How to align your Jeep Wrangler TJ

Oh and that's the driver's side tyre - the passenger side tyre was even worse - almost completely smooth on the outside...
Yeah, I can imagine the steering felt a little off...
 
I set the toe-in on my Jeep using the following method:
- Raise the front axle high enough for the tires to clear the ground and place stands under the axle
- use short wood or sheet metal screw and thread it into a tire sipe approximately center of the tread of each tire.
- rotate tires until the screw heads are facing forward and measure the distance between the screws.
- rotate tires until the screws are at the back of the tires just below the lower control and and take another measurement.
- compare measurements and adjust until the front measurement is 1/8 - 3/16” shorter than the rear measurement.
- re-center steering wheel if necessary.
I’ve been using that method for at least 15 years without issue.
 
Spacers are the same length. Can't get much easier.

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Stupid question, but does tire size impact the required toe in or is it always 1/16"-1/8"? Is that the factory specification?
It’s always 1/16”. The purpose for the slight toe in is the friction on the road forces the tire out (when moving forward), so you’re tire is actually at 0” toe in motion. Factory specification is 0.25* I believe.
One more question that I have is whether you should align it at 1/16" - 1/8" no matter what Tire size you are running? Is there any difference between this number for 31" vs 33" vs 35" tires?
OK.. I know this was asked ten different ways. I'm going to ask again.

I am looking at a set of the alignment plates. I prefer not having to jack up the jeep and remove the wheels to do a spot check on alignment. The difference in cost is maybe $40 bucks which I'll recoup in time saved by being able to leave the wheels on.

I have 33's. In the original post the metal bar was marked at the center point and then 16.5" fore and aft and adjustments were taken at the 16.5" mark front and rear. All of the alignment plates I find are about 24". Are we still shooting for the same 1/16" toe in even though one method measures 16.5" fore and aft of center and the other method measures 12" fore and aft of center?
 
I have a set of the toe in plates which I have found all but useless on most truck tires. Between raised letters and some tires have the tread running down the sidewall. You may get lucky but didnt trust all letters being the same height when we are only dealing in 1/16" increments Most race car tires have the letters painted on so you don't have the raised letter issue. keep in mind too that most tires are not the diameter they are advertised being not that it is all that critical
 
OK.. I know this was asked ten different ways. I'm going to ask again.
Take a tape measure and hook it on your mud terrains, same spot on each side. Do the math based on that. I can help with the math for whatever angle you want based on tire size, I'm sure others can too. You don't need all that other crap.
 
OK.. I know this was asked ten different ways. I'm going to ask again.

I am looking at a set of the alignment plates. I prefer not having to jack up the jeep and remove the wheels to do a spot check on alignment. The difference in cost is maybe $40 bucks which I'll recoup in time saved by being able to leave the wheels on.

I have 33's. In the original post the metal bar was marked at the center point and then 16.5" fore and aft and adjustments were taken at the 16.5" mark front and rear. All of the alignment plates I find are about 24". Are we still shooting for the same 1/16" toe in even though one method measures 16.5" fore and aft of center and the other method measures 12" fore and aft of center?
Nope. I just used the other calculator to help @JMT realise that he doubled his result.

As a synopsis, so we don't confuse the matter any further:

30" tire
0.30 degrees total = 0.15"
Range:
0.18 degrees total = 0.095"
0.42 degrees total = 0.22"

31" tire
0.30 degrees total = 0.16"
Range:
0.18 degrees total = 0.97"
0.42 degrees total = 0.23"

33" tire
0.30 degrees total = 0.17"
Range:
0.18 degrees total = 0.1"
0.42 degrees total = 0.24"

35" tire
0.30 degrees total = 0.18"
Range:
0.18 degrees total = 0.11"
0.42 degrees total = 0.25"

etc

I hate to say this but I’m going to add to the "confusion" (or, adding to the clarity!?) The specification says .15 degrees +/- 0.06 degrees per wheel, but it also says 0.06 degrees max Right/Left difference . I believe this is to accommodate variation in ‘heading" (where the average of the wheels is pointing vs vehicle centerline) so I believe it should be .24 to .36 degrees total when measuring between the wheels.

@TJim and @JMT I appreciate what you added to this thread. I design vehicles and engines for a living (aeroapace and marine) and write specifications for them, so it warms my heart to see people care about the numbers. "In God we trust, in everything else we check."

I’m on stock Rubicon tires (~30.5") so my range if measured using tire diameter would be .128" to .189" or between 1/8" and 3/16."
Measuring at 12" would be .050" to .074" (1/16" +/- 1/32").
 
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I love the attention to detail. I am in finance and being accurate is a necessity. That said, how likely will it be that the alignment methods shared here will be accurate to 0.24-0.36 degrees?

I ditched the idea of the alignment plates
 
I love the attention to detail. I am in finance and being accurate is a necessity. That said, how likely will it be that the alignment methods shared here will be accurate to 0.24-0.36 degrees?
Very likely and just about 100% likely if you take your time with the measurement. I was getting tires for my Jeep when the shop told me it'd need to have its toe-in checked and set or the new tires would start wearing prematurely. I declined and explained I set my own toe-in all the time and it worked perfectly well. They started arguing, saying I couldn't possibly have gotten it good enough with my method. They insisted they at least check it for free, only charging me if it was off and it needed to be adjusted. I agreed and they ended up sheepishly agreeing my toe-in was perfect. Of course I was watching the numbers they were getting during their check too lol.
 
I changed my factory Trac bar to an adjustable one today and I used this method for alignment and centering the steering wheel. This write up is priceless! I did not realize how easy this process could be. My leading and trailing edge were the same measurement so I dialed in 1/16 of toe in. Thank you Jerry for the write up!
 
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Thanks for this DIY Jerry! And others who have added insights to the thread. I've never worked on coil spring solid axle suspensions prior to purchasing a TJ and this thread really helps in understanding. (y)
Think I'll be doing an alignment today
 
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Well, I thought I was going to check the alignment......but the tie rod is definitely not straight. There is a visible bend and the toe in is 5/16". Makes sense the two would be related. But to be clear...tie rods on TJ's are supposed to be straight? Right?
 
Well, I thought I was going to check the alignment......but the tie rod is definitely not straight. There is a visible bend and the toe in is 5/16". Makes sense the two would be related. But to be clear...tie rods on TJ's are supposed to be straight? Right?

Correct. The stock tie rod should be straight. The ZJ tie rod has a jog in it on the driver's side.
 
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So I am probably overthinking this, but thought I would post to see if anyone else has ran into this scenario. What a great thread learned a lot. Thanks in advance for any insight. I haven't yet adjusted anything since my Tie rod is seized at the moment and waiting for the PB Blaster to work from last night. So I haven't had a chance to adjust the tie rod to see how it correlates to this measurement. Hopefully the Dia. below makes since.

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The 1/16" alignment for all tire sizes always bothered me. The math doesn't work.
I read through all 18 pages and was glad to see @TJim stuck to his guns (around post 300) and showed why it doesn't work.
1/16 to 1/8 might be close enough for most, especially if you're not very accurate with your measurements.
Even if it's wrong, it might be better than what you started with.

https://robrobinette.com/ConvertToeInchesToDegrees.htm