- Joined
- February 9, 1999
- Messages
- 11,923
- Reaction score
- 133
- City, State
- Vail, Arizona
- Year, Model & Trim Level
- 1992 XLT 4x4
You want to match the gears to the tire size and to what you want to do with it..
IMHO, 3.73 with stock sized tires seems to be a good ratio for around town and wheeling without sacrificing your highway usage. If you are not towing and spend most of your time around 75mph you will want a numerically lower (higher) ratio. More like a 3.55. On flat ground the 3.27 with stock tires was ok, but you see a hill and you slow down so I wouldn't recommend that.
Let's say you think the 3.73 with stock tires is right for you.. Now figure how much bigger your new tires will be. Just for sake of a number, let's say 32" tires...
So, a 32" tire is really more like 31.5" tall.. and stock (235x75r15) is 29" tall so the the 32" tire is about 8% taller. That means to keep all things equal you need a gear ratio that is about 8% numerically higher which would be 4.05 which doesn't exist. The next closest would be 4.10..
So, with a 4.10:1 gear ratio and around 32" tall tire you would be about the same gear ratio as you were with stock tires and 3.73:1 gears.
One extra thing to think of.. Bigger tires weigh more, therefore as you go up you not only need to change the gears due to increased rotational diameter of the tire but due to the weight of the tire..
hopefully all that rambling helps make some sense of this.
~Mark
IMHO, 3.73 with stock sized tires seems to be a good ratio for around town and wheeling without sacrificing your highway usage. If you are not towing and spend most of your time around 75mph you will want a numerically lower (higher) ratio. More like a 3.55. On flat ground the 3.27 with stock tires was ok, but you see a hill and you slow down so I wouldn't recommend that.
Let's say you think the 3.73 with stock tires is right for you.. Now figure how much bigger your new tires will be. Just for sake of a number, let's say 32" tires...
So, a 32" tire is really more like 31.5" tall.. and stock (235x75r15) is 29" tall so the the 32" tire is about 8% taller. That means to keep all things equal you need a gear ratio that is about 8% numerically higher which would be 4.05 which doesn't exist. The next closest would be 4.10..
So, with a 4.10:1 gear ratio and around 32" tall tire you would be about the same gear ratio as you were with stock tires and 3.73:1 gears.
One extra thing to think of.. Bigger tires weigh more, therefore as you go up you not only need to change the gears due to increased rotational diameter of the tire but due to the weight of the tire..
hopefully all that rambling helps make some sense of this.
~Mark