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Unread 05-20-2013, 09:50 PM   #1
rubicon17
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finally got alignment printout with pics, need advice

what would you change? i know the caster needs to go back some toward 5.5 but how many turns is 1 degree on rc arms? does the thrust angle mean the rear axel is not centered? i redid my front axel and ended up shifting it 1/2" to the passenger side and it looks perfect now, also i had them rotate the backs to the front while there and it still pulls to the right slightly, like a 3-4 out of 10, maybe to much caster? let me know what you guys think. tire size is 286/75/16 mtr, 33"



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Unread 05-20-2013, 09:58 PM   #2
03Rubikidd
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Your rear thrust angle is a measurement of the rear toe. Since it is solid axle, the only way to adjust it would be changing the lower rear control seems to adjustable one's. Your caster seems fine in my opinion. The sight pull might be caused by a tire.
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Unread 05-20-2013, 10:12 PM   #3
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i like the caster but it does have a small vib around 50 and im sure now its the front dshaft. i read 5.5 is optimal. and also i rotated the tires to see if it had any effect on the pull but its the same, just a slight right pull when i let off the wheel. its enough sometimes i have to hold it to the left abit.
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Unread 05-20-2013, 10:34 PM   #4
Patrick H
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Thrust angle isn't rear toe, it's the measurement of the rear axle and front axle being square to one another. As shown in the printout, rear toe is .11 degrees, and the thrust angle is -.27, which is a bit high. Negative toe on one side, and positive toe on the other side of the rear axle indicates it isn't square under the Jeep.
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Unread 05-20-2013, 10:36 PM   #5
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I would leave the caster alone. Less caster would cause less steering return-to-center tendancy, and they will only cause a pull if they are drastically different left to right(yours are fine). Your camber (nonadustable on TJ) would cause a slight pull to the left, so I doubt that's your pull. Your rear axle is side tracking to the left, so the front toe is adjusted to compensate for that.

I would normally suspect a tire related pull and do a straight track/road force check of the tires, but very difficult and inaccurate to do on mud terrain tires.

Only thing i can guess is it's sensitive to road crown. The road will have a very slight curve side to side to help rain runoff, so if you are always in the left lane or on a 2 lane road, the road crown for you is sloping to the right, and that might be the pull you are feeling. Try driving on a divided highway in the left lane and see if the pull is less.
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Unread 05-20-2013, 10:52 PM   #6
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its odd because some roads its great, others i feel like im having to steer to the left a little. the roads here are ****ed. i have 5100s and its still like a tank, i have the tires at 26lbs.
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Unread 05-21-2013, 07:57 AM   #7
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blaine, jerry, unlimited, imped what would you guys adjust? you know how many turns i should go in with the front lowers?
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Unread 05-21-2013, 08:30 AM   #8
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what lift height, what track bars, what are the control lengths set at?

7 caster is a little high for 33s with a lift. depending on lift height, that may hose your pinion angle a little. I prefer 6-6.5...but there is a enough variability in one axle housing to another that it may be fine...you'd have to check yourself.

the thrust angle is likely a result of the axles being off-centered, and/or control arm lengths being bad lengths compared to the frame. it's high, but not real bad....will result in slight dog tracking.
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Unread 05-21-2013, 09:00 AM   #9
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i have 4" springs with 3/4" spacer on the front and iron rock offroad front and rear adjustable trackbars. im not to sure the exact length on the arms but the front uppers are 15" and the lowers are over 16. probably 3-4 turns out from 16". is the thrust angle a measurement of the rear axel? like i said im fairly confident the front is now centered good i moved it over 1/2" to the passenger side. the rear needs to go the same way some to. changing the caster will not affect toe will it?
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Unread 05-21-2013, 11:56 AM   #10
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Quote:
Originally Posted by rubicon17 View Post
i have 4" springs with 3/4" spacer on the front and iron rock offroad front and rear adjustable trackbars. im not to sure the exact length on the arms but the front uppers are 15" and the lowers are over 16. probably 3-4 turns out from 16". is the thrust angle a measurement of the rear axel? like i said im fairly confident the front is now centered good i moved it over 1/2" to the passenger side. the rear needs to go the same way some to. changing the caster will not affect toe will it?
changing caster will effect toe slightly.

i don't know what 3-4 turns out from 16" means. use a tape measure to determine eye to eye length.

thrust angle is a comparison between rear axle and geometric centerline of the vehicle.



it's basically dog tracking, going down the road sideways by 0.25 or whatever. If it's 0, then the rear axle directly follows the front axle, which both follow the centerline of the vehicle (frame).
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Unread 05-21-2013, 12:59 PM   #11
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i mean i turned then out that many full turns after i set them to 16". would it effect toe enough to be concered if i turn then in 2 or 3 full turns? and would the thrust angle cause it to pull to the right? is the thrust angle only changed by the adjustable control arms or trackbar? just for the heck of it i measured between the center of the tires side to side the other day and i kept coming up with 1/2" or so less on the driver side than the passenger side. i just cannot for the life of me figure out why in the hell it pulls to the right and why it is harsh on rough holes, some potholes and dips in the roads i feel it in the steering wheel like the trackbar is loose and the axels is flopping around but others its a ok, its tq to 74ft lbs on both ends. i have bilstein 5100s that are brand new but ****ty rc coils and joints. i have checked the preload on the arms and they are good. took all 4 apart last weekend on the front and they were still like new.by the thrust angle reading can you tell which way the axel is canted?
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Unread 05-21-2013, 01:35 PM   #12
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Don't worry about how many turns to turn the joints. Worry about the measurements. And don't assume from left to right or front to back the lengths of the arms will be identical. Get comfortable with what you're measuring and it will start to make sense. I would be looking to square up the rear axle, and lower my caster by 1 degree. The rest is fine.
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Unread 05-21-2013, 02:14 PM   #13
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thats what im hopeing to do today but i have no idea what 1 degree would be equal to? as for the rear would that thrust angle mean the driver side is setback more the passenger side or other way around?
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Unread 05-21-2013, 02:36 PM   #14
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Quote:
Originally Posted by rubicon17 View Post
thats what im hopeing to do today but i have no idea what 1 degree would be equal to? as for the rear would that thrust angle mean the driver side is setback more the passenger side or other way around?
Sounds like step one is for you to get an angle finder and learn how to use it and where to put it. The rear could be either way..... you will have to measure the wheelbase, see how far it's off and decide if you want to make the long side shorter by shortening the those rear links or the short side longer by lengthening those rear links. Or a combination until you get the same measurement on both sides. Based on your print out you need to bring in the drivers side a bit.
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Unread 05-21-2013, 03:56 PM   #15
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by driver side in do you mean shortening lower rear control arm on that side or lengthening it? does anyone know if the thrust angle would cause my pull to the right? and the whole reason i took it in is because i cant find anywhere to measure caster with accuracy. i am going to just turn the front lowers in 2 full turns each and see how it does.
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