Noob questions - Towmax tires on Edge M21

[evolvingpowercat]

My 2011 Edge M21 has 4 Towmax 14" "C" rated tires on its dual axles, Total load capacity of 6800 lbs, the Max loaded weight of the trailer is 4500 pounds. It appears to have the original TowMax tires on it, they have plenty of tread.

1. Should I replace with another set of "C" rated tires when its time to replace, or would it make sense to buy the same size but "D" rated next time, they cost about 20 percent more than "C" rated.

2. The lug nuts are all torqued at leat to spec, I checked them myself.

3. I ran my hands around in and out sidewalls of all 4 tires and feel no bulges or other anything else strange. The tread does not seem to have any obvious abnormalities either.

4. I put 50 lbs in all 4 tires when cool and have rechecked 5 days later and all are holding the pressure.

5. The RV dealer delivery tech that repacked all the wheel bearings before delivery says they were fine but he also delivered the trailer to me with on 30 lbs of air in each tire when the trailer sticker and tire sidewalls clearly say 50 lbs so am taking his statements with a grain of salt. Also have no clue if or how many curbs the original owner drove these over before I got it.

Anything else I should be doing please ?

 

[TravelTiger]

As a TowMax hater, I would just say, watch them like a hawk. Look closely for indentations or cracks in the sidewall, and any stretching of the tread, or the gaps between the raised tread pattern that start to appear wider. Seems like your tires might be OK for now.

Another suggestion I read is to use a UV inhibitor, such as this.

Erika

 

[evolvingpowercat]

Thanks. I just found a interesting Tire Tech Information post on TireRack.com that states ST tires are only speed rated to 65 MPH at the normal inflation and load conditions.
Never saw this mentioned in the Heartland Owners Manual and the tech that delivered my trailer to me never mentioned any safe speed limit of 65 MPH due to ST type trailer tires when towing. Is this a possible cause for tire failures. I sure see lots of people pulling trailers doing much faster than 65 MPH.

The Tire Rack post says add more air pressure when using the tires between 65 MPH and 75 MPH. Is this right and I just now am learning about it ? I am thinking of going from 50 to 55 PSI before taking a 300 mile round trip this starting tomorrow with the M21 where I will be using 75 MPH speed limit Rural Interstate on my route - comments?


Special Trailer (ST) Tire Speed Ratings
Industry standards dictate tires with the ST designation are speed rated to 65 MPH (104 km/h) under normal inflation and load conditions.
However industry standards also stipulate, if tires with the ST designation are used at speeds between 66 and 75 mph (106 and 121 km/h), it is necessary to increase 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.

 

[evolvingpowercat]

I stand corrected - Heartland "does" state in the owners manual that ST tires are speed restricted to 65 MPH (page 36). They do not document any scenario where above a speed above 65 MPH is OK when pulling a trailer with ST tires, so guess we are each "on our own" deciding if the Tire Rack tech note about adding air if using above 65 MPH is valid or not.

 

[TravelTiger]

I can't find the reference now, but my understanding is that the molecules that make up the rubber can degrade faster due to excess heat generated by driving over the tire's speed rating. So basically, you are asking for a failure to occur, sooner. We try very hard to not exceed 65, no matter the speed limit signs. We were once passed by a truck pulling a trailer at 70+ in 100 degree weather. About 15 miles down the road, on the shoulder, there they were, with a blowout.

E

 

[danemayer]

The portion of the tire in contact with the road is flattened a bit, flexing the steel belts. This generates heat. The faster you go, the faster the flexing occurs and the harder it becomes for the tire to dissipate the heat. When you drive fast, you're accelerating wear of the tire's internal structure and increasing the likelihood of failures like blowouts.

Underinflated tires flex more with similar results.

Now think about taking a paperclip and bending it back and forth. The faster you bend, the hotter the metal gets and the sooner it breaks.

 

[evolvingpowercat]

Thanks, I appreciate the confirmation that common sense should prevail and I should just set the cruise control to 65 MPH and not push things, in particular given all the "china bomb" posts I see on this forum.

 

[TireHobby]

RV trailer tire history is so important that you should never drive out of the dealers lot with anything less than new tires, put on at PDI. Then, check the tire pressures before leaving. Then, and only then, will the tire history be your responsibility.

You know, at 30 psi, your tires were considered flat when delivered. The industry standard says any tire being operated with less than 80% of it’s recommended tire pressure is considered in the “run flat” condition and should be removed from the rim for inspection.

ST tires manufactured under the Goodyear brand name are the only ones that can be manipulated with tire pressure to increase speed. Other manufacturers only allow full sidewall pressures and 65 mph.

　
TireHobby

 

[evolvingpowercat]

> never drive out of the dealer's lot with anything less than new tires ...

Thanks, I file that away for the future when its time for travel trailer # 2.