A few years ago they made some changes and it does look like the new HD is a good tire with few problems but time will tell. Stay away from so called ChinaBomb tires such as TowMax, TrailerMax and many others.