Gear ratio/speedo gear

[dimension12]

I physically counted drive shaft turns. I have 3.73 gears. My speedo gear has 31 teeth. Pretty simple and straight forward.
Now the twist.
Using the formula rpm x tire diameter / 60 x 336 = gear ratio I come up with 4.11. The GrimmJeeper program also shows 4.11 ratio by the rpms I am turning. Around 3000 at 70mph.
I have a 99 4.0 32rh 231tc
Any ideas why

 

[jchadscud]

From the other thread...If your measured tire size is 31, you’re right on. I have no idea why your tires say 33 but measure 31. Check the actual number on the tire. Maybe they aren’t 33?

 

[JMT]

I physically counted drive shaft turns. I have 3.73 gears. My speedo gear has 31 teeth. Pretty simple and straight forward.
Now the twist.
Using the formula rpm x tire diameter / 60 x 336 = gear ratio I come up with 4.11. The GrimmJeeper program also shows 4.11 ratio by the rpms I am turning. Around 3000 at 70mph.
I have a 99 4.0 32rh 231tc
Any ideas why

Somethings not right with the formula.
3000x33= 99,000

60x336=20,160

= 4.91

 

[dimension12]

Somethings not right with the formula.
3000x33= 99,000

60x336=20,160

= 4.91

2600 at 60mph

 

[dimension12]

From the other thread...If your measured tire size is 31, you’re right on. I have no idea why your tires say 33 but measure 31. Check the actual number on the tire. Maybe they aren’t 33?

They are 33s. I have them aired down to 35. They measure 15.5 from center of hub to ground. If aired up to 45 not on the jeep they measure 32.8 brand new.