Packard Forum Index » Post-War (1946-54)

Quote:

I went with the largest WWW radial tire from Coker I could buy. P235/75R15 BF Goodrich. I guess I could go back to bias ply tires.

I took my numbers from the specs listed for the car. I'll look at the tires next time I'm out there, but the odometer seems very close for miles covered/ miles shown.

Anyway, look at the manufacturer's web site, they'll give you tire dia, rolling distance and revolutions per mile. You'll find that different brands and even different model tires from the same company are different even when the size designation is the same. Quote:

The tires on my car are Firestone FR380 P225/75R15.

According to the Firestone website, they turn 736 times per mile. The owner's manual says that I have 3.23 gears so my engine is turning at 2377rpm at 60 mph. Elsewhere in the servive manuals, I beleive I saw it claim the the engine turns 2250 times per mile. That's a about a 5% difference.

I guess I need to find tires that turn 697 times per mile. The P235 would be better at 721tpm.




firestonetire.com/productdetails/QuickSearch/FR380
Then click 'specs' and then 'show all attributes'

There is something funny with the speed vs speedometer. Have you tried timing yourself between mile markers on the interstate or using a GPS? It sounds like your speedo is way off somehow. This can be corrected in minutes with a speedo gear change.

I put the 225-75-15 made by Cooper for Diamondback (called the fury) on my Clipper - the GPS (which is basically dead-on accurate for speed) tells me that my speedometer reads about 9-10% high. So 72 mph on the speedo is actually about 65 mph.

Is it the gearing and tire sizes that are off? Or does the speedo need to be cleaned and lubed? Has the spring lost some of it's tension?

Question, I would like to buy a GPS. The statement that yours is dead on makes me want to buy the one you have. What make/brand is it and where can I buy one? Thanks

Depending on the type of cell phone you have, you may already have a GPS. Just need to download and install the appropriate app on it.

Kev, I'm pretty much still in the dark ages when it comes to my cell phone. It does nothing except act as a phone. Doesn't even have a camera for pictures. Pretty old Sprint phone.

Kev, I'm an old electronics and computer guy. I am still having trouble calling a computer application an "APP". House power is still 60 cycles not 60 htz. to me. Still can't bring myself to say Hertz. Not even sure if that is the correct spelling.

As an old electronics guy I'm surprised you are not familiar with Hertzian waves. Refers to the 19th century physicist not the car rental agency.