Seeking Alignment Help - 2.5" RHD JLUR 2020 w 35" BFGKO2

[MaggieJeep]

Hi all,

Below is my Alignment Report and I believe the man said that my Caster is out but did not say what mod I need.

I have a 2020 RHD JLUR on 35" BFGKO2 with 2.5" Teraflex Spacer Kit with Front Lower Control Arms.

What do I need to bring everything to stock alignment? I believe I also need a Rear Trackbar Relocation Bracket, correct me if I am wrong.

Links below as to what is currently installed on the vehicle.
JL / JT: Sport Control Arm Kit – Front Lower (1.5-3.5” / 2.5-3.5”)
JL 4dr Sport/Sahara: 2.5” Performance Spacer Lift Kit & Shock Extensions

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[SilverSurfer]

It would normally be the upper and lower control arms that affects caster.

How much longer are those TF lower control arms than the stock Rubicon one's?

 

[Yellow Cake Kid]

The specs at the control arm page you linked too indicate that your replacement lower control arms are 24-5/8" long.

That is significantly longer than the suggested lengths published by several well regarded aftermarket manufacturers of adjustable length control arms.

The OEM length for a stock suspension is 24", while lengths suggested for several popular 3.5" lift kits range from 24" through to 24-1/2".

Keep in mind that a 1/4" increase in length will result in approximately 1.5 degrees of caster, so the extra length on your arms can result in some notable increases in caster angle.

You may want to look at options for a shorter control arm.

 

[MaggieJeep]

The specs at the control arm page you linked too indicate that your replacement lower control arms are 24-5/8" long.

That is significantly longer than the suggested lengths published by several well regarded aftermarket manufacturers of adjustable length control arms.

The OEM length for a stock suspension is 24", while lengths suggested for several popular 3.5" lift kits range from 24" through to 24-1/2".

Keep in mind that a 1/4" increase in length will result in approximately 1.5 degrees of caster, so the extra length on your arms can result in some notable increases in caster angle.

You may want to look at options for a shorter control arm.

That's actually what I suspected as well. Teraflex Adjustable arms had the arms recommend at 24 1//4" but the non-adjustable at 24 5/8".

Will changing the lowers only fix this or do I need the uppers as well? Should I just go for a bracket?

It would normally be the upper and lower control arms that affects caster.

How much longer are those TF lower control arms than the stock Rubicon one's?

Not sure what stock is but 24 5/8" is the non-adjustables.

 

[Yellow Cake Kid]

Hi,
Using a set of adjustable, or at least shorter, lower control arms with OEM uppers will allow you adjust the caster angle to your preference, but adding a set of adjustable uppers will let you place the axle fore and aft with more flexibility, which can be helpful if you have strong preference for where the wheel sits and moves in the wheel well.
I don't have an opinion about the bracket.

 

[MaggieJeep]

Hi,
Using a set of adjustable, or at least shorter, lower control arms with OEM uppers will allow you adjust the caster angle to your preference, but adding a set of adjustable uppers will let you place the axle fore and aft with more flexibility, which can be helpful if you have strong preference for where the wheel sits and moves in the wheel well.
I don't have an opinion about the bracket.

Thanks for that, I will look into purchasing both actually.

What about the rear toe? It seems very positive to one end due to the 2.5" lift, you reckon the bracket will correct it? What about the front toe? Does front toe matter a lot? What does toe correction actually help with?

 

[Yellow Cake Kid]

With regards to the rear toe, I will suggest that it is the result of an extremely complicated combination of factors. The rear toe is not explicitly adjustable, but can easily be affected by other parameters.
The left and right control arms may not be exactly congruent in length. The pivot brackets may not be welded in exactly matched locations. The axle assembly may have some misalignment.
The rear toe measurement will also be related to the thrust angle, which can be managed for minimization by properly sizing the track bar. I often observe people at this forum voicing concern about their Jeep's poor handling while they focus increasing their caster settings, but are unconcerned with excessive thrust angle conditions. A thrust angle makes a significant contribution to the steering characteristics of the vehicle.

Minimizing the rear Thrust Angle is helpful, and doing so will probably improve the rear toe side to side symmetry. I think, but may be mistaken that positive 0 degrees 8 minutes equates to +0.133 degrees. If you adjust the track bar length to reduce that to less than 0.05 degrees you will also recenter the rear toe somewhat so that your 1.3mm total toe is more symmetrically balanced on the axis of the vehicle.

With regards to the relocation bracket vs and adjustable bar, or perhaps and adjustable bar and a relocation bracket. Maybe some one can voice a preference for which solution is most suitable for your set up. I would start with an adjustable bar. I hope someone else will add some info for you.

With regards to the front toe. You can find hundreds of articles describing the effect of the front toe parameters. As a quick simplification, the toe setting will affect how the tires wear. If the toe is set badly it can contribute to the forces which cause the vehicle to pull or drift towards the side of the road. The ideal would be to have the toe set symmetrically, but often times very subtle biasing choices are made to address the realities of road conditions and the vehicle parts wear.

The settings will also affect the steering feel when you enter and exit turns, so you can adjust for positive or negative total toe to make the vehicle steer to your taste.

Some of the ideas regarding front toe are about structure and therefore pragmatic, while others are about road feel and therefore opinions apply.

I have tried to be helpful without telling you what to do, because I think that there are many ways to balance the choices and ultimately, you and your local work shop will need to make those choices. Good luck.

 

[MaggieJeep]

With regards to the rear toe, I will suggest that it is the result of an extremely complicated combination of factors. The rear toe is not explicitly adjustable, but can easily be affected by other parameters.
The left and right control arms may not be exactly congruent in length. The pivot brackets may not be welded in exactly matched locations. The axle assembly may have some misalignment.
The rear toe measurement will also be related to the thrust angle, which can be managed for minimization by properly sizing the track bar. I often observe people at this forum voicing concern about their Jeep's poor handling while they focus increasing their caster settings, but are unconcerned with excessive thrust angle conditions. A thrust angle makes a significant contribution to the steering characteristics of the vehicle.

Minimizing the rear Thrust Angle is helpful, and doing so will probably improve the rear toe side to side symmetry. I think, but may be mistaken that positive 0 degrees 8 minutes equates to +0.133 degrees. If you adjust the track bar length to reduce that to less than 0.05 degrees you will also recenter the rear toe somewhat so that your 1.3mm total toe is more symmetrically balanced on the axis of the vehicle.

With regards to the relocation bracket vs and adjustable bar, or perhaps and adjustable bar and a relocation bracket. Maybe some one can voice a preference for which solution is most suitable for your set up. I would start with an adjustable bar. I hope someone else will add some info for you.

With regards to the front toe. You can find hundreds of articles describing the effect of the front toe parameters. As a quick simplification, the toe setting will affect how the tires wear. If the toe is set badly it can contribute to the forces which cause the vehicle to pull or drift towards the side of the road. The ideal would be to have the toe set symmetrically, but often times very subtle biasing choices are made to address the realities of road conditions and the vehicle parts wear.

The settings will also affect the steering feel when you enter and exit turns, so you can adjust for positive or negative total toe to make the vehicle steer to your taste.

Some of the ideas regarding front toe are about structure and therefore pragmatic, while others are about road feel and therefore opinions apply.

I have tried to be helpful without telling you what to do, because I think that there are many ways to balance the choices and ultimately, you and your local work shop will need to make those choices. Good luck.

Thanks Cake,

I appreciate it but shops here don't really assist you much with Jeeps, they are better with Petrols and 7series. I tend to avoid local Jeep shops because they are more inclined to SELL you stuff they don't understand than assist you and educate you like the shops in USA.

I'd prefer if you tell me what I can purchase to assist with making the vehicle back to stock.

 

[Jamrock]

Interesting discussion so far.

Just to expand on what @Yellow Cake Kid has said.
This video explains how your suspension geometry changes when you add a lift.

Lifted Jeeps look great. However, there is often a price to be paid in terms of gas mileage and the quality of the ride.

Please follow up and let us know how things turn out.

 

[Yellow Cake Kid]

...tell me what I can purchase to assist with making the vehicle back to stock.

Hi Maggie,
I am not trying to be obtuse. I can sense your frustration but do not think I have all the answers for you. I have a fascination for Jeep suspension inspired by a lifetime of experience in other fields of mechanical and suspension applications. I don't have any professional experience in the Jeep world and don't have much experience as a Jeep consumer. It is just that most of the issues are universal in nature. Making the transition to an enthusiasm for a Jeep has been interesting for me, but I realize that many Jeepers have been working on their Jeeps for deacdes and can offer more pertinent advice than I.

Having said that, you need shorter lower control arms, you might as well get some adjustable ones. If it were me I would get the lowers and the uppers and keep the wheel centered in the wheel well while setting the compromise between caster and pinion.

If it were me, I would get an adjustable track bar for the rear, and the front too, and get the shop to set it so the Thrust Angle is at the absolute minimum.

Keep in mind that, for what ever reason, most alignment shops buy a really expensive alignment rack, put your vehicle on it, confirm it is a vehicle, and then take it off to give it back too you. Alignment shops are used to not being able to adjust many parameters, so if you bring in a Jeep that has adjustable parameters you may have to inspire them to go the extra mile and use the capability that the adjustable parts provide. Some folks are effective at creating good will, while others are better at waiting to complain on the internet about bad service. When you go to the alignment shop, strive to inspire them to step it up and help you with the adjustments.

Now, for the can of worms. My Caster is set to 5.5* on my JLU Rubicon with a 3.5" lift. My Thrust Angle measures between 0.01 and 0.02 degrees. Most here will say that 5.5* caster is insufficient for stability, but it's fine, for me, probably because everything else is in good order. I did not want to get into comparisons etc. because I don't have the bona fides, but when I see the common advice to set the caster to a little more than 6.5* I wonder why anyone would want to put up with too much caster just to mask a problem caused elsewhere. Also, I think that many of the ill effects observed by owners of lifted Jeeps should be attributed to botching the Scrub Radius, which is somewhat unavoidable when lifting a Jeep and increasing the articulation, but not fixed by mucking with excess caster and turning the vehicle into a bob sled..

I went with a complete "matched" lift package and had the help of a crew that installs the same package over and over again. They did a fantastic job, despite the fact that they permitted me to hang out and participate. Good guys!!!

You can certainly piece together a package of pieces and parts, but you will have to get in to the details to make it all work.

One way to go is to buy pieces parts that come from a matched package and eventually acquire all the parts in a step by step sequence. That didn't suit my taste, I just made the leap from OEM to all fixed up.

One thing to keep in mind, the steering angle inclination was designed for the OEM sized tires, if or when you up size the tires, the steering feel is going to change and there is not a whole lot you can do about that other get used to the new feel.

Your Jeep has some room for improvements, as evidenced by the alignment records, so you can look forward to that, but when you get it all squared away it's going to feel like a lifted vehicle, not a stock vehicle.

Good luck. I am off on a field trip, so I hope some of the other folks here will contribute some useful advice.

 

[Nick p]

Regarding the rear track bar bracket. Teraflex make one. I have one on my RHD 2 dr and it fits perfectly and re-centers the rear axle.

on the castor as many have said you need to shorten the front lower arms or refit the OE arms with bracket. Another Cheap option is the OE Mopar arms out of the 2” lift kit, it doesn’t matter LH or RH drive.

 

[Jamrock]

From what I understand, the caster angle is set by the lower control arms. I would start with a set of adjustable lower control arms for the front.

I would gradually adjust the length and test.

@Yellow Cake Kid it is always fun to hear you engineering types speak. Especially when you are trying to break things down so us non-engineering people can understand

Without giving away any secrets, what type of technical work do you do?

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