Hey all, I just picked up an 83 F-350 Dually with the 6.9 and T19 earlier in the week. Im really happy with the truck so far; but I need to replace at least 4 tires. I've been searching CL for some decent used tires until I can afford a full new set in a few paychecks.

Every tire website I have seen online says that 215/85/16 were stock, is this right? The truck currently has mismatched 235/85/16 all the way around. I would like to stick with the taller tires; 31.7" for the 235s vs 30.3" for the 215s.

Anyways I guess my question is what is the widest tire I can safely run on the back without needing spacers? If i can go any wider than 235 it would make finding a set of used tires a bit easier since I will have more options to browse from.

 

Stick with stock tire size.

My father had a C30 Silverado Cheyenne from 1986 with a 454 and dual rear wheels. Everywhere you look for used tires around here, they were almost always worn down to the threads.

The reason being, dually tires are sized so that when under a load, the sidewalls won't bulge out so much that they rub and cause the tire to fly all to crap on you.

The other reason why you need dually specific tires is the load rating. If you get a light truck tire instead of the heavier rated dually tires that you SHOULD put on the truck, the sidewalls will tend to bulge more when put under the same load.

This means, that when you get new tires, you have to get dually specific tires (which they only make in certain sizes, mind you), and none of the tire places around here would stock dually tires! They had to order the tires, or you order them to your house and bring them in for mounting and balancing.

Look on the drivers side of the door jamb for the Certification label on your truck. It should list stock tire size there.

Stick with the stock size, and make sure they're a dually rated tire!

Wouldn't want a tire to come out from under the truck when you're going 55 + mph down the road.

If you want to run different tires, look into wheel spacers for your truck.

 

We run the 235/85's on the 92, the sidewalls touch, but not enough to cause wear. If they would, they certainly would on that truck. The load rating is the most important factor, load E all the way. 215 is the proper size for the duallies though. Width wise, the 235 works, but with the taller sidewall, will touch. 245/75 works out ok too, maybe about the same amount of sidewall rub as the 235/85.If you try anything wider than that, you will have major rub, and potential for rocks to wedge in and cut through. The conditions the 92 is run in will test any tire, proper size or not. The way my sister runs that poor thing, all the weak links show themselves pretty fast. We have switched off the the 245/75 due to being more common. It has gotten harder to get 235/85 tires these days. Just not as common as they once were.

 

Yes I know all about load indexes, definitely staying with load range E.
I don't want to go down to 215/85s as they are too short imo. Its nice to be able to drive a reasonable speed on the highway; and my in town speed limits are 40mph, and 45 in some areas. With the 235s its almost perfect for cruising around town at 40; though even taller tires would be even better. (Maybe I'll look into bigger rims in the future as well).

I have about two-three finger width space between my rear tires with no load and about 60 psi in the tires. I was mainly wondering how wide I could go, because sometimes I find a good set of 265/75s(nearly the same OD as 235/85) for dirt cheap. Mind you this would also be temporary until I can afford a good set of 6 new tires.

I'll need to pull a wheel off one night and see if it already has spacers, from what I've read it seems like I have more room than most between the rear wheels.

Thanks, gents.

 

Don't look at the top of the tires, pay attention to the bottom, that is the location of concern. I guarantee there is no finger room there. I do not recommend 265 tires at all.

 

Round ones with tread is my recommendation.

Top of the tires looks the same as the bottom. The space in between is what is impotent.

 

Kind of my point... the space between the tires at the bottom will not be exactly the same as the space at the top between the tires. Even 215's will squat just a little.

 

Interesting - my 86 came with 235's on it and they do not touch, an easy 1/2" at the bottom, granted no real big loads yet but near rated pressure they don't seem to deform much. Maybe there's a difference in the offset on the 80-86 wheels.

Cheers,
- Jeff

 

I do recall there are a different offset rim for the duallies now that you mention it, not sure if it is by year, but there is a variance.

 

I know mine came with 215/85 R16s. I had to get another rim right after I got it in 94, I ad a spare tire, but no rim. Local junkyard had a set of rims someone had replaced with aluminum rims. Go do a Google search on the rims, at one time all three manufacturers took the same rims on the 8 lug pattern. We actually put two of mine on a P30 chassis Winnebago to see how much difference the P-metric tires were from the original 7.00 X 16 tires. I have never had a problem with loads, even the proverbial "ton of bricks". Twice I have loaded it to the top of the bed with bricks, neatly stacked, and actually had the assist springs solidly on the pads with the truck noticeably down in the back.

The first time was on our scout camp and not over 15mph, the second time was a run at highway speeds for probably 35-40 miles including a metal grating draw span. Only noticeable difference, the truck rode great!

 

Have to watch the hole center on the Chevy rims, even the dually rims have the narrower center hole. Dodge was not an issue. The other thing to watch for is the lineup hole pin. They put that on the rims to keep the valve stem clocked such that you can get at the inner valve stem. Not sure if the older rims had that or not.

 

That's the first time I have heard that explanation for the pin. I have asked that before, and no one really seems to know.

I noticed the wheels I mounted that had the pin, were on a 89 f350 cab/chassis, and the lug nuts it used had a large flat washer made to them. I am familiar with lug nuts that have the taper that seats into the wheel, so I thought the pin was there to keep the wheel from working back and forth under the lugs, since the washer type lug didn't fit down into the wheel.

But that was the only thing I could come up with at the time, your explanation seems more plausible.

 

215s were the stock size on a 2wd
235s were the stock size on a 4wd

The rims have a different offset between a 2wd and 4wd giving you that much more room w a 4wd.

2wd truck have 5.00" offset
2wd vans have a 5.15" offset
4wd trucks have a 5.35" offset

Now with that said, I have seen LOTS of people run 235s on a 2wd truck with no issues. If it really does bother you get a 0.7" spacer to run between the 2 back wheels