First, sorry it's so long. I'm trying to be thorough.

I'm planning on getting new tires from Costco soon. We full time RV, so our X pulls our travel trailer and carts the 6 of us (4 adults 2 children and 3 dogs) around. We don't typically go off road but most of the campgrounds are gravel or dirt and mud can happen. Also grades are present and some are gravel or dirt.

What I'm looking for by posting this is some general tire advice and advice on options we're looking at.

Stock specs say 45psi front and 55psi rear. What the heck should I be running?!? I've been running 80psi mostly and still get wear indicating I'm too low on pressure (wearing slower on center of tires). If nothing else should I be running a percentage lower on the front when towing or in passenger mode?

One option is to sell our current set after buying wheels on Craigslist and putting new tires on them. It's been easier for me to sell full sets rather than tires or wheels separately. The other option is to just put the new tires on our current set of OEM wheels and try to get what we can out of the used tires.

I'm also interested in what tire sizes I should consider.
Costco told me the largest size they could put on for us is LT285/75-16 those would be huge compared to the 235/85R16 Cooper Discoverer A/T3 that I have on now. Stock is 265/75R16D.

Tire specs:
Current: LT235/85R16 (31.7in tall 9.25in wide)
Stock: LT265/75R16 (31.6in tall 10.43in wide)
Big: LT285/75R16 (32.8in tall 11.22in wide)

Tire model options (Stock Size):
Michelin LTX M/S2 $195.49 each 16/32 tread 60k mile
Michelin LTX A/T2 $195.49 each 13.5/32 tread 70k mile

Details:
2000 Limited Excursion V10 4x4 4.3 dif
Current tread 30% with the outside wearing more
Currently 65psi at 2600ft for commuting and 80psi all around for towing
Regular rotations done
7500 Travel Trailer
12500 Tow Hitch
12500 4-way Sway control

 

Don't know about pressures and stuff as I don't tow...yet! But every Costco I have been to will only install OEM tire size. If you want a different size they will only mount them to the rims and you have to bring them in...I have had the same experience in TX, PA, and CO with different Costco's.

 

Same as Walmart.

 

Just an update for posterity. I've spoken to a couple of Costco's tire departments now and they tell me the will not deviate from stock. The go on to say they can go 2% off from stock. That's why I was told the largest they could put on was LT285-75R16. It's 4/5 of an inch taller. I'm more interested in height than width to get what little I can in fuel economy as we have the 4.3 ratio differential.

Does anyone have 286/85R16 and stock springs? Will I have any fit issues?

 

If they're stock wheels, you'll have no fitment or rubbing issues with the 285s.

Edit- I presume you meant 285/75-16.

 

Also, make sure they're load range E!

 

Lol. Mixed the number up a bit there. I did mean 285/75-16

 

Required tire pressure is a matter of tire size ( volume ) and the weight to be carried.

Here is a tire inflation and load chart. ( this one is on Toyos website but it is an industry standard and does not vary by manufacture )

https://www.toyotires.com/tires-101/...flation-tables

The stock excursion tire is a 265/75/16 so I did a quick cut and past of the chart to show the PSI for different weights.

you mentioned 80 psi so lets use that.

each tire @ 80psi can support 3415 psi or 13,660 pounds, roughly 30% over the GVW rating of the excursion.

the reason the door sticker list 50 and 55 is because with a 265/75/16 tire the tire will support
@ 50 psi 2270 x 2 = 4540
@55 psi 2390x 2 = 4780

total weight 9320 pounds

the excursion GVW is 9200 pounds
https://www.fleet.ford.com/truckbbas...1/excursCD.pdf

So as long as you are not exceeding the GVW of the vehicle 50-55 psi is the correct pressure for a 265/75/16 tire

edit.... if you change TIRE SIZE then use the correct tire pressure from the chart. larger volume tire will require less PSI and a smaller volume tire requires more PSI..... note i said volume not diameter.

 

I ran the Michelin LTX MS2 LT265/75R16 for many years on our 2003 Excursion (took to 183K miles from new) and on the 2005 Excursion up to about 175K miles. Then, I converted to 18" wheels from 2004 King Ranch truck. Still running Michelins

I've towed very heavy (travel trailer) quite a bit--I'd guess over 80K miles since 2003 between the 2 trucks Never an unusual tire wear issue. I typically run 80 psig rear and 75 psig front. I'll occasionally reduce pressure to 70 psig front/rear if not towing for long periods.

Your unusual tire wear is probably due to defective tires or wrong load range. You definitely need load range E.