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Tires For Your CJ-3B


The choice of tires for a rebuilt Jeep is something that is often put off because of the difficulty in shopping around to see what's available, or because of the confusion of different tire styles and numbering systems. I hope this page will be some help, by providing comments and recommendations from a number of readers of CJ3B.info.

(Note: see the bottom of the page for a description of how to interpret and convert different measurements of tire size.)

Doug WilsonCJ-3B Universal Jeeps came with either 15-inch or 16-inch diameter wheels, but in the 1950s both wheel sizes came with narrow "non-directional tread" military-style tires mounted. These days, there are a lot more choices in tires, and a lot of different uses that people put their Jeeps to. The production of large, aggressive off-road tires has become a significant part of the tire industry, catering to drivers who spend a lot of recreational time on challenging trails. For a roundup of currently available off-road rubber, see "Tire Truth" in the March 2001 issue of Jp magazine. And further down on this page, see a discussion of factors to consider in putting large tires on a flatfender. It's an option, but may require mechanical modifications.

The tires on Doug Wilson's 1954 CJ-3B (in the photo) are 9.50x34x15 Super Swamper TSL's, driven by the original Hurricane engine through a beefed-up drive train, and cleared by a 3-inch lift. They've carried him through countless obstacles at off-road events including 20 Jeep Jamborees.
 

NDT Tires

WadeLawrence Wade's use of his 1955 CJ-3B (right) has always been a bit more on the relaxed side. "I was 20 years old and in the Air Force when the Jeep was purchased. While on leave, most of my time was spent riding around in the Jeep dating a little girl who was later to become my wife, and we did a small amount of trail riding, like going to the woods to gather Christmas Trees." These days they like to go to vintage car shows, so the perfect tires for this Jeep are still the original 7.00x15 non-directional treads.

Lawrence is looking for some new ones, and said on the Bulletin Board, "I'm interested in a supplier for the 15-inch NDT military tires. Coker Tire listed the 15-inch until recently, but they are no longer in stock. I waited too long, and I don't think my 46-year-old NDT military tires will last forever."

Bert replied (and others on the Bulletin Board agreed): "The best place to buy the non-directional tires in 15 and 16-inch sizes is Wallace Wade Specialty Tires in Dallas, Texas."

Chuck commented: "I live 50 miles from DC and have found there to practically be a glut of these tires on the market. Wallace Wade and Coker Tire sell NDT's in the 6.00X16 version (listed on the Coker website for $61.00) and 7.00X16 (for M38A1s). But also, don't rule out your local tractor or farm implement suppliers."

Uday Bhan Singh finds a similar situation in India: "Here in India 6.00-16 NDMS are produced, sold and used in large numbers. Tyre makers like MRF and many others still manufacture them in 8-ply rating. Regarding the quality of these tyres, they are tough, and very long lasting." If carburetors from India and steel body tubs from the Philippines can be successfully imported into North America, why not non-directional tires?

The NDT tires have taken a lot of Jeeps over a lot of rough ground in the past sixty years (see a recent photo of Rob Wallace's 1958 CJ-3B in Australia for example), but Ed Wilson raises a big limitation to NDT tires: "I would dearly love to run NDT's. They look the best to me on a classic flatfender. However, in my Blue Ridge Mountains, they are near worthless off-road, and downright dangerous on wet or slick pavement. Compared to what is available on the tire market today, the NDT doesn't measure up in performance."

Ernie has this suggestion: "For you guys with the ND military tires that want better wet and snow traction, take them to a large tire shop and get them siped. They make dozens of cuts in the tread from side to side, it's like having lots of little fingers gripping the ground, then you will have both the look and better traction. It works well on radials and I assume it would work with bias tires too."
 

Other Narrow-Track Tires

RedmondI'm not actually sure what style of tires originally came on my 1959 CJ-3B, since Kaiser-Willys moved away from the NDT tires. Anyway the cost of ordering tires from a specialty supplier led me to look for what was available locally. These 6.50-16 LT (light truck) 4-ply snow tires (left) were made in Canada and seemed to be something close to the original size, but which would be effective in the woods and the snow. I don't think these particular tires are still available, but there are other narrow-track 15 and 16-inch tires with a more modern-style tread. Some suggestions from the Bulletin Board:

Drac: "I have tried all types of tires on 4WD vehicles and have found the narrow, grip type tire to perform the best in mud and snow. Trouble is trying to find some. Cooper Tire still makes a 7:00-15 bias ply tire as well as a 7:50-16 but I think that is too big for my Jeep. A big consideration is the width of rim the tire will fit on. Most tires won't fit on the narrow 4.5" rims. As far as the NDT type tires go, and not speaking from personal experience, this type of tires is supposed to be just horrible in the snow."

Chuck: "I agree with the comments about the limitations of NDT's, but there is also a NDCC ('non-directional cross-country') in the same sizes which actually provides wet weather traction and stability. The military NDCC tires were used on M38A1s and some MUTTs. They are almost duplicates of the regular NDT's except for the fact that the tread bars are angled back thus allowing for superior traction over the NDT's. If you're eager for the NDT look but not fond of highway skating, these are the tires for you!

"Firestone, as of July 2000, were making 6.00X16 "Town and Country" LT bias ply tires. Don't let the name fool you, as I've driven right by a CJ-5 with 33" Super Swampers, in 18" of snow. There are also other manufacturers out there so I wouldn't limit my search to just the big three. A local tire shop which specializes in tractor and earth moving machinery tires is my personal favorite as they understand that bigger is not better in certain conditions."

In 2005, Henry Dorati in Hawaii asked on the Bulletin Board about modifications to his 3B because he was getting stuck on muddy trails. Several people suggested he replace his old tires before even thinking about engine swaps, and he replied, "Alright, I went out and bought some Goodyear 245/75/16 MTR sidewall mud tires; kinda look like Swampers. I took it to the beach down the street where there's some sand dunes I couldn't go up before. I made it up in 4-high -- probably could have done it in 2 wheel drive!"

Chuck added: "Good option on the tires Henry. I like the old bias ply myself, 6.50 X 16 in a mud/snow tread. Dinah, my '56, still sports the Town & Country's from 1956 but I will have to get some new ones from Miller Tire.

"My M38A1 has 7.50 X 16 Denman knobbies and has pulled out alot of the resort folks in their Hummers during snow season and has yet to be outdone on any hill (my wording for mountains). I have yet to attempt a trail I was not able to traverse in any of my old Jeeps (will leave the Wrangler out of this one). As any decent mechanic can tell you, brute HP isn't going to get you anywhere if it isn't transfered to the wheels, just as torque will get you nothing but a conversation if it isn't transfered the same way. You can sink a ton of bucks into lockers, spring-overs, headers, etc. but it seems your main mission is to get up the hill. This will dictate that traction be your main concern. A nice skinny tire with aggressive tread would be the prime mover in this. If later you find you need more HP or torque, then address those issues as you go. The 134 coupled with the T-90 has always seemed the ultimate setup for me when traversing 60 degree angles and 2+ feet of snow and I've never had use of a winch!"

Jim Marski: "Check out Goodyear's 215/85R16 AT/S tires. They are a modern radial with a high narrow look and excellent traction. I run them on my 1953 CJ-3B (60K JPEG) and one of my 3A's."

For European owners, here's a suggestion from Erik v/d Peppell in the Netherlands: "The tyres used on my 1954 CJ-3B (70K JPEG) are a Norwegian brand called Stormil. The type is D100M, size 6.50R16C radial. It's a kind of M&S tyre that can be used on the road as well as off-road. I have used these tyres for almost 3 years and I must say that I'm satisfied by their performance. Also they were not as expensive as getting tyres from the USA (not to mention the time it takes)."
 

Wider Tires

CharnokBy 1963, the Universal Jeep was being supplied with a newer-style, wider tire. Adam Charnok's photo of a 1963 CJ-3B (right) shows the original Goodyear Suburbanite size 7.60x15 "Super Cushion" tires which were still installed when he sold the Jeep in 2002.

The 3B in a post-1961 factory photo (below) shows a similar but not identical tread.
 

FactoryDrac: "I have found a tire dealer in Winnipeg, Canada that has a supply of newer used military radial tires that might be OK. They are available in 6:50-16 or 7:50-16 and are very aggressive. They will fit the narrow rim as well. The dealer's name is Kroy Tire, and they are selling them for CDN$45.00 each."

Evan Palmer recently found some current radial tires which look about right on his 16-inch rims: "I didn't know much about the designation of tire sizes, and so when I went to put on the 7.50x16s they were way too tall. I guess a 6.50x16 is more like it. Anyway, there were none of those to be found that weren't the military tread (NDT), and I wanted something better for the highway/offroad. I almost bought those wagon wheel 15-inch white rims, but I ran into some tires at Pepboys that worked out great. I was able to keep my original rims and put on some 245/75R16 tires with a nice offroad tread (50K JPEG). The ride is a lot smoother and they did great on a 4x4 test run."
 

How to Choose

Ed Wilson

Ed Wilson: "Over the years I've run NDT's, directional 6-ply truck tires, M+S radials, recaps, 15 and 16-inch rims, etc. And I am in the process of looking for a new set right now. It makes little difference what tweaks and upgrades you've made to your vehicle if you don't have tires that translate ALL your driving inputs into the best possible traction.

"I would think the best way to choose tires is determining the type of surface and use they will see the most. If I had a Sunday afternoon cruiser, I'd run the NDT's just for looks. Or if I depended on the Jeep for some transportation in foul weather, I'd go with a Mud & Snow radial. My beat-up work Jeep that spends half its time off road and pulling a trailer probably could benefit some from a heavier lug type of tire. Pulling a trailer off road really highlights tire performance! Of course we all know the small sacrifice in top speed and ground clearance running 15" wheels. And the wider the tire, the more the tendency to 'float'. A narrow tire concentrates the weight and usually gives a better bite.

"For all-round use, the 16" Dunlop LT 215/85 16R radials I am currently running have been great. They ride much better than the heavier truck tires, quieter on pavement, and have performed well in snow and off-road situations. I don't have a source for them right now, but I believe similar tires are marketed under several different brand names."
 

Bigger Rims and Tires

MishWilliam Mish's highly-modified 1955 CJ-3B (left) rides on 33x12.50x16.5 BF Goodrich mud tires mounted on aluminum rims. But to transfer the power of his V-8 to those big tires reliably, every part of his drive train, with the exception of the Spicer 18 transfer case, has been replaced with heavier-duty units.

Marco Acosta asked on the Bulletin Board: "I have a 1953 CJ-3B, 100% restored to stock specifications. I have Khuomo Adventure MT Tires (235/75R15), also I have a set of larger BF Goodrich All Terrain Tires (10.5x31x15). I have two questions: 1. What is the best rim size for the BFG Tires? 2. Normally I drive my CJ3B on muddy roads; altitude on the trails is around 11,000 ft. (yes, they are high mountains). Switching my tires from the small Khuomo to the big BFG tires, will I lose a lot of power? And is this option bad for the stock suspension and steering?"

Chuck replied: "From my experience, the best width rim would be 8 inches. Anything wider exposes the side walls to abrasion. You're moving up in tire diameter by more than 2 inches, so yes, you will lose some power.

John Hubbard: " I understand the need for a wider tire for mud, and this factor may have led you to these choices. My only comment is regarding your desire to keep the Jeep 100% stock when you are changing the look of the Jeep so much with the tire choice.

"A stock suspension with 31" tires is cutting it pretty close -- you will get some body rub and I would think some rubbing on the front springs while turning. And taller, wider tires will be a good workout for a manual steering setup, both on the driver and on the Ross gearbox and all the associated pivot points. The knuckles on the Dana 25 will be put to the test. A steering stabilizer would be a requirement for the wide BFG tires I would think.

"So a mild lift -- maybe just in the form of a helper spring (extra 1" lift) or slightly raised shackles, and maybe a steering upgrade, would seem to me to follow along the same lines as the tire changes you are contemplating. You are making changes to the tire size (definitely non-OEM size) for a certain function, and you need to upgrade other systems to make this change safe and useful.

"Power-wise, I would think if you have 5.38 gears and a fresh F-head, the low-end power would not be much of an issue."

And that brings us back to Doug Wilson (at the top of this page).

Thanks to all the contributors. More tire suggestions are welcome. -- Derek Redmond
 

Tire Size Information

Dimensions

Calculating the Dimensions of a Tire

Example: 185/60R14 radial tire.

The first number is the width of the tire in millimeters, measured from sidewall to sidewall. To convert to inches, divide by 25.4. In the example above, the width is 185mm or 7.28".The second number is the aspect ratio. This is the ratio of sidewall height to width, so a lower number indicates a lower-profile tire. Multiply the width by the aspect ratio to find the height of one sidewall. In the example above, 185x.60=111mm or 7.28"x.60=4.36". The final number (14) is the diameter of the wheel in inches.

To calculate the outside diameter of a tire, take the sidewall height and multiply by 2 (remember that the diameter includes 2 sidewalls) and add the diameter of the rim to get your answer. To calculate the diameter of the example radial: 185mm x .60=111mm x 2=222mm + 355.6mm(or 14") = 577.6mm or 22.74"

The Powerdog Industries Tire Size Information calculator gives the dimensions for any metric size, such as the following:

SpecificationSidewallRadiusDiameterCircumferenceRevolutionsDifference
165/80-155.2 in12.7 in25.4 in79.8 in794 / mile0.0%
185/70-155.1 in12.6 in25.2 in79.2 in800 / mile-0.8%
195/65-155.0 in12.5 in25.0 in78.5 in807 / mile-1.6%
205/60-154.8 in12.3 in24.7 in77.6 in817 / mile-2.8%

Converting Numeric Tire Sizes to Metric Sizes

While today's P-metric passenger tire sizes have existed since the early 1980's, the restoring of vintage vehicles has kept yesterday's Numeric and Alpha Numeric tires from disappearing.

Numeric tire sizes such as 6.00x15 were used between 1949 and the 1970's. The first number represents the width in inches, but the exact height cannot be determined from the tire number (unless the total diameter is included as a third number on newer off-road tires, as in 10.5x31x15). Aspect ratio varied from 1.00 to about .80, so numeric tires should typically be replaced with today's 80- or 85-series tires. This is especially important if the original wheels are to be used. Lower profile sizes will usually result in too wide a tire with too much gap between the wheelwell opening and the top of the tire.

Note: Alpha Numeric tire sizes were introduced on original equipment in the late 60's and became widely used in the early 70's. These tires were identified with a letter which indicated the tire's load capacity, followed by a "R" if radial ply construction, the tire's aspect ratio and wheel diameter. So while G78-15 (28.01"), G70-15 (27.5") and G60-15 (26.4") tires are all rated to carry the same load, their different aspect ratios resulted in the different diameters listed.

The Tire Rack Tire Size Conversion Chart can identify the closest current size equivalents for numeric sizes, such as: 6.00-15 = P165/80R15.


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Last updated 11 December 2005 by Derek Redmond redmond@cj3b.info
http://cj3b.info/Tech/Tires.html
All content not credited and previously copyright, is copyright Derek Redmond