Replacing 14" Marathons with 15" Marathons

Bill, I see where you say your reason for changing from 14 to 15 inch tire was to reduce the number of tire failures. Is this a real problem with the tires that come with the TrailManor? I had a wheel and tire guy look at my unit (2720SL) and he said there was nothing he could do to improve the factory system. He did say that I should change the tires to a load range D instead of the load range C that comes with the unit. I was thinking you made the modification for extra ground clearance. I didn't know that there has been a problem with tire failures.

2007 2720SL
Toyota 4Runner Ltd Supercharged

Sal- That has been the main reason for the conversions. I am in the midst of it right now. The issues have been with overloading the OEM 14" tires that have a 1870lb load capacity and that is where the failures seem to be taking place. To the best of my knowledge, nobody has kept their original TM setup (no lift kit) and tried to put on the bigger 15" D load rated wheels and tires. Not sure if they would fit. The lift kit for my 04 2720SL is 40.00+ shipping which is cheap cheap cheap. Seems like a no brainer although the wheels and tires are much more than the lift kit. Just some preliminary numbers I have are three rims at approx 50.00 each, tires at 80-100.00 each, plus balancing and tax. Your looking at 400.00 plus but I felt it was worth it to have peace of mind knowing I may be loaded to say 3800 lbs and am 1000 miles from home and really dont want a catastrophic tire failure. Can you say "peace of mind".

Another problem with the 14" rims, is I couldn't find a load range D ST tire for the 14s. I kept load range C tires after my 15" conversion, but they are rated @ 2150 lbs.....almost a 600 lb. combined maximum weight limit over the Cs". If they give me a problem, then I can step up to the D rated, since several tire manufacturers make them for th 15s. I went to the 15 Cs to give the TM a little better ride than the stiffer sidewall Ds.

Chap

I have gone to a half dozen different tire places here in Florida and they all have problems getting in the D load range 15" Marathons and the ones that can are pretty pricey. Cheapest I found was 140.00/tire, plus the rim and balance. Gets expensive. I did however find a couple that sell and/or push the Denman and swear by them. They have an 8 ply 225/75/15 in a D load range at 2540 for 93.00/tire. I did tell them too that I wanted to make sure the rim was rated to handle at least a 2000 lb load and I did have a couple guys say the rims werent rated and that they dont rate rims. I shyed away from them just from what I have read on here. Anyone had any luck with the Denmans? Looks like I may be a guinea pig here if not.

Originally Posted by FightinIrish

I have gone to a half dozen different tire places here in Florida and they all have problems getting in the D load range 15" Marathons and the ones that can are pretty pricey. Cheapest I found was 140.00/tire, plus the rim and balance. Gets expensive. I did however find a couple that sell and/or push the Denman and swear by them. They have an 8 ply 225/75/15 in a D load range at 2540 for 93.00/tire. I did tell them too that I wanted to make sure the rim was rated to handle at least a 2000 lb load and I did have a couple guys say the rims werent rated and that they dont rate rims. I shyed away from them just from what I have read on here. Anyone had any luck with the Denmans? Looks like I may be a guinea pig here if not.

I was going to show you that Tire Rack had the Load Range D marathons for $97, if that was what you really wanted. If you scroll down to read the first user comment there, they have a travel trailer user experiencing the same thing we have about them with 14 inch Marathons. It appears that the trailer forums he belongs too, have done the same thing we are trying, and switching to heavier plys and other brand names. It was almost a dejavu thing in reading it.

http://www.tirerack.com/tires/tires....1=yes&place=26

Chap and Bill have done this conversion recently. Maybe they will chime in with their wheel choices. (Hint-Hint)

If you can get the DOT code off the Denman's, then we can see who actually manufactures them. The more guinea pigs, the better. We need a full sty.

Originally Posted by wmtire

Chap and Bill have done this conversion recently. Maybe they will chime in with their wheel choices. (Hint-Hint)

After I decided to go with the 15" wheels, I still wanted to stay with the "C" rated tires, mainly to give the TM a little softer ride than the stiffer sidewall "Ds". The 15 "Cs" have almost a 600 lb. combined maximum load capacity over the 14s, so I figure that ought to be plenty of fudge factor. Only a couple of manufacturers offer the 225/75R15s in the "C" rating. I decided on the Titan ST225/75R15 C RADIAL ST II TLs. The tire store confirmed that they rotate stock, and have recent manufacture dates on their tires. When I went to get the tires, they were already 3 yrs. old!!! They didn't sell many of the "Cs", and failed to mention that on the phone. The only other brand they carried were Carlisles. Again . Since I was already there, the Carlisles were made in week 50 & 51 of 2006, and several tire dealers had told me that they have had no problems with Carlisles, I went on and bought them. Hopefully, the Carlisles of past have greatly improved. We will see over the next couple of years. I only have 2000 miles on them so far, but that has included some pretty rough back roads.

A footnote: The trailer guy that looked at my brakes and bearings, made mention that I should go with a stiffer sidewall, since the Carlisles looked squishy to him. But he mainly deals with heavy horse trailers and dump trailers that use bias plyed tires. But if these tires don't work out well, I will go to the "Ds" when the time comes. If these work out OK after 3 or 4 yrs and many miles, I might stay where I am......I like the cushioned ride, and things seem to stay in place in the TM, even on bumpy roads. Again, we will see.

Chap

We just got back from a 400 mile trip with the new 15" wheels and Load D Bias tires. I had them balanced when I bought them. The trailer rode very well on the highway and handled nicely. I also drove a few miles on the sand. Some of it up into sand dunes towing the trailer. It worked better than I thought it would. The trick is letting at least half the air out of all the tires. I did need 4 Low to do it. Without the trailer I can drive most areas in 2wd and only need 4wd for the steep hills.


It was nice to be able to take a shower and not use the heavily ladden chemical toilets on the beach.

[Bill]

I just finished a 3200 mile trip with the new tires, and I'm pleased to report that I have nothing to report.

As you know from the lead post in this thread, I made the switch from 14" Marathons to 15" Marathons several months ago, thanks to the help and generosity of Bobby at WMTire. Shortly after making the conversion, I made a few short trips with the new tires, maybe a few hundred miles, but nothing long enough to draw conclusions from.

Then on Oct 14, my wife and I left Maine with a fully loaded TM behind. We headed south through West Virginia, then Kentucky, a bit of Illinois (where my wife witnessed the exceedingly rare phenomenon of ball lightning!), Missouri, Kansas, and on to our cabin in Rocky Mountain National Park northwest of Denver. Of those 2300 miles, most was good Interstate, but about 300 was "New Jersey Interstate" (broken pavement and potholes) and about 100 miles was gravel. No problems.

After two weeks in the cabin, we finished the trip with 600 more miles of Interstate in Colorado and New Mexico, and 300 miles of secondary roads in Arizona. Still no problems, a situation I love.

I initially ran the tires at about 60 psi, but the "New Jersey Interstate" shook things up a bit. I dropped them back to about 56-58 psi, and the shake was noticably better.

Now it is true that 3200 miles is not enough to draw firm conclusions about blowouts, flats, and so forth. But I can say that the tires ride well, they do not hit the wheel well covers or the frame, and in general I am pleased. Thanks, Bobby.

Bill

[rickst29]

I run the Marathons on my 2619 way lower than that-- only 46-48 PSI when warmed up. Even 55 PSI was shaking up my Trailer contents pretty badly. But I've got the "big" axle too, which is awfully stiff on the small TM, so maybe you don't need to deflate 'em as far as I do.

The Goodyear table probably indicates a value closer to mine (high 40s) than yours (mid 50s) for our TMs. Are you gonna try reducing it lower, or do you want to keep the PSI up a bit for driving fast on Interstates?

(I of course have TPMS, too, and that's a big confidence builder for running at the low tire pressures I use.) Thanks for the report!

[fcatwo]

We've been away but in scanning the last few pages of this thread I don't see any mention of garage door heigth problems. Everything about the TM is a compromise of some sort and adding lift kits and larger tires can make those with roof air so tall they don't fit through some garage doors. Not a problem for most but something to keep in mind.