Ratios @ 100 MPH
Thread Starter
JK Newbie
Joined: Jul 2010
Posts: 3
Likes: 0
From: Centurion, South Africa
Ratios @ 100 MPH
I currently run 33s (285/70/17 BFG KM2) on a Rubicon Unlimited Auto with stock ratios, but I would like to go to 35s.
I live in South Africa where our speed limits are a bit different with lots of changing elevation.
I want to cater for a best case scenario as this is my DD and also use it for long distance excursions.
I would like to the best available power, but not sacrificing the life of the motor.
What would my RPM be with 5.13 or 5.38 ratios @ 100 MPH.
This the fastest I will ever run.
I have looked at all the charts, but they are all for 70 MPH.
Are there guys running these setups that can comment?
I live in South Africa where our speed limits are a bit different with lots of changing elevation.
I want to cater for a best case scenario as this is my DD and also use it for long distance excursions.
I would like to the best available power, but not sacrificing the life of the motor.
What would my RPM be with 5.13 or 5.38 ratios @ 100 MPH.
This the fastest I will ever run.
I have looked at all the charts, but they are all for 70 MPH.
Are there guys running these setups that can comment?
JK Super Freak
Joined: Jul 2009
Posts: 1,457
Likes: 2
From: B.F.E, MI
It probably is not a good idea to plan on running a JK at sustained 100 mph speeds (even if you can with the 3.8). I would not trust the tires, nor the drive train, especially with 5.13 or 5.38 gearing.
And the thing is just not designed to handle in a stable manner at that speed. Even at 85 mph your "oh crap" options are limited. With a high center of gravity and long travel progressive suspension an unexpected set of bumps at high speed can make the JK unstable (don't ask how I know this).
Good acceleration is fun in any vehicle, but sustained high speed driving is a a different ball game with a whole nother set of rules. The JK does not meet the rules.
IMO, your risk factor would be very great.
Please reconsider your plans.
And the thing is just not designed to handle in a stable manner at that speed. Even at 85 mph your "oh crap" options are limited. With a high center of gravity and long travel progressive suspension an unexpected set of bumps at high speed can make the JK unstable (don't ask how I know this).
Good acceleration is fun in any vehicle, but sustained high speed driving is a a different ball game with a whole nother set of rules. The JK does not meet the rules.
IMO, your risk factor would be very great.
Please reconsider your plans.
Last edited by Yankee; Jun 13, 2011 at 06:22 AM.
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Thread Starter
JK Newbie
Joined: Jul 2010
Posts: 3
Likes: 0
From: Centurion, South Africa
Thanks guys for all the feedback.
The plan is not to run at a constant 100 mph, but I hear your concerns.
Also said, I adapt my driving to the road conditions.
I have run @ 93 MPH over 250 miles (fairly straight road) feeling very comfortable on 33s.
Maybe a different story on 35s.
A more realistic speed would be about 85 MPH.
The KM2 are also rated for 100 MPH as per BFG for a Q rated tyre.
http://www.bfgoodrichtires.com/tire-...-t-a-km2-tires
Do you guys maybe know the RPM @ 85?
The plan is not to run at a constant 100 mph, but I hear your concerns.
Also said, I adapt my driving to the road conditions.
I have run @ 93 MPH over 250 miles (fairly straight road) feeling very comfortable on 33s.
Maybe a different story on 35s.
A more realistic speed would be about 85 MPH.
The KM2 are also rated for 100 MPH as per BFG for a Q rated tyre.
http://www.bfgoodrichtires.com/tire-...-t-a-km2-tires
Do you guys maybe know the RPM @ 85?
