Correcting the speedo with the right sized tires.

fordhombre · Post by **fordhombre** » Thu Jan 26, 2006 1:39 pm

Okay, me speedometer's a little off, i'm actually going slower that it's saying. I know my tires are a little shorter than they need to be.

I have the original rims, so I was wondering if I put on some 235-75s, would this possibly correct the problem? Or would maybe 225-75s work better?

Also, the motor is a 351w with a C4 transmission, could this also be throwing off the speedometer?

Thanks in advance!

jzjames · Post by **jzjames** » Thu Jan 26, 2006 4:37 pm

Someone replacing the speedmeter cable from original could throw it off, much more than tires I think... That was the situation with my other truck.

SportCustom · Post by **SportCustom** » Thu Jan 26, 2006 4:51 pm

A 225/70-15 would be closest to what your truck had stock.

If it is an f-100 it would have had G78-15 which is roughly 27.68 overall diameter.

235/75 - 15 = 28.9 = Reading is about 4 mph to slow
225/75 - 15 = 28.3 = Reading is about 2.5 mph to slow

I did these calculations assuming that the trans and rear are original to the truck. If these have been changed this could change the reading as well. Also the speedo cable has a gear that interfaces with the trans. If this gear is the wrong one for your setup it will throw the reading off also.

Todd

fordhombre · Post by **fordhombre** » Thu Jan 26, 2006 6:15 pm

Found a pair of new Firestone tires fot $144.54.

WITH whitewalls!

spartman · Post by **spartman** » Thu Jan 26, 2006 6:31 pm

Make sure your life insurance is paid up if you use those firestones.

fordhombre · Post by **fordhombre** » Thu Jan 26, 2006 7:26 pm

I too, was once scared of Firestone, but are they still having problems? I found some others for about 10 bucks more. They're like...Goodyear Sport tires at Wal-Mart, but no white-walls...

Post by **FORDification** » Thu Jan 26, 2006 9:39 pm

You WANT whitewalls? For God's sake WHY??

19674x4 · Post by **19674x4** » Thu Jan 26, 2006 10:52 pm

FORDification wrote: You WANT whitewalls? For God's sake WHY??

amen brother :twisted:

fordhombre · Post by **fordhombre** » Sat Jan 28, 2006 10:53 am

does no one appreciate the magnificant wonder......

that is white walls?

The things of beauty. The glistening object in the sun that takes you back, and reminds you there are beautiful places in the world!

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Correcting the speedo with the right sized tires.

Correcting the speedo with the right sized tires.

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