Thrust Angle & Alignment Question

Chris @ GATR · 03-14-2007, 02:04 PM

Hey guys. Got my lift and tires on and I went to get the toe and caster corrected on the TJ today. I noticed that my thrust angle is out by about 2*. My alignment tech suggested correcting it if I wanted optimal tire wear and optimal drivability. I don't really have an extra $350 to spend on upper and lower CA's at this point, so my question is...

Will being out by 2* really chew on my new BFG's? Of course, I'd rather it be "on", but I understand it is a Jeep.

What is the least expensive correction?

Opinions?

Xlr8n · 03-14-2007, 02:56 PM

All you need to adjust on a solid axle jeep with a 2" lift is toe-in. You can easily do it yourself for free.

Chris @ GATR · 03-14-2007, 03:05 PM

Did you notice that I said the toe and caster are already done? Thanks.

Anyone like to chime in on the original question?

Dogman · 03-14-2007, 03:11 PM

Wouldn't the thrust be adjusted by trackbars?

Dogman · 03-14-2007, 03:14 PM

Ah, I see where LCAs would come in to play.

Chris @ GATR · 03-14-2007, 03:21 PM

Trackbar centers the axle left and right, but doesn't change the angle to the frame.

BDuece · 03-14-2007, 05:36 PM

I have the cam bolts on mine. With that said my cam angle is 5.5. About .5* out. I belive 6 - 8 is the range, 7 being optimal. My cam bolts are adjusted as far as possible. Cam angle will not affect tire wear. It will make the stearing feel light, since the cam angle is low. Higher cam angles will make the steering feel heavy.

**crgrissom** · 03-14-2007, 06:08 PM

Quote:

Originally Posted by Chris Hyde

Hey guys. Got my lift and tires on and I went to get the toe and caster corrected on the TJ today. I noticed that my thrust angle is out by about 2*. My alignment tech suggested correcting it if I wanted optimal tire wear and optimal drivability. I don't really have an extra $350 to spend on upper and lower LCA's at this point, so my question is...

Will being out by 2* really chew on my new BFG's? Of course, I'd rather it be "on", but I understand it is a Jeep.

Opinions?

The axle brackets are not very precisely located on the TJ axles in general, so there are probably lots of TJs with bad thrust angles. The only thing you can do is get adjustable control arms and set the axle square to the frame by adjusting them correctly. Good reason for the upgrade.

Chuck

**Jerry Bransford** · 03-14-2007, 06:55 PM

Quote:

Originally Posted by BDuece

I have the cam bolts on mine. With that said my cam angle is 5.5. About 1.5* out.

No, 5.5 is not 1.5 out for a lifted TJ like yours is now. In fact, for your height, 5.5 degrees of caster angle is right on where it should be. Yes the optimal factory setting is 7 degrees but the TJ does better with less Caster angle with bigger tires. In fact, even trying to push the front caster angle back up to 7 degrees will cause excessive front pinion angle which can cause the front driveshaft's lower u-joint to start vibrating. The front pinion angle takes precedence over the caster angle. So keep it right at 5.5 degrees, that's right where it should be. And there will also be a bit of a difference between the left and right-side caster angles but that is supposed to be there, the factory welds the knuckles on purposely to give a bit more caster angle on one side.

kercher · 03-14-2007, 07:10 PM

how does one measure castor angle? I did my toe in from all the posts, but I have no idea how to do that.

**Jerry Bransford** · 03-14-2007, 07:46 PM

Quote:

Originally Posted by kercher

how does one measure castor angle? I did my toe in from all the posts, but I have no idea how to do that.

If someone knows how to measure the caster angle with accuracy and consistency without an alignment rack or other special alignment tool, I'd love to know how to do that too.

**numchuck** · 03-14-2007, 09:16 PM

Hey Chris . . . tell us about your lift . . . also - has your jeep ever been wrecked ?

Chris @ GATR · 03-14-2007, 09:19 PM

2" BB.....1" PA BL.....Stock Shocks. As far as I can tell, the Jeep has never been wrecked. It has no signs at the core support, bumper mounts or on the frame. Unless someone did a really good cover up job, then I would say it is immune to any accidents so far. Also to Jerry, 5.5* is where I was before cam bolts. I guess I was ok?

LjRubicon · 03-14-2007, 09:20 PM

all you need is a adj trackbar not LCA's. the axel is not center it is to the left. i do alignment on jeeps alot(work for a jeep STEALership) teraflex has a good trackbar. that is what i have.

Chris @ GATR · 03-14-2007, 09:23 PM

Ahh, so an axle can get out of "square" with the frame because of my type of lift and cause ultimately cause the axle angle/alignment to be out? I thought a trackbar corrected the axle "centering". (left and right), not diagonal/square adjustment.

03-14-2007, 05:36 PM	#7
BDuece Registered User Join Date: Sep 2005 Location: Massachusetts Posts: 312 Profile Gallery Classifieds My Jeeps	I have the cam bolts on mine. With that said my cam angle is 5.5. About .5* out. I belive 6 - 8 is the range, 7 being optimal. My cam bolts are adjusted as far as possible. Cam angle will not affect tire wear. It will make the stearing feel light, since the cam angle is low. Higher cam angles will make the steering feel heavy. __________________ Bill, http://www.thisisforthesoldiers.org

03-14-2007, 09:20 PM	#14
LjRubicon Registered User Join Date: Jul 2006 Location: FL Posts: 10 Profile Gallery Classifieds My Jeeps	all you need is a adj trackbar not LCA's. the axel is not center it is to the left. i do alignment on jeeps alot(work for a jeep STEALership) teraflex has a good trackbar. that is what i have.