The Stovebolt Site Forums The Parking Lot Big Bolts 7.5-20 tire size

I think the rims are 20”. Maybe 7-7.5 wide rim. I can’t convert the size to current tire sizing. Do I need to measure the tire height and side wall height? 10 ply load range e. Are they still available?

A lot of tire sellers have handy charts on their sites or in catalogs showing tire sizes and/or rim sizes and what will fit.

The antique tire suppliers like Coker Tire and Diamonback Tires ( www.dbtires.com ) can convert the bias ply sizes to their modern equivalents.

If the tires are still on your rims, write down the size and look them up or call Coker or Diamondback.

Tell us what year and model truck you're putting these tires on, it helps us help you better.

7.50 x 20 tires should be on a 6" wide rim.

Also, are you looking for steering or traction tires?

Mike B

Looking at Ppacker's previous posts it looks like these tires are for his 1948 6100 Tow Truck posted about here in the GTT previously. To provide a better place for on-topic answers to this "Big Bolt" tire question, I have moved Ppacker's threads to the Big Bolts forum for further discussion and help. Best of luck with finding the tires you are searching for!

The 7.50 20s I have on the steering axle on my 46 2 ton rub a little, but I wish I would have went with 8.25s on the rear to get a little more road speed. I'm more interested in that tow unit, that's a cool design, is it a Weaver? Is it fuctional, hopefully you can find parts for it if needed.

1948 Chevy 6100 2 ton tow truck. Determined motor was replaced with 1960 261 block and heads. Have video of motor running when I bought it a few years ago. Rochester 1bbl carb. Trans is 4 speed , sm420 with a chain driven pto installed for a power winch. Might be like m18 winch ? Original hand crank and cable still on truck. Has 2 speed rear. Currently identifying and buying parts. Bought small needed stuff for the restoration. Still working on brakes and suspension. Should be 14” front and 15” rear brakes. Hoping drums are good. Found a post with a number for brake shoe relining. Haven’t called yet. Haven’t found out generator number 9U 02737 5F7 on a remanufactured tag. 12 or 6v?
I work full time and flip houses and rentals on the side so sometimes I’m not able to get back here for awhile. Hoping to start this in a year after I finished renovating 2 houses.

Here are picture of the tires. Two closeups are the front and tge far one is the rear.

7.5-20 is what is on the truck and specs from a manual say same tire. Didn’t know size can help speed. Would be nice to go faster than 50. Since I have 6:11,8:13 rear gears. I’m guess at the rim width. Not sure where to measure from so it could be anywhere from 6 to 7.5. Looks like 20” rim. Tires look the same on front and back. There is some sort of adapter on the front that goes from 6 lug to 5 lug.

Bought it because of the tow rig. Paid 4500$. Was licensed to tow in 1978 in North Dakota. Found insurance and registration. I have not had a chance to crank it by hand. Found a cast iron pulley and bushing to fix the broken one. Little bit of welding and it will be good as new. 🤞 found a whole tow sling that has all the parts.

I think it is a Manley.

That's not an adaptor on the front hub, all the chevy 2 tons of your era are built like this. I'm sure your rims would hold a 8.25 or a 7.50 tire. Make sure the rims aren't widow maker rims! Also known as Firestone RH5's. The lock ring has to be visible on the outside of the rims for them to be safe and useable. The rims that have the lock ring in the center of the rims are very dangerous and should not be used!!

It's hard to tell in your very first picture if I'm looking at gloss black paint or rust holes in the lock ring. If it's rust DO NOT air that tire up if it's flat as you run the risk of having a failure where the ring blows off taking arms and heads as it goes.

Be safe around the multi piece rims and get professional help so no one gets hurt.

Mike B

You will find that 7.50/20’s are very expensive however I found these which were way less $$. I haven’t received them yet but I’m hoping they will be satisfactory. NUTECH N1002 HIGHWAY 750-20 tires. Gallagher tire out of PA has them

I just bought new tires for my 3100 and I was in awe at what they cost but those Nutech,

Okay. I didn’t plan on adding air but definitely not now. They probably are split rims.

ALL 20" rims are multi piece rims with lots of different names like lock ring, split ring, split rim etc. Yours are not split rims (Firestone RH-5 "widow makers") which come apart in the middle of the rim, they are either split ring or lock ring which come apart at the tire bead...they can be 2 or 3 piece and are still serviceable if in good condition.

Mike B

I took a closer look at the rims. They are not looking real good. The picture in the post is mostly paint and will need sand blasted to see whether they are usable. So right now I’m looking into new rims. I found post that recommends 8.25x22.5 and 9R22.5 tire. Contacting accuride to see their options. I know I have 4.75 center bore and most likely need to have spacer machined to fit the hub. I believe I have 10 lug rear dually and 5 lug front. Don’t know front bore yet.

Your front and rear rims are all the same (10 lug with 4.75" center hole), the front only uses half as many lugs, the rest are just empty holes.

Yes, you'll need to add bushings to modern rims to bring them down to your 4.75" center. Finding a narrow rim for the 8.25x22.5 tires will be the challenge.

Mike B

Tubeless 22.5 rims started in late ‘50’s with advent of tubeless tires. They are rare now, look around, you might be lucky to find some, 5” rim width, fit 9 x 22.5 tires just fine, otherwise use 19.5” rims and tires with hub spacer for modern tires.

Ed

Your rear brakes are 16 X 3 if your rig has its original parts.

Mike