The original-series Cub Cadet tire fitment guide (narrow-frame, 1960s–70s)

The short answer: an original narrow-frame Cub Cadet runs an 8-inch rim up front and a 12-inch rim in back — typically 4.80/4.00-8 or 16x6.50-8 fronts and 23x8.50-12 or 23x10.50-12 rears. Confirm the rim diameter first, then match the sidewall; the size in a fifty-year-old manual isn’t always what’s bolted on today.

The original Cub Cadets — the narrow-frame machines International Harvester built from 1961 into the early 1970s — are some of the best-made garden tractors ever put together, which is why so many are still running. They were also built before tire sizing was standardized, and half of them have been re-wheeled at least once. (Machine-specific fitment, like our Cub Cadet 1450 guide, lives on the fitment pages.) Here’s how to get it right.

Start with the rim, not the old size

The one thing that almost never changes on these machines is the wheel diameter. Across the original narrow-frame series — the Original, 70, 100, 122, 123, 124, 125, 126, 127, 128, 129, 147 and their siblings — the layout is remarkably consistent:

So before you worry about tread or width, confirm those two numbers. Read the rim diameter off the wheel, or measure across the bead seat. Once you know you’re on an 8-inch front and a 12-inch rear, you’ve eliminated 90% of the wrong tires — anything with a different rim number simply won’t go on.

The sizes we see most

With the rim confirmed, here are the tire sizes that come across our floor for these machines. Think of these as the common configurations, not a guarantee for your exact serial number:

Fronts (8-inch rim)

• 4.80/4.00-8 — the classic narrow front. A rib tread here keeps the steering light and precise, which is what you want on a front.
• 16x6.50-8 — the wider turf front you’ll see on machines set up with turf wheels front and rear. Same 8-inch rim, more footprint.

Rears (12-inch rim)

• 23x8.50-12 — the common turf rear. Good all-around grass tire, easy on the lawn.
• 23x10.50-12 — a wider turf rear if the machine was set up (or re-wheeled) for more footprint and flotation.
• 6-12 ag (R1 lug) — the tire to run if you actually work the tractor: a plow, a blade, a tiller, or a hill. Chevron lugs for bite, at the cost of tracking on soft lawns. This is the old two-number farm size — the 6 is the width, the 12 is the rim.

If the two-number ag sizing looks strange next to the three-number turf sizes, it’s just a different (older) system — the how-to-read-a-tire-size guide breaks down all three formats you’ll meet on a machine this age.

Turf or ag: pick by what the tractor does

This is the real decision on an original Cub Cadet, and it’s about the job, not the year:

• Mowing and showing — turf rears (23x8.50-12 or 23x10.50-12), like the Kenda K500 Super Turf, which covers both sizes. Grip the grass, don’t tear the lawn, keep the machine looking like a garden tractor.
• Plowing, tilling, pulling, or hills — ag/R1 lugs (6-12). These tractors were built to work, and the original ag lug is what makes the driveline useful. Add wheel weights or fluid if you’re pulling hard.

Don’t forget tubes

The steel wheels on these machines are old, and the bead seats are often pitted or lightly rusted after decades outdoors. On an original Cub Cadet I almost always recommend running an inner tube — it seals against a less-than-perfect rim and saves you the frustration of a tire that slowly leaks down every week. Match the tube to the tire size and the valve to the wheel’s valve hole.

How to order without a mistake

1. Confirm the rim diameter on each wheel — 8 front, 12 rear on the originals.
2. Read the current tire size off the sidewall if it’s legible.
3. Decide turf vs. ag by how you use the tractor.
4. Add tubes if the wheels are old (they usually are).
5. If anything doesn’t line up — an odd rim, a mismatched pair, a widened wheel — call before you buy.

You can browse rears by size on our 23x10.50-12 and shop-by-size pages, and the fronts and lugs live on the tractor tires page.