Return of Steering Challenges

[AnnDee4444]

Wide tires and offset rims affect the camber. Many Jeeps run wide tires on offset rims which throws the camber way off.

This is not correct. Tire size & wheel offset has nothing to do with camber.

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[Jebb]

You don't hear it discussed because it can't be adjusted without new ball joints/shims which most don't really recommend.

You “adjust” it with relation of tire diameter vs wheel offset. For example, 33” tires on 10” rims produces more scrub radius (positive camber) than 35” tires on 8” rims with same backspacing.

Just pointing out that it’s a factor in steering response. It’s rarely discussed because many aren’t aware of it.

 

[Jebb]

This is not correct. Tire size & wheel offset has nothing to do with camber.

It does not change the camber angle - it changes the contact patch location on the road. Read the link I posted.

 

[AnnDee4444]

It certainly does. Read the link I posted.

You are getting camber & scrub radius mixed up. They are not interchangeable.

From you link after removing the BS for clarity:

"Scrub radius is... defined by the location of the point in space where an imaginary line traced down through the centre of the suspension column crosses the one drawn vertically down through the very centre of the tyre. "
​

And the definition of camber, from Wikipedia

"Camber angle is the angle made by the wheels of a vehicle; specifically, it is the angle between the vertical axis of the wheels used for steering and the vertical axis of the vehicle when viewed from the front or rear."​

 

[Jebb]

You are getting camber & scrub radius mixed up. They are not interchangeable

I understand it very well. The two measurements are not interchangeable - they are related. Camber is used to create a desired scrub radius for a given wheel and tire diameter - the “factory” design. When you change tire diameter and/or wheel offset you alter that scrub radius - which changes the tire contact patch location on the road - which alters the intent of the factory camber selection. The camber angle will still measure “in spec” but the response is different because the tire contact patch on the road is in a different place (i.e., the scrub radius is different).

 

[AnnDee4444]

I understand it very well. The two measurements are not interchangeable - they are related. Camber is used to create a desired scrub radius for a given wheel and tire diameter

Yes, but changing the wheel offset does not change the camber. You stated in "Wide tires and offset rims affect the camber". You could remover the wheels completely and still measure the camber, because it's literally built into the axle (on the JL). Look at how a camber gauge works, and imagine what effect a different sized wheel/tire would have:

When you change tire diameter and/or wheel offset you alter that scrub radius - which changes the tire contact patch location on the road - which alters the intent of the factory camber selection.

I agree.

 

[Jebb]

Yes, but changing the wheel offset does not change the camber. You stated in "Wide tires and offset rims affect the camber".

Touché - I should have said it affects the effective camber. As you said, the actual camber angle doesn’t change - which makes this effect hard to see and measure. To maintain the factory scrub radius (effective of camber angle) tire height and wheel offset have to maintain the right ratio.

 

[AnnDee4444]

Touché - I should have said it affects the effective camber. As you said, the actual camber angle doesn’t change - which makes this effect hard to see and measure. To maintain the factory scrub radius (effective of camber angle) tire height and wheel offset have to maintain the right ratio.

I'm not sure I follow, but I'll try to describe where I think you are going: the measured scrub radius is not equal to the 'effective scrub radius'. Basically, it's how camber effects where the pneumatic center of the tire is located, therefore altering the effective scrub radius.

I've never seen this discussed online and I'm not sure this has any practical use on the JL, due to it's mild camber angles and large sidewalls.

 

[Jebb]

I've never seen this discussed online and I'm not sure this has any practical use on the JL, due to it's mild camber angles and large sidewalls.

What I am trying to point out is that changing tires and/or wheels - not just lift kits and control arms - can adversely affect steering geometry. It’s true for all vehicles with modern, 3-trim-axis Ackermann steering. The JL is no exception.

 

[NPE102414]

What I am trying to point out is that changing tires and/or wheels - not just lift kits and control arms - can adversely affect steering geometry. It’s true for all vehicles with modern, 3-trim-axis Ackermann steering. The JL is no exception.

This isn’t really a mystery, let’s put aside the Wrangler platform for a moment and think about a car or suv you own or owned. How many times in your life have you changed tire brands and the car you were so used to became a different car, sometimes good and sometimes bad. Tires obviously affect steering, handling, braking. and pretty much every aspect of the cars drivability. The JL is obviously a different animal because a large majority of owners completely change what the engineers at Jeep designed. My suspension and steering is unrecognizable from when I picked it up, in a good way though.

 

[thadius65]

Update - removal of the Teraflex Apline IR track bar and reinstall of the OEM provided a positive outcome. Possibly the need for a Teraflex front axle bracket kit? Not sure why, but possibly the additional caster causes a geometry issue similar to a lift (mine is stock JLUR). Please go easy on me as I am pretty green in all of this.

I talked to the PSC technician yesterday and got some clarification on positive caster setting. It seems the +6-+7 caster is for tires in the 37+ range. I was told to ease the caster back to +5.x for some balance between handling and return to center of the steering wheel. Of course this means the need for adjustable LCAs as the stock LCAs will only provide +4.x and the longer Mopar (1/4" longer) provide +6.x.... So to get between, I need 1/8". I think once I get this set, I will have it as good as it can get.

Trial and error seems to be best medicine to get my Red Rubi where she needs to be.

 

[NPE102414]

Update - removal of the Teraflex Apline IR track bar and reinstall of the OEM provided a positive outcome. Possibly the need for a Teraflex front axle bracket kit? Not sure why, but possibly the additional caster causes a geometry issue similar to a lift (mine is stock JLUR). Please go easy on me as I am pretty green in all of this.

I talked to the PSC technician yesterday and got some clarification on positive caster setting. It seems the +6-+7 caster is for tires in the 37+ range. I was told to ease the caster back to +5.x for some balance between handling and return to center of the steering wheel. Of course this means the need for adjustable LCAs as the stock LCAs will only provide +4.x and the longer Mopar (1/4" longer) provide +6.x.... So to get between, I need 1/8". I think once I get this set, I will have it as good as it can get.

Trial and error seems to be best medicine to get my Red Rubi where she needs to be.

I really hope you didn’t do all this chasing a ride your JL isn’t capable of producing in the first place. By no means do you need a track bar relocation bracket. The track bar should run in line with the drag link, and without a lift over 4” you shouldn't change either. You’ll just cause more problems!

 

[word302]

I really hope you didn’t do all this chasing a ride your JL isn’t capable of producing in the first place. By no means do you need a track bar relocation bracket. The track bar should run in line with the drag link, and without a lift over 4” you shouldn't change either. You’ll just cause more problems!

You shouldn't change your track bar without a lift over 4"? That's not very good advice at all. First of all, the factory track bar is junk. Any amount of lift is going to pull your axle off center, how much you want to put up with is up to you. Agree that the track bar bracket is not necessary unless you flip your drag link.

 

[NPE102414]

You shouldn't change your track bar without a lift over 4"? That's not very good advice at all. First of all, the factory track bar is junk. Any amount of lift is going to pull your axle off center, how much you want to put up with is up to you. Agree that the track bar bracket is not necessary unless you flip your drag link.

I think you misunderstood me, I meant he shouldn’t relocate the track bar, not shouldn’t change it. He mentioned a track bar bracket which I assume he means a relocation bracket. I also meant that he shouldn’t be relocating the track bar or flipping the drag link without a lift of at least 4”.

 

[thadius65]

I think I was misunderstood. I was just trying to say that I didnt understand why the new track bar was causing steering to be worse. No bracket used, was on factory mounts.

Also, I am not chasing what isnt possible, I am chasing what I had when PSC and Steering stabilizer was first installed. That was ruined by either track bar or caster of +6.1 on a stock JLUR. PSC suggested that initially, now are saying +5.

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