Towmax shouldn't be rated for any speed in our opinion.
maximum speed towing a 3260 fifth wheel
- Thread starter SmithFamily
- Start date
Towmax shouldn't be rated for any speed in our opinion.
Jim.Allison
Well-known member
Tow max are speed rated at .65 mph. Anything over that you are taking your life into your own hands. LOL.
On the milage issue. Some of you guys have added larger aftermarket tires to your rigs. 1 inch larger diameter equals 3.14 inches larger circumference. I did this and my mileage went down according to the odometer readings. Doing the math I discovered that I was traveling 4% further than the odometer was showing, factoring that in my milage is about 10 mpg at 65 with a Ram 2500 with 6.7 Cummins and a BC3650RL if I'm not pulling grades. My distance was verified by my GPS.
Advice, get rid of anything resembling a Tomax, install TPMS and hold your max at 65. There are plenty of things you can do to improve you overall speed 1 being making the best of every stop. It takes time when ever you exit the highway.
On the milage issue. Some of you guys have added larger aftermarket tires to your rigs. 1 inch larger diameter equals 3.14 inches larger circumference. I did this and my mileage went down according to the odometer readings. Doing the math I discovered that I was traveling 4% further than the odometer was showing, factoring that in my milage is about 10 mpg at 65 with a Ram 2500 with 6.7 Cummins and a BC3650RL if I'm not pulling grades. My distance was verified by my GPS.
Advice, get rid of anything resembling a Tomax, install TPMS and hold your max at 65. There are plenty of things you can do to improve you overall speed 1 being making the best of every stop. It takes time when ever you exit the highway.
Crumgater
Well-known member
Speed is one thing... temperature is another... and they add up together.
While driving (a small car on business) the HOT highways of Arizona (sunny and 115F air temp) just West of Phoenix on I-10 where the speed limit goes up to 75, I would see at least one blowout at the side of the road a day - most were 5th wheels. Could have been blowmax issues, but I'm thinking they were going too fast on HOT pavement, and the combination overheated the tire, causing premature failure.
While driving (a small car on business) the HOT highways of Arizona (sunny and 115F air temp) just West of Phoenix on I-10 where the speed limit goes up to 75, I would see at least one blowout at the side of the road a day - most were 5th wheels. Could have been blowmax issues, but I'm thinking they were going too fast on HOT pavement, and the combination overheated the tire, causing premature failure.
alwayslooking
Member
Dave makes a good point. Additionally, everyone should understand the definition of "limit". It means "not to exceed." So, if you're going 65, you're probably at some point "exceeding" the limit. Add a hot day, potentially under-inflated tires....
I remember the day that we just drove . . . didn't matter what the outside temperture was!
And it wasn't that long ago!
BUT... We weren't pulling rigs that contained washer/dryers, convection ovens, residential French door fridges, a gazillion gallon water tank, hydraulic slides, leveling systems, oh...and don't forget the TVs and the electronics to pull this all off. Life is a give and take and we learn quickly that so is rving.
JohnD
Moved on to the next thing...
Jim.Allison
Well-known member
Re-enforcing your comment......As a former Border Patrol Agent, I used to walk the deserts of southern AZ. The desert floor can reach 130 to 140 degrees, I can only imagine what road surface temps can be. Once I was driving on the Papago Indian reservation with Chevy Suburban full of arrestees, when my A/C compressor blew a seal and released all the freon from the system, I'm sure it was from the heat. It was like driving in the fog until it cleared.
The desert in that region is unmerciful and it is like being on another planet, I don't think anywhere in Texas compares. Best advice; have great tires, and for 5ivers travel in the morning and evening and don't push those rigs, you cannot compete with mother nature. BTW, for some reason I never lost a tire except through punctures. Luck of the draw.
The desert in that region is unmerciful and it is like being on another planet, I don't think anywhere in Texas compares. Best advice; have great tires, and for 5ivers travel in the morning and evening and don't push those rigs, you cannot compete with mother nature. BTW, for some reason I never lost a tire except through punctures. Luck of the draw.
Shortest Straw
Caught In A Mosh
From Tire Rack:
[h=3]Special Trailer (ST) Tire Speed Ratings[/h] Industry standards dictate tires with the ST designation are speed rated to 65 MPH (104 km/h) under normal inflation and load conditions.
However Goodyear Marathon and Power King Towmax STR tires featuring the ST size designation may be used at speeds between 66 and 75 mph (106 and 121 km/h) by increasing their cold inflation pressure by 10 psi (69 kPa) above the recommended pressure for the rated maximum load.
Do not exceed the wheel's maximum rated pressure. If the maximum pressure for the wheel prohibits the increase of air pressure, then maximum speed must be restricted to 65 mph (104 km/h).
The cold inflation pressure must not exceed 10 psi (69 kPa) beyond the inflation specified for the maximum load of the tire.
Increasing the inflation pressure by 10 psi (69 kPa) does not provide any additional load carrying capacity.
I spent a good amount of time researching tires as I am not one to drive 65 mph anywhere. I was curious as to how much of a tire upgrade was needed to ensure I did not get a blow out myself. My curiosity was peaked when I started seeing the folks on here with the big 5ers blowing tires left and right and did not see the TT crowd mentioning any issues, myself included. Each summer we go to Lake Mac in NE with a group. In any given year there are 12 to 15 rigs from pop ups on up. None of us have ever had a blow out on these trips towing 75 to 80 mph. Couple this real time data to the FMCSA ST tire standards testing and I get more confused. To say that an ST tire is only safe to be towed at 65 mph is bunk when they only test them for endurance at 50 mph... For the speed testing they only test them at 88 percent of the load rating. So IMO they should not go down the road anywhere close to 65 mph. So although I am a bit more schooled on tires and how they test them, I cannot find any data out there that really helps me make a decision.
So I have to believe that maybe murphy has as much to do with things as anything else. You can say I should not tow my tt faster than 65 because you wont, that is ok by me. But is it ok for everyone? Absolutely not. Some folks out there should not be driving at all much less pulling an rv. Comfort level and knowing your limitations is as important as pre trips and taking care of your equipment.
Just last week we were going across TN. I heard on the CB of a "gator", blown tire, in the road. We were about rv number 6 in a long line of rv's. We had already changed lanes to miss it, the first 3 saw it and changed lanes as well. Number 4 ran it over, took out his plumbing, spewed waste all over the road, and blew his rear tire as well. Maybe just paying attention is important enough...
[h=3]Special Trailer (ST) Tire Speed Ratings[/h] Industry standards dictate tires with the ST designation are speed rated to 65 MPH (104 km/h) under normal inflation and load conditions.
However Goodyear Marathon and Power King Towmax STR tires featuring the ST size designation may be used at speeds between 66 and 75 mph (106 and 121 km/h) by increasing their cold inflation pressure by 10 psi (69 kPa) above the recommended pressure for the rated maximum load.
Do not exceed the wheel's maximum rated pressure. If the maximum pressure for the wheel prohibits the increase of air pressure, then maximum speed must be restricted to 65 mph (104 km/h).
The cold inflation pressure must not exceed 10 psi (69 kPa) beyond the inflation specified for the maximum load of the tire.
Increasing the inflation pressure by 10 psi (69 kPa) does not provide any additional load carrying capacity.
I spent a good amount of time researching tires as I am not one to drive 65 mph anywhere. I was curious as to how much of a tire upgrade was needed to ensure I did not get a blow out myself. My curiosity was peaked when I started seeing the folks on here with the big 5ers blowing tires left and right and did not see the TT crowd mentioning any issues, myself included. Each summer we go to Lake Mac in NE with a group. In any given year there are 12 to 15 rigs from pop ups on up. None of us have ever had a blow out on these trips towing 75 to 80 mph. Couple this real time data to the FMCSA ST tire standards testing and I get more confused. To say that an ST tire is only safe to be towed at 65 mph is bunk when they only test them for endurance at 50 mph... For the speed testing they only test them at 88 percent of the load rating. So IMO they should not go down the road anywhere close to 65 mph. So although I am a bit more schooled on tires and how they test them, I cannot find any data out there that really helps me make a decision.
So I have to believe that maybe murphy has as much to do with things as anything else. You can say I should not tow my tt faster than 65 because you wont, that is ok by me. But is it ok for everyone? Absolutely not. Some folks out there should not be driving at all much less pulling an rv. Comfort level and knowing your limitations is as important as pre trips and taking care of your equipment.
Just last week we were going across TN. I heard on the CB of a "gator", blown tire, in the road. We were about rv number 6 in a long line of rv's. We had already changed lanes to miss it, the first 3 saw it and changed lanes as well. Number 4 ran it over, took out his plumbing, spewed waste all over the road, and blew his rear tire as well. Maybe just paying attention is important enough...
danemayer
Well-known member
As I understand it, the speed rating is based on the tire's ability to shed heat. The faster you go, the more heat. At some point, the tire can't shed the heat that builds up. The internal temperature then climbs and climbs and climbs, eventually damaging the fibers. A speed rating of 65 mph is saying that above 65 mph, the tire cannot shed the heat that builds up.
Damage is irreversible and cumulative. The blowout may occur many miles/months down the road, just after you verified the inflation and have been driving at 60 mph.
The heat is caused primarily by flex. Tire Rack's advice is probably based on the idea that over inflation reduces flex, reducing heat buildup. The flip side of this is that under inflation increases flex, increasing heat buildup.
But notice that they don't attribute the recommendation to the manufacturer. Tire Rack can give you any advice, good or bad, and you can be sure if there's a bad outcome they will point you to the manufacturer.
JohnD
Moved on to the next thing...
Our old 1978 Coachman Cadet 24' had some unknown no-name brand I had never heard of off-road LT tires on it when we bought it, and they were already old then.
We owned that trailer for 12 years and I drove 70-90 mph almost all the time with that . . . never ever thought about tire issues . . . checked the pressure maybe one or twice each summer.
Took it to Taos, New Mexico many times and all over Colorado . . .
And . . . (I know this will get manys' goats here) . . . only did the wheel bearings once in all of those 12 years (first year we owned it) and never a problem with those, either!
Anyway, those tires were still on that old Coachman when we traded it in for our previous 2013 Heartland Trail Runner in September of 2012.
And I'll bet they are still on it today!
Now, the Trail Runner had BlowMax tires on it . . . we never had the blowout issues that many have had, and even I tried to atribute the BlowMax problems to big heavy 5th-wheel trailers (which is where the problem seems to be), and not so much with the smaller and lighter bumper pull trailers, but my theory got shot down many times here.
However, I got scared to death by reading all of the BlowMax stories . . . and worried every time I pulled it out of the driveway!
One thing about that Trail Runner . . . it had the rear kitchen so was heavy in the back, plus the axles were so close together that any time I ever inched over 65 mph, that thing would start to sway, despite having a good weight distribution setup with a sway bar.
So that alone made me keep it under 65 mph.
Our new Prowler had BlowMax tires on it at the dealership . . . but we left them behind when we pulled out with our new 5th-wheeler!
I'd like to go faster as I know the 5th-wheel setup would make it much easier to do, but I will keep the speed down to 65 for now!
We'll be pulling it over Wolf Creek Pass in a couple of weeks for a few days of leisure at Blue Mesa!
We owned that trailer for 12 years and I drove 70-90 mph almost all the time with that . . . never ever thought about tire issues . . . checked the pressure maybe one or twice each summer.
Took it to Taos, New Mexico many times and all over Colorado . . .
And . . . (I know this will get manys' goats here) . . . only did the wheel bearings once in all of those 12 years (first year we owned it) and never a problem with those, either!
Anyway, those tires were still on that old Coachman when we traded it in for our previous 2013 Heartland Trail Runner in September of 2012.
And I'll bet they are still on it today!
Now, the Trail Runner had BlowMax tires on it . . . we never had the blowout issues that many have had, and even I tried to atribute the BlowMax problems to big heavy 5th-wheel trailers (which is where the problem seems to be), and not so much with the smaller and lighter bumper pull trailers, but my theory got shot down many times here.
However, I got scared to death by reading all of the BlowMax stories . . . and worried every time I pulled it out of the driveway!
One thing about that Trail Runner . . . it had the rear kitchen so was heavy in the back, plus the axles were so close together that any time I ever inched over 65 mph, that thing would start to sway, despite having a good weight distribution setup with a sway bar.
So that alone made me keep it under 65 mph.
Our new Prowler had BlowMax tires on it at the dealership . . . but we left them behind when we pulled out with our new 5th-wheeler!
I'd like to go faster as I know the 5th-wheel setup would make it much easier to do, but I will keep the speed down to 65 for now!
We'll be pulling it over Wolf Creek Pass in a couple of weeks for a few days of leisure at Blue Mesa!
JohnD
Moved on to the next thing...
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