Change wheel size for better tires?

[RUSSELL5000]

I found the following cut-away view. I am sure lots of folks here on the forum know this stuff - new to me, however. I'll do some reading to try to get a better understanding of what goes into making one tire "better" than another. I thought all you had to do was look at the specifications chart - since the weight of tires with the same specifications can vary by 40% then there must be more to it then that.

http://www.maxxis.com/media/420089/layered_tire.pdf

 

[Jeepr]

LT tires are OE on multiple trailers so I am going to call BS.

Yeah, I checked with a friend that is a Highway Patrol Officer and he that's the stupidest thing he's ever heard. So, consider that argument closed.

 

[Mingoglia]

Yeah, I checked with a friend that is a Highway Patrol Officer and he that's the stupidest thing he's ever heard. So, consider that argument closed.

FWIW, I have highway patrol officers in my family (4 actually) and even they admit *most* of their colleagues have no clue when it comes to equipment details like we're talking about here with tires.... it's the DOT man that would take issue with it, but I digress.

With that being said, I too have seen LT tires as OE equipment on some heavier toy haulers and heavier luxury fifth wheels.

 

[MichaelOverfield]

I'm working on putting together some pictures/diagrams and descriptions for the cut away views of the tires for comparison.. but some initial finds from my cuts last eve.

I have the bulged (failed) Goodyear Marathon ST, size 215/75R14 LRC tire. I confirmed the bulge was due to de-lamination of the plys, specifically between the radial steel plys.

I also took an older P-tire, not close in size, but from my Saturn.. so I EXPECT much less from it, it is Dunlap, SP60 size P175/70 R14 84S tire. It has a 1 ply side wall.

So I did a cut away on these two tires to compare construction. Both have 2 steel plys, and appear to have comparable thickness in the radial section (Tread). The smaller Dunlop is slightly thinner on the sidewall, but we are talking maybe 1/16" or so, I almost can't see the difference.. but will get out the calipers later and take accurate reads..

So, what I can conclude from this it the following, side wall of a small, low load P-tire is similar to the supposedly tough ST tire.. leading me to further confirm the larger factor is inflation pressure when it comes to determination of the give/flex of the tire.. as I had suspected.. more to follow.

I also can further say, despite the age, there is no way the Goodyear tire should have seen this kind of ply separation. I was at Walmart to have the new tires put on the new rims, and notices in the pile of old tires there was another Goodyear Marathon tire (recognize the tread pattern) in the stack that had a failure along the radial/tread, but worse than mine, an actual blow-out. plenty of tread remaining, like mine.. there is ZERO cracking or dry-rot on any of my GY tires.. so be aware.

 

[RUSSELL5000]

MichaelOverfield,

Watching with interest.

Question: is it safe to conclude tire sidewalls are equal due to similar thickness? What about type of materials used, fashion of manufacture,...?

 

[MichaelOverfield]

Russel,
At this point I would not say for sure they are equal, but I'm comparing a small car tire rated for about 1000# to a trailer tire rated for near twice that. I can say the side walls are not even close to twice thickness, strength/stiffness. As that relates to the claim ST provides more rigidity from side wall looks dubious. Now I do think rated pressure is a better Indicator.

 

[MichaelOverfield]

Pictures for Tire/Wheel size and suspension upgrade project thus far

These pictures show (in no particular order) the old and new tires/wheels, the frame cracking issue and my solution of a cross brace to relieve the bending stress on that portion of the I beam frame, the new welded on spring mounts to go from axle above spring, to axle below spring, Old broken 1800# spring, and new 2400# spring, and the newly received rubber equalizers and shock kit parts.. not installed yet.. that is going to be interesting as I can already tell more fabrication of parts is needed to make these work as well.

 

[RUSSELL5000]

I will be following with interest.

 

[MichaelOverfield]

Made some more progress last eve (next two braces made, and I extended the center brace to account for going from a 4" equalizer link to a 2" link. I also needed to do this to provide clearance for the grease fittings on the new one, since my bolted brace was interfering... argh... I'll take and add more pictures as I get them. The cross brace was not my original idea, I got a technical publication from the Dexter Axle site that showed welded cross braces from angle iron steel. In my case I went with the galvanized fence posts, since they were cheap, strong, not too heavy, and galvanized means no rust worries (no weld issues either, so long as it is steel and not stainless). The reason I did not weld them on the frame was to make it possible to remove them for access under the trailer when/if needed. The original garbage plastic corrugated cover was replaced years back when mice had invaded.. I pulled it off to find a total mess of unsupported wires and plumbing, and a very poorly held in place water tank.. I fixed all those issues and went back on with insulated (1/4" foam board) over galvanized steel roof panels installed back to front, with stainless self drilling/taping fasteners, and some steel rivets between panels, so still removable if needed, but much, much better, and mice can not chew through the steel, hence no more mice invasion. At this point I feel like I've almost rebuilt this trailer..

 

[TLane]

Interesting that the crack appears to be well away from the spring hanger. Is there an internal brace at that point? Did you add the angle iron brace just above the hanger? I'd love to see pictures of your steel underbelly. Did you do anything to seal the ends of the steel where it meets the frame? I need to do similar mods to my trailer!

 

[MichaelOverfield]

TLane,
Yes, there is a cross brace welded just above the cracks, there are 4, one above each wheel, all directly below the cross brace. The I-Beam is pretty thin metal on the vertical section, so it was just a poor design. The angle braces on the forward most and aftermost spring hangers are from the OEM, clearly some consideration was there for it needing such support. I previously did a hasty weld repair on the cracks, but they re-appeared.. the new braces should solve it permanently.

For the steel panels.. they are sealed with expanding foam, then trimmed and painted (foam is not UV stable, and looks better). The 1/4" foam board was glued to the panels when put in place, though I don't think the glue held up, it ended up being held by the screws into the frame and sandwiched between the steel panels and the frame rails.

While I was in there fixing things, I also foam insulated the sides, and installed a thermostat controlled pipe freeze prevention heater, I prefer not to winterize, and climate is pretty mild in Western Washington, so I have it plugged in and kept above freezing with minimal electric use. Also works as a back up for power/water loss to the house if needed.

I'll try to add some pictures later in the next update to show the bottom cover better.

 

[MichaelOverfield]

Bottom Panel Details for those interested...

Here is 2 showing the bottom galvanized steel panels installed to replace the junk plastic OEM basement cover. Just got all 3 cross frame supports on last eve.. looking to get an axle or two on this eve if all goes well.. more to follow.

 

[TLane]

Thanks for the pictures! It looks much better than what I have under my trailer, so I'll add that to the list of things to do.

 

[MichaelOverfield]

Determined the likely root cause of the frame cracking. When I measured the distance side to side, between the spring mounts, I went with 66 inches (slightly more than they were, expecting to make it a tight fit), this based in part on the spacing on the axles. In order to install the new cross supports, I had to force them in, slightly pushing the frame rails apart to do so. Then putting on the axles on I noted I had to further push the springs apart to get the fit with the axles, so that tells me with little doubt, the OEM install left the axle and springs putting a constant pressure on the frame to spread the I-beams apart.. so the only place they were held to keep that from happening was the OEM cross beams, and just below that cracks appear from a constant stress which no doubt would increase and decrease with road vibration and load.. hence eventual fatigue failure and a crack appears.. in 4 places just below those OEM cross supports. I expect this load to be completely removed and taken within the new bolted supports I installed, so that should be the end of it, but it again shows just how poorly the OEM did in construction in the first place.

 

[MichaelOverfield]

Ok, pictures later once I get them uploaded, but the road test was yesterday with the new suspension and the new Hankook tires.

Rock solid! No sway, I did not see any additional flexibility in the tire sidewalls with many attempts to shake the rig both on the road and off (some have said this is the disadvantage of P-metric tires, but I just don't see it on the specific size/spec I used, but these are XL tires (extra load range)). Traction for braking is great, I actually think it is pulling me to a stop, so a adjusted the controller down a bit.

I had an observer on radio to see if there was any out of balance condition, and none noted (I did have the wheels balanced).

Now, to be fair, not only new tires, but also the new stiffer springs, Dexter rubber equalizers, and the shocks.. so all together the results are really great..

I even purposely filled the fresh water tank, and both grey and black tanks to give extra load to see if it changed anything.

There is only one final adjustment to make, I had to raise my hitch point, since the entire rig is now about 6 inches higher, and my adjustment was off by about 1.5 to 2 inches.. so I'll make that change to cover it and it should be all set.

I will also try to get the measurements of the various tire types, and pictures to show, I'm even more convinced of the great ST tire myth now.

 

[SnoKing]

Our 2005 Cardinal got crack in the I-beams in the same location, which is where the cross lattice racks are welded to the back side of the I-beams webs. Common problem on Cardinal and other trailers.

Here is the Lippert bulletin on it.

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Here are some pictures of my repair.

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Fish plates were punch welded over the crack welds.

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2x2x1/8 tubes werei installed side to side at the three hanger locations.

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Lipperted has been know to pay all or part of this repair.

Snoking

 

[MichaelOverfield]

Thanks for the data and pictures! More to prove the general cheapness of OEM construction. Those cross braces look really strong, also see you have shocks as well, and that is a heavier rig than mine. Since I have enclosed basement and associated cover, I went with the bolted on cross braces so I could remove for maintenance if needed, since it seems I do that more frequently and for longer than I ever get to camp in this rig!!

 

[MichaelOverfield]

I know I still owe final pictures.. have them on the camera and still need to transfer to PC to post.. but I did a near 1000 mile trip on the new suspension and tires.. it continued the positive performance from the test drive, with occasional cruising speeds of 70 MPH, and due to some idiots out there an occasional burst to near 80MPH.. that and all kinds of roads, from interstate to steep gravel, rough roads, winding curves and mountain passes, nearly off road in a few places traveled.. and it did well in all conditions, and I don't have to worry about a stupid 65MPH speed rating. At rest stops I checked tire temperatures, and they were barely above ambient, which was near 100 degrees on part of the drive. I'm convinced these Hankooks are a solid choice for replacement of LR C ST tires on 15" rims. There is no apparent sidewall weakness as some have suggested, actually they seem more secure than the GY Marathons they replaced, and were about $30 less per tire, enough in my case to just about cover the new rims and leave the 14" behind.

 

[Joseph Donnelly]

I ran over 4200 miles mostly at 74 mph last month with my box trailer and show car, no issues with Maxxis 275-15 D tires made 45th week of 2013.

 

[GAmes]

I replaced my 15inch, load range D Marathons with 16 inch load range E Michelins today. Now my truck and trailer have the same size tires.