Tire pressures - Fiberglass RV


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Old 10-04-2011, 02:17 PM   #1
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Tire pressures

Sis has been complaining that her Compact Jr seems to be really "jiggly" going down the road; she's having a number of vibration-related failures (bolts unscrewing, etc). I wonder if I have the tire pressures right; I've just been pumping them up to the max pressure stated on the sidewall. Perhaps a lower pressure, if safe, would reduce the vibration a bit.

Is there a chart anywhere giving load capacity vs pressure for various tire sizes? ...and, failing that, anecdotal evidence would be acceptable
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Old 10-04-2011, 02:38 PM   #2
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On second thought, never mind; I found a chart with a bit of googling; plus advice to pump them right up to the rated pressure, and that reducing pressure doesn't change the ride enough to be noticeable.
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Old 10-11-2011, 04:56 PM   #3
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Quote:
Originally Posted by Steve Hilby View Post
Sis has been complaining that her Compact Jr seems to be really "jiggly" going down the road; she's having a number of vibration-related failures (bolts unscrewing, etc). I wonder if I have the tire pressures right; I've just been pumping them up to the max pressure stated on the sidewall. Perhaps a lower pressure, if safe, would reduce the vibration a bit.

Is there a chart anywhere giving load capacity vs pressure for various tire sizes? ...and, failing that, anecdotal evidence would be acceptable
This may be a tangent but a Compact Jr likes to be a bit front heavy to behave well and with the kitchen and closet in the back it tends to be a bit rear heavy. Try adding a little tongue weight and see what the results are.
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Old 10-11-2011, 05:09 PM   #4
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The tire pressure should be what the camper manufacture states, not necessarily the same as printed on the tire.

A lower pressure will give a softer ride. It has been said that some Car dealers under inflate tires so the test drive of a car is softer.

A proper inflated tire will have even wear all across the tire treed. An overly inflated tire will have excessive wear down the middle of the treed and an under inflated tire will wear out the edges of the treed.

Check with someone that has the same camper to see what the manufacture recommends.
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Old 10-11-2011, 05:25 PM   #5
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Originally Posted by Darwin Maring View Post
The tire pressure should be what the camper manufacture states, not necessarily the same as printed on the tire.

A lower pressure will give a softer ride. It has been said that some Car dealers under inflate tires so the test drive of a car is softer.

A proper inflated tire will have even wear all across the tire treed. An overly inflated tire will have excessive wear down the middle of the treed and an under inflated tire will wear out the edges of the treed.

Check with someone that has the same camper to see what the manufacture recommends.
Trailer manufacturer's recommended tire pressures are irrelevent when it comes to 40 year old Fiberglass Trailers.
Even if they mattered it could only apply to the original tires or identical ones. This trailer is old enough that tire technology has long since made any sticker obsolete.
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Old 10-11-2011, 06:17 PM   #6
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I always go by the tire manufacturer's max. pressure rating. After all, they make and test them. It's what they do. What does a guy who makes trailers know about tires, other than that they are black and sorta round? I never saw a trailer manufacturer yet who didn't install the cheapest tires they could find to put on a trailer just to get it out the door.

I would not reduce the tire pressure, because that will introduce more flex in the sidewalls. Flexing creates heat and fatigue, neither of which are conditions you would want in a tire. Most blow-outs are caused by under-inflated tires.

I would however, wonder about the tires/wheels being balanced or not. That, IMO, would have more effect on vibration and bouncing than inflation issues. If your tires aren't properly balanced you can't expect them to run true.

You take care to balance the tires on your car or truck...why would anyone think it is any less important to balance them on your trailer as well?
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Old 10-12-2011, 11:22 PM   #7
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Steve--- my CJ would bobble around over 65mph--- tell Corey to slow down!!!! Also, make sure she has enough tongue weight. (we talked about this before)
But, if she is having problems shaking things loose, overinflating possibly may be a factor. What tire pressure are you running? I used passenger tires on our CJ and had no problems for the 3 years we had it. And, as long as the tires are not over loaded (which I doubt- her axle weight is prob in the neighborhood of 1500#--- 750# per tire) a little less pressure will let the sidewalls flex a little and take up some of the shock. Larry
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Old 10-12-2011, 11:35 PM   #8
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Tire pressure has been discussed to death in several forums. The best recommendation is go with MAX pressure as printed on the sidewall. Remember that's cold pressure measured in the morning before the trailer is on the road. Reducing tire pressure can only cause problems. Remember the Ford Explorer/Firestone Tire thing. Ford was reducing the tire pressure in an attempt to make the Explorer ride softer. The end result was tire blowing out and a number of deaths. This should be a lessons learned.
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Old 10-12-2011, 11:44 PM   #9
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Originally Posted by Casita Greg
Most blow-outs are caused by under-inflated tires.
Yes, but "under inflated" and "less than MAX inflation" are two different things.

MAX tire pressure is needed when you have MAX load on the tire. I think we need to remind people that MAX means MAXIMUM and does NOT mean NORMAL or PROPER. What do trailer manufacturers know about tires? Well, they know how much of a load is on the tire. They also get information from tire manufacturers about what pressure should be used for a certain load. Tire manufacturers know a lot about tires. I trust their recommendations about inflation.

Too much tire flex will happen when the load is too much for the inflation. This is true at MAX sidewall pressure, too! When a tire is overinflated for the load on it, more force is transmitted to the suspension, trailer frame, trailer body, trailer contents, trailer coupler, hitch, and tow vehicle. We do see tire failure on these forums, but you know what else we see? Cracked frames! I would bet money that we would see fewer blowouts AND fewer cracked frames if trailer tires were PROPERLY inflated.

According to trailer tire manufacturers, the tires should both be inflated to the same pressure, and should be inflated based on the tire that has the higher load.
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Old 10-12-2011, 11:54 PM   #10
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Originally Posted by Byron Kinnaman
Remember the Ford Explorer/Firestone Tire thing. Ford was reducing the tire pressure in an attempt to make the Explorer ride softer. The end result was tire blowing out and a number of deaths. This should be a lessons learned.
Yes, Ford was running a pressure LOWER than the proper pressure for the load on the tire. I am not recommending that anyone use a pressure that is improper. Always running at MAX pressure is like ALWAYS taking the elevator to the top floor... Always listening to your radio at MAX volume... A football player always throwing the ball as far as he possibly can. There is a proper tire pressure based on the load (weight) on the tire. Higher than that is WRONG. Lower than that is WRONG. Some people choose to run the wrong pressure. That's a personal decision. Lower than the proper pressure can damage the tires, higher than the proper pressure can damage the suspension, frame, trailer, coupler, or hitch. The PROPER pressure shouldn't cause damage to anything.

On MY Scamp, MAX sidewall pressure is 50 PSI. The PROPER pressure, according to both Scamp AND Goodyear, is 15 PSI. My tires DO NOT run hot... I check tire temperature with an IR thermometer. Even at ambient temperatures in the mid 90s, the trailer tires do NOT overheat. This is actual data, not my personal gut feeling on the issue.
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Old 10-13-2011, 02:10 PM   #11
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I ran max pressure (65 psi) for about 4K out of my 7K Alaska trip last year. At max pressure I could see the center tread of the tire wearing down very quickly, and the edges had no wear. For the last 3K of the trip, I ran 50-55 psi, got better tread wear, and trailer felt less bouncy during towing. So I'd also say go with proper pressure for load.
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Old 10-13-2011, 04:16 PM   #12
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I have towed about every non commerical trailer there is in my long life.
I have never had a tire blow out on any of my trailers.
I had a Scamp that had an inflation sticker on it that said 50 pounds. I inflated the tires to 35 and put about 15000 miles on them before I sold the trailer and they were in excellent shape.
Your inflation rate should be based on the weight of the load being carried.
Correct air pressure allows the face of the tread to meet the with the road in the most efficient manner.
To much and your going to wear the center of the tread and to little will wear the edges.
Maxed air pressure on a small trailer is going to make it very uncomfortable tow. You will feel every little bump in the road.
Use a little common sense and take ALL advice given here with a grain of salt, including mine.
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Old 10-13-2011, 05:25 PM   #13
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I have spent enough time on tires to have enough confidence to pick the right tire for each application on my own equipment. There are plenty of wikisperts out there who are wrongly convinced and well intentioned.
If you don't have the knowledge or experience required to make the necessary decisions yourself, then buy your tires from a reputable source and take their advice.
Be reminded that most fiberglass trailers have fiberglass wheelwells, and that a blowout could easily mean a lot more than just a tire replacement.
It is irrefutable and the opinion of every knowledgeable tire supplier that underinflation is the most common cause of catastrophic tire failure.
Tire pressure monitoring systems were not mandated because people made it a habit to drive around on overinflated tires.

It seems that it is always the extremes which are cited to make a point, whether it is appropriate tire pressures or the size of Tow vehicles.
I guess one must have some intelligence in order to have it insulted
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Old 10-13-2011, 10:37 PM   #14
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Boy, Floyd is so right! 1st time camping resulted in a $1200 repair after blowout!
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