The Stovebolt Site Forums The Parking Lot Tons 'o Fun Tire size for optimum fuel mileage

I have a 64 C30, that came with 750-16 (duals in rear) I have been told that 215-85-16, is the equivalent size. My question is: Is there any other size that would still fit the duals, that would have a taller profile, thus better mileage?? Someone told me I could get away with 225-85-16, but I think that would just be a tad wider, but no taller.

8R19.5 tires are tall (31-33") and skinny, and should get reasonable mileage in comparison to the other sizes you're considering.
They look good on a 1 ton truck too in my opinion.

Grigg

I've thought about the 19.5 wheels, but man are they pricey! I was hoping to find an older R/V or something that had some rust free wheels, and decent tires, but they are hen's teeth hear in the North-East. If I were to find some, would they bolt right up to my hubs? My current wheels are split-rims, and have the flat lug nuts.........what would it take to mount a set of 19.5s off of lets say a P-30 bread truck, or P-30 R/V chassis?

Try putting a post in the parts wanted forum. Aside from a tour of your local junk yards, that may be the easiest route.

Anyway you slice it, the upgrade to 19.5 wheels wont be cheap, but I think it is the best longterm alternative. What I found when I looked for mine was that while used wheels were available, they would not accept the original style hubcaps for my 51. If I kept looking I may have found the right wheels, but I ended up swallowing hard and bought new custom wheels; they look great and should outlast me. In my evaluation, when I considered the time to find them, cost of replacement hubcaps (I had none), cost of shipping, reconditioning, the new wheels weren't that expensive. I was fortunate that the mfg happend to be located not far from me, so I avoided cost of shipping, so that helped too.

If you want to stick with the 16s, 235/85/16 is about the tallest you'll find that will still work.

Kerry3, you're looking for dual wheels right, and they are available on many P-30 chassis vehicles like you mentioned. No hubcaps so no worries like the Ned had about his single wheels.

I think they can be found cheap if you look and have patience.
The dual 19.5" wheels are not odd or unusual or rare, it's the single ones that are a tad hard to find.
Search craigslist too, you may find someone selling 8R19.5 tires that happen to be on rims you want...
Just start looking, you'll find them.

Grigg

some folks on ebay have been listing some 19.5 dually rims from p30 step vans. they're in ohio i think. i you run into somebody who's into the 4bt cummins they'll usually know where some some p30 wheels are. the p30's are a common source for the 4bt. that's how i got my 19.5 wheels.
there's been some talk about these wheels not looking quite right on the older trucks (like my ad) because they don't have enough handholes. i've come up with a trick to get 4 more of them in the center.
won't require any special tools or machine work. when i get it done i'll take pics & submit it for a tech tip.

Does anyone here have access to a 19.5 wheel, that would be kind enough to measure the flat inside surface (where the brake drum would rest)?? If so, I would be eternally grateful! I have decided to go the 19.5 route, but am concerned that my brake drums might be too big.

Worth checking for sure, but I seriously doubt you have any problems with brakes fitting.

The wheel you're looking for is probably an Accuride part number 29015 (or similar) found on page 28 of this catalog
A 19.5x6" rim with a 5" offset, so center of rim out to the mounting surface is 5". and the ID of a plain 19.5" rim is in the neighborhood of 16.5"

Grigg

Thanks for that info Grigg. I was worried that the rear duals would not clear, as I have heard it is a possiblity. The rear drums on this truck are quite large.....I need to go measure now.......

Kerry3, those p30 wheels clear the drums on my 50 3800 great. the rear end is the same as yours. I think the later drums sit a little farther inboard. these wheels will work great for you

Well, I scored a set of six (like new) 19.5 wheels and tires from a scrap yard that took them off of a GM bread truck before they crushed it. They bolt right up, and the center hub is a precise fit (I think that means they are "hub centric"), but the lug holes are a bigger diameter. Will it be OK to run these as is? (duals in rear) I was thinking of getting lug nuts with the tapered seat vs. the flat seat nuts that the truck had originally. I know the correct way to do this would be to take the hubs off, and install larger studs, but if I keep them nice and tight, is this really neccessary for a truck that will be getting light service driving? Just wondering what you all think......

Nice Job on the wheels and tires!

Correct, they are hub piloted.
Therefore you do not want tapered lug nuts contacting the wheels. Two options, one is flange nuts. Other and the one I'm sure you should use is clamp plates with matching lug nuts.
Here's a picture, actually from a bred truck front axle...
http://rides.webshots.com/photo/2776297030080251109YhSQdn

They could then use tapered seat nuts to match the tapered seat in the clamp plates, but that does not make them stud centered wheels... some of the old clamp plates use flat ended nuts.

Another option along with the clamp plates would be to replace the 1/2" studs you have with 9/16" studs like newer trucks use, probably requires some machine work.

Grigg

Thanks Grigg! If I use the plate (which didn't come with the wheels) won't I need longer studs? Also, does anyone know where I can get the plates and appropriate nuts to do this?

Plates, try the same junk yard, otherwise they are expensive from GM, I asked about them a few years ago....

Longer studs, perhaps, and if so then might was well do the machine work and use 9/16" studs.
NAPA among other auto parts places has the studs and nuts.

Grigg

I wouldn't worry too much about the stud hole diameter. The wheels are cnetered off the hub, and once torqued to the proper spec, the hole size won't make any difference.