Bigger Tire help
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Joined: Dec 2015
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From: Concord,NC
Bigger Tire help
Ok, so I have a 2015 3.5 Ecoboost and I changed my stock wheel and tire size from 17" wheel/265/70R17 to an 18" 305/65R18 wheel with BF Goodrich AT KO2. I LOVE how it looks, but motor and transmission do not. My truck is already shifting to 4th gear at 35-40mph. I can't afford a tuner for another month or so. I just spent 1700.00 on wheels and tires and 1100.00 on exhaust. How bad will it hurt my truck for a month. Drive about 25-30 miles a day.
Help seriously welcomed!
Help seriously welcomed!
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Joined: May 2010
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From: DC
Originally Posted by Stray70
Ok, so I have a 2015 3.5 Ecoboost and I changed my stock wheel and tire size from 17" wheel/265/70R17 to an 18" 305/65R18 wheel with BF Goodrich AT KO2. I LOVE how it looks, but motor and transmission do not. My truck is already shifting to 4th gear at 35-40mph. I can't afford a tuner for another month or so. I just spent 1700.00 on wheels and tires and 1100.00 on exhaust. How bad will it hurt my truck for a month. Drive about 25-30 miles a day.
Help seriously welcomed!
Help seriously welcomed!
I know a lot of folks on here will say all you need is a tune but I would suggest gears. Changing the gears will provide your driveline the mechanical advantage needed to take the excess load off the transmission and to reduce the need for the engine to be in boost as much - which will result in better MPGs.
There are plenty of easy calculators on the web which will tell you what ratio is needed to put your final ratio back to or close to stock.
After that, get a tune.
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Joined: Dec 2015
Posts: 85
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From: Concord,NC
As long as you aren't beating on the truck you'll be fine.
I know a lot of folks on here will say all you need is a tune but I would suggest gears. Changing the gears will provide your driveline the mechanical advantage needed to take the excess load off the transmission and to reduce the need for the engine to be in boost as much - which will result in better MPGs.
There are plenty of easy calculators on the web which will tell you what ratio is needed to put your final ratio back to or close to stock.
After that, get a tune.
I know a lot of folks on here will say all you need is a tune but I would suggest gears. Changing the gears will provide your driveline the mechanical advantage needed to take the excess load off the transmission and to reduce the need for the engine to be in boost as much - which will result in better MPGs.
There are plenty of easy calculators on the web which will tell you what ratio is needed to put your final ratio back to or close to stock.
After that, get a tune.
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Joined: May 2010
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From: DC
Originally Posted by Stray70
Thanks! So just google tire size gear ratio calculator?
Thread Starter
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Joined: Dec 2015
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From: Concord,NC
Senior Member
Joined: May 2010
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From: DC
Originally Posted by Stray70
I think the gear ratio on my 2015 3.5 ecoboost is 3.31. Old tire diameter is 31.7 and new tire diameter is 33.6. According to the calculator it calls for 3.508 gear ratio. The 3.5 ecoboost goes from 3.31 to 3.55 gear ratio. So do I go to the 3.55?
If you think you might go with a larger tire in the future, get the matching gear. Changing gears isn't cheap so you don't want to do it more than once.
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From: Concord,NC
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From: Big Easy
Which is why most people get a programmer and custom tunes. I have 3.31 gears and went up 2" in tire size as well as a 4" lift, the programmer took care of it as well as the speedometer. Can be changed at will and no gears needed.
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Thread Starter
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Joined: Dec 2015
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From: Concord,NC
What programmer did you get that does both? And does it void the warranty? I have a 6 year 100,00 mile warranty.