Tire Manufacturer claims 10% load reduction for every 10 MPH over 65 MPH

[jeeplj8]

I am posting this as a new thread as I thought it had such a general application, everyone should see this info.

Please look at page 2 of this thread:
http://www.forestriverforums.com/for...res-43403.html

In it you will see a direct response from Maxxis, a leading tire manufacturer, to a dealer inquiry about their speed rating on tires.

The general take away from their post is that you need to deduct 10% from the max load carrying capacity stated on a tire for every 10 MPH over 65 MPH. In other words, at 76MPH you tires are only capable of 80% of their load carrying capacity.

[w4drr]

I just wonder if that formula can be applied to all ST tires. Maxxis is considered by many to be one of the best manufacturers of trailer tires. When they make that claim, I'm sure they are speaking of their tires in particular. For many of us, our original tires are cheap Chinese tires that only got on our trailers by virtue of the fact they were the lowest bidder.

Bob

[jeeplj8]

Originally Posted by w4drr

I just wonder if that formula can be applied to all ST tires. Maxxis is considered by many to be one of the best manufacturers of trailer tires. When they make that claim, I'm sure they are speaking of their tires in particular. For many of us, our original tires are cheap Chinese tires that only got on our trailers by virtue of the fact they were the lowest bidder.

Bob

So far in my research I have found 4 tire manufactures that claim (directly or indirectly) a speed rating higher than 65 mph. At this point I think the safe interpretation is that any ST trailer service tire rated for speed higher than 65 should use this formula to find load capacity above 65 MPH.

[Herk7769]

This makes perfect sense.

Goodyear increases Speed Rating by adding otherwise unnecessary air pressure (above that required for the load - short of max sidewall and rim pressure).

Sort of looking at the same issue from the other direction.

[w4drr]

I generally play it safe and hold my speed to 65 anyway. And something to remember, in many states the speed limit for towing is sometimes less than the posted limit. Typical is 55 MPH, but I don't think that limit is actively enforced. Right off hand, I have never heard of anyone getting busted for going over the towing limit, but still at, or below, the posted limit.

Bob

[jeeplj8]

Originally Posted by herk7769

This makes perfect sense.

Goodyear increases Speed Rating by adding otherwise unnecessary air pressure (above that required for the load - short of max sidewall and rim pressure).

Sort of looking at the same issue from the other direction.

What is interesting to me is that Goodyear is advocating raising tire pressure 10 psi ABOVE the max posted on the tire, while Maxxis is stating you should NEVER go above the "MAX" psi.

In other words, Goodyear is saying it is OK to go to 75 psi on a 65 psi tire, which may not be OK on other brands.

Well, at least it is simple and straightforward...

[ependydad]

Originally Posted by jeeplj8

What is interesting to me is that Goodyear is advocating raising tire pressure 10 psi ABOVE the max posted on the tire, while Maxxis is stating you should NEVER go above the "MAX" psi.

In other words, Goodyear is saying it is OK to go to 75 psi on a 65 psi tire, which may not be OK on other brands.

I have never read Goodyear's words that way, but you're not the first that I've seen interpret them that way. I got the impression that you shouldn't exceed the tire's sidewall maximum pressure nor the wheel's maximum pressure.

The only way to achieve the higher speed rating is if you look at the load table and adjust the pressure according to your load. For instance, my load on a load range E Maxxis tire is 65psi required. Since my tire + wheel can support up to 80 psi, I can safely go to 75psi on the tire and drive up to 75mph without exceeding any ratings.

Maybe I'm misinterpreting it.

[OldCoot]

Too confusing for my feeble mind. I'll stay with 65psi and 65 mph max.

[ependydad]

Originally Posted by OldCoot

Too confusing for my feeble mind. I'll stay with 65psi and 65 mph max.

LOL- true that. I'll stick with 80psi and 65mph max, too.

But, I like knowing that there's a margin for adjustment there if I need it for some reason.

[OldCoot]

I think for a short distance(1.0 -2.0 miles), getting above 65mph is not going to harm anything, sustained speeds in excess of 65mph will no doubt do irreparable damage that will appear later. JMO.

[Herk7769]

Originally Posted by jeeplj8

What is interesting to me is that Goodyear is advocating raising tire pressure 10 psi ABOVE the max posted on the tire, while Maxxis is stating you should NEVER go above the "MAX" psi.

In other words, Goodyear is saying it is OK to go to 75 psi on a 65 psi tire, which may not be OK on other brands.

Well, at least it is simple and straightforward...

You need to re-read that. It says up to 10 PSI above the pressure required for the load; but no higher than the sidewall or rim rating.

[jeeplj8]

not to get all lawyery, but:
•
Based on these industry standards, if tires with the ST designation are used at speeds between 66
and 75 mph (106 km/h and 121 km/h), it is necessary to increase the cold inflation pressure by 10
psi (69 kPa) above the recommended pressure for the rated maximum load.

The "recommended pressure for the rated maximum load" is in fact 65 psi. Goodyear is specifically advocating using a tire pressure above "rated maximum load" for high speed driving. They do note this does not increase the load carrying capacity.

[ependydad]

Originally Posted by jeeplj8

not to get all lawyery, but:
•
Based on these industry standards, if tires with the ST designation are used at speeds between 66
and 75 mph (106 km/h and 121 km/h), it is necessary to increase the cold inflation pressure by 10
psi (69 kPa) above the recommended pressure for the rated maximum load.

The "recommended pressure for the rated maximum load" is in fact 65 psi. Goodyear is specifically advocating using a tire pressure above "rated maximum load" for high speed driving. They do note this does not increase the load carrying capacity.

I think Goodyear's terminology is confusing, at best.. I read "rated maximum load" as being equal to *YOUR* maximum load on the tire. Meaning, the PSI required to carry the load that you're putting on the tire.

In fact, looking at this page on
GoodyearRVTires.com, they use the same terminology, but it reads slightly differently:

• Select a tire with load carrying capacity designed to handle the maximum load point
• For each axle determine the correct inflation pressure needed for that size tire to handle the maximum load

I think their reference to "maximum load" isn't the maximum load that the tire is capable of carrying, it's the "maximum load" you're putting on the tires. Because, poking around that GoodyearRVTires.com site- their recommendation is that you weigh each individual wheel and then go with the highest weight/load capacity required and keep the tires at the same PSI.

BUT- it's definitely unclear.

[jeeplj8]

"Maximum rated load" is not so much a technical term (well OK it is) but a legal term. The legal description is exactly what is posted on the tire. This was of course a little issue that came up between Firestone and Ford a few years ago. Despite testimony about industry standard rating techniques, it was agreed, and specifically stated by the court, that the legal definition of "maximum rated load" is what is printed on the side of the tire.

I am simply pointing out, and am very confident in this statement, that Goodyear has publicly stated that they recommend exceeding their own "maximum rated load" pressure.

Something tells me their internal counsel has not reviewed that statement.

[ependydad]

Originally Posted by jeeplj8

What is interesting to me is that Goodyear is advocating raising tire pressure 10 psi ABOVE the max posted on the tire, while Maxxis is stating you should NEVER go above the "MAX" psi.

In other words, Goodyear is saying it is OK to go to 75 psi on a 65 psi tire, which may not be OK on other brands.

Well, at least it is simple and straightforward...

Well, I think it may be a moot point. If you have a 65 psi tire, you're running a load range D tire. That also means, you're likely running on rims that are limited to 65 psi. (Or, am I making that part up?) Goodyear does specifically state to not exceed the rim/wheel maximum pressure.

Though, out of curiosity - I've emailed Goodyear with the question. We'll see if they respond.

[ependydad]

Originally Posted by jeeplj8

"Maximum rated load" is not so much a technical term (well OK it is) but a legal term. The legal description is exactly what is posted on the tire. This was of course a little issue that came up between Firestone and Ford a few years ago. Despite testimony about industry standard rating techniques, it was agreed, and specifically stated by the court, that the legal definition of "maximum rated load" is what is printed on the side of the tire.

I am simply pointing out, and am very confident in this statement, that Goodyear has publicly stated that they recommend exceeding their own "maximum rated load" pressure.

Something tells me their internal counsel has not reviewed that statement.

Interesting, I didn't know that.

[jeeplj8]

Well, since I apparently had nothing better to do and could not let this go, I contacted Greenball directly as they are the only company I am aware of that specifically lists their tires speed rating at L (75mph) on their website with no caveats. A very nice lady in their customer service department put me in touch with an engineer who stated "Our Maximum Rated Load is calculated at our speed rating. So that means we calculated it at 75 mph."

[pt1655]

I must be an old fart but I choose to tow at 60mph. I like knowing towing at that speed is easier on tires, suspension,the truck and myself. My 2012 Dodge Ram1500 4X4 5.7L Hemi with Husky weight distributing hitch and tow package is tow rated at 8500lbs and our 25' Surveyor SP220 weighs 5000lbs loaded so I am a bit over half of our rating so I feel comfortable at that speed. Sorry if I don't do 75 or 80 like some of my friends here in Az towing their 40foot fifth wheels on our 75mph posted highways. One friend in particular has had 2 blowouts at those speeds recently on his 38' fifth wheel on relatively new trailer tires and wonders why.

[bakken]

Thanks guys for all the info.
It is great to know that putting Maxxis tires on my fifth was the correct move.
By upgrading to D-rated tires, I have the capability to run all day at 85 mph!
Of course, I don't run at 85 mph, so those tires should last a long, long time.
Maxxis, worth every penny.

[OldCoot]

Originally Posted by pt1655

I must be an old fart but I choose to tow at 60mph. I like knowing towing at that speed is easier on tires, suspension,the truck and myself. My 2012 Dodge Ram1500 4X4 5.7L Hemi with Husky weight distributing hitch and tow package is tow rated at 8500lbs and our 25' Surveyor SP220 weighs 5000lbs loaded so I am a bit over half of our rating so I feel comfortable at that speed. Sorry if I don't do 75 or 80 like some of my friends here in Az towing their 40foot fifth wheels on our 75mph posted highways. One friend in particular has had 2 blowouts at those speeds recently on his 38' fifth wheel on relatively new trailer tires and wonders why.

Agree, those that have to tow at speeds in excess of 60-65 justify it saying they don't want to impede the flow of traffic. I guess they think the others can't see them or something. I will continue to impede traffic by creeping along @ 60-65.