I'm looking for some info and/or experience on tire/rim combinations.

I currently have 16x8 inch aftermarket wheels, and 285/75 tires, but I am looking at replacing the tires with 305/70's with an E load rating (Terra Grapplers). I like the higher rating and the way it sounds the terra grapplers wear pretty good.

I do some pulling, mainly forage boxes and other equipment, and will eventually put in a 5th wheel plate. but will putting essentially a 12" wide tire on an 8" rim decrease the sidewall stability, or cause premature failure?

I have some friends who run up to 12.5" wide tires on 8" rims. however, these are on 1/2 ton trucks that rarely, if ever, pull a load, much less a load the ol' cummins is capable of pulling.

Rocco

 

What's the recommended rim width for the tire you are considering?

Running tires on too narrow rims does several things. By squeezing in the sidewalls, you change the angle of the sidewall to the load, thereby reducing sidewall strength. Also, by squeezing in the sidwalls, you bow out the tread. This will cause the tires to wear in the center of the tread. Several of the major tire companys have great websites with good info on this topic.

 

You will be fine. I just bought some 16x8's with the exact tire you are wanting to buy. I will probly replace with the same tire.

The 305's are made for the narrower rim. I see people running them all the time on the stock rims. Heck, I see people running 315's on stock rims.

 

Because you see 'em doing it doesn't make it right or SAFE! Again, what does the manufacturer say about minimim wheel width for the tire size?

 

According to Nitto's web site a LT305/70 R16 Terra Grappler (weight rating 3525 lbs @ 65 psi) will fit an 8.o - 9.5 inch wide rim, recommended ideal is 9 inch. You will be fine with an 8" wheel.

CLICK HERE to go to their Terra Grappler page, click on the SIZES AND SPECS button in the black area about centered and it will take you to the spec page for the tire.

Dave / Believer45

 

305's is a pretty tall tire for a 5th wheel. Also load range is not everything... a 3042 # @ 80 PSI tire is probably better than a 3525# @ 65 PSI tire.

 

Per Nitto web site, 285/75 R 16 is 32.68" tall, a 305/70 is 33.07" tall - 39/100" taller. 1.2% taller gearing - height seems to be pretty close.

As for pressure, njoverkill, you are right on the money - higher pressure will allow less sidewall flex and make a more stable, although less smooth, ride.

Dave / Believer45

 

The tire isn't supporting the weight, the air pressure is.

The tire is there to keep the air where it belongs, and to provide traction with the road surface.


After these wear out, I'm going back to "E"s, and I don't even tow anything.


phox

 

I went to the Nitto website thru Believer45's link, and read their tire specs. if they say a 305/70 will work on an 8" rim, they must have the testing to back it up.

although i've been warned about the rough ride of a 10 ply tire, i don't think it would be that big of a deal for me. i would like the extra stability though.

now to decide if i want to put in a leveling kit to fit 'em