Tow Dolly Tires Cracking

[Dennis Dean]

As usual this forum provides some good info from users and not just the manufacturer words. Tom and Vette thx for the research and info. I am still very happy with my purchase of my Dolly but these are things I honestly would not have been thinking of with a dolly. I think I will treat them like my coach tires and make sure I spray some Aerospace 303 on each tire and cover them while they are in storage or none use. I also think that barring any abnormal happening I will just plan on replacing them at the 4-5 year mark no matter what, at $150 ($70 a piece)for both tires I don't see this as a big cost for the safety of my dolly and towed car. Thanks again for the info.

[vettenuts]

I have one spare but think I will order a second so I have a complete change while on the road. Also, this is something I intend to watch closely going forward so hopefully it can be correlated with some type of activity if it happens again, especially since Kenda hasn't figured it out yet either.

[KenNJ]

Well I checked today and found I also have the cracks. Mine are date coded 3314. Guess I will have to start the warranty process.

Still glad I was alerted to this problem by the original post. Now I just have to see if I can get both tires replaced before my next trip. If I cannot, man am I ever going to be ticked off. The strange thing about this is my tread wear is excellent. Go figure

[vettenuts]

Looks to me that a larger wheel/tire might fit. Wondering if that is worth further investigation. Also, do other dollies have a suspension or are their axles solid mounted. Wonder if this is unique to ACME or do other dolly tires suffer the same fate. Of course, if not for this thread, I would have never looked that close at my tires.

[twinboat]

My Sthil Tow dolly has solid axle stubs welded to the frame with no suspension. It has what look like standard 14 inch trailer tires. They look fine after about 18,000 miles.

The big difference, I strongly believe, is that the turntable, sitting on Teflon slides, puts less side stress on my dolly tires in turns.

The Acme, with no turntable or steering wheels, needs to pull your car tires into a turn.

All front suspensions are designed to return to straight ahead by using the weight of the car. ( Caster )

That, along with forcing the wheels to turn against the resistence of the non operating power steering, adds to the side stress on the tires.

If my car was on the dolly and not hitched, I could pull the tongue side to side because of the turntable. One dolly tire would roll foward and the other backwards.

I can't imagine being able to do that with an Acme dolly, if strapped down tightly.

One other force fighting your turn is the fact that in a turn, the inside wheel turns more degrees then the outside wheel of any vehcile. That will also stress the straps and the tires.

The Acme has its plus's but I don't think tire wear is one of them.

[hdzcar]

Add me to the list of growing customers with cracks in their tires. Tires have date code of 18/14. Both tires have a small crack. I started out with 90 psi and later lowered to 75 psi. I have a new spare that has never been mounted that I haven't checked yet.
I'll be on the phone in the morning sorting this out starting with Kenda 1st. The only other tire manufacture that I can find that makes this size tire in this load range is Carlisle Tires.

[vettenuts]

Wonder if we should all post our tread depth?

From a quick look, it also appears all the posted tire issues are within 2014. Not sure that means anything other than we probably all put similar mileage/wear on them.

[vettenuts]

Originally Posted by hdzcar

Add me to the list of growing customers with cracks in their tires. Tires have date code of 18/14. Both tires have a small crack. I started out with 90 psi and later lowered to 75 psi. I have a new spare that has never been mounted that I haven't checked yet.

I'll be on the phone in the morning sorting this out starting with Kenda 1st. The only other tire manufacture that I can find that makes this size tire in this load range is Carlisle Tires.

Anybody have experience with Carlisle tires? Have been looking at their catalog. The on-line discussion of the travel trailer folks paints a poor picture of their tires.

[c92vette]

As I read through to posts on this thread I thought I would add to or answer some of the questions and comments if not for your enjoyment but for my own sanity. Being retired from the test and evaluation part of the aerospace industry things like this peak my interest.

R Bob asked:
"Why would a tow dolly need 70-90 psi. since the vehicle being towed uses less than half that amount? Could it be possible to pressurize tow dolly tires close to the amount required on the vehicle being towed?"
vettenuts replied "tire pressures are set by the tire manufacturer to carry the required load." Furthermore this is based on the engineering and test evaluation the manufacturer has done on the tire design. Passenger car tires are made to give comfort to the rider in the vehicle through vehicle control. They are also made to work with the suspension of the vehicle therefore pressures for those tires will be different than for the dolly application.

vettenuts also commented about heat transfer through the braking system which is a good point. Tires get the worst of everything from heat transfer due to heavy braking, sun baked highways, road friction, carry loads, and a plethora of other inputs. Transfer from the hot highway and load the tire is carrying is where the most heat comes from. Braking action tends to build heat quickly if it is severe. Had vettenuts thought to measure the air pressure in the tires at the rest stop he would have found them to be higher than originally set. This is why you find on the tire sidewall the pressures listed as cold.

I think Forza Tom hit the nail on the head with his observation about Kenda having issues in manufacture. Kenda is a division of Americana Tire and Wheel and they just don't make trailer tires. They also make tires and tubes for motorcycles, bicycles, as well as other applications. I have them on my Cannondale Triathlon bike with great success. I've hit speeds in excess of 45 MPH on the bicycle and the Kenda tires have been rock solid underneath.

Brockx suggested inflating to 90 psi given the load but I believe this may be contributing to the issue. I did not see the cracks between the treads until I increase the pressure to 90 psi. His statement that he ran 70 psi for over 10k miles, albeit a lighter load than I, lends support to the issue at hand. I ran 70 psi for 3k miles and only upped it when I noticed a wear pattern that may have been due to under inflation. I'm not to sure if this is the real cause but until Kenda can test and evaluate the issue I will lower my pressures to 70 psi. For the rest of you go with your own comfort level as to the pressure in your tires.

Now, let's look at speed vs tire rotation (RPM). 60 MPH equates to 1 mile per minute or 5,280 feet per minute (FPM). The dolly tire travels 5 feet per revolution or 1,056 revolutions per mile (5280/5) and since it has done this in 1 minute the RPM is 1056. At 70 MPH travel is increased to 6,160 FPM. Using the same formula as above the dolly tire rotates 1232 RPM or and increase of 176 RPM or less than 17%. At 80 MPH the dolly tire is at 1408 RPM or 352 RPM faster than at 60 MPH but now we are at a 33% increase in RPM. Still I don't think the difference from 60 to 70 MPH is enough to cause the failure or cracking of the tires. These cracks are longitudinal to the tire rotation so I feel it is a stress issue rather than a speed issue.

As for the question of solid axle vs suspended on a dolly I know of no dollies that have a suspension. The interaction of the weight of the towed vehicle reacting through its suspension and the road acting into a dolly suspension could set up some kind of an unwanted flutter action. This would make for a very hard to control situation unless there were expensive dampeners installed to counteract all this movement. The cost of a $2k or less dolly may just double if that were the case. For a set of $150 tires this does not seem economical or marketable.

twinboat makes some good comments on the EZE Tow dolly configuration which does place more side load or stress on the tires versus other dolly configurations. Acme does recommend a turn of no more than 90 degrees when using the dolly. Anything beyond that increases the side loading of the dolly and the tires receive the brunt of the load. But even turning less than 90 places side loads on the tires and this may be what is lending to the failures. Another point is the arm or length between the pivot point of the coach and the dolly. The rear of my coach swings out considerably when turning and the dolly has to react to this multiplied movement in order to follow the coach. The return to straight after the turn isn't smooth either. The dolly gets swung back and forth pretty good behind the motorhome versus a pickup truck that will have a shorter arm from the pivot point to the dolly. This is what I believe we are encountering with these cracks forming between the treads. Somehow the tire is being forced into a side load that places to much stress on the tread belt and the failure is the cracks we are seeing. This along with a manufacturing issue may be why we are experiencing this problem.

More to come.

[vettenuts]

On the heat related issue I mentioned, I don't recall the temperature on my TPMS but the temperature change from start on the dolly sensors are more than the tires on the coach. Don't recall the temperature that particular day, but you couldn't touch the wheels with your hand when I stopped at the rest area.

Wonder what the maximum allowable pressure is for the tires. I know that the TPMS companies recommend setting the upper pressure limit for the alarm 20% higher than the cold temperature. I found that I needed to set it higher because the dolly tires change by more than that when towing.

[vettenuts]

Originally Posted by c92vette

twinboat makes some good comments on the EZE Tow dolly configuration which does place more side load or stress on the tires versus other dolly configurations. Acme does recommend a turn of no more than 90 degrees when using the dolly. Anything beyond that increases the side loading of the dolly and the tires receive the brunt of the load. But even turning less than 90 places side loads on the tires and this may be what is lending to the failures .

Found this, see page 28. Lateral force and improper pressure seem to be major contributors, however I still think these tires are also running hot.

http://www.gtradialtrucktires.com/en...ok-ver-3-2.pdf

[Old Radios]

OK, read through all of the replies but maybe I missed it. I did not see one case of anyone getting the dolly axle weighed. If you get the weight of the dolly axle with the car on it you can look at the tire manufacturer's chart and it will tell you the pressure you should be running. If you haven't taken it to your local truck stop and gotten it weighed you are just guessing. I'm betting some here haven't even gotten their RV axles weighed to find out the recommended tire pressure.

I'm not an engineer and yes the tires may very well be defective but at the same time over inflation could add to the cracking problem.

[vettenuts]

So, based on the mileage others are getting and finding cracks, if I make the cross country trip we have planned I will need three sets of tires?

[KenNJ]

Yeah, I agree this tire issue is not playing well for any of us. It will be interesting to see if EZTow offers more info or recommendations.


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