Thanks Roger for the detailed technical explanation. It makes a lot of sense. Never thought of that, but for Auto tire, we always have gone by what is on the door, never bothered about any other numbers no matter what the load or weather condition !. We are new to this, but will check the tire specifications and also the trailer manual. I think for the trailer, the more loaded it is, the PSI has to be correspondingly more, but still with the limits of course !. Otherwise, it can bounce like Cva34 mentioned !
Usagi5678
Senior Member
Tire pressures
Dh always checks the tires when they are cold. Early in the AM. We are on our fourth RV and have never had a tire blowout.
Dh always checks the tires when they are cold. Early in the AM. We are on our fourth RV and have never had a tire blowout.
Roger, again you make a thoughtful post. I can't argue with your reasoning, and agree that the tire manufacturer's advice is the only one worth following.
And, vehicle tires are a completely different animal too, from trailer tires. Vehicle manufacturers choose an inflation pressure that gives a pleasant ride for the occupants and satisfies the requirements for traction, fuel economy, handling, and possibly tire wear. Yes, inflating to a pressure higher than what is on the door sticker will give a rougher ride, possibly less traction on a dry road (but better traction in a hydroplaning environment), better fuel economy due to less rolling resistance, more center wear in the tire tread if the tread is not making full contact, but the tires will run cooler due to less sidewall flexing. If underinflated, there will be a softer ride, very squirrely handling if they are severely underinflated, lower fuel economy and they will run hotter, more edge wear on the tread, but possibly better traction in mud or snow. In other words, as we both know, there are trade offs.
Now, my truck has placarded the tire pressures to be 35 PSI. I'm reasonably sure that pressure is based on the "Curb Weight" (as delivered weight) of the truck. The maximum pressure on the tire's sidewall is 44 PSI. I've weighed my truck on a CAT scale and many times at the landfill and I know it weighs 6500#. The Curb Weight was supposed to be a bit over 5500#. My bed cap has added about 300# to the Curb Weight, but my truck still weighs a bit over 1000# more than the curb weight. For this reason, I inflate my truck's tires to 40 PSI. The ride is fine, traction is great, handling is great and tire wear is perfect.
A trailer is a different beast. It does not need a particularly soft ride, and the only requirement for traction is for braking and to keep the trailer on the road when rounding curves. The tires have a simple tread. If the road is rough, I slow down. But, the tires have to carry the trailer's weight. I've weighed my trailer too, and it weighs about 3500# with no water in the fresh water tank (3800# GVWR) . Yes, the trailer tongue weight is about 500#, but the WDH transfers about half that weight back to the trailer's axle, so it's carrying about 3250#, or 1625# per tire with no water. My OEM tires were rated to only 1820#. My current tires are rated to 2540# when inflated to 65 PSI. I appreciate that margin of safety.
So, I'm taking the weight of my truck and trailer into account when I choose a tire pressure. And, I've not had any problems with these pressures.
- Jack
And, vehicle tires are a completely different animal too, from trailer tires. Vehicle manufacturers choose an inflation pressure that gives a pleasant ride for the occupants and satisfies the requirements for traction, fuel economy, handling, and possibly tire wear. Yes, inflating to a pressure higher than what is on the door sticker will give a rougher ride, possibly less traction on a dry road (but better traction in a hydroplaning environment), better fuel economy due to less rolling resistance, more center wear in the tire tread if the tread is not making full contact, but the tires will run cooler due to less sidewall flexing. If underinflated, there will be a softer ride, very squirrely handling if they are severely underinflated, lower fuel economy and they will run hotter, more edge wear on the tread, but possibly better traction in mud or snow. In other words, as we both know, there are trade offs.
Now, my truck has placarded the tire pressures to be 35 PSI. I'm reasonably sure that pressure is based on the "Curb Weight" (as delivered weight) of the truck. The maximum pressure on the tire's sidewall is 44 PSI. I've weighed my truck on a CAT scale and many times at the landfill and I know it weighs 6500#. The Curb Weight was supposed to be a bit over 5500#. My bed cap has added about 300# to the Curb Weight, but my truck still weighs a bit over 1000# more than the curb weight. For this reason, I inflate my truck's tires to 40 PSI. The ride is fine, traction is great, handling is great and tire wear is perfect.
A trailer is a different beast. It does not need a particularly soft ride, and the only requirement for traction is for braking and to keep the trailer on the road when rounding curves. The tires have a simple tread. If the road is rough, I slow down. But, the tires have to carry the trailer's weight. I've weighed my trailer too, and it weighs about 3500# with no water in the fresh water tank (3800# GVWR) . Yes, the trailer tongue weight is about 500#, but the WDH transfers about half that weight back to the trailer's axle, so it's carrying about 3250#, or 1625# per tire with no water. My OEM tires were rated to only 1820#. My current tires are rated to 2540# when inflated to 65 PSI. I appreciate that margin of safety.
So, I'm taking the weight of my truck and trailer into account when I choose a tire pressure. And, I've not had any problems with these pressures.
- Jack
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phoneguy1212
Member
Maybe I'm just an old fool, aren't these rims made of steel? So how could adding 15 more pounds of pressure to them cause any type of damage to the rims. I'm also a big supporter of not running tires at max pressure. During summer I run less air to allow for expansion and run more air in winter for the opposite reason. That's on my truck and trailer. I'm also not a believer of changing out the tires every five or six years. I change them when they get worn or don't hold air for for a couple of months without needing topped off. So I see no reason for not to go with the D tire and if you're not maxing out the weight run the tires at 60 psi. I'm sure the steel rims can handle it just fine. I hope I didn't upset the masses with simple logic, wasn't my intention.
Last Monday, we picked up our trailer. The RV guy who worked on our trailer also recommended to go with the D rated tires, but to always keep the PSI a few pounds lower than the max. rating as has been suggested here !. But he said that it is a good idea to replace the tires every 5 or 6 years even if they are not losing pressure for safety reasons !. Our tires are holding air just fine for now, but they are worn and he said that the glue that holds the diff. layers in the tire will not hold well in the summer heat when the tires are old and worn out.
uma - everything I've read on trailer tires says to replace them if they are 5 years old. Furthermore, I've read in the same sources that the tread is not designed to be the wearout guide, but that age is.
As I recall, the stresses on the trailer tire's sidewalls weakens them and after 5 years, they are not reliable. I could possibly find these sites where I read this, but I think they are fairly easy to find if you do a bit of a search. I believe two such sources are etrailer.com and RVLife.
Again, I will point out that lower pressures allow more sidewall flexing and that causes more tire heating.
I think I've beaten the dead horse enough, so I'll lay off this thread now, unless something really outrageous is posted.
- Jack
As I recall, the stresses on the trailer tire's sidewalls weakens them and after 5 years, they are not reliable. I could possibly find these sites where I read this, but I think they are fairly easy to find if you do a bit of a search. I believe two such sources are etrailer.com and RVLife.
Again, I will point out that lower pressures allow more sidewall flexing and that causes more tire heating.
I think I've beaten the dead horse enough, so I'll lay off this thread now, unless something really outrageous is posted.
- Jack
anchorwood
Advanced Member
Uma;
I would like to make a couple of points.
First, on load range D tires. Each time you go up a letter in load range (like from B to C, C to D, or D to E) you get a stronger, heavier-built tire. They used to be rated by plies (back in the not too distant past, especially before radial tires), as in 4 ply rating, 6 ply rating, or 8 ply rating and on up. A load range D tire rating is equivalent to the old 8 ply rating. By the time the industry switched to the letter designations, the ply rating had little to do with the tire construction, as for instance 8 ply rated tires didn't have anywhere near 8 plies. So the change made sense, avoids confusion.
Among other things, each higher load range tire has heavier duty sidewalls than the lower rated ones. And in fact, all trailer tires supposedly have stronger sidewalls than automobile tires because, for a similar size, trailer tires may be loaded much heavier than car tires, and the sidewalls may be stressed more for other reasons. Think of how much more likely it is that when a trailer is pulled around a corner, the driver will cut it a little too close and bounce the trailer up onto the curb. Or since your trailer is wider than your tow vehicle, it's really easy just to drag the trailer tires against the curb.
You have a dual-axle trailer. Trailers with multiple axles subject the trailer sidewalls to a lot more stress than single-axle trailers. Since the tires are held rigidly in a straight ahead orientation, when you turn a corner, the tires on one or both axles will be dragged slightly sideways. If you make a very sharp turn, the effect gets worse and rubber scraped off the tire treads will be obvious, especially if you are on concrete where it is easy to see the black marks.
I make pretty sharp turns every time I park my trailer at home because the space I put it in is at a right angle to my driveway. The stress this puts on the tire sidewalls is just one of the reasons I went with the stronger load range D tires. Another consideration is that trailer manufactures don't want to spend more money than they have to, so most are not going to put a stronger tire on than the minimum rated for the weight of the trailer. Since I was replacing 18 year old tires after I bought my Hi-Lo anyway, I chose to go with a tire built a little better than the manufacturer put on it. The cost of upgrading tires on just a single trailer is pretty minimal if you are buying new tires anyway.
Now, once again on inflation pressures. The load range D tires likely won't need any more pressure than the range C tires did, because you didn't change the weight of the trailer any. You can make sure by looking at the tire manufacturer's air pressure chart.
Many people say that the D tires are better because you can put more air pressure in them. But all you accomplish in so doing is subjecting your trailer to a lot of shaking and vibration. And you make the tire more likely to be damaged by potholes or running over some debris on the road, and if it is damaged, risking a serious exploding tire which can cause a loss of control and more serious damage to your trailer. Losing air more slowly is not as likely to cause as serious problems.
The rationale others give for putting 65 pounds of air pressure in my Trailer tires is that most tire failures are a result of NOT having adequate pressure in tires, which causes greater flexing of the tires, which causes heat buildup, which causes tire failure. That's true enough. But if I put the amount of air in the tire the manufacturer says is the right inflation for the weight the tire is carrying, it's not going to over flex and overheat. Because the tire manufacturer has done all his homework and knows how his tires should be inflated.
But, if you don't put in the maximum 65 psi, you won't have the maximum load carrying ability, they say. Well, the maximum load capacity (at 65 psi) for my tires would be a trailer weighing almost 4 tons. Since my tow vehicle and hitch setup is designed for a maximum of 5500 pounds, and my actual trailer is a bit less than that, who cares if the tires can't carry 4 tons? When am I going to need that?
Well, I guess I will also stop "beating a dead horse" on this subject. Happy trailering, everyone.
Roger
I would like to make a couple of points.
First, on load range D tires. Each time you go up a letter in load range (like from B to C, C to D, or D to E) you get a stronger, heavier-built tire. They used to be rated by plies (back in the not too distant past, especially before radial tires), as in 4 ply rating, 6 ply rating, or 8 ply rating and on up. A load range D tire rating is equivalent to the old 8 ply rating. By the time the industry switched to the letter designations, the ply rating had little to do with the tire construction, as for instance 8 ply rated tires didn't have anywhere near 8 plies. So the change made sense, avoids confusion.
Among other things, each higher load range tire has heavier duty sidewalls than the lower rated ones. And in fact, all trailer tires supposedly have stronger sidewalls than automobile tires because, for a similar size, trailer tires may be loaded much heavier than car tires, and the sidewalls may be stressed more for other reasons. Think of how much more likely it is that when a trailer is pulled around a corner, the driver will cut it a little too close and bounce the trailer up onto the curb. Or since your trailer is wider than your tow vehicle, it's really easy just to drag the trailer tires against the curb.
You have a dual-axle trailer. Trailers with multiple axles subject the trailer sidewalls to a lot more stress than single-axle trailers. Since the tires are held rigidly in a straight ahead orientation, when you turn a corner, the tires on one or both axles will be dragged slightly sideways. If you make a very sharp turn, the effect gets worse and rubber scraped off the tire treads will be obvious, especially if you are on concrete where it is easy to see the black marks.
I make pretty sharp turns every time I park my trailer at home because the space I put it in is at a right angle to my driveway. The stress this puts on the tire sidewalls is just one of the reasons I went with the stronger load range D tires. Another consideration is that trailer manufactures don't want to spend more money than they have to, so most are not going to put a stronger tire on than the minimum rated for the weight of the trailer. Since I was replacing 18 year old tires after I bought my Hi-Lo anyway, I chose to go with a tire built a little better than the manufacturer put on it. The cost of upgrading tires on just a single trailer is pretty minimal if you are buying new tires anyway.
Now, once again on inflation pressures. The load range D tires likely won't need any more pressure than the range C tires did, because you didn't change the weight of the trailer any. You can make sure by looking at the tire manufacturer's air pressure chart.
Many people say that the D tires are better because you can put more air pressure in them. But all you accomplish in so doing is subjecting your trailer to a lot of shaking and vibration. And you make the tire more likely to be damaged by potholes or running over some debris on the road, and if it is damaged, risking a serious exploding tire which can cause a loss of control and more serious damage to your trailer. Losing air more slowly is not as likely to cause as serious problems.
The rationale others give for putting 65 pounds of air pressure in my Trailer tires is that most tire failures are a result of NOT having adequate pressure in tires, which causes greater flexing of the tires, which causes heat buildup, which causes tire failure. That's true enough. But if I put the amount of air in the tire the manufacturer says is the right inflation for the weight the tire is carrying, it's not going to over flex and overheat. Because the tire manufacturer has done all his homework and knows how his tires should be inflated.
But, if you don't put in the maximum 65 psi, you won't have the maximum load carrying ability, they say. Well, the maximum load capacity (at 65 psi) for my tires would be a trailer weighing almost 4 tons. Since my tow vehicle and hitch setup is designed for a maximum of 5500 pounds, and my actual trailer is a bit less than that, who cares if the tires can't carry 4 tons? When am I going to need that?
Well, I guess I will also stop "beating a dead horse" on this subject. Happy trailering, everyone.
Roger
anchorwood
Advanced Member
Uma;
One more thing I forgot. Make sure the load range D tires are not so much bigger you will have a problem mounting and dismounting them.
The specs on the load range D tires I put on my trailer showed they were only one tenth of an inch wider than the range C tires I took off. So I thought that would not be a problem. But when I mounted the new tires on the trailer, I had a good deal of difficulty; it just seemed like there was less room.
This might not be a problem if you don't have close fenders. On my Classic model, I was afraid of breaking the plastic fender skirts.
Roger
One more thing I forgot. Make sure the load range D tires are not so much bigger you will have a problem mounting and dismounting them.
The specs on the load range D tires I put on my trailer showed they were only one tenth of an inch wider than the range C tires I took off. So I thought that would not be a problem. But when I mounted the new tires on the trailer, I had a good deal of difficulty; it just seemed like there was less room.
This might not be a problem if you don't have close fenders. On my Classic model, I was afraid of breaking the plastic fender skirts.
Roger
Hi Roger, the tire we are looking at is the Maxxis D 205/75R15 at Sams Club, I thought of going with the D, since it is the same size as the C tire, but the C tire is listed as 6-PR and the D is listed as 8-PR. So I thought, if both are the same size, the stronger the safer !. But, I understand now that just because it can take more PSI, we don't have to put so much air, but stick closer to the PSI rated for C tires, for better traction and bump free ride !. But I thought the tire size will be exactly the same between the C & D since both are 205/75R15. It just occurred to me as I was writing this that the 1/10" might be due to the additional thickness of the D tire - the 8-PR. Anyway, thanks for letting me know.
anchorwood
Advanced Member
Uma,
Another consideration that makes sense if you follow the logic of my earlier posts, is the wheels that were original to your trailer are just fine for mounting the load range D tires of the same nominal size. Because there's no reason to over-inflate the tires to any 65 pounds. The actual pressure you use, if you adhere to the Maxxus inflation chart, will be a lot less than that, and the wheels will be well within their rated pressure.
A much better strategy for making sure your tires don't get UNDER inflated, is to use some sort of pressure sensors in the tires that have a read-out in your tow vehicle. Many other people on this forum have done this and could make recommendations. That way you will get an alarm before the tire pressure has fallen to dangerous levels. Much better idea than over-inflating, in my opinion.
Roger
Another consideration that makes sense if you follow the logic of my earlier posts, is the wheels that were original to your trailer are just fine for mounting the load range D tires of the same nominal size. Because there's no reason to over-inflate the tires to any 65 pounds. The actual pressure you use, if you adhere to the Maxxus inflation chart, will be a lot less than that, and the wheels will be well within their rated pressure.
A much better strategy for making sure your tires don't get UNDER inflated, is to use some sort of pressure sensors in the tires that have a read-out in your tow vehicle. Many other people on this forum have done this and could make recommendations. That way you will get an alarm before the tire pressure has fallen to dangerous levels. Much better idea than over-inflating, in my opinion.
Roger
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