265/60-18 Vs 275/55-20
#1
09-21-2006, 06:53 PM
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265/60-18 Vs 275/55-20
I have an 06 with 5 spoke 18" wheels, 265/60-18 tires, and 3.55 gears. I purchased a set of F150 6 spoke 20" wheels and was thinking about installing a set of 275/55-20 Pirelli tires. The diameter of my current 265/60-18 tires is 30.5". The diameter of the 275/55-20 Pirelli tires is 31.9". The 20s have a 1.4" larger diameter which results in a 4.6% slower rpm.
Today, I went by the Ford dealership and saw an 07 truck just like mine but with the 6 spoke 20" wheels, Pirelli 275/55-20 tires, and 3.55 gears.
1) Will I lose pickup power by going to the larger diameter tires?
2) What's the difference between the 07 with 275/55-20 tires, and 3.55 gears and my 06 with 265/60-18 tires and 3.55 gears?
Today, I went by the Ford dealership and saw an 07 truck just like mine but with the 6 spoke 20" wheels, Pirelli 275/55-20 tires, and 3.55 gears.
1) Will I lose pickup power by going to the larger diameter tires?
2) What's the difference between the 07 with 275/55-20 tires, and 3.55 gears and my 06 with 265/60-18 tires and 3.55 gears?
#3
09-22-2006, 01:58 PM
Hi.
Technically, yes - you have changed your effective gearing slightly, but SOTP you probably won't notice in a vehicle this heavy. It's just not that big of a change.
As for Xcal2 correction: you will be correcting your speedo, to get that back to accuracy, and also correcting the shift points in the process. The revs are the revs; you are not directly altering that - as a result of the above change, you will indicate a slightly lower rpm for a given speed.
The difference between the '07 and an '06 with the same diff ratio (and provided they didn't change the tranny ratios) is the '07 will indicate a slightly lower rpm for a given road speed.
Cheers
Bubba
Technically, yes - you have changed your effective gearing slightly, but SOTP you probably won't notice in a vehicle this heavy. It's just not that big of a change.
As for Xcal2 correction: you will be correcting your speedo, to get that back to accuracy, and also correcting the shift points in the process. The revs are the revs; you are not directly altering that - as a result of the above change, you will indicate a slightly lower rpm for a given speed.
The difference between the '07 and an '06 with the same diff ratio (and provided they didn't change the tranny ratios) is the '07 will indicate a slightly lower rpm for a given road speed.
Cheers
Bubba
Last edited by MGDfan; 09-22-2006 at 02:09 PM.
#4
09-22-2006, 02:24 PM
Join Date: May 2006
Location: Baton Rouge, LA
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Originally Posted by MGDfan
Hi.
Technically, yes - you have changed your effective gearing slightly, but SOTP you probably won't notice in a vehicle this heavy. It's just not that big of a change.
As for Xcal2 correction: you will be correcting your speedo, to get that back to accuracy, and also correcting the shift points in the process. The revs are the revs; you are not directly altering that - as a result of the above change, you will indicate a slightly lower rpm for a given speed.
The difference between the '07 and an '06 with the same diff ratio (and provided they didn't change the tranny ratios) is the '07 will indicate a slightly lower rpm for a given road speed.
Cheers
Bubba
Technically, yes - you have changed your effective gearing slightly, but SOTP you probably won't notice in a vehicle this heavy. It's just not that big of a change.
As for Xcal2 correction: you will be correcting your speedo, to get that back to accuracy, and also correcting the shift points in the process. The revs are the revs; you are not directly altering that - as a result of the above change, you will indicate a slightly lower rpm for a given speed.
The difference between the '07 and an '06 with the same diff ratio (and provided they didn't change the tranny ratios) is the '07 will indicate a slightly lower rpm for a given road speed.
Cheers
Bubba
