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Old 02-06-2010, 08:00 PM   #7
flatlander757
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Re: Jeep TJ Alignment Bible

Quote:
Originally Posted by bb62471 View Post
My everyday driver is a 2005 TJ Wrangler X, and I didn’t feel I needed a monster truck so I decided to go with 30-31" tires instead of the 27" that came on my TJ. To accommodate the larger tires, I was going to need to get a couple of inches more clearance for the tires. I ended up installing a set of 2 inch coil spring spacers to lift my ride height slightly. After I installed the spacers, I re-set the toe to 1/8" and drove the jeep. It felt slightly unstable, but I knew I tightened everything back up. I did not rotate, or balance my tires. Nothing else was changed. I drove my Jeep locally for the next few days to work and back (only 4 miles per day round trip).
The next weekend I drove to Sacramento to visit family. When I reached a crappy rough highway (HWY 80) the front end felt wobbly. As I approached 40-45 MPH and I hit a bump on the right front, I got the sensation I was driving on triangle shaped front tires that were out of sync. My garage door opener and other crap on the dash leapt off onto the floor and my butt puckered! Scared the hell out of me. I slowed and it went away as I came to a stop. Every time I tried to go over 40 MPH the wobble came back with a vengeance. I ended up taking surface streets (keeping the speed under 40), until I found a much smoother roadway to take home. Once I was on a new stretch of Highway (N/B 99), I was finally able to get up to 70 MPH w/o wobble. Drove the rest of the way home worried I might die, but it drove fairly normal.
The next few days, I searched the internet as many of you have I’m sure. After reading all the posts available, I started inspecting my jeeps front end. After 2 days of intense scrutiny of all the components, I came to the conclusion, nothing was worn, loose or broken. What the hell???
I decided to purchase a magnetic base angle gauge ($5.00). I used it to check the angle of my CASTER and found it was over 3 degrees above spec. (top ball joint farther back than lower ball joint total of almost 11 degrees from zero). I ended up re-setting my CASTER back to 7 degrees and re-set my toe again to 1/8". Guess what? my wobble went away. Over the next few weeks, I put about 700 miles on it with everything in place as it was with the wobble. I even drove the same stretch of highway 80 several times to make sure the wobble was gone. I felt confident the disease was cured, so then I bought my new tires and rims. Now with an additional 600 miles on the new tires, I know I beat it.
I’m not trying to say that all of you with Death Wobble (or what you think is DW) can decrease your CASTER and fix all your woes… What I am saying is it DID fix mine.
I know that some of you will not believe this, but if you think about how a shopping cart with a bent caster wheel reacts when pushed forward, our DW does virtually the same thing. Think about how CASTER angle works, if you had lets say 45 degrees of positive Caster, your wheels would probably wobble at 10 MPH just by going over small pebbles. Anyhow, if anyone has questions, don’t hesitate to ask. For those skeptics out there, keep spending money on parts instead of thinking outside the box. I fixed my DW for about $10.00, how much have you spent trying to fix yours?
Oh.. and before anyone asks...
NO, I did not replace my steering stabilizer, shock, dampener or whatever you want to call it.
As long as your alignment is set up right, there is NO NEED for one.
No other parts were replaced or tightened. All I did was re-set the CASTER back to about +7 degrees.
Right... as stated in the original post... this was regarding excessive positive caster, such as the 11 degrees you had.

Quote:
*I believe* this causes instability/death wobble because big tires(33”+) have a lot of sidewall play as there is a lot more of it, so basically the entire rim is trying to wobble left and right inside the tire. German cars have a ton of caster without problems, but they have 17-19in wheels, skinny and stiff tires, and less play in the steering systems (rack and pinion vs. steering box and linkages).

That is my take on caster angles vs. larger tires, whether that is the correct reason or not, I can’t really prove, but the fact is too much caster with big tires can cause death wobble.

Same reason that 35s generally run better with about 5 degrees of caster vs experiencing random-to-frequent occurrences of death wobble with OEM 7 degrees specification.



FWIW my TJ is now on a D60 and D70HD and is my daily driver(though I still have a lot to finish up before I can really wheel it... working on building a front driveshaft as money comes in). I have played around with caster and have found that 6 to 7 degrees works best with 40s.

So I'd say it's important to note that alignments are sometimes not a "set in stone" science... If you have an odd setup then you gotta go through some trial and error and LET IT EAT!



And here's a video to back up that you do NOT NEED A STEERING STABILIZER TO FIX WOBBLES!!



It's only up to 45mph, but it's been up to 70mph before I get any kind of wobbles. I don't have the desire to drive it much faster so it is good for me!
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-Tony- Sold my Z28 looong ago. Now sporting an '03 TJ.
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