Upgrading Tires from 15" to 16"- 2006 Cougar 285 EFS

[Texas Bob 140]

On our annual trip from Double Oak, TX to South Padre Island, TX we blew out two tires and the wheel opening J wrap, fender and wheel well liner and damaged the wheel. The blowouts were within 5 miles of each other. The tires were ST225/R/15/D's. One was a 4 year old Goodyear Marathon with little mileage on it that blew a hole the size of a tennis ball in the sidewall. The second tire was a Mission that had never been used and was the spare and had been covered its entire life. The Mission spare shredded after 5 miles and caused the damage. Weight on the tires is around 8,000 lbs. as measured on the Cat scale at the local truck stop and all tires were aired up to 65 PSI. I also have Tireminder sending units on each tire and there was no warning of any problem.

I'm planning on upgrading to a 16" wheel with a BFG Commercial T/A LT225/R/16/E tire. The BRG's have a diameter of 29.4" per BFG and the Goodyear ST's have a diameter of 28.3" Center to center distance on the tandem axles is 33" so I will have clearance between the wheels of about 3.6". There is plenty of room between the ST's and the frame of about 3" and the new tires will have the same width.. I have checked out the slide out mechanism and the closest the slide out bar/track comes to the ST tire is somewhere between 5 1/2 to 6 inches.

The limiting factor seems to be the distance from the tire to the wheel well liner. On the present ST's, the distance is 2 1/2" at rest. With the LT tires, that should be reduced to about 2". Interestingly, there is no real liner on this trailer - it appears to be plastic coated fabric which looks like the cheap plastic coated tarps they sell at the home stores. I will jack up the front wheel, hang the back wheel and measure the distance from the front tire to the liner in a few days. Anyone know what would be the minimum safe distance?

I plan to replace the wheels with 80 PSI wheels and metal valve stems.

Any thoughts or counsel, especially anyone who has made this modification to this year and model trailer, is appreciated. Thanks.


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2003 Ford F250 6.0 Lariat
2006 Cougar 285 EFS

[hankpage]

Bob, When I replaced the ST tires on my my '07 the tolerance that was the biggest concern for me was the section-width on the tires. In order to avoid rubbing on the sides of the slide mechanism I had to go with narrower tires ... LT215/85/R16E Michelin X-Ribs. Section-width info is hard to find on some tires as most just give tread width. I have found that the narrower tire squirms less while backing and turning putting less stress on suspension and they also seem to reduce rolling resistance. Good luck and measure everything several times and be sure the wheels are the same offset as the old ones.(I think mine were 0" offset) I think you are on the right track with your research, Hank ....... Oh! and by the way ..... Welcome to the forum.

[Texas Bob 140]

Hank,

Thanks for your comments and encouragement. I retracted the slideout and climbed under the trailer to see if there were any restrictions between the 225/15/R/D tires on the trailer and the slideout mechanism. I noticed that there is a square bar that runs between the two slideout tracks on the inside of the tires. I measured the clearance and it is about 1" from the widest point on the tire which I believe is the section width. The distance between the top of the two tires to the wheel well is 2 3/4" and 2 1/4". I checked the section width spec for the 16" - 225/16/R/E tires and it is the same as the existing tires. So I think I have the clearance measurement to the square bar covered.

I ordered a Trailer Aid online and it should be here in a day or two. I'll pull the trailer on to it and with one wheel hanging, measure the distance between the jacked wheel and the wheel well to see if I will have adequate clearance or not for a 16" tire.

[bg71361]

Be sure to check the distance between the tires the 16" will be taller, I went with 245's because of this.

[LittleJoe]

" there is no real liner on this trailer - it appears to be plastic coated fabric which looks like the cheap plastic coated tarps they sell at the home stores. "


I fashioned pieces of galvanized material to slide over the edge of frame and between bracketry. Took a bit of doing but on completion, I have a proper inner fender and don't have to worry about stones wearing through the plastic crap and water soaking into the floor. I also sprayed rockerguard on all to make it visually pleasing.

[fla-gypsy]

I see no issue with your plan. If you choose not to do the wheel/tire upgrade there are better ST tires available that will give good service.