2015 23D Wheel / Tire upgrade 14" to 15"

[pjmcvey]

Same Old Story:
Just had my second GYM tire blow out, the first was just 536 miles into my first trip back in September 2015.
Now had my second at about +4500 miles, these are the 14 inch OEM GYM tires that came on the AS I purchased new in July 2015. Thankfully, I had added a TPMS, caught the deflation early and did no damage to the Trailer.
I have read many of the threads on this swap, seems most of the trouble was on the 14 inch GYM tires made in China.
I have decided to move to a 15 inch wheel and tire to get Michelin LTX tires which give some higher ground clearance and allow higher speed when needed. I usually travel around 65mph, but there are times that 70 mph plus is needed to keep safe from slowing traffic. The 15 inch wheel / tire combo has a higher speed rating.
Going to: Sendel T02-56545T wheels (15" x 6", 5 / 4.50", 0 offset) and the Michelin 235/75R15 LTX MS tires. Need to double check the load rating since these are LT truck tires.
If anyone has any words of caution or suggestions - go for it.
Pat
This is my first post...

[switz]

Those Michelin 235/75R15 LTX MS tires are not truck tires but passenger car tires. Michelin has not made a 15" light truck tire in my memory. The payload must be derated 10% for trailer use per this Federal Regulation:

49 CFR 571.110
Tire selection and rims and motor home/recreation vehicle trailer load carrying capacity information for motor vehicles with a GVWR of 4,536 kilograms (10,000 pounds) or less.

S4.2.2.1
Except as provided in S4.2.2.2, the sum of the maximum load ratings of the tires fitted to an axle shall not be less than the GAWR of the axle system as specified on the vehicle's certification label required by 49 CFR part 567. If the certification label shows more than one GAWR for the axle system, the sum shall be not less than the GAWR corresponding to the size designation of the tires fitted to the axle.

S4.2.2.2
When passenger car tires are installed on an MPV, truck, bus, or trailer, each tire's load rating is reduced by dividing it by 1.10 before determining, under S4.2.2.1, the sum of the maximum load ratings of the tires fitted to an axle.

S4.2.2.3
(a) For vehicles, except trailers with no designated seating positions, equipped with passenger car tires, the vehicle normal load on the tire shall be no greater than 94 percent of the derated load rating at the vehicle manufacturer's recommended cold inflation pressure for that tire.
(b) For vehicles, except trailers with no designated seating positions, equipped with LT tires, the vehicle normal load on the tire shall be no greater than 94 percent of the load rating at the vehicle manufacturer's recommended cold inflation pressure for that tire.

I have used that size Michelin (LTX (P) 235/75R15 XL) on both the 2013 25FB International Serenity and our current 2015 23D International Serenity. We went with the SenDel T03-56545T wheels on the 23D as they match the 16" SenDel T03-66655T wheels on our 31' Classic. One needs to run them at 44 psi for best results (per Andy Thompson at CanAm in London, Ontario who has installed thousands of them on Airstreams) and that pressure worked fine for both trailers for us.

My 23D scale numbers are:

Camping Ready 23D my scales 9 May 2016 Full water and propane tanks

Tongue………928
Front….1,280……1,246 - total front axle 2,526
Rear…..1,376……1,233 - total rear axle 2,609
Total Axles………5,135
Total Trailer….6,063

Thus my versions of this tire had a sidewall load rating of 2,183 pounds @ 50 psi and had to be derated to 1,985 pounds. The left rear tire load is less than 70% of the tire's rated capacity.

Note that this specific Michelin tire model has been replaced with the "Defender" series and I have yet to see one in person to read the supposedly slightly higher load rating.

We also installed a Dill1506-453 TPMS system and used Centramatic wheel balancers (about $224 with UPS charge delivered from Texas) model "200-221 standard". We upgraded the wheel fastening hardware to McGard 24138 Chrome Cone Seat Wheel Locks and McGard 64010 Chrome Bulge Cone Seat Style Lug Nuts (1/2" - 20 Thread Size) available on Amazon.

[rmkrum]

Thanks. Great information!

[PKI]

The Defender version of the LTX adds a bit of load capacity, but the prior version had sufficient capacity for the 23.

Extra speed - Faster is not needed for safety. Do not, repeat, do not sell yourself on this flawed concept. Slower lets the vehicles merge without you slowing rapidly to prevent an accident. Slower down hill keeps you in the right lane so the faster folks can get around. Slower lets you back away from clumped tailgaters. Slower gives you the capability to increase speed slightly to smooth out a lane change, move away from a pacer, or merge into traffic from an entrance ramp.

However, more speed capacity should corespond to better construction and materials. Those are very good tire parameters to embrace.

The only problem with this upgrade is finding a new owner for the 14s. Pat

[switz]

I left the Airstream stock 14" wheels and GYM Load C tires at Colonial when I picked up the trailer. They got some battle spares.

However, our 2015 23FD had been on their lot since September 2014 and I picked it up in July 2015. So the tires could easily have been over a year old (based upon our 2014 Classic starting down the line just before Christmas break of 2013 and the stock 15" GYM tires were from July of 2013).

As a matter of interest, the 15" Micehlins were 2.2" larger in diameter than the stock 14" GYM tires so the 23D trailer was elevated to the same elevation as our 25FB on the same model tires. Thus the ground clearance increased by 1.1" all the way around on the 23D.

We also used the same settings on the Hensley Arrow hitch we transferred from the 25FB to the 23D.