WD Hitch adjustment needed for switching from 15" to 16" tires?

[D2LLIO]

Hi Streamers everywhere,
The tires on our 2015 FC 25 FB Twin are going on 3 years old in October. If I decide to purchase new tires and also decide to switch from my 15" GYM's to a 16" Michelin or other brand, will that 1" increase in tire size require an adjustment to my WD hitch setup (Blue Ox)? I'm thinking the tire size increase will only "lift" the trailer a half inch at most. Am I missing something?
Thanks in advance for your advice/guidance!
Frank "D2" DiTullio
p.s. attaching a pic of our "Georgia" as we were heading out to spend a long weekend in Fredericksburg, TX

[HowieE]

If your hitch was adjusted correctly and you raise the trailer height 1 in you should just raise the height of the hitch head on the shank by 1 in. That may not be the case here.

Check that the 16 in tires raise the trailer 1in. That difference is more than likely less than an inch. Things to consider are the tire diameters, tire pressure to determine the net gain in height.

Measure the trailer frame height front and rear and adjust till the trailer is parallel to the ground while disconnected from the TV. Remeasure after the new tires. That is the amount you want to change the hitch head height by to retain the original conditions.

[steverino]

When switching the tires on my 27 FB from the 15" Marathons to the 16" Michelins, I noted approximately a 1/2" increase in ride height, but no need to readjust WD.

[Wayne&Sam]

What Steverino said.

[m.hony]

I didn't change anything when I switched to 16" wheels and LT tires.
You are essentially raising the trailer 1/2" 20 feet behind the hitch point.
The trailer isn't raised enough to matter.

[gypsydad]

Maybe an odd question, but why are you switching to 16"? I see many folks do this, but not sure the economics or benefit is there? Enlighten me the cost or ride benefits...maybe I will need to spend more money some day also!

[xrvr]

16 inchers are available in LT tires, better than ST tires....more choice in brand of tires, etc.

[tjdonahoe]

Originally Posted by avionstream

16 inchers are available in LT tires, better than ST tires....more choice in brand of tires, etc.

With the short light trailers a P size tire may be enough without going to a 16",

[m.hony]

I have P-metric tires on my 3,500# GVW utility trailer.
The tires have a load carrying capacity of 1,800# each.

[jimfa440]

Originally Posted by D2LLIO

Hi Streamers everywhere,
The tires on our 2015 FC 25 FB Twin are going on 3 years old in October. If I decide to purchase new tires and also decide to switch from my 15" GYM's to a 16" Michelin or other brand, will that 1" increase in tire size require an adjustment to my WD hitch setup (Blue Ox)? I'm thinking the tire size increase will only "lift" the trailer a half inch at most. Am I missing something?
Thanks in advance for your advice/guidance!
Frank "D2" DiTullio
p.s. attaching a pic of our "Georgia" as we were heading out to spend a long weekend in Fredericksburg, TX

You will raise the AS by 1/2" at the axle. You will not change the weight distribution, it's all still there and not moved fore or aft. If your WD hitch was set up correctly, you shouldn't have to change a thing.
Happy Airstreaming

[switz]

We went from the stock 15" GYM ST225/75R15D (that were rated 2,540 pounds @ 65 psi and were 28.3" tires in diameter) on our 2013 25FB International Serenity to the 15" Michelin LTX (P) 235/75R15 XL tires sidewall rated 2,183 pounds @ 50 psi and derated to 1,985 pounds for trailer use and were 28.9" in diameter. The trailer was raised 0.3". These Michelin tires were inflated to 44 psi and had no issues when the trailer loaded scaled 6,900 pounds of which 1,175 pounds was tongue weight. So the four tires were supporting on average 1,431 pounds. Plenty of load margin. No need for the 16" tires which have to have higher pressure so the trailer would get a stiffer ride.

Our 2014 31' Classic came with the same 15" GYM tires captioned above. We did up-grade to the 16" SenDel T03-66655T wheels the factory used at that time along with 16" Michelin LT225/75R16/E LTX M/S2 tires rated rated 2,680 pounds @ 80 psi and are 29.2" in diameter (also used by the factory). Thus raising the trailer about 0.45" with the taller tires. We know the actual individual tire loads so carry 73 psi in these tires.

[Ronman]

So glad to see this post. We just went to 16's on Friday. All looks fine but it's nice to hear from others. Thx

[gypsydad]

Originally Posted by avionstream

16 inchers are available in LT tires, better than ST tires....more choice in brand of tires, etc.

There are many threads here, from happy users of LT 15" tires from Michelin and other manufacturers. The comment about stiffer ride, and higher pressure on 16" tires, I am not able to dispute, but I know from owning 4 AS's now, that there are plenty of 15" choices out there...the extra expense of going to a 16" wheel and tire is not worth the hassle to me....but that's just me.

[D2LLIO]

Thanks to all of you who responded with valuable input for me to consider. This Forum is great!

[switz]

The 15" Michelin LTX (P) 235/75R15 XL tires are passenger tires with an XL = extra load rating. Thus they must have the sidewall load rating derated by 10% for trailer use. Thus the 2,183 pounds side wall rating @ 50 psi must be derated to 1,985 pounds for trailer use. The issue is that there are no truck 15" "LT" tires available from major brands in the USA.

That 15" Michelin tire has enough capacity for any model 25 or 26 and can be used even on the 27/28 models. I carried 44 psi on the 2013 25FB International Serenity Michelins and now in the 2015 23D International Serenity with the same model tire. Here are the actual scale numbers for our 23D

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

There is more safety margin with the 15" Michelins on our 23D than the 15" GYM tires rated 2,540 pounds installed on our 2014 Classic. That is why we immediately installed the 16" SenDel T03-66655T wheels and 16" Michelin LT225/75R16/E LTX M/S2 tires rated 2,680 pounds @ 80 psi. Plus those are the same tires and wheels installed by Airstream on model 25 trailers and larger as an extra expense option.

[rmkrum]

What pressure do you run those tires...80psi or some lesser number? I have a 23FB International.

[switz]

We run 44 psi in the 15" Michelin LTX (P) 235/75R15 XL tires installed on the 23D International Serenity. That is the pressure recommended by Andy Thompson at CanAm in London, Ontario, Canada and the same pressure we used on the 2013 25FB with that same model tire that was about 900 pounds heavier at a loaded weight of 6,900 pounds.

We run 73 psi in the 16" Michelin LT225/75R16/E LTX M/S2 tires installed on our 2014 31' Classic. That is the pressure that worked out based upon the individual wheel weights of the Classic and using the load chart for that tire. To be anal, 72.5 psi would be the intermediate pressure to use...

[Slow roll]

Based on your experience - would you recommend upgrading the Goodyear 15 with top of the line cooper or Michelin 15's or upsizing all together to the 16"LT?

[switz]

The 16" tires and wheels will fit on any 25' or longer Airstream trailer. The stock 15" GYM ST225/75R15D tires rated 2,540 pounds @ 65 psi were 28.3" in diameter on our 2014 31' Classic. When upgraded to the 16" SenDel T0-66655T wheels and Michelin LT225/75R16/E LTX M/S2 tires rated 2,680 pounds @ 80 psi with a diameter of 29.2", the trailer was raised about 0.45".

Our Classic's scale numbers are:

Classic Scale numbers May 2014

……1200……——1200

2034……2042—4076

1921…….2062—3983

Total weight——9259

The lighter left rear reflects the removal of the six gallon water storage in the original water heater which was replaced with a propane only instant on water heater. The tire load table for this tire is:

80psi 2,680 (E)
75psi 2,560
70psi 2,440
65psi 2,335 (D)
60psi 2,190
55psi 2,060
50psi 1,940 (C)
45psi 1,790

We could run 72.5 psi but round up to 73 psi on the 16" Michelins.

[HowieE]

Please denote your axles weights by axle. Not sure how you are running less weight on what looks like the rear TV axle in the last line of weights.

If your trailer is in fact just over 3900 lbs 60 psi would work