magnum

Recently, I changed over from the stock 265x75x16 michelins that my 2500 came with. I went with the Dualer REVOs in a 285x75x16. (Love 'em BTW)

Anyway, heres the 64K question. The stock tires were 655 revolutions per mile. The new ones are 631 revolutions per mile.

The difference is approximately 96%....So... if my speedo now states 60mph and I take 60 x 1.04 -- I get 2.4.

Would my true speed be approx 62 1/2 mph? ??? ???

MikeyB

That is correct. A buddy of mine installed the 285/75/16 Bridgestone REVOs on his Superduty and loves them. His speedo is off by that much also.

MikeyB

Dr. Evil

Mikey,

Friends don't let friends drive Fords.... ;D

MikeyB

[quote author=Dr. Evil link=board=10;threadid=23539;start=0#msg221416 date=1071076540]
Mikey,

Friends don't let friends drive Fords.... ;D
[/quote]

Can't help it, he's a diehard Ford fan.

MikeyB

tanderson2002us

I run 315/75 R16s and I think I am about 8 - 10 miles off. Don't know though by any equation......just my girl friend following behind me one day..........

How did you get the revolution numbers? ???

Hey phox....you run 35s........got any data?

CTDinMT

[quote author=Dr. Evil link=board=10;threadid=23539;start=0#msg221416 date=1071076540]
Mikey,

Friends don't let friends drive Fords.... ;D
[/quote]
Every Ford guy needs a friend w/ a CTD. It's cheaper than a tow truck! ;D, I know, I've towed the same Ferd twice :-Steve

magnum

tanderson--

I just go the "tire rack" , enter your model vehicle and year. It will then post the size tires that should have come on your vehicle. CHOOSE "select custom size" then enter the size you would like. It will then pull up the tires that are available.
Above each tire selection will have a bar, the first selection will the "Specs" Punch that one, then scroll down till you find your size. In the far right column will list the revs per mile.

PS 315x75x16 turn 599 revs per mile. Check that # against your stock size then look it up.
If your stock tires were 265's then your revs per mile would be about 655, or 91% of what you're running now. at 60 on your speedo your actual speed would be 65.4 mph

blackjack

I have the same 285"s and my old 265's like you. I went to dml tire and wheel calculator site and found it to be a 3.6% diff. soo 60 x 103.6% = 62.16 etc...

Redleg

No luck using the tire rack.

215' to 235's, I just figure 2-3 mph faster? 13 mpg probably being 14 mpg? 1 mile on the odometer about .8?

Thanks , Don

PHX_ATC

Don

Here's a link that's pretty cool for tire size calcs. I've double checked it with my GPS and it's pretty close.

I know, I know, it's a Miata teeny weeny girly car website, but hey, it works.

http://www.miata.net/garage/tirecalc.html

Xplorer

did just the same thing-285's on 16x8" wheels. went from 245's though. GPS says that I'm doing 65 mph when speedo reads 60mph. Love my revos,worked great in the snow we just got.

cwbronc

yea here is another link I found on this site. http://www.dakota-truck.net/TIRECALC/tirecalc.html

With that being said, I have a 95 12v and was wondering if I get larger tires say...315 : what would I need to do to calibrate the speedo and odo?

tanderson2002us

I saw the TrueSpeed (spelling?) sensors online yesterday and at those prices ($200 - $250) I think I would prefer to rely on my radar deterctor and do the math in my head.........

Going from 245/75 R16s to 315/75 R16s I came up with the following...........

Odometer (mph) 20 30 40 50 60 70
Actual (mph) 24.4 36.6 48.8 61 73.2 85.4

Anybody know of a cheeper alternative??????? ???