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Friday, October 25, 2019

New Truck with old Trailer, Sway (Stability) issues

I was asked by the moderator of an RV trailer forum to jump in on the topic by one of the members. Here is my response. I thought the info might be of interest to others.

My prime area of expertise is on tires, but I have also done extensive long-distance towing with a C3500 (454 gas) Dually with an 8' slide-in camper in the bed and pulling a 26' enclosed trailer with a  Camaro race car,

 tools, etc inside. I have towed from OH to FL and Calif and even made a trip on the Blue Ridge Pkwy while towing the race car trailer so I think I understand the handling situation of a loaded truck and trailer.

Some observations on info in some of the posts in this thread.

"P" type tires on the TV should be an indication that the TV should probably be limited to single axle "pop-up" or small boat trailers. It is important to remember that P-type tires must be "de-rated" in load capacity by 10% as they are not intended for truck or trailer application. Multi-axle trailers almost always indicate the need for a real truck (not just something that looks like one) This would mean LT type tires and 3/4 or 1-ton vehicle rating.
HERE is a good post on how to match a Truck & Trailer. It is much better to do a little work and learn the ratings of both your truck and trailer than relying on the salesperson telling you that you can pull a 5-ton trailer with a Ford Ranger just so he can make the sale.

P vs LT type tires. No, they do not make tires "between" these two types. If there is no P or LT before the numbers in the size then it is what is known as a "Euro-Metric" type tire and with an inflation of 36, it is definitely a P-type tire.
The P and LT and ST designations are found in tires designed and intended for highways in America. The inflation level molded on the tire sidewall is the give-away.

35 or 36 is standard Passenger type tire
50, 65, or 80 or higher is an LT type tire or a trailer only ST type.
In Europe, they use a "C" after the size to identify "Commercial" use i.e. LT. Don't confuse this with Load Range C which is the US Light Truck Load Range (old ply rating)

Tires marked "XL" or "Extra Load" are Passenger type tires (Max infl. 42 or 51 on some) that aren't quite LR-C Light Truck tires. This type was originally intended for "Station Wagons" which have been replaced by SUV but are many times used on light duty trucks as a cost-savings measure. (Passenger are really LR-B or "standard" load except for the XL passenger tires, but none say LR-B)

Vehicle "Sway" is a function of the tire inflation and the suspension design and vehicle loading. When inflated to the sidewall pressure there can be different sidewall stiffness but the difference should not be significant within the same Type tire and same Load Range.

Weights. Empty weights are really of little value in determining what will run down the highway safely. Fully loaded and hooked up individual axle loads are what is needed. With trailers (and motorhomes) it is even better to know the scale weight on each individual tire position when the vehicles have been loaded to their heaviest, as many RVs have been found to be 500 to 1,000# out of balance side to side. No, you don't have to get on a scale every trip but should have at least one set of readings when fully loaded.

Increased tire inflation will almost always result in improved stability.

New Tire "squirm". When you apply any new tire to any vehicle you may notice for the initial 100 to 200 miles less stability than on the tires you just took off. This happens for a few different reasons.
1. All tires have a "release agent" that allows them to be removed from the curing mold. This is a slippery substance that will wear off in a few miles.
2. When you buy new tires you are not making a clean, apples to apples comparison. You, as the driver, are comparing a worn older tire with a new full tread tire. Even if the tires were identical in construction and rubber compound you will get crisper and more solid handling with a worn tire (less tread) than a new (more tread) tire. In car racing, our tires may only have 2/32 or 3/32 tread depth while new tires come with 8/32 to 12/32 or more tread depth. In some classes of racing that require the use of "street" tires new tires have most of their tread "shaved" off with the express purpose of improving handling.

Getting scale weights. While you may not want to make a special trip to a truck scale or gravel pit or feed supply to get your individual tire loads you can at least stop at a truck stop on the Interstate on your next trip to get a reference number for each axle.
HERE is a worksheet to allow you to calculate individual position weights.
and HERE is a Youtube video on how to weigh on a truck scale.

Trailer tire inflation:
To lower the Interply Shear (force trying to create a tread separation) You should run AS A MINIMUM the inflation required to support 110% of the MEASURED load on the most loaded tire. Better yet run the tire sidewall inflation number. You can learn more from THIS Google search or go to my blog and read up more than you ever really want to know about the tire mechanics involved in the tire construction.

Hope this helps.

Friday, October 18, 2019

Run-Flat tire device questions.

Starting in 1972 I worked on a number of different "Advance Tire" projects Some were looking at an "aftermarket" device that could be placed inside a tire to offer some "Run-Flat" capability. Foam Aluminum and foam Urithane were used. These worked but were too heavy and expensive for general use by the trucking industry and they were not willing to pay the penalty of the original cost and the loss of load capacity for the truck. Visually they would resemble the Rettroband. Here is a picture of a similar device.  Having watched the Rettroband video it appears they have a unique method of "attaching" the ring which was one of the areas we did not finalize.
I was also the project leader on the original "Run-flat" tires applied to the people mover train at the then-new DFW airport. This approach involved filling the air chamber with a rubber foam material (not urethane but flexible rubber)  I believe that this is the approach used on some military vehicles today.

This is not some secret "magic" stuff that is being kept from public use by the military as some have suggested and it is not some "Area 51" SiFi material. Just rubber with a blowing agent. If you were willing to spend maybe $500 - $1,000 a tire, limit speed to an average speed of 25 - 30 mph and do a complete redesign of your front suspension to handle the 150 to 200-pound increase in tire assy weight, I believe you can have this on your vehicle. Oh, you also would need to be willing to scrap the wheels when your tire wears out and you can not dismount a foam-filled tire.  Other "run-flat" military systems use a flat base multi-piece wheel with an internal ring along the lines seen here.
Note how the flat base multipiece wheels are assembled.

Other approaches involved going from 22.5 wheels to 26.5 diameter wheel while retaining the same OD, width and load capacity as the original 11-22.5. We even had about 600 special wheels manufactured and we applied these wheels and tires to hundreds of HD trucks. I posted info on my tire blog about these tires. The problem with these tires is they needed new wheels. While these tires provided significant improvements in vehicle control with a sudden loss of air on the front. the trucking industry did not feel the improved safety outweighed the increased cost of new wheels.

The Tyron system does not appear to offer any support of the tire tread or feature to limit the "drop" which IMO is an important feature of limiting the degradation or loss of vehicle control due to "blowout" but is intended as I understand it to prevent the flat tire from being dislodged from the wheel.

Friday, October 11, 2019

You Tube videos on RV tires.

Earlier this summer I had the opportunity to be interviewed about RV tires on the RV Show USA with Alan Warren.

Take a look.

The second part focused on "China Bombs"

Friday, October 4, 2019

My tire says "Regroovable" What does that mean?

"Tireman9; I directed a question to you and did not get an answer?
My Goodyear tires say they are re-groovable. Do you approve of this and who does it? I am located in Indiana. TIA
RVForum writer"

I remember the question and thought I answered but can't locate the original question.

Anyhow.  "Regroovable" is on many HD truck tires. It means the tire was designed and made with extra thick rubber under the tread pattern. Many truck tire shops can cut a partial pattern into the remaining rubber after the tire has been significantly worn. There are guidelines provided by the tire companies on the depth etc.

HERE is a short video. You may notice that in the example the tire is a "Lug" or heavy Traction" tire as used on the rear of units such as Dump trucks.

Regrooving only provides more tire wear miles and will not extend the long term life of a tire based simply on age.

You would still be constrained by the published guidelines of 10 years max no matter what the visual inspection indicates and the act or "regrooving" the tread paternwill do nothnig to improve a tire's durability.

A downside of a tire being "Regroovable" is that the heavy, thick tread will almost certainly give you worse fuel economy as most of the tires e"energy" is consumed n the tread regon