Tire size confusion.

[REK1]

I have this 1981 K30 dually and it currently has 235/85R/16 tires one it. When I search that tire size multiple vendors state will not fit my specific vehicle. The rear tires seem to have ample spacing as I have had them off already and no type of spacer between the rims. Anyone with experience on a K30 dually and proper tire setup?
Appreciate any and all info you folks may have. Also any good recommendations on a all terrane 6 tire set?

 

[DoubleDingo]

Most likely came with 9.5-16.5 tires, and someone switched to 16 inch rims and 235/85/16 tires. Nothing wrong except the computers. Keep rocking the tire size on there

 

[Robert Bare]

What DD said. Some came with that large, depends on how the truck was ordered, but the size you have is one of the most common today, I have seen. And, yes, todays online and tire shop size charts are terrible for older vehicles.
Way back my dad had a 74 SRW camper special with 16.5 split rims, what a nightmare.

 

[TotalyHucked]

Just ignore what the websites say (and even the salesman at the counter) about it "not fitting" your vehicle. Even with newer stuff, they're wrong alot of the time. Put whatever tire size you want on there

 

[REK1]

Thanks for the feedback guys.

 

[fast 99]

We had several C and K 30's-year range was 74-85. We did run 235's on a couple trucks but with either low air pressure or high weight sidewalls would rub. This is a totally bad thing in DOT's mind. We never got red flagged [parked], but that was a distinct possibility. State Patrol was a little forgiving on it but yours may not.

Some trucks were original 16.5 and converted to 16 for ease of maintenance. 215 tires sidewalls were plenty far apart. Problem we ran into was broken belts, usually before they were run out. This may not be a problem in your case. We ran near or over max GVW consistently.

 

[Grit dog]

235 85s are bout perfect I think with no lift and no spacers.
255 85s if you want a taller wider tire but idk how much space between the duals will be left without spacers. You’ll lose about 3/4” going 255s.

 

[REK1]

We had several C and K 30's-year range was 74-85. We did run 235's on a couple trucks but with either low air pressure or high weight sidewalls would rub. This is a totally bad thing in DOT's mind. We never got red flagged [parked], but that was a distinct possibility. State Patrol was a little forgiving on it but yours may not.

Some trucks were original 16.5 and converted to 16 for ease of maintenance. 215 tires sidewalls were plenty far apart. Problem we ran into was broken belts, usually before they were run out. This may not be a problem in your case. We ran near or over max GVW consistently.

Yeah, I most likely will never see that kind of weight. (never say never ) right? I just recently got this truck back. My dad sold it back I think in the mid 90's there about. Its exactly how he had it other than an extra 5K on the odometer. two previous owners after my pops never even did a title change. Was still in my dads name up to 2015. Anyhow I will just stay with the same size it is currently sporting. Just a more aggressive tread.

Thanks again Square Bodies...

 

[REK1]

235 85s are bout perfect I think with no lift and no spacers.
255 85s if you want a taller wider tire but idk how much space between the duals will be left without spacers. You’ll lose about 3/4” going 255s.

Taller sounds beterer considering them 4:55 gears. Like you mentioned I don't want to sandwich them rears for sure.

 

[Grit dog]

4.56 is tough duty without OD or huge tires if you want to do more than haul heavy or drive around town.
Even 4.10s and 35s suck above 60 mph with a 3 speed trans.
I’d say 255s are ok if you have a little clearance between the duals. I’d take anything over 1/4” and be fine with it unless hauling heavy frequently or long distance.
JMO.

 

[bucket]

I believe it's @Dooley that runs the 255/85 on his trucks and it looks/works well. Maybe I'm remembering wrong though.