Another tired subject?

This is so important we want to run it now, although we just ran an entire article about nothing but maintenance and inspections. We hope you’re not too tired (so sorry for the pun) to read this one too. We think this is worth spending the several minutes it will take to read it.

We ran our trailer tires, Goodyear Marathons, five full years before we noticed a tread separation — in the width of the tread there was a clear edge where the under-plies had sort of allowed a herniation, if you know what I mean. You can see the article we wrote on it here. It wasn’t a big deal to me because we were due to replace the tires — five years is the recommended maximum life for trailer tires, by most accounts.

We bought trailer tires called Triangle. They are Chinese and the price was great. They are eight-ply rated, but don’t have eight plies. Go figure. We’ve had them most of a year and they look fine. Keeping good tires is good insurance against failures. Air pressure is extremely important, too.

When your tires are low or lose their pressure while towing, you need to know right away. A tire pressure monitoring system like Pressure Pro can tell you almost instantly when a tire has flatted. If you don’t know it and continue towing, the tire tread can become like a whip and destroy the inside of your trailer’s wheel well. We saw a Bambi in Bozeman, MT, with damaged wiring and plumbing in the wheel well. Pretty expensive, I’ve heard the repairs can reach $three thousand or more. You can find other tire pressure monitors at some tire dealers and on Amazon.com. These seem pricey at $400 but remember, you are likely to avert serious damage to your wheel and RV if you quickly detect loss of tire pressure.

I’d ONLY use trailer tires for my trailer. They are designed for the stresses a trailer places on the tires. Trailer tires ARE different. And I do NOT use maximum air pressure on my tires when towing. I use Goodyear’s tire pressure chart to match my trailer’s axles weight and tire to the recommended (by Goodyear, the tire’s manufacturer) tire pressure. Why wouldn’t I believe a huge successful company’s engineering?

So, for my trailer and tire (if a Goodyear), here’s how it would work. I know, from weighing at Flying J or other truck stop’s CAT scales (costs $9.00) my trailer’s weight is 6,000 pounds (ignoring the hitch weight at the truck’s rear — just considering the weight on the tires). If that weight was equally distributed on my trailer’s four tires then I would have 1,500 pounds load on each tire. My tires are ST225 75R 15.

This, according to the chart, calls for at least 30 psi air pressure. BUT, my trailer’s weight distribution is probably not ideal and I’ve never had each tire’s load weighed separately (you can do it, but I’ve never encountered it). So let’s say I have half-again the weight on a pair of the tires (a high enough exaggeration since it means one side of the trailer weighs 4,500 pounds and the other side only 1,500 pounds). So 1,500 plus 750 is 2,250 pounds load on each tire.

The chart for my ST225 75R 15 tires now calls for at least 55 psi. Not the maximum pressure of 65 psi, which is required for the tires’ maximum rated load of 2,540 pounds each.

Okay, what difference does all this make? It impacts the ride harshness in your sweet little trailer and all it’s little storage areas. A hard (high inflation) tire rides harder. I don’t want to jar my trailer any more than necessary. Tires are rated for loads at specified pressures, why try to out-think generations of trained engineers regarding the proper air pressure?

Yet many Airstreamers recommend nothing less than maximum pressure. I don’t know, but I wonder if this might come from towing heavier loads than the rating for their tires, or perhaps their trailer’s tires don’t have as much spare capacity as ours. The proper tire pressure depends upon your tires’ rating and your tires’ manufacturer recommendation. Not what I say. For me, I run 55 psi (cold) air pressure in my trailer’s tires for all towing days. When it is colder outside, I increase the pressure to 55 psi. When it is hotter outside, I reduce the (cold) pressure to 55 psi.

My tire pressure monitoring system makes all this a lot easier, because I can see the tire pressures on display readily before every day of towing without walking to, and removing the cap on, each tire. I just check the tire monitor and scroll through the trailer’s tires. And I see the current pressures. By the way, the Pressure Pro alarm settings for my tires are also based upon 55 psi, the tire pressures when I initialized the control panel. I could change this nominal pressure setting by redoing the setup configuration for the sensors and monitor.

Tires for trailers aren’t permanent things. Trailer tires are damaged by road hazards but also by things you don’t see. And, age is not a friend to your tires. Take care of your RV trailer’s tires, they’ll take care of you. Simple enough!

Jim and Debbie
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©2009 Dreamstreamr

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