Summer tire pressure and heat build-up?

[Rickf1985]

I am certainly glad to hear all is well and that you have had no problems. You have learned quite a bit about tires I see but the one thing we will continue to disagree on is the contact between the tires. In your case as long as it is only a kiss now and then you might be alright. I say might instead of should because I have had to change far too many tires in the same size as what you are running. The 16" duals were used for many years on all of the major brands of light trucks and a lot of people fell into the "bigger is better" trap. Runing a tow truck meant I got to see a lot of those people. You may have a strange set of rims with more backspacing? I can't put 235/85-16's on my Dodge because it will leave only about 3/8" between the duals.

[DRMousseau]

Those tires touchin' on the dual set, is what concerned me the most and got this whole thing started. And those rims??? When I did the rear brakes, I found the dual rims to be coined safety rims. Kinda disappointed me, as I had assumed they were the same as the front split-ring rims that I actually like!!! I can change tires on split-rings ANYWHERE,.... but I have no equipment to change tires on safety rims.

I was told to watch my tire pressures under load. Since they're radials, I should jus KEEP them at 85psi and jus watch my weight and check them often when loaded heavy. I couldn't tell him what my weights were, but it IS important to know. That loss of spacing under load??? Means the tires are stressed more and subject to more "action" or movement which will cause greater heat buildup.The wear factor is non-existent,... they don't rub one another, they touch. The contact between tires WILL be a concern if it's excessive and causes added action,... "bulging into one another causing abnormal sidewall action. Especially on rolling or uneven roads that rhythmically shifts the loading on the tires." I got good suspension, but these still tend to rock and sway and I should be aware of this more.

I haven't talked to these guys since my recent trip,... their only concern for me was that I wasn't overloaded for the tires I have. "They're rather light", but assured me I should be ok. The front set ran much warmer than the duals,... that was easily corrected when I adjusted inflation to 85psi instead of 75psi. They still ran warmer than rear, jus not as much. The inside set on the duals ran jus slightly warmer than the outside set. Remember,... I'm jus using an IR reader to judge this. Couldn't tell any differance by hand, but readings on sidewalls and tread were consistent in relationship, and I can only assume that warmer air passing under the vehicle reduced the heat dissipation slightly on the inside set. Didn't notice any difference from muffler side to the other side though.

REALLY need to get weighed under my various loadings!!! Should have done this when I left Florida, and I didn't. There's less opportunity to do so here in Northern Michigan.

[DaveVA78Chieftain]

The caution on the Dodge chassis is that the rims were originally designed for bias ply tires and are only rated for around 85-90lbs max.  You can dmage the rim if you raise the pressure to high.

Dave

[Sasquatch]

Too hot is 195 degrees F.  The last company I worked for I was part of a team designing tire pressure and temp monitoring systems for RV's (diesel pushers).  Tons of interactions with the tire manufacturers. 

[Rickf1985]

Too hot is 195 degrees F.  The last company I worked for I was part of a team designing tire pressure and temp monitoring systems for RV's (diesel pushers).  Tons of interactions with the tire manufacturers.

That is interesting info, I would love to see that in writing. The only reason I say that is road temps out west and even here in the east during hot summer sunny days can exceed that and driving for long distances on that road will push the tires uncomfortably close to that temp. I would think there would be a higher safety factor built in. Granted I have never sen my RV tires that hot but I have seen my trailer tires at 170  after a long down grade where I had to be using the brakes more than usual.

[DRMousseau]

Yep, and that 195 degrees is right in line from all I've gathered from those in the labs and the field too,....
..."If you see ANY temps exceed 200 degrees in your tires in ANY way,.... you should be concerned. The best indicators were the tires themselves."

And yes Dave,.... I remember radials being introduced into use with a lot of controversy in the early 70's. Rims not being designed for such was a part of all that. And last year, I was running max pressure at max loading on the ol' Winnebago!!! Pushin' the envelope in a risky manner. IMO,.... after all I've learned, I still don't feel radials are safe or satisfactory on heavy equipment, and not too thrilled with them for everyday use on typical passenger applications either. They tend to allow and promote poor driving behavior that jus couldn't be approached with conventional bias tires. But those latter opinions are personal and somewhat "political" in nature of my own,... best left to quiet discussions in the summer shade of a big tree while sippin' a cool drink with one another.

And Rick!!! There IS a safety factor in this matter,.... it considers various internal and unseen temps as well as increases in pressure due to heat build up from ambient temps and friction. And it IS a rather large margin of safety,... but no one will be specific for obvious reasons. If ya stay within the stated range of the sidewall specs,.... and keep operating temps below that 195-200F range, all is good. Although still unnerving not really knowing that margin. And I still tend to watch tires closely,.... the tires of others too, as well as my own. Some family and friends have no idea of what they take for granted and rely on everyday.