Important ST tire SPEED information

[Tireman9]

Originally Posted by dcasr

_________________

A key part of this discussion is knowing the actual weight on EACH tire, otherwise we are just guessing. I've used the CAT scale many times, every which way to get the most accurate weight I can, and I can get an axle weight, but the scales didn't let me drive with one axle on the scale and one off to the side---wasn't room enough.

The state weight inspectors sometimes have an individual pad that a truck can drive up on for one tire. On the internet I saw one scale for around $200 and many of them for $1,300 and up. What is your opinion on this?

+dcasr

Having your own scale might be nice if you have no other ues for your money. IMO you only need individual tire weights once. This tells you your balance. After than you can use the truck axle scale once a year to confirm you don't have weight creep.
Only exception would be if you discover major unbalance and end up mooving a lot of stuff around or even of loading a lot of stuff.


Call around to local grain or farm supply businesses. Gravel and some cement dealers also have scales where you can get just one side of the RV on the scale.
This worksheet will help you do your own calculations.
Check on-line RVSEF on their schedule.

[mojo]

There are Escapes RV parks that have individual tire scales and people to do the weighing. Located in FL, TX, & AZ.

[CruizinDux]

Varies by are obviously but don't forget county owned and maintained ag scales. In my area, the county has installed a few single axle scales on the outskirts of Eug/Spfd . Not manned,free, just drive on, weigh shows on a monitor. Room to swing side for a single tire weigh. I wasn't sure of the accuracy but my last weigh, the county was there calibrating. Nice too, it',s a mile from the TT Storage😀
Bob

[switters]

Not sure if anyone is still following this thread, but I just bought a 2018 FC 23FB. I've been watching videos to learn about it, and someone mentioned the issue of the stock tires being only rated for 65 mph. Does the information posted in this thread pertain to the stock Airstream tires? It sounds like I can increase PSI by 10 if I want to drive between 66-75 mph, and that will still be safe? I have no intention of towing a trailer >75 mph.

[Dan and Liz]

Tire brand and size?

[Mattirs]

Originally Posted by switters

Not sure if anyone is still following this thread, but I just bought a 2018 FC 23FB. I've been watching videos to learn about it, and someone mentioned the issue of the stock tires being only rated for 65 mph. Does the information posted in this thread pertain to the stock Airstream tires? It sounds like I can increase PSI by 10 if I want to drive between 66-75 mph, and that will still be safe? I have no intention of towing a trailer >75 mph.

If you have the Goodyear Marathon tiers that is true, but it does not increase the load carrying capacity. It also makes for a rougher ride in thr trailer bouncing things around a lot inside.

Thanks
Matti

[switters]

I assume it's the brand/size that the 2018 Flying Cloud 23FB came with (15" Goodyear Endurance), but I'll have to report back with a definite answer. The trailer is still on the dealer's lot. We bought it, but it's having solar and a trailer hitch installed (for a bike rack) and we haven't picked it up yet.

[n2916s]

The Goodyear Endurance tires have a speed rating of N which is 87mph. They are standard equipment.

[OldDogGone]

I don't completely understand everything in the thread above. So these may be elementary questions but here they are:
1. On single-axle 22FB I currently have one fairly new Goodyear Marathon and one similar age Maxxis M8008 (this is due to accident to tire in west TX). So I have one tire with 65 max psi and other with max 80 psi. This is due to the load rating, correct? i.e. D rated versus E rated? If you keep both within 5psi of max is the uneven max unsafe or adverse affect handling?
2. If I go ahead and replace now do I need the 10-ply tire since my Sport Bambi came equipped with the 8-ply tire? Original GY Marathon was D rated? discontinued and replaced by GY Endurance E rated? that is what i was told by local dealer. He will sell me two GY Endurance for $373 or two Taskmaster Contender for $249; he tells me the Contender is 80 psi max which would be E rated? I think both of these tires come in D and E so not sure I am comparing apples to apples.
Thanks for any feedback

[CruizinDux]

No shortage of threads on GYE. Personally I tossed the GYM's at about 18K miles and have the GYE's with 3 XC trips (OR to the east coast) and about 40K miles on them.

IMO, loose the GYM ASAP, and go with 3 GYE's and keep them in balance and rotation. Tires are cheap, TT damage is considerably more and with a Bambi, our per tire load & margin above payload is a critical factor. Bottom line, weigh you trailer, know the per tire load and how trailer loading L vs R & F vs B affects that. Fresh Water and propane are key variables. Personally no experience on the Maxxi's but certainly there are those on this forum that do,. Once forums comment that directed me elsewhere was "...they have a great warranty "


As they say...Free advise is what you pay for it. Read from the start and listen to Tireman9 and CapriRacer's very sound advice

https://www.airforums.com/forums/f43...ml#post2384141


Also consider Nokian's. I only went with the GYE's because I knew they would fit in the spare holder. The Nokians are incrementally larger and I was leaving on a XC trip the following week. I saw them a lot around town in Eugene (previous residence) on TT's and horse trailers. Now made in TN I believe. Almost the same spec as the GYE E rated.

[BayouBiker]

Originally Posted by billrehberg

I don't completely understand everything in the thread above. So these may be elementary questions but here they are:
1. On single-axle 22FB I currently have one fairly new Goodyear Marathon and one similar age Maxxis M8008 (this is due to accident to tire in west TX). So I have one tire with 65 max psi and other with max 80 psi. This is due to the load rating, correct? i.e. D rated versus E rated? If you keep both within 5psi of max is the uneven max unsafe or adverse affect handling?
2. If I go ahead and replace now do I need the 10-ply tire since my Sport Bambi came equipped with the 8-ply tire? Original GY Marathon was D rated? discontinued and replaced by GY Endurance E rated? that is what i was told by local dealer. He will sell me two GY Endurance for $373 or two Taskmaster Contender for $249; he tells me the Contender is 80 psi max which would be E rated? I think both of these tires come in D and E so not sure I am comparing apples to apples.
Thanks for any feedback

Load carrying capacity and handling considerations are largely a function of pressure so keep them evenly inflated at about 60 psi. Even then, It is not a good idea to run mismatched tires due to more subtle differences in handling characteristics so consider replacing them as soon as is practical. The handling difference may enhance sway tendency due to differences in cornering stiffness which will increase Yaw and induce some periodicity while cornering.

You are correct D rated tires are designed for 65 psi and E 80 psi.

E rated tires in principle will be more durable and less likely to fail catastrophically. this is particularly true if you slightly overinflate them relative to load. So if your load dictates 55 psi, running them at 62 will greatly reduce risk. Higher pressure even more so, though there are handling considerations particularly if your vehicle is near max towing capacity you will want to refrain from high trailer tire pressure.

Hope that gives you some idea on how to choose the tire that is right for your trailer.

[CapriRacer]

Originally Posted by billrehberg

I don't completely understand everything in the thread above. So these may be elementary questions but here they are:
1. On single-axle 22FB I currently have one fairly new Goodyear Marathon and one similar age Maxxis M8008 (this is due to accident to tire in west TX). So I have one tire with 65 max psi and other with max 80 psi. This is due to the load rating, correct? i.e. D rated versus E rated? ....

Correct

Originally Posted by billrehberg

....... If you keep both within 5psi of max is the uneven max unsafe or adverse affect handling?......

You want to keep the tires at the same pressure, not a pressure relative to the max!

Originally Posted by billrehberg

....... 2. If I go ahead and replace now do I need the 10-ply tire since my Sport Bambi came equipped with the 8-ply tire? Original GY Marathon was D rated? discontinued and replaced by GY Endurance E rated? that is what i was told by local dealer. ......

No, you don't NEED the 10 ply, but why not upgrade since you have the chance.

Originally Posted by billrehberg

...... He will sell me two GY Endurance for $373 or two Taskmaster Contender for $249; he tells me the Contender is 80 psi max which would be E rated? .....

Correct

Originally Posted by billrehberg

........I think both of these tires come in D and E so not sure I am comparing apples to apples.
Thanks for any feedback

The Endurance only come in E, and if I looked this up right, so does the Taskmaster Contender.

Consensus is that the Endurance is the one known tire that works. Everything else is either unknown or known not to work.

[JohnandDonna]

Ok, I have been told by my AS dealer and verified it with my local Goodyear dealer. Endurance ST tires should be set at 80 psi cold regardless. And yes they are rated up to 87 MPH. I personally try to stay 65/70 on the interstates but have gotten up to 75 on a couple of occasions passing.

[Tireman9]

Originally Posted by billrehberg

I don't completely understand everything in the thread above. So these may be elementary questions but here they are:
1. On single-axle 22FB I currently have one fairly new Goodyear Marathon and one similar age Maxxis M8008 (this is due to accident to tire in west TX). So I have one tire with 65 max psi and other with max 80 psi. This is due to the load rating, correct? i.e. D rated versus E rated? If you keep both within 5psi of max is the uneven max unsafe or adverse affect handling?
2. If I go ahead and replace now do I need the 10-ply tire since my Sport Bambi came equipped with the 8-ply tire? Original GY Marathon was D rated? discontinued and replaced by GY Endurance E rated? that is what i was told by local dealer. He will sell me two GY Endurance for $373 or two Taskmaster Contender for $249; he tells me the Contender is 80 psi max which would be E rated? I think both of these tires come in D and E so not sure I am comparing apples to apples.
Thanks for any feedback

Since your OE tires were Load Range D (8-PR)You should run nothing lower. Your Vehicle certification indicates 65 psi. You should run nothing lower.
Ideally you have bee on a Truck scale with the trailer fully loaded to the heaviest you ever expect to be.
Consulting Load & Inflation tables you can learn the absolute MINIMUM inflation you would ever run.
Due to the fact that trailers are being dragged around every turn and corner there are much higher internal stresses in this application so you need to take extra precaution to lower Interply Shear which means run at least LR-D inflation i.e. 65 psi. Normal advice is to inflate all tires on an axle to the same level.
Yes th words on the tire sidewall can lead to the idea that you should never see inflation higher than that number but the real issue is that the tire has a Maximum load capacity which is based on the tire being inflated to the pressure indicated so in reality the inflation number is the MINIMUM you should run to support that load (see we are back to knowing your load and inflating accordingly)
Since you have LR-D & LR-E tire on the RV and since all tires should run the same inflation you should be setting the inflation, when the tires are at ambient temperature to the LR-D inflation which is 65.


If you stay with your OE size and want to use Goodyear tires that is OK to go with their LR-E tires. They can carry more load.
SO with the scale reading in hand and consulting the Load tables you have an advantage of being able to select an inflation that will give you a Reserve Load of at least 15%.
Example: your tire size is ST225/75R15 scale reading is 3550# on the axle. Add 20% to get a good margin and you get 4.600 or 2,330# for each tire. An ST225/75R15 needs a Minimum of 60 psi to support 2330#.
Now since I advise you add 10# to that inflation so you do not need to mess with inflation when the weather cools down (2% pressure change with each change of 10°F) you would have a target inflation of 66 psi when using your hand gauge.


With those numbers I would set my low Pressure warning on my TPMS to 60 Psi. You can leave the TPMS Temperature warning level at the factory 158°F (70°C) and you can set the High pressure warning to 66PSi + 25% or 83 psi.
Hope this helps.

[Tireman9]

Originally Posted by JohnandDonna

Ok, I have been told by my AS dealer and verified it with my local Goodyear dealer. Endurance ST tires should be set at 80 psi cold regardless. And yes they are rated up to 87 MPH. I personally try to stay 65/70 on the interstates but have gotten up to 75 on a couple of occasions passing.

I read CapriRacer after doing my example post. I agree with what he has said. I would offer the following information.


1. When the formulas fo calculating tire load for ST type tires were first developed (1960's) the load capacity was based on a stated 65 mpr Max operating speed.
2. The formula has not been changed so I do not understand why the speed can be increased but need no adjustment in load capacity or operating speed.
3. Truck tires used in RV application have a max operating speed stated by Michelin and Goodyear in their RV Data books of 75
4. The addition of "Speed Symbol" was done in 2018 in response to import duty changes that penalized tires without a Speed Symbol
5. All ST type tires went from 65 to much higher speed almost overnight at the end of 2018. While some may have made construction changes to allow some increase I do have to wonder how all tire companies managed to do that in a matter of weeks.
6 The Speed test is intended for "Passenger" tires and in reality is a heat resistance test.


Question: If tire companies can make St type tires that are capable of going 87 or in some cases 99 or higher, Why can't they do the same for their LT tires (Class-C RV or Class-A RV?) Just asking.


Yes the GY endurance has construction features that in my opinion mean it is probably better than the GY Marathon. However If the Marathon was recognized as not particularly great with a 65 mph max operating speed, why not consider the improvements seen in the Endurance simply good enough to get more than two years use out of the tires rather than going faster and possibly ending up with tire failure but at a faster speed?
If it were me I would be shooting for longer tire life rather than faster speed, but that's just my opinion.

[OldDogGone]

your tire size is ST225/75R15 scale reading is 3550# on the axle. Add 20% to get a good margin and you get 4.600 or 2,330# for each tire. An ST225/75R15 needs a Minimum of 60 psi to support 2330#.
Now since I advise you add 10# to that inflation so you do not need to mess with inflation when the weather cools down (2% pressure change with each change of 10°F) you would have a target inflation of 66 psi when using your hand gauge.

My trailer weight is 3480; close to your example weight above; when I run through the calculations from you, I get 2088 / tire. So I should still go for 66psi even though slightly lower weight / tire?

[BayouBiker]

Bill,

From the chart You'd need a minimum of 48 psi, then adding 10% would move you to 53 psi. If you exceed 65 mph then 58 psi would be better.

[ITSNO60]

If I recall Tireman9 and others revised their advice on ST tires and now recommend inflating them to the value printed on the tire sidewall in all cases instead of using load and inflation tables to arrive at a lower pressure than is stated on the sidewall. I remember reading it on one of Roger's posts but I can't find reference to it on his blog.

[BayouBiker]

He has indeed recommended that, I believe from a tire safety and longevity perspective, particularly when one has the OEM tires on the trailer and the Airstream label provides that guidance.

But if you look above, he was providing Bill guidance on replacement tires and used the inflation tables so I just finished the guidance using his formula. Perhaps he will speak to the difference.

[ITSNO60]

My post wasn't directed to anyone in particular, I was just wanting to bring it up since reading this thread yesterday, I felt that it would be pertinent here. I first tried to find Roger's revised advice from a while back but was unsuccessful.