I have been looking and I find a lot of choices in the 265/75/16 size tire which size is very close to the ST 235/80/16 that are on my trailer. Many have a load rating of 123(3417#). I don't see people using this size tire as an alternative and am wondering why? All of the experts please enlighten me.
Look at the minimum rim width. Most 16" trailer wheels at 6 or 6.5" wide. the LT265 have a minimum rim width of 7". My truck has that size tire and then are on 8 or 8.25 wide rims. Although they have about the same diameter as the LT235, they are wider and require a wider wheel. The way most trailer suspension are currently built the extra width is an issue with the spring placement and fender skirts.
From Michelin on the LTX M&S2
LT235 Rim 6-7.5", Section Width 9.3 on 6.5" rim, dia 31.7
LT265 Rim 7-8", Section Width 10.5 on 7.5" rim, dia 31.7
Trailer wheels are zero offset wheels, and finding wider trailer wheels for these tires with zero offset might be difficult. Also they do not meet the requirement of 7K axles, and there are a lot of solutions for 6K and down axles. So that leaves axles de-rated to 6750 like Keystone does, however most have axle spacing that does not allow the use of a tire in that diameter. It would be a lot of money to spend to see if they fit.
The best upgrade for Keystones 6750 GAWR situation is Goodyear G614's, which are the same diameter as the stock ST235/80R16, or to upgrade to 17.5" rims and 215/75R17.5 LRH tires. Note this quote and document is choosing new tires.
"The regulation below needs your attention. It dosen't say what kind of tires must be used as long as they meet the axle's requirements. Don't put your safety in the hands of others. Do some more research, please.
Also Jimnlin posted this about the use of LT265's on trailers the other day in another thread:
"This from Dunlap; (a google has much more of the same info from other sources)
Dunlap
RIM WIDTH
Correct rim width ensures flex at the designed flex point in a tire sidewall for optimum tire performance.
If the rim is too narrow, the flex point moves toward the shoulder area, creating heat buildup in the shoulder, which reduces tire life and could result in failure.
If the rim is too wide, the flex point moves towards the rim area, causing heat buildup in the lower sidewall, which reduces tire life and could result in failure.
Within the acceptable range of rim widths, one can select wider or narrower rims than the measuring rim. Selection of a wider rim, from within the approved range, (T & RA tables) stiffens the sidewall and improves handling at the expense of handling. If carried too extreme, either too narrow or too wide of a rim, it can result in uneven tread/pavement contact pressure causing uneven wear and potentially reduced traction, or increased vulnerability to bead dis-lodgement. "
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Somewhere in a Fifth Wheel - Where it does not Snow
I understand the load requirements and I have read that information you posted before (very useful). I checked and the Marathons have a rim width of 6 to 7.5 inches. The 265's require a rim width of 7 to 8 inches. SO if you rim will accept a 7 to 7.5 inch tire both tires should be OK. Both have a pressure requirement of 80 psi for maximum load. So I am still not sure why they cannot be used.
Most OEM 16" trailer wheels at 6 or 6.5 wide as stated earlier! Fitting the wider and larger diameter tire on a new wider wheel under a Montana might be an issue! The BFG Commercial TA list a diameter of 31.4" BTW. If you solve the diameter issue, width may still be an issue along with finding new zero offset trailer wheels. Just because the rim requirements overlap, does not mean what is currently installed falls in that overlap area!
When changing from ST rated tires to LT tires most manufacturers recommend going up one size to compensate for the less stiff side wall on the LT tires. Finding one that is close to the same size would (my opinion) be the wrong way to go. go up several sizes for best results. There is a tremendous amount of lateral forces put on the side walls when turning corners with a tandem axle trailer.
Good luck / Skip
2011 F-150 HD Ecoboost 3.5 V6. 2550 payload, 17,100 GCVWR - 2004 F-150 HD (Traded after 80,000 towing miles) 2007 Rockwood 8314SS 34' travel trailer
US Govt survey shows three out of four people make up 75% of the total population
This article helped me understand the tire situation for our Montana and make a decision:
I have asked many times for someone to explain how a ST tire can be rated to carry more weight than a LT tire in a similar size, without a good answer.
The answer lies in what is called reserve capacity. To quote from Trailer Parts Superstore and this same statement exist on just about every tire site:
HEAVY DUTY 'LT' TRUCK / TRAILER TIRES
'LT' signifies the tire is a "Light Truck/Trailer" series that can be used on trailers that are capable of carrying heavy cargo such as equipment trailers.
If a tire size begins with 'LT' it signifies the tire is a "Light Truck-metric" size that was designed to be used on trailers that are capable of carrying heavy cargo or tow vehicles. Tires branded with the "LT" designation are designed to provide substantial reserve capacity to accept the additional stresses of carrying heavy cargo.
So what is reserve capacity? It is capacity beyond the rating of the tire, capacity that is held in reserve. This reserve capacity comes from the heavy-duty sidewall of the LT type tires. LT's rank at the top of the list when we look at P, ST and LT tires.
Now I finally have an answer to how a ST tire can be rated to carry more weight than a LT tire of similar size.
The ratings of ST tires infringe into the reserve capacity of the tire. This is double bad, because the design of the ST gives us a tire with less reserve capacity to start with as it has a lighter sidewall to start with as most ST tires are much lighter than their LT counterparts.
To quote one tire site:
"Put a different way, the load carrying capacity of an ST tire is 20% greater than an LT tire. Since durability is strictly a long term issue - and the results of a tire failure on a trailer are much less life threatening than on a truck - the folks that set up these load / inflation pressure relationships allow a greater......ah......let's call it load intensity."
There it is in print to be read. They make a calculated decision to give the ST tire a higher load rating because a failure is less life threatening.
I have on a number of occasions pointed out the weight difference between the different tires and have been told that does not matter. Well it does matter. The rubber in the average tire only makes up around 40 some percent of its weight, the rest is in the steel belts, gum strips, steel beads, and the carcass plies. The remaining 60 or so percent of the stuff in a tire is what builds in the reserve capacity.
So to review again, here are some weights:
1. Michelin XPS RIB LT235/85R16 LRE (rated to 3042lbs) Weight 55.41
2. Goodyear G614 LT235/85R16 LRG (rated to 3750lbs) Weight 57.5
3. Bridgestone Duravis R250 LT235/85R16 LRE(rated to 3042lbs) Weight 60
4. BFG Commercial TA LT235/85R16 LRE(rated to 3042lbs) Weight 44.44
5. Uniroyal Laredo HD/H LT235/85R16 LRE(rated to 3042lbs) Weight 44.44
6. GY Marathon ST235/80R16 LRE(rated to 3420lbs) Weight 35.4
So which tires on the list have the most reserve capacity? Well that is not a completely simple answer, as one of the tires is a G rate 110 lb tire and the rest are LRE at 80lb inflation. So if we disregard the G614, then the Michelin XPS RIB and the Bridgestone Duravis R250 due to their all-steel ply construction will have the most reserve capacity inherent in their construction. The twin Commercial TA and Laredo will be next and the Marathon would have little or no reserve capacity available because it was used up in its higher load rating, AND because of it's much lighter construction it had much less inherent reserve capacity to start with.
So what have we learn from this?
I think that the first thing that we learned was that a LT tire can be used at or near it max rated loading without having issues, as they built with "substantial reserve capacity to accept the additional stresses of carrying heavy cargo".
The second thing we may have learned is why ST tires are failing on mid to larger 5th wheels, in that they do not have inherent reserve capacity beyond that rated max loading. Again this is because they have less reserve capacity to start with and their greater "load intensity" used up any reserve capacity that might have been available.
Now, here is an interesting bit of information. I just called Maxxis Tech Line and asked the weights for two tires.
ST235/80R16 LRD 3000 lb rating at 65 lbs of air weights 38.58
ST235/80R16 LRE 3420 lb rating at 80 lbs of air weights 43.43
What??? The Maxxis load range E tire weights almost the same as the Commercial TA?? This is a ST tire that has heavier construction than the GY Marathon at 35.4 lbs. So it has more inherent reserve capacity due to its heavier construction.
Those that claimed its virtues maybe did not know why it was a better ST tire than some of the others, but there it is! It is a heavier built tire with more reserve capacity.
So as one chooses a replacement tire or is asking for an upgrade on a new trailer please get educated on where the reserve capacity exist. Is it inherent in the tire you choose or do you have to factor it into the weight rating of the tire you choose.
Those with heavy trailers that are switching to 17.5 rims and tires rated to 4805 lbs and getting a double injection of reserve capacity, in that they are using a tire with lots of inherent reserve capacity and the tire has much more capacity than the application. It is all starting to make sense.
Dick and Joyce
2010 Montana 3665RE
Dodge 2500HD Maxi Cab Laramie Edition
Diego, Norm, & Bitsy
I understand the load requirements and I have read that information you posted before (very useful). I checked and the Marathons have a rim width of 6 to 7.5 inches. The 265's require a rim width of 7 to 8 inches. SO if you rim will accept a 7 to 7.5 inch tire both tires should be OK. Both have a pressure requirement of 80 psi for maximum load. So I am still not sure why they cannot be used.
skipnchar wrote: When changing from ST rated tires to LT tires most manufacturers recommend going up one size to compensate for the less stiff side wall on the LT tires. Finding one that is close to the same size would (my opinion) be the wrong way to go. go up several sizes for best results. There is a tremendous amount of lateral forces put on the side walls when turning corners with a tandem axle trailer.
Good luck / Skip
Here are quotes from Carlisle Tire:
"Trailer-tire sidewall stiffness is a
compromise between P and LT designs." & "Trailer tires
typically employ heavier steel or polyester cords and somewhat lighter
sidewall construction than light-truck tires"
We have a whole new set (6 total) of LT 3400+ pound capacity tires you are mentioning. They are only slightly wider and just a tad taller. I was slightly worried about tight turns with a little wider tire but as it turns out there is no noticable difference at all. And one of the many pluses is the wonderful highway manners over the ST tires. Tows like a dream. More pluses include being able to get warranties, cost, manufacturer options (virtually none with ST sizes)All tires set to max pressure of course and each axle is now running tires that are 800+ lbs over-rated. I think that is recommended since I left the ST camp. My tire guy, who I've trusted for 15 years, was very comfortable with this change as well. I was $1,200 out the door with road hazzard warranties, lifetime rotation and balancing. My other option would have been the Goodyear 614's that were $345 each and no warranty available. Those would have been over $2,200 out the door WITHOUT a warranty.
08 Jayco Recon ZX 40' 3 axle T/H, dual A/C, 2006 RAM 3500 Cummins Dually, Pac Brake, Banks CAI, Monster Exhaust, 3.5" RAM intake, 51 Gal aux tank w/ tool box, 265/70/17 Goodyear Wrangler SA Pro Grades, Reese Sig series 24K hitch. DVD/NAV/Backup Camera.
rsg63 wrote: We have a whole new set (6 total) of LT 3400+ pound capacity tires you are mentioning. They are only slightly wider and just a tad taller. I was slightly worried about tight turns with a little wider tire but as it turns out there is no noticable difference at all. And one of the many pluses is the wonderful highway manners over the ST tires. Tows like a dream. More pluses include being able to get warranties, cost, manufacturer options (virtually none with ST sizes)All tires set to max pressure of course and each axle is now running tires that are 800+ lbs over-rated. I think that is recommended since I left the ST camp. My tire guy, who I've trusted for 15 years, was very comfortable with this change as well. I was $1,200 out the door with road hazzard warranties, lifetime rotation and balancing. My other option would have been the Goodyear 614's that were $345 each and no warranty available. Those would have been over $2,200 out the door WITHOUT a warranty.
So did you have to buy wider wheels and if so maybe you can give details about make and model to others that are thinking about this tire size. Seems that this works out on T/Hers as they seem to have the axle spacing and fender skirt clearance required, and generally sit higher from the factory. It is not however a tire size for everyone due to, OEM wheel width, axle spacing and clearance issues.
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