Will Low Rolling resistance Trailer Tires be worth it?
 

Tow Vehicle: 2010 Prius.
Trailer: 1432 Jon boat w/ 7.5hp Merc 2 stroke (700 pounds maybe)
Tires: It is about 100 bucks for standard 4.8-8 trailer tires from walmart, or I can buy the wheels from amazon for 50, and gets some 165/65/14 re92's from tirerack. Will it make the trailer roll a little better? Currently im getting about 27mpg at 68 mph as indicated on the scan gauge.

Try going 60 mph instead, small trailer tires have a low max speed rating anyway

Most likely, your poor mileage is aerodynamic. Can you do anything to streamline the boat/trailer package? Maybe a PVC tapering frame frame covered in something like thick plastic sheeting?

I would do it not for the fuel economy savings but the savings the bigger tires will get in how many miles they last. I switched my PWC trailer from 8's to 13's because the 8's seemed to wear down to the cords in just a year. The 13's have been on for 4 years now and still look new. I used to think I had an alignment problem but it was just the tiny tires couldn't take it.

I pull a jetski on a trailer with my Prius and can hardly tell the difference in fuel economy. Then again, I keep it at 60 MPH or below. I'd say that fuel economy is to be expected for the size and speed.

Easiest thing to improve fuel economy would be to cover the top when it's in tow.

https://www.coversuperstore.com/medi...ory/291_st.jpg

I'm going to say it probably wouldn't be worth it. I really doubt you would drive the trailer enough to break even, or wear out either set of tires. As herektir said above, trailer tires usually have a low speed rating, something like 80 mph, if that. I wouldn't feel comfortable operating a tire close to the speed rating for longer than an hour. Personally I would stick to 65 mph max speed for towing with medium-large sized trailer tires. Small trailer tires I wouldn't want to go faster than 55 mph. Inflate your tires at the max cold pressure before trips, if stored inside, keep them away from electric motors(fridges) as they emit ozone that can damage the tires. If stored outside, keep them covered so the sun won't damage them as quickly.

Wait until the tires are ready for replacement before you consider something like this. Also consider that trailer tires are specifically built with very stiff sidewalls so they have less sway. If you don't like sway, don't even consider stepping down to a passenger car tire. LT(light truck) tires have stiffer sidewalls, but trailer tires are stiffer still.

Those 14 inch tires are going to be so much taller than the 8 inch wheels that aero will eat up any rolling resistance savings.
But those 8 inch tires are junk, replacing them with something bigger is a good idea.
That's why I used 12 inch steel belted 10 ply tires.
Just using any steel belted radial will give better rolling resistance than a bias ply.

See:
http://ecomodder.com/forum/showthrea...5-a-34939.html

http://ecomodder.com/forum/showthrea...kes-34956.html

I don't know your tire rolling diameters, but by ratio, the 13's should roll
1 and 5/8ths farther per revolution than the 8's, and run cooler. If you consider bearing resistance, the 8's roll the bearings 8/5ths while the 13's roll them 5/5ths. In addition, 8's fall deeper into there relative circumference than 13's causing more difficulty pushing through potholes and sudden grade rises. (Think of roller skates on uneven sidewalk slabs.)

Why are you towing something with a Prius at 70mph anyway....? Isn't that woefully dangerous?