Drive shaft and geometry changes after lift and upsizing tires

[Artiead]

I am putting a 2.5inch lift and 37inch tires on 2019 JL Rubicon. Do I also need to make any changes to geometry and drive shaft or other components? Was gonna go with 35” but 37” as suggested for overall look. Any thoughts as feedback are appreciated. Thanks.

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[Carlton]

At 2.5 inches of lift your driveshaft should be fine. This is true, unless the kit ends up giving you much more than 2.5 of lift. If it does, you can add geometry correction brackets or lower control arms to fix it.

35 vs 37 inch tires will have no impact on driveshaft angle. You will want to recalibrate for larger tires however.

 

[walweb]

I am putting a 2.5inch lift and 37inch tires on 2019 JL Rubicon. Do I also need to make any changes to geometry and drive shaft or other components? Was gonna go with 35” but 37” as suggested for overall look. Any thoughts as feedback are appreciated. Thanks.

Depending on the lift you get, I have a Rock Krawler 2.5" lift and it came with adjustable front and rear control arms. I couldn't tell you if they were needed, but I did take the time to adjust mine so that the Pinon was at same angle as driveshaft.

 

[Tech Tim]

With a 2.5" lift and no geometry changes, your JL with have a little less caster than it did stock. This will make the steering feel a little more "twitchy" at highway speeds. That bothers some people and doesn't bother others. Really depends on your driving style and what you're used to.

 

[Arterius2]

Depending on the lift you get, I have a Rock Krawler 2.5" lift and it came with adjustable front and rear control arms. I couldn't tell you if they were needed, but I did take the time to adjust mine so that the Pinon was at same angle as driveshaft.

what does the rear control arms adjust?

 

[Roky]

what does the rear control arms adjust?

You can set your pinion angle so your driveshaft is straight from axle to transfer case. Also you can center your wheel in the wheel well. This doesn’t bother a lot of people but with my ocd it drove me crazy. Lol. Here’s before and after on back wheel.

 

[Arterius2]

You can set your pinion angle so your driveshaft is straight from axle to transfer case. Also you can center your wheel in the wheel well. This doesn’t bother a lot of people but with my ocd it drove me crazy. Lol. Here’s before and after on back wheel.

Thanks! learned something new today.

 

[kobejo34]

With a 2.5" lift and no geometry changes, your JL with have a little less caster than it did stock. This will make the steering feel a little more "twitchy" at highway speeds. That bothers some people and doesn't bother others. Really depends on your driving style and what you're used to.

The front LCA fix this?

 

[Tech Tim]

The front LCA fix this?

Yes and No.

A longer front LCA will rotate the axle to bring back the caster closer to stock.

That said, there is still geometry in play. By lifting the frame, the controls arms are at a steeper angle, changing the original engineered geometry, creating a slightly higher roll center.

Geometry brackets (or what some people call drop brackets) lower the frame mounted control arm pivots back closer to stock. Lessening the control arm angle and keeping the roll center closer to stock.

They also bring the caster back closer to stock.

Red arrows show where the UCA and LCA were originally from the factory.

Green arrows show where the geometry bracket (this one is TeraFlex) lowers the control arm pivots down towards stock levels.

 

[Chocolate Thunder]

Yes and No.

A longer front LCA will rotate the axle to bring back the caster closer to stock.

That said, there is still geometry in play. By lifting the frame, the controls arms are at a steeper angle, changing the original engineered geometry, creating a slightly higher roll center.

Geometry brackets (or what some people call drop brackets) lower the frame mounted control arm pivots back closer to stock. Lessening the control arm angle and keeping the roll center closer to stock.

They also bring the caster back closer to stock.

Red arrows show where the UCA and LCA were originally from the factory.

Green arrows show where the geometry bracket (this one is TeraFlex) lowers the control arm pivots down towards stock levels.

Thanks for this info Tim and the visual aid to make it easier to understand. These geometry brackets are not absolutely necessary for a 2-2.5” lift with the longer Mopar LCA, but should still give improvement in ride and steering feel, correct? And about how much ground clearance do they sacrifice?

 

[Tech Tim]

Are they absolutely necessary? NO.

I would use them on anything 2.5" or more.

Loss of ground clearance is arguable (and people will... )

You do not lose ground clearance, they are no lower than they were when stock.

The frame goes up with the lift, so you do gain clearance in the center of the vehicle, where it really matters... break-over angle.

 

[kobejo34]

Thank you Tim

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