245 75 16 SAME AS 255 70 16 ????????

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Fast question......my tire dealer only has the 255 70 16 size tire that I need in the 245 75 16 size.....am I safe to go with the 255 70 16???????
BOB
 
Obviously, they aren't the same.

The question should be, is there enough of a difference in the two, to matter.

Are you just replacing one tire, two tires, or all four tires with the different size?
 
It's very close. Speedometer will be off by about 1mph, overall vehicle height will be 0.2 inches lower, and you'll be doing 10 more revolutions per mile.

I'd do it.
 
Originally Posted By: JRed
It's very close. Speedometer will be off by about 1mph, overall vehicle height will be 0.2 inches lower, and you'll be doing 10 more revolutions per mile.

I'd do it.


Actually, the speedometer will be off by .882 mph, overall height will be .207 inches lower, and you'll be doing 9.105 more revolutions per mile.
 
Originally Posted By: Bamboooo
Actually, the speedometer will be off by .882 mph, overall height will be .207 inches lower, and you'll be doing 9.105 more revolutions per mile.


I'm going to go out on a limb here and say that you're not familiar with the term 'significant digits'.
lol.gif
 
Originally Posted By: N3OO
Fast question......my tire dealer only has the 255 70 16 size tire that I need in the 245 75 16 size.....am I safe to go with the 255 70 16???????
BOB

Depends on the width of your rims and whether you're replacing just one tire or two/four.
 
The same? No. Will they work? Maybe. If you are going from a P-series tire to a P-series tire, the load ratings should be the same. If you are going from an LT tire to a P-series tire, I'd be careful.

The above posts all make mention the speedo will be of by 1mph or so. At what speed? A better comparison is by percentages and then stating the mph difference at a stated speed. In this case, about 1.3% off, or about 1 mph off at 75 mph.
 
Let me restate what MNgopher said:

If the tires are both P type tires, then those 2 sizes are interchangeable.

If the 245 is an LT, then - NO!!!!! - the tires are not interchanegable
 
Originally Posted By: Bamboooo
Originally Posted By: JRed
It's very close. Speedometer will be off by about 1mph, overall vehicle height will be 0.2 inches lower, and you'll be doing 10 more revolutions per mile.

I'd do it.


Actually, the speedometer will be off by .882 mph, overall height will be .207 inches lower, and you'll be doing 9.105 more revolutions per mile.


The speedometer will be off by X mph only at a given speed. It's not accurate to say it'll be off by 1 mph or .882 mph unless you also say at what speed (60 mph, etc).

It's more accurate to say that when you change to a taller or shorter tire, your speedometer is off by a certain percentage.
 
OH well....don't matter now....I got the 255 70 16"s.....put then next to the 245 75 16 and my evil eye eye'd them up , be darn if I could tell a difference.....in fact the 255's looked taller which shouldn't be. Probably being that the 245's were wore down and the 255's were new full tread huh?
Any how , I got new Mich LTX MS2's.

But I thank you all for your thoughts/ help.
BOB
 
Originally Posted By: leeharvey418
Originally Posted By: Bamboooo
Actually, the speedometer will be off by .882 mph, overall height will be .207 inches lower, and you'll be doing 9.105 more revolutions per mile.


I'm going to go out on a limb here and say that you're not familiar with the term 'significant digits'.
lol.gif



You Go, girl!
 
245-75-17 = 30.47" overall diameter
255-70-16 = 30.06" overall diameter
Difference of .41" overall diameter

From what I have read in the past, for every 2/10's of an inch in diameter, you change the speedometer accuracy ~1%. So, according to the measurements here, there is a change of ~2%

Your speedometer now may read 2% faster at speeds. Which will now show ~1 mph faster at 50 mph(51 mph), ~1.5 mph faster at 75 mph(76.5 mph) and ~2 mph faster at 100 mph(102 mph). All insignificant! At least you'll be showing a faster speed reading for the purpose of speeding tickets.

Your odometer may also gain more miles thus, throwing off your MPG should you keep track of MPG. But, I doubt it as I don't see any differences between my:

Stock Steelies used for winter only, 205-65-16 = 26.49...Although my Pirelli P4 A/S in this size spec shorter @ 26.3 according to Pirelli/TireRack.
Summer only tires, 225-55-17 = 26.74...A difference of ~ .44"

Actually showing my speed to be slower than I am actually going so, I need to be watchfull.
 
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If most vehicles I've seen are any indicator, being off 1 or 2 mph at 65 mph is within the error in the speedometer.
 
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