19.5" tires _ Metric or Inch?

IMHO you will be very happy with the 24570R19.5 to replace those 8R19.5.
They are slightly wider, offer a larger footprint, and a since the sidewalls
are a little shorter they are a little more stable.
Double-check the size difference, but in most applications they work very well.
The 8R19.5 has been a discontinued size by most major manufacturers for years.

In the tire industry 40 years; seen it all and done most of it.

I switched to the metric ( Hankooks ) stay with the 8R's. It will keep the rpm's down which is lower engine noise. I did not notice any handling changes. Also my mileage dropped slightly. The tires weight about 20-30 lbs heavier than the 8r's. I would go back if I could.

wny_pat wrote:

427435 wrote:
You might check the dimensions of a 245/70-19.5 tire. It should be a little larger diameter, but the spacing at the duals might get tight.

And make sure that size will properly fit your wheel width!!! Usually guys when moving up from 19.5 tires end up putting them on the steer axle only, because they help the handling. But when put on the rear duals, they kiss sidewalls!

245's might....but 225-70's dont on a P30 setup

427435 wrote:
You might check the dimensions of a 245/70-19.5 tire. It should be a little larger diameter, but the spacing at the duals might get tight.

And make sure that size will properly fit your wheel width!!! Usually guys when moving up from 19.5 tires end up putting them on the steer axle only, because they help the handling. But when put on the rear duals, they kiss sidewalls!

You might check the dimensions of a 245/70-19.5 tire. It should be a little larger diameter, but the spacing at the duals might get tight.

225 does not have larger diameter

So we do not rehash things a simple search would have turned up this thread from the last two weeks there are more previous but if needed the OP can search for them
Click on
8r19.5 to metric

The 8r19.5 are for sale on EBAY
Samsomn asking $198.00 DELIVERED but make him an offer if you are getting multiples. I have bought 3 and they are good after about 1000 miles paid about $180.00 ea IIRC

elno wrote:
Tires sized 8R19.5 have a diameter of 33.1 inches, and 225/70 R19.5 tires are 32 inches in diameter. 8R19.5 tires will rotate 628 times in a mile, and 225/70R19.5 tires rotate 644 times.

Sorry, makes no sense.

If the 225/70 has a larger diameter, it will NOT have fewer revolutions per mile.

In reality, the 8R is larger diameter/fewer revolutions per mile.

Here's a bit from "E How"----


eHow
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The Effects of Changing From 8R19.5 to 225/70 19.5 Tires

The Effects of Changing From 8R19.5 to 225/70 19.5 Tires
By Tim Plaehn, eHow Contributor

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The 19.5-inch wheel size is used on medium-duty trucks and motor homes. The 8R19.5 tire size is a tall profile tire that would probably be mounted on an older vehicle. The 225/70 R19.5 is a modern, low-profile tire for the 19.5 inch truck rim. Changing to the newer size from 8R19.5 tires would make finding new tires a much simpler process. The Goodyear RV tire website notes this is a popular conversion for the owners of older motor homes. Have a question? Get an answer from a Mechanic now!
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Wheels

To convert from 8R19.5 to 225/70 R19.5 tires may require the purchase of new wheels. The 8R19.5 size can fit on a 5.25-inch-wide wheels, and the low-profile 19.5 tires require 6-inch-wide wheels. Besides a better fit of tire to rim, the wider wheels will provide enough dual-wheel spacing for 225/70 R19.5 tires. Dual-mounted tires should never touch, and the 5.25-inch rim is too narrow to give proper dual-wheel spacing for the newer tire.
Tire Diameter

Tires sized 8R19.5 have a diameter of 33.1 inches, and 225/70 R19.5 tires are 32 inches in diameter. Changing tire sizes will result in a speedometer that indicates faster than the vehicle is actually moving. 8R19.5 tires will rotate 628 times in a mile, and 225/70R19.5 tires rotate 644 times. The result is a 2.5 percent speedometer error with the new tires. The Goodyear website states that no gearing change is required for this amount of error.
Load Capacity

Both the 8R19.5 and 225/70 R19.5 tires have load range F capacity ratings. This makes the capacity for the two tires sizes similar but not exact. The low-profile 225/70 R19.5 tire has a load capacity of 40 to 140 lbs. higher depending on the vehicle location of the tire. A set of six 225/70 R19.5 tires mounted on a truck, replacing 8.R19.5 tires, would increase the tire set load capacity by 440 lbs.


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