Bigger tires and rims?

We put on about 6,000 miles going to Colorado Springs rally and then out to Oregon, thru California wine country and back to Florida in about 5 weeks. We had two blow outs on the new tires, but thats all of the problems we had. My question is: Can we buy 225/78/15 tires and rims and run them, instead of the 215/78/14's. (Weight and tire pressure w3as not a factor, because I checked all of the time.) Will they be better, stronger, safer? etc.
By the way we had a great time at Colorado Springs,CO. they know how to put on a great time. Jack & Mary

Are you sure you're not putting too much load on your TM axle with the WDH? An improperly adjusted WDH can overload the trailer axle, ruin tires, burn up bearings, etc.

[Bill]

Jim -

I don't think so. Seems to me that if you cranked up your WDH to the point where the tow vehicle's rear wheels came right off the ground, you still couldn't put any more than half the tongue weight on the TM axle, the other half being on the tow vehicle's front wheels. Have I missed something here?

Bill

[fcatwo]

Bill

I'm no engineer but what happens to the ton or so the rear axle is supporting before hitching the trailer when you lift it off the ground? Doesn't any unloading of the rear axle go forward and back? I remember seeing a picture in an Olds advertisement years ago of a front wheel drive Oldsmobile with the rear wheels removed and a trailer hitched to it. The front wheels of the Olds and the trailer's wheels were carrying all the weight. I suppose they welded it all together to get the picture but I'll bet it was a hand-full in a parking lot :-). That picture has influenced my perspective on WDHs to a great degree.

Jack and Mary had thier WDH installed by "The Car Store" while at the Jubilee. The folks who were doing the work impressed me with their knowledge of TMs and RVs in general. I would tend to assume that they installed the WDH properly. Assuming that was the case, what else could have caused their problems?

Jack and Mary, did your trailer suffer any damage from the two blow outs? Sorry for your problems but glad you are all right.

Bll

I weighed my TV axles and TM axle last year. The weight on each of the three axles was pretty much the same. 3200 to 3300 pounds per axle.

If I had a WD hitch, and if I could tighten the bars to lift the TV rear wheels off the ground and if the total weight was evenly distributed across the TV front axle and the TM axle, then the weight on each of the two axles would be about 5,000 pounds. This would clearly exceed the TM axle rating.

In fact, my TM axle weight was 3380 pounds. If I shifted 120 pounds back to the TM axle then I would max it out. Therefore, the factory advise when I called them was rather sound. They recommended that I NOT use a WD hitch. Mainly because I have a TV with enough capacity that I do not need one. However, shifting too much weight back on to the TM axle is clearly not a good idea.

It seems to me that if you wanted to carry as much stuff as possible in the TM then you must NOT use a WD hitch.

If you NEED a WD hitch then you clearly can not put as much stuff in the TM as you could without the WD hitch.

[mjlaupp]

Jack & Mary,

To answer your question about fitting 15 inch tires and rims. The consensus is that there is not enough room under the TM for 15 inchers without either the optional heavy axle or the optional lift kit.

Will the 15 inch tires be safer? Probably no difference.

Will the 15 inch tires be better? Only you can answer this one.

Will the 15 inch tires be stronger? Yes, if you get load range D tires. The OEM 14 inch tires are load range C. You can get load range C 15 inch tires that, because of their larger size over the 14 inch, provide more load capability.

Mike

[fcatwo]

I've been researching this subject for some time and can add a little to Mike's post about Maximum loads -- all from Goodyear's site:

ST 215/75 R14-"C" @50PSI is 1870lbs per tire or 3740lbs for two.

ST 225/75 R15-"C" @50PSI is 2150lbs per tire or 4300lbs for two.

ST 225/75 R15-"D" @50PSI is 2150lbs per tire or 4300lbs for two.

ST 225/75 R15-"D" @65PSI is 2540lbs per tire or 5080lbs for two.

Note that the C & D 15" tires have the same max weight ability at 50PSI. They also have identical dimensions/specifications so I have to wonder if they may be the same tire with just different numbers on the sidewall.

5-lug on 4-1/2" circle 15"X6" steel wheels that fit the 3500lb TM axles are readily available from Camping World and Cabellas or can be ordered by any tire shop. They are only rated to support the 2150lb load-range "C" 50PSI tire however (or the "D" at 50PSI). You'll need 6-lug 15X6 wheels to support the full 2540lbs available with the load-range "D" tires @ 65PSI and they only fit the 5000lb axles.

IMO the extra 560lbs of max load capacity added by moving to 15" load-range "C" 50PSI tires that fit the 3500lb axles may be all we need to stop blowing tires. This does not change the axles 3500lb rating of course but no one has reported a problem with axle failure -- just tires.

Someone mentioned earlier however that TM does not recommend this because they have not tested that tire and wheel combination. Given that our 2619 has at most 3200lbs on the axle I'm inclined to do it anyway unless someone can point out something I've missed --- what to do with the old wheels is a problem however.

I should mention that someone on this site has already done this and reported no problems.

[Bill]

Originally Posted by fcatwo

Bill

I'm no engineer but what happens to the ton or so the rear axle is supporting before hitching the trailer when you lift it off the ground?

Frank -

You are exactly right. In my zeal to make my point, I mis-stated my point, and I apologize for that. What I meant (but didn't say) was that if you cranked up the WDH far enough to return the hitch ball to its unloaded height, thereby removing all of the tongue weight from the rear end, that tongue weight would split more or less evenly between the tow vehicle front axle and the TM axle. But this wouldn't overload the TM axle to anywhere near the extent that you described.

You certainly could crank the WDH up higher than that, so that you actually started to lift the rear end of the tow vehicle above its unloaded height. Why anyone would do it, I have no idea. And how anyone would do it without noticing it, I have no idea. But if you were to do it, it would continue to put more and more weight to the TM axle, and the tow vehicle front axle, just as you said. And in the extreme, this could badly overload the TM axle.

Bill

[fcatwo]

Bill

I knew you probably didn't mean what you said but I didn't want to leave it laying there for newbies to digest.