Hi All, Our tires have to be replaced. We are planning to buy the D rated tires - 205/75R15. I read that the rim has to be rated for the higher PSI. So can the current wheel/rim handle the D rated tires or do we need to put in upgraded wheels. Also planning to go with the Maxxis tires. Thanks !
Hi, uma - I had the same question many years ago when I mounted D-rated tires on my OEM rims that were stated to be for C-rated tires. The problem, if there IS one, is the pressure you would inflate the D-rated tires to get their improved weight limit handling capability. To get the improved weight handling from the new tires, you should inflate them to 65 PSI, rather than the 50 PSI that the C-rated tires need. If you only inflate the D-rated tires to 50 PSI, they essentially act the same as C-rated tires, and you gain nothing.
I was told, I think by RichR on this forum, that the OEM rims were capable of handling 65 PSI, and just looking at the way they were constructed, I agreed and took a chance and inflated the tires to 65. I had no problems whatsoever with the higher pressure in my upgraded tires on the OEM rims, so, I'd say, just do it! I believe other members have done this too, with no problems.
After about 3 years, using the OEM rim and better tire combination, I had the trailer modified so I could mount larger, 225/75R15 tires. This size required that I use new rims with a 1/2" wider bead width. With a lot of searching, I found some that were rated to 65 PSI, so now I'm good pressure-wise again. You MAY be able to find rims that would fit your smaller tires and the trailer axles that are rated to 65 PSI. If you can, it would probably be wise to get them, but I wouldn't loose sleep over this if you don't.
I THINK I'm making sense here, but if not, feel free to ask me to explain better.
- Jack
I was told, I think by RichR on this forum, that the OEM rims were capable of handling 65 PSI, and just looking at the way they were constructed, I agreed and took a chance and inflated the tires to 65. I had no problems whatsoever with the higher pressure in my upgraded tires on the OEM rims, so, I'd say, just do it! I believe other members have done this too, with no problems.
After about 3 years, using the OEM rim and better tire combination, I had the trailer modified so I could mount larger, 225/75R15 tires. This size required that I use new rims with a 1/2" wider bead width. With a lot of searching, I found some that were rated to 65 PSI, so now I'm good pressure-wise again. You MAY be able to find rims that would fit your smaller tires and the trailer axles that are rated to 65 PSI. If you can, it would probably be wise to get them, but I wouldn't loose sleep over this if you don't.
I THINK I'm making sense here, but if not, feel free to ask me to explain better.
- Jack
Hi Jack, Thanks a lot. It was very helpful info. When u say, the trailer modified, does that involve raising the axle ? The mechanic who worked on our trailer suggested that he can raise the axle by about 3" so that we will have more clearance and it will save the hoses etc. when the road is uneven. Is raising the axle sufficient for using the larger 225 wheels ?
anchorwood
Advanced Member
Jack is a very helpful and respected source on this forum in his many comments. I do have to differ in one respect to his comments above, however.
The 65 psi on the tire sidewall is the maximum inflation pressure, not the pressure the manufacturer recommends for all situations. There is no such one-fits-all pressure. Every trailer manufacturer publishes a pressure chart for each tire they make. The greater the load on the tire, the higher the pressure required for safe operation.
Inflating to the maximum pressure when it's not called for by the manufacturer's chart will guarantee two things: The tires will provide very little cushioning and the rough ride will be hard on the trailer, and it will cause over-inflation wear in the center of the tire tread. In addition, the manufacturers say that over-inflation can subject the tire to more damage going over road hazards.
Now, in Jack's defense, what he said is what you will be told by most other trailer owners and most tire retailers. Some get downright angry if you challenge this "urban legend" that everyone should inflate to the maximum permissible pressure. But tire sellers are not the experts, the manufacturers are. Retailers, if they even know the difference, don't want to be bothered by trying to figure out what will be the weight on a tire in your circumstances and looking up the correct pressure. That is actually your responsibility, not theirs. They just cover their behinds by giving everyone a one-size-fits-all answer.
In my case, I bought Maxxis load range D tires also, but looked up and printed out the inflation chart. I really don't need to run more pressure than about the mid 30's for my loaded 22 foot Hi-Lo. I do run a little extra to be safe, about 42 pounds, but that's my personal preference. If you want to criticize me for not following my advise, I plead guilty, but it's only by a few psi.
The other thing is, the load range D tires really are constructed better than the range C tires, and you get that benefit at whatever comparable inflation you are using.
Anyone can check this out just by doing a search on whatever tires you want to know about, find the manufacturer's site and look for the inflation charts. If you think about it, would you put 80 psi in your car tires if that's what it said on the sidewall for maximum allowable pressure?
I'm sure I will get flack for going against the common advise.
The 65 psi on the tire sidewall is the maximum inflation pressure, not the pressure the manufacturer recommends for all situations. There is no such one-fits-all pressure. Every trailer manufacturer publishes a pressure chart for each tire they make. The greater the load on the tire, the higher the pressure required for safe operation.
Inflating to the maximum pressure when it's not called for by the manufacturer's chart will guarantee two things: The tires will provide very little cushioning and the rough ride will be hard on the trailer, and it will cause over-inflation wear in the center of the tire tread. In addition, the manufacturers say that over-inflation can subject the tire to more damage going over road hazards.
Now, in Jack's defense, what he said is what you will be told by most other trailer owners and most tire retailers. Some get downright angry if you challenge this "urban legend" that everyone should inflate to the maximum permissible pressure. But tire sellers are not the experts, the manufacturers are. Retailers, if they even know the difference, don't want to be bothered by trying to figure out what will be the weight on a tire in your circumstances and looking up the correct pressure. That is actually your responsibility, not theirs. They just cover their behinds by giving everyone a one-size-fits-all answer.
In my case, I bought Maxxis load range D tires also, but looked up and printed out the inflation chart. I really don't need to run more pressure than about the mid 30's for my loaded 22 foot Hi-Lo. I do run a little extra to be safe, about 42 pounds, but that's my personal preference. If you want to criticize me for not following my advise, I plead guilty, but it's only by a few psi.
The other thing is, the load range D tires really are constructed better than the range C tires, and you get that benefit at whatever comparable inflation you are using.
Anyone can check this out just by doing a search on whatever tires you want to know about, find the manufacturer's site and look for the inflation charts. If you think about it, would you put 80 psi in your car tires if that's what it said on the sidewall for maximum allowable pressure?
I'm sure I will get flack for going against the common advise.
Here is what my Wifes cousin did with his Hi-Lo to raise it. DaveL
http://www.hilotrailerforum.com/f24/adding-lift-kit-leaf-springs-17t-2289/
http://www.hilotrailerforum.com/f24/adding-lift-kit-leaf-springs-17t-2289/
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cva34
Senior Member
Got to agree great write up...I said it for years Max load on side of tire means with Max load...lower pressure with lighter loads....I see examples of it daily..We travel a road used by fishermen with there Alum boats (lite load) bouncing down road like a Basketball..
tires are a shock absorbed also...otherwise we would have steel tires like a train or for smother ride aluminum ..(kind of extreme example)
Wear pattern on tires tell a story...(thats usually true but alignment and faulty tire can make it lie) If your Wearing out middle too much air press/if Wearing out outer edges too little pressure....
something I do to help me come up with a decent tire pressure (if I'm having a problem) .Is get on smooth hard surface(without too many turns ) and chalk (like kids use on sidewalk)several wide strips across tire ..then tow it a short distance and get out and look at wear pattern chalk...It tell a story....Maybe in walmart parking lot on Sunday morn when it mostly empty.So you don't get Run Over...
Hope this makes CENTS
Interesting
I had new tires put on a few years ago and went with d tires. I , too, had always assumed (had heard) to run at max pressure. However, this year I had the place where I store it check my bearings and when they put everything back together they put 45 lbs pressure in the tires. These guys have been at the same location for over 50 years and the old man originally sold air streams. They now do a variety of trailers with lots of cargo trailers and toy haulers. At any rate- they , also, tended towards inflating to the mfg ( trailer) suggested rating on the tires which was not 60lbs. They acknowledged the caveat of new tires being better constructed- but I ended up running them at 50 just because .... Just because I always had.
However, maybe 45 would even be better.
Rick
I had new tires put on a few years ago and went with d tires. I , too, had always assumed (had heard) to run at max pressure. However, this year I had the place where I store it check my bearings and when they put everything back together they put 45 lbs pressure in the tires. These guys have been at the same location for over 50 years and the old man originally sold air streams. They now do a variety of trailers with lots of cargo trailers and toy haulers. At any rate- they , also, tended towards inflating to the mfg ( trailer) suggested rating on the tires which was not 60lbs. They acknowledged the caveat of new tires being better constructed- but I ended up running them at 50 just because .... Just because I always had.
However, maybe 45 would even be better. Rick
Sigh! I just did a long response and lost it, so, starting over.
First, to uma's question about raising the trailer: My trailer was raised when I had the axle moved forward as documented in this thread: http://www.hilotrailerforum.com/f19/my-trailer-overloaded-412/ By going to 225/75R15 tires, the trailer was raised a total of 2", (1-1/2" for the axle spacer and 1/2" for the larger tire radius). I've since modified the skirting on the street side so the tire on that side looks about centered too.
Since your trailer has tandem axles, you have to worry about the clearance between adjacent wheels. The additional 1/2" radius on each tire will decrease that spacing by 1". And, it will decrease the clearance between the tires and the ends of the wheel wells accordingly too. If the axles are too close, they could possibly be spaced farther apart during the lifting if the wheel wells are wide enough.
I am very happy with my 2" height change, but think 3", or 3-1/2" could be a bit much. It raises your entry step by that much, your towing height (and wind resistance) and you will have to raise you tow vehicle's tow ball by that much.
The larger tires DO require wider wheels (6" bead width vs 5-1/2" width), so that's an additional consideration.
Since you have tandem axles on your trailer, you do not have the problem I had, with a 3500# axle/wheel/tire limit and a trailer that weighed about that much. Your 2-axle design has a total weight limit of 7000#. I doubt you would benefit much from the larger tire, or even a Load Range D tire, if your trailer is leveled properly, so that the load is evenly distributed over both axles. However, I DO like my Load Range D tires, and I think they would give you a slightly higher margin of safety.
A larger tire does, however rotate more slowly at a given speed, and that means it runs a bit cooler, due to less rapid sidewall flexing and less road frictional forces, but those effects may be minimal.
See my next post regarding inflation.
- Jack
First, to uma's question about raising the trailer: My trailer was raised when I had the axle moved forward as documented in this thread: http://www.hilotrailerforum.com/f19/my-trailer-overloaded-412/ By going to 225/75R15 tires, the trailer was raised a total of 2", (1-1/2" for the axle spacer and 1/2" for the larger tire radius). I've since modified the skirting on the street side so the tire on that side looks about centered too.
Since your trailer has tandem axles, you have to worry about the clearance between adjacent wheels. The additional 1/2" radius on each tire will decrease that spacing by 1". And, it will decrease the clearance between the tires and the ends of the wheel wells accordingly too. If the axles are too close, they could possibly be spaced farther apart during the lifting if the wheel wells are wide enough.
I am very happy with my 2" height change, but think 3", or 3-1/2" could be a bit much. It raises your entry step by that much, your towing height (and wind resistance) and you will have to raise you tow vehicle's tow ball by that much.
The larger tires DO require wider wheels (6" bead width vs 5-1/2" width), so that's an additional consideration.
Since you have tandem axles on your trailer, you do not have the problem I had, with a 3500# axle/wheel/tire limit and a trailer that weighed about that much. Your 2-axle design has a total weight limit of 7000#. I doubt you would benefit much from the larger tire, or even a Load Range D tire, if your trailer is leveled properly, so that the load is evenly distributed over both axles. However, I DO like my Load Range D tires, and I think they would give you a slightly higher margin of safety.
A larger tire does, however rotate more slowly at a given speed, and that means it runs a bit cooler, due to less rapid sidewall flexing and less road frictional forces, but those effects may be minimal.
See my next post regarding inflation.
- Jack
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Now, regarding inflation pressures. I am not offended by your thoughtful post, anchorwood, and am NOT giving you flack here. cva34, what you posted DOES make "cents" too. I'm just going to post what I've found about this issue.
First, the manufacturer's specifications regarding tire pressure and load limits: https://www.maxxis.com/catalog/tire-122-129-st-radial-m8008 Scroll down below the specifications section to the "LOAD/INFLATION INFORMATION FOR ST METRIC TRAILER TIRES". There, you will see that a D-Rated tire should be inflated to 65 PSI to achieve its maximum load rating. A C-Rated tire should be inflated to 50 PSI. A long time ago, I read on a similar MAXXIS page that inflating to a lower pressure reduced the load carrying ability of the tire, regardless of its load rating.
If you follow their link to their FAQs, you'll see a warning about under inflation increasing the risk of road hazard damage, uneven tire wear and tread separation. There is NO warning about over inflation, but naturally, common sense is needed there. I do know that lower inflation pressures increase tire sidewall flexing, which cause higher tire temperatures. And, higher tire temperatures degrade tires. A higher Load Range tire inflated properly will have less sidewall flexing than the lower Load Range tire or one that is under inflated.
I've maintained my Load Range D tires at 65 PSI cold since mounting them. I see NO wear in the tire's center. Whatever wear there is, is distributed evenly across the tread. It's possible the trailer is experiencing a rougher ride, but I see no evidence of it.
I've had NO problems since mounting Load Range D tires, but had cord separation on both OEM Load Range C tires, with less than 5,000 miles on them.
So, that's my opinion here. I'm happy with it and take no umbrage with contrary opinions. People should feel free to follow whatever works for them.
- Jack
First, the manufacturer's specifications regarding tire pressure and load limits: https://www.maxxis.com/catalog/tire-122-129-st-radial-m8008 Scroll down below the specifications section to the "LOAD/INFLATION INFORMATION FOR ST METRIC TRAILER TIRES". There, you will see that a D-Rated tire should be inflated to 65 PSI to achieve its maximum load rating. A C-Rated tire should be inflated to 50 PSI. A long time ago, I read on a similar MAXXIS page that inflating to a lower pressure reduced the load carrying ability of the tire, regardless of its load rating.
If you follow their link to their FAQs, you'll see a warning about under inflation increasing the risk of road hazard damage, uneven tire wear and tread separation. There is NO warning about over inflation, but naturally, common sense is needed there. I do know that lower inflation pressures increase tire sidewall flexing, which cause higher tire temperatures. And, higher tire temperatures degrade tires. A higher Load Range tire inflated properly will have less sidewall flexing than the lower Load Range tire or one that is under inflated.
I've maintained my Load Range D tires at 65 PSI cold since mounting them. I see NO wear in the tire's center. Whatever wear there is, is distributed evenly across the tread. It's possible the trailer is experiencing a rougher ride, but I see no evidence of it.
I've had NO problems since mounting Load Range D tires, but had cord separation on both OEM Load Range C tires, with less than 5,000 miles on them.
So, that's my opinion here. I'm happy with it and take no umbrage with contrary opinions. People should feel free to follow whatever works for them.
- Jack
Jack,
There may be other threads where it is mentioned, or I just missed it, but I didn't see where Uma says she has tandem axles. At any rate- on MY 2001 my tandem axles DO NOT equal 7000lbs. They are more like 4500 or 4800 combined. I will have to check, now, because I think the total gvw for that trailer is 5000 and I know they are combined to equal less than that. The additional weight is supposed to be carried by the hitch. WE had a discussion on this some years ago.
On raising the trailer- I did raise mine 3 inches, I believe. It does raise everything a bit, but I didn't notice a decrease in mileage. I DID notice a reduction in dragging the rear of the trailer going in and out of gas station aprons, though.
Rick
There may be other threads where it is mentioned, or I just missed it, but I didn't see where Uma says she has tandem axles. At any rate- on MY 2001 my tandem axles DO NOT equal 7000lbs. They are more like 4500 or 4800 combined. I will have to check, now, because I think the total gvw for that trailer is 5000 and I know they are combined to equal less than that. The additional weight is supposed to be carried by the hitch. WE had a discussion on this some years ago.
On raising the trailer- I did raise mine 3 inches, I believe. It does raise everything a bit, but I didn't notice a decrease in mileage. I DID notice a reduction in dragging the rear of the trailer going in and out of gas station aprons, though.
Rick
We were posting at the same time Rick. I was under the impression that the tandem axles were each 3500#, if not, then that design is just as bad as mine. Yes, the tongue weight is "sort of" subtracted from this, but if you throw in the WDH, it lifts the rear of the tow vehicle, which transfers some of that weight back to the trailer axles as well as to the front axle of the tow vehicle.
My comment on wind resistance was not meant to be a deal-breaker, but I suspect there IS a small reduction in fuel economy. I certainly notice the additional height of the entry step though, but suppose an additional inch is not a deal-breaker either.
I think my original trailer height would have resulted in dragging the rear parts now that I've moved to Pine, where my driveway is a steep hill from the street. So, I'm glad it was raised before I got here.
- Jack
My comment on wind resistance was not meant to be a deal-breaker, but I suspect there IS a small reduction in fuel economy. I certainly notice the additional height of the entry step though, but suppose an additional inch is not a deal-breaker either.
I think my original trailer height would have resulted in dragging the rear parts now that I've moved to Pine, where my driveway is a steep hill from the street. So, I'm glad it was raised before I got here.
- Jack
Thank you all, great tips and points to consider. I was looking for a 8 ply tire, but Sams Club had the 8 ply in only the D rated tires in the Maxxis brand. After reading all the replies, we are leaning towards buying a good C rated tire and keeping it inflated to the recommended max. PSI. Reg. the axle, the mechanic said he can raise the axle by about 3" for about $700 to save the hoses etc., but I don't think he was going to also be spacing the axles apart for that price which is required for the 225 wider tires. But after reading this thread, decided not to raise it at this time ! Hopefully we won't have any issues with the hoses etc. when we go to the national forest campgrounds.
-- Uma
-- Uma
Usagi5678
Senior Member
Bought our tires at our RV dealer and had them mounted at Dunn tire.
Just sharing my experience. When the tech was done mounting the tires on our old rims he told us to run the tires 5lbs. below what was posted on the side wall. This is to allow for expansion in hot weather. On our new to us 1996 Classic we ended up purchasing new rims and tires. The old rime were only rated for 40lbs. The new tires can be rated to 65lbs. Very important to read what is posted on your rims and tires. Sent the old rims to the recycle pile.
Just sharing my experience. When the tech was done mounting the tires on our old rims he told us to run the tires 5lbs. below what was posted on the side wall. This is to allow for expansion in hot weather. On our new to us 1996 Classic we ended up purchasing new rims and tires. The old rime were only rated for 40lbs. The new tires can be rated to 65lbs. Very important to read what is posted on your rims and tires. Sent the old rims to the recycle pile.
Thank you !. We are also new and this is our first travel trailer. Still learning and getting it fixed and we are yet to take a real long trip !! We have been thinking about this, and as Cva34, anchorwood & hilltool have also mentioned, keeping the PSI a few lbs lower seems to be best. As Jack said I think the D tires are rated for 65 lbs and the C tires are much less. Will also check with the installer about the rims and change them if we have to . Now that the cold season is here, we are thinking it may be a better idea to wait until just before the next trip to put the the new tires. Also I read that putting tire covers is a good idea during the cold months especially when not in use !.
I'm sorry, Usagi5678, but I don't think your RV tire installer knows what he's talking about. If you read any owner's manual for any vehicle and find where it talks about inflation pressure, you'll see that the number cited is a "cold inflation pressure". What you inflate the tires to BEFORE the vehicle is driven and the tires heat up.
Now, my 1707T trailer came with 205/75R15 LR C Goodyear Marathon tires as OEM. There is a placard on the side of the trailer that says the cold inflation pressure is 50 PSI. This seems a standard pressure for LR C tires. The cold inflation pressure for LR D tires, to get the advertised load carrying ability is 65 PSI.
I have tire pressure monitors on all my tires and a display that shows their pressure and temperature inside my truck. Yes, when my LR D tires inflated to 65 PSI are driven over asphalt roads in the summer in Aridzona, and elsewhere, their pressure goes up to about 70 PSI, especially if they're on the sunward side. The temperature in them goes up to between 95 - 105 degrees too, depending on sun loading.
If you read further, in whatever manual you have, you'll learn that you SHOULD NOT let air out of any tire to reduce it to the "cold value" if it is warm. Tires are designed to run at the higher pressure when hot and that pressure will fall back to the cold value when the vehicle is not moving. If you DO reduce the pressure, you are driving on under-inflated tires, which is also cited as the leading cause of tire failure.
Do NOT inflate your LR C tires to 45 PSI cold! This causes increased sidewall flexing, higher heat buildup, increased possibility of tread separation. Additionally, the load carrying capability of the tire is reduced.
There IS one time you MIGHT consider reducing the pressure in the tires of your tow vehicle: if you are driving through snow or deep mud. The lower pressure here MAY increase your traction a little bit because it puts more tire (possibly even some of the sidewall) in contact with the slick surface. I've never done that, but I've seen a video where a concrete delivery truck whose tires are normally inflated to 100 PSI were reduced to 20 PSI to get through a muddy stretch.
Tire covers are an excellent idea, uma. It reduces the degrading effects of UV light in sunlight.
- Jack
Now, my 1707T trailer came with 205/75R15 LR C Goodyear Marathon tires as OEM. There is a placard on the side of the trailer that says the cold inflation pressure is 50 PSI. This seems a standard pressure for LR C tires. The cold inflation pressure for LR D tires, to get the advertised load carrying ability is 65 PSI.
I have tire pressure monitors on all my tires and a display that shows their pressure and temperature inside my truck. Yes, when my LR D tires inflated to 65 PSI are driven over asphalt roads in the summer in Aridzona, and elsewhere, their pressure goes up to about 70 PSI, especially if they're on the sunward side. The temperature in them goes up to between 95 - 105 degrees too, depending on sun loading.
If you read further, in whatever manual you have, you'll learn that you SHOULD NOT let air out of any tire to reduce it to the "cold value" if it is warm. Tires are designed to run at the higher pressure when hot and that pressure will fall back to the cold value when the vehicle is not moving. If you DO reduce the pressure, you are driving on under-inflated tires, which is also cited as the leading cause of tire failure.
Do NOT inflate your LR C tires to 45 PSI cold! This causes increased sidewall flexing, higher heat buildup, increased possibility of tread separation. Additionally, the load carrying capability of the tire is reduced.
There IS one time you MIGHT consider reducing the pressure in the tires of your tow vehicle: if you are driving through snow or deep mud. The lower pressure here MAY increase your traction a little bit because it puts more tire (possibly even some of the sidewall) in contact with the slick surface. I've never done that, but I've seen a video where a concrete delivery truck whose tires are normally inflated to 100 PSI were reduced to 20 PSI to get through a muddy stretch.
Tire covers are an excellent idea, uma. It reduces the degrading effects of UV light in sunlight.
- Jack
Interesting again.
I checked my "placard" today on side of trailer and the OEM tires were 13". It is faded and I can't read more than that but I am assuming they were "c" tires( and remember them being such) . The recommended cold pressure on the card was 35psi- This is on the 22ft 2001 towilight with dual axles. I put a d tire on a few years ago, again a 13 ( couldn't get 14s to fit) and I run those at 50. Again, I don't have a real rational reason for doing this other than it seemed a compromise between the 65 the D is rated for and the 35 on the trailer.
For more confusion, I checked the brochure (from this library) on that year trailer and the brochure says it has axles rated for 2910 each. However, the placard indicates a GVWR of 4500 and each axle rated at 2200, which is a bit less than 2910 and, also, a combined rating 100 lbs less than the the maximum trailer rating. Again- I assume they assumed the extra 100 lbs goes to the hitch.
So.... Ill go with card on the axle and trailer ratings but just goes to show that counting on MFG recomendations from HI-LO may need to be taken with a few grains of salt. I've had maybe four different suggestions on what pressure to run tires at.
Rick
I checked my "placard" today on side of trailer and the OEM tires were 13". It is faded and I can't read more than that but I am assuming they were "c" tires( and remember them being such) . The recommended cold pressure on the card was 35psi- This is on the 22ft 2001 towilight with dual axles. I put a d tire on a few years ago, again a 13 ( couldn't get 14s to fit) and I run those at 50. Again, I don't have a real rational reason for doing this other than it seemed a compromise between the 65 the D is rated for and the 35 on the trailer.
For more confusion, I checked the brochure (from this library) on that year trailer and the brochure says it has axles rated for 2910 each. However, the placard indicates a GVWR of 4500 and each axle rated at 2200, which is a bit less than 2910 and, also, a combined rating 100 lbs less than the the maximum trailer rating. Again- I assume they assumed the extra 100 lbs goes to the hitch.
So.... Ill go with card on the axle and trailer ratings but just goes to show that counting on MFG recomendations from HI-LO may need to be taken with a few grains of salt. I've had maybe four different suggestions on what pressure to run tires at.
Rick
Thanks, Rick - I MAY have been bit too "general" in my post on tire pressures. I should have said the 50 PSI for C, and 65 PSI for D applied to a particular group of 15" tires. I just looked at the MAXXIS chart again and note they do not sell D-rated 13" tires. Your tire's sidewall should show the Max Cold Pressure though, and I'm positive that pressure gives them the best weight bearing capability.
Looks like, on the MAXXIS chart, 35 PSI would be for a B-rated 175/80R13 tire though, and it would provide a weight bearing limit of 1100# per tire, or 2200# per axle, which is what your placard states. Your OEM tires may have been B-Rated. Are your tires 175s?
What brand are your D-rated tires? I've not seen anything rated that high in a 13" tire.
- Jack
Looks like, on the MAXXIS chart, 35 PSI would be for a B-rated 175/80R13 tire though, and it would provide a weight bearing limit of 1100# per tire, or 2200# per axle, which is what your placard states. Your OEM tires may have been B-Rated. Are your tires 175s?
What brand are your D-rated tires? I've not seen anything rated that high in a 13" tire.
- Jack
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I was looking for the best brand of tires and then I found the following info on etrailer.com reg. tire pressure !
__________________________
Special trailer tires should be inflated to their maximum air pressure. The value for the maximum air pressure should be listed along with the value for the maximum load on the tire's sidewall. These values will usually designate the maximum load at a maximum psi. For example, if the tire is rated at 1,610 lbs maximum at 65 psi, the tire can carry 1,610 lbs of weight if the air pressure is at the maximum of 65 psi. At the maximum air pressure, the tires will perform and wear best, and get the best gas mileage.
If your sidewall recommends 80 psi then that is what you would need to go with.
If a trailer tire is inflated to a lower air pressure than the maximum, the amount of weight that the tire can carry will be reduced. If a heavier load is put on the trailer tire than what is recommended for that air pressure, the sidewall of the tire could heat up and cause the tire to fail.
You should always inflate your tires when they are cold.
__________________________
Special trailer tires should be inflated to their maximum air pressure. The value for the maximum air pressure should be listed along with the value for the maximum load on the tire's sidewall. These values will usually designate the maximum load at a maximum psi. For example, if the tire is rated at 1,610 lbs maximum at 65 psi, the tire can carry 1,610 lbs of weight if the air pressure is at the maximum of 65 psi. At the maximum air pressure, the tires will perform and wear best, and get the best gas mileage.
If your sidewall recommends 80 psi then that is what you would need to go with.
If a trailer tire is inflated to a lower air pressure than the maximum, the amount of weight that the tire can carry will be reduced. If a heavier load is put on the trailer tire than what is recommended for that air pressure, the sidewall of the tire could heat up and cause the tire to fail.
You should always inflate your tires when they are cold.
anchorwood
Advanced Member
Oh my. Tire pressures.
Forget about trailer tires for just a minute.
Looking at the door post on my 2013 Subaru Forester, it says the tire pressure should be 28 pounds. Now, the tires say on the sidewalls that the maximum pressure in these particular tires is 40 pounds. Do I rush out and put 40 psi (pounds per square inch) in my tires? Of course not.
If you've looked into auto tire pressures, you may know that a couple pounds more pressure will improve cornering and high-speed handling. You also would know that more pressure means less contact area with the pavement, resulting in less traction and longer emergency stopping distances. And the ride quality suffers with higher pressure: rougher, more vibration.
If you read your operator's manual, you will find a figure for the maximum load the vehicle is rated to carry. This takes into account not only the tires, but other components of the car. The manual will probably also note that with loads approaching the maximum, tires should be inflated to a higher psi. In general use, you shouldn't need to be concerned about this. But if you are loaded down moving your household goods to another state in the summer when it's 104 degrees in the shade (higher on the pavement)and you want to drive 75 mph or more, then you should pay attention to tire pressure.
If you bother to weigh your vehicle (or the load on the individual tires), you can look up on the tire manufacturer's chart to see how much you should increase the tire pressure. But you'll probably guess. In any case, nobody will inflate their tires to the maximum allowable pressure unless they think they are near the maximum allowable load.
Why should the basics be any different with trailer tires? Well, they're not.
Let's assume, for simplicity, that my 22' Hi-Lo weighs 5500 pounds, which is the maximum rated tow weight of the weakest link in my towing setup. And assume that I have loaded the Hi-Lo to the maximum allowable. If we assume that 500 lbs is on the tongue, that's 5000 pounds on the trailer tires, or 1250 pounds on each of the 4.
About 3 or 4 years ago, I put new Maxxis 8008 tires on my 22' Hi-Lo, and upgraded from load range C to D, for some safety cushion. When I look at the Maxxis inflation chart for these tires carrying the weight we calculated above, it says the proper inflation is a little over 25 psi. Well. The 42 psi that I have been using is way overkill.
In the real world, the assumptions I made are not quite realistic. I'm not capable of loading my trailer so each tire carries exactly the same weight, and with my weight distribution hitch, there's probably not 500 pounds on the hitch. So the ideal inflation is probably somewhere greater than 25 psi. Still not likely to require my 42 pounds. The chart says 40 psi is adequate to carry 1610 pounds, or 6440 for the 4 tires, which is way, way over the maximum 5500 pounds I'm supposed to be pulling.
But, the common recommendation of most trailer owners and a lot of retailers is to inflate to the maximum psi shown on the tire sidewall. Now, according to the chart from Maxxis, if I put 65 psi in my trailer tires, that's appropriate for a maximum load of 2150 pounds per tire, or a trailer weighing 8600 pounds!!! When are you going to load a 22 foot Hi-Lo that heavy? Never.
And you know, common sense tells you that the ride in the trailer will be very rough. Now, driving on mostly paved roads, you may or may not see any damage as a result. Here in the West, with a lot of gravel, washboard roads that shake you around in the best of circumstances, you are taking a big chance getting to a lot of desirable camp sites. One old concrete road I could not get off of for about 10 miles set up a vibration from all the joints in the concrete that practically shook the fillings in our teeth. When I got home, the outer shell of the lower part of the dutch door had come loose, and I was not running at any 65 psi. I also refer you to the comment by cva34 earlier in this thread about his observations.
The only people who are authorities on tire inflation are the manufacturers. Not your buddy or the guy who fixed your tire or some salesman at the tire shop.
Now, I spent about 2 or 3 hours last night looking up references at different manufacturers' sites. Most say very little about over-inflation. Probably because the dangers of under-inflation are so dramatic in comparison. But those who did mention it, said over-inflation can cause damage from potholes and debris in the road. Some also mentioned that over-inflation can cause explosive tire failure, much more dangerous than a slower loss of air.
No way am I going to put 65 psi in my Hi-Lo trailer tires. But I know some of you won't be convinced.
Forget about trailer tires for just a minute.
Looking at the door post on my 2013 Subaru Forester, it says the tire pressure should be 28 pounds. Now, the tires say on the sidewalls that the maximum pressure in these particular tires is 40 pounds. Do I rush out and put 40 psi (pounds per square inch) in my tires? Of course not.
If you've looked into auto tire pressures, you may know that a couple pounds more pressure will improve cornering and high-speed handling. You also would know that more pressure means less contact area with the pavement, resulting in less traction and longer emergency stopping distances. And the ride quality suffers with higher pressure: rougher, more vibration.
If you read your operator's manual, you will find a figure for the maximum load the vehicle is rated to carry. This takes into account not only the tires, but other components of the car. The manual will probably also note that with loads approaching the maximum, tires should be inflated to a higher psi. In general use, you shouldn't need to be concerned about this. But if you are loaded down moving your household goods to another state in the summer when it's 104 degrees in the shade (higher on the pavement)and you want to drive 75 mph or more, then you should pay attention to tire pressure.
If you bother to weigh your vehicle (or the load on the individual tires), you can look up on the tire manufacturer's chart to see how much you should increase the tire pressure. But you'll probably guess. In any case, nobody will inflate their tires to the maximum allowable pressure unless they think they are near the maximum allowable load.
Why should the basics be any different with trailer tires? Well, they're not.
Let's assume, for simplicity, that my 22' Hi-Lo weighs 5500 pounds, which is the maximum rated tow weight of the weakest link in my towing setup. And assume that I have loaded the Hi-Lo to the maximum allowable. If we assume that 500 lbs is on the tongue, that's 5000 pounds on the trailer tires, or 1250 pounds on each of the 4.
About 3 or 4 years ago, I put new Maxxis 8008 tires on my 22' Hi-Lo, and upgraded from load range C to D, for some safety cushion. When I look at the Maxxis inflation chart for these tires carrying the weight we calculated above, it says the proper inflation is a little over 25 psi. Well. The 42 psi that I have been using is way overkill.
In the real world, the assumptions I made are not quite realistic. I'm not capable of loading my trailer so each tire carries exactly the same weight, and with my weight distribution hitch, there's probably not 500 pounds on the hitch. So the ideal inflation is probably somewhere greater than 25 psi. Still not likely to require my 42 pounds. The chart says 40 psi is adequate to carry 1610 pounds, or 6440 for the 4 tires, which is way, way over the maximum 5500 pounds I'm supposed to be pulling.
But, the common recommendation of most trailer owners and a lot of retailers is to inflate to the maximum psi shown on the tire sidewall. Now, according to the chart from Maxxis, if I put 65 psi in my trailer tires, that's appropriate for a maximum load of 2150 pounds per tire, or a trailer weighing 8600 pounds!!! When are you going to load a 22 foot Hi-Lo that heavy? Never.
And you know, common sense tells you that the ride in the trailer will be very rough. Now, driving on mostly paved roads, you may or may not see any damage as a result. Here in the West, with a lot of gravel, washboard roads that shake you around in the best of circumstances, you are taking a big chance getting to a lot of desirable camp sites. One old concrete road I could not get off of for about 10 miles set up a vibration from all the joints in the concrete that practically shook the fillings in our teeth. When I got home, the outer shell of the lower part of the dutch door had come loose, and I was not running at any 65 psi. I also refer you to the comment by cva34 earlier in this thread about his observations.
The only people who are authorities on tire inflation are the manufacturers. Not your buddy or the guy who fixed your tire or some salesman at the tire shop.
Now, I spent about 2 or 3 hours last night looking up references at different manufacturers' sites. Most say very little about over-inflation. Probably because the dangers of under-inflation are so dramatic in comparison. But those who did mention it, said over-inflation can cause damage from potholes and debris in the road. Some also mentioned that over-inflation can cause explosive tire failure, much more dangerous than a slower loss of air.
No way am I going to put 65 psi in my Hi-Lo trailer tires. But I know some of you won't be convinced.
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