proper tire pressure for 3326

SMCrane1554 · 10-01-2017, 04:23 PM

We own a TM 3326 with new Goodyear Endurance ST215/75R14 tires. Discount Tire inflated them to 60 lbs. Max pressure is 65 lbs. The TM manual says 14" tires should be inflated to 50 lbs. Can anyone clear up my confusion?

Stewart Crane

SMCrane1554 · 10-01-2017, 04:51 PM

Found the tire specs decal on the side of the TM

mecicon · 10-01-2017, 08:10 PM

Quote:

Originally Posted by SMCrane1554

We own a TM 3326 with new Goodyear Endurance ST215/75R14 tires. Discount Tire inflated them to 60 lbs. Max pressure is 65 lbs. The TM manual says 14" tires should be inflated to 50 lbs. Can anyone clear up my confusion?

Stewart Crane

Quote:

Originally Posted by SMCrane1554

Found the tire specs decal on the side of the TM

Use max according to tire sidewall, IMHO.

tentcamper · 10-01-2017, 08:35 PM

I have the same tire. I inflate them to 65. But if I was not driving at times over 65 MPH, I would inflate them to 55 PSI. But I run my tires with extra PSI's

The right answer is read the goodyear tire chart below and calculate what your PSI should be. You should inflate them to the right PSI per the load that you will be carrying on each tire. Don't forget to reduce your tongue weight.

Goodyear a few years ago had a service bulletin stating that if you were going to travel faster then 65 MPH to add 10 PSI to the inflation chart. That is what I have done with my tires because at time to time im over 65
MPH.

BrucePerens · 10-01-2017, 10:26 PM

I guess the 14 inch rim is load-range "D" then. I have the 15 inch one and it's load range "E", and has this big honking "80 PSI" in a circle molded into the sidewall! Discount Tire pumped it up to 70. I pumped it up to 80. I think the side in the sun got to 94 PSI when being pulled on a hot day. I have steel rims and can't find a pressure rating for them.

Padgett · 10-02-2017, 07:32 AM

At 80 psi a tire has no compliance and will rattle everything inside the trailer. 65 has some and is the peak for LR D. At 65 mine have a load rating well over 4,000 lbs.

**Bill** · 10-02-2017, 08:23 AM

Stewart -

The tire pressure stated in the TM manual, as well as the pressure stated on the TM decal, only refer to the tires that were on the TM when it left the factory. If you change the tires, then the pressure recommendations may change. This is true no matter what TM model you have.

As Mecicon said, the pressure that is stated on the tire (molded into the tire sidewall) is the governing number, and should always be trusted. Padgett, as I recall you found some sort of weird dual rating on the TM decal, and never figured out what it meant. But always, always, trust the rating molded into the tire.

Bruce, in my experience, the pressure rating for the steel rims (not the tires) is stamped inside the rim, where you can't see it without removing the tire. Unless I am reading it wrong, your first sentence seems to jump between rim pressure rating and tire pressure rating. The rim rating should always be equal to or higher than the tire rating, of course, but there is no guarantee that the tire jockey made sure this was true. In other words, it is quite possible to put a Load Range E tire (80 psi) onto a rim that is rated for only 65 psi. This can lead to rim failure, of course.

Bill

BrucePerens · 10-02-2017, 01:01 PM

Quote:

Originally Posted by Padgett

At 65 mine have a load rating well over 4,000 lbs.

That's for both tires together, not the one, isn't it Padgett? 4000 pounds isn't a tremendous load margin for a Trailmanor. There are a lot of references that say under-inflation is a major cause of tire failure. This is a concern to me, having spent about $1500 on tires over my last two trips: three tires on the trailer, and 4 on the Grand Cherokee after I got a rock through one of the factory tires at less than 19,000 miles on a paved but seldom-cleaned road, and it's 4-wheel-drive. The Grand Cherokee now has nice Continental on/off road tires.

I also am curious about how much tire vibration is transmitted through the rubber axle.

We should be scientific about this and put an acelerometer in the Trailmanor, rather than rely on received wisdom. There's a tutorial on setting up an Arduino with one here.

tentcamper · 10-02-2017, 02:40 PM

I don't know about inside the trailer. But empirical knowledge tells me there is a difference. I do know with my Van, when I increasing the tire PSI from 36 to 40 there is a noticeable difference in the harshness of the ride. To quote my DW the first time we took a trip with the tire PSI up by 4 PSI. "What did you do to the van, it rides like a truck?" I would think 15 or 20 PSI higher it would be much more hash.

That is why I follow the engineering spec's by the GY engineers with the endurance ST tire load to PSI chart. See my above post. But I do add 10 PSI for speed. Bring them up to 65 PSI for the load range E 225x75x15 endurance's. My tire shop agreed with my use of the GY chart and my calculations using the chart, which they had GY chart at their shop.

But I would error on the high side when using the chart. Never wore out a set of trailer tires, so a little more wear in the center is no big deal.

Padgett · 10-03-2017, 12:38 PM

My tires are 2150 lbs each which is a lot better than the 1870 rating for the stock tires. Keep in mind that the GVWR for mine is 4217 lbs less 430 lbs tongue or about 3800 on the tires except I never am near the 700 lbs "cargo" and usually tow with dry water tanks (- 200 lbs).

Originally t came with 215x75/14s and someone must have realized the rating did not match the load hence the extra sticker.