RRO OME yj conversion...start with axle shims - Page 2 - JeepForum.com
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post #16 of 34 Old 04-15-2020, 08:29 PM
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I'm not following the part about installing whatever was on there. There were shims on the spring pack already? Some photos might help. If you spun a shim around so that the thick end moved 180 degrees, the shim degree is half of the change in caster. Flipping it around end for end doubles up the degrees since as one end of the axle perch goes up and one goes down.

Regarding the transfer case drop, the proper thing to do if you have driveshaft vibrations is to leave the skidplate alone and convert to a double cardan driveshaft. Keep the ground clearance you're gaining with the lift. Tcase drops are a Band-Aid IMO.

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post #17 of 34 Old 04-15-2020, 08:57 PM
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Let's say they are 3 degrees...since the camber comes in at 4.8, then that 'should' be 1.8 with no shim at all IF your shim is 3 degrees.. But you did say it was 1.8 with the shim on backwards. That doesn't seem right to me.

But if the axle were to sit at 2.8, then adding the shim (IF it's a 2 degree common shim) would get you at 4.8 one way and .8 the other which 'feels' more like what's happening.

So my vote goes for 2 degrees, meaning a 4 degree shim would be the ticket (6.8). Yes? No?
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post #18 of 34 Old 04-16-2020, 03:40 PM Thread Starter
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Hello. Thanks for the replies.

The shim was already on the spring back when I purchased them. These are ARB OME heavy duty yj springs.. I first installed them as they were from the factory and the caster was at 1.8 degrees. I called Rocky Road outfitters to talk to them and they told me to spin the shim 180 degrees and see where the caster is then. After that the caster was at 4.8 degrees. These are all caster measurements from an alignment shop btw.

So if I read your response correctly a 4 degree shim will only result in 2 degrees of caster change correct?

Is there a way to determine from the info I have what degree shim I need to arrive at the 5-7 degree caster I need? I know I can't stack them or I'd just put a 4 degree shim on top of it and call it good. What I can't determine is what size shim is on there now otherwise it would be easy.

I agree on the transfer case drop. I would like to do the double cardan but I dont have funds to charge the yokes after the yj spring conversion. It is on my list for the future however.

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post #19 of 34 Old 04-16-2020, 03:43 PM Thread Starter
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I guess the other route I could take is to remove the shims that came with the springs and go have it measured then add the correct shim to get it to spec. I was trying to avoid doing it twice more since I've already removed it after install to spin the shims. But if that's what it takes I suppose I could.


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post #20 of 34 Old 04-17-2020, 01:43 PM
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I don 't think so. What's important is the caster angle with no shim. From the information you provided, I believe a 4 degree shim would put you at about 6.8 degrees caster. What you have installed gets you to 4.8, according to your post. Since STACKING shims is a very bad idea, you want one that will get you 2 MORE degrees than the one you have. I'm betting the shim you have is either 2 or 2 1/2 degrees, so 4 is a winner.
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post #21 of 34 Old 04-20-2020, 11:41 AM
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No matter the angle, get steel shims and new u-bolts. I've had problems with aluminum shims and reused spring u-bolts. (I know lots of people have been fine with reusing them. My personal experience has been twice in the last 20 years I've had an axle u-bolt come loose and both times were on u-bolts that had been reused.)
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post #22 of 34 Old 04-21-2020, 01:29 PM
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Quote:
Originally Posted by gutthans View Post
Let's say they are 3 degrees...since the camber comes in at 4.8,
Don't confuse caster and camber. If you have 4.8 degrees of camber you have problems.
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post #23 of 34 Old 04-21-2020, 02:17 PM
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Quote:
Originally Posted by 80cj View Post
Don't confuse caster and camber. If you have 4.8 degrees of camber you have problems.
My typo...know better, was late for me, I think...
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post #24 of 34 Old 04-23-2020, 10:31 PM
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Quote:
Originally Posted by Techlight View Post
The shim was already on the spring back when I purchased them. These are ARB OME heavy duty yj springs.. I first installed them as they were from the factory and the caster was at 1.8 degrees. I called Rocky Road outfitters to talk to them and they told me to spin the shim 180 degrees and see where the caster is then. After that the caster was at 4.8 degrees.
Are both of those measurements positive caster, meaning the top of the knuckle is leaning towards the rear, relative to the centerline of the axle looking at it from the side?

The only way you could have gone from 1.8 degrees positive to 4.8 degrees positive is if the thick end of the shim was originally at the rear half of the spring pack, and it couldn't have been a very thick shim because you get 2x the machined degrees of the shim when you swap it end for end. A 1.5 degree shim is probably less than 1/2" thick at the thick end.
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post #25 of 34 Old 04-24-2020, 10:33 AM
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Quote:
Originally Posted by CSP View Post
Are both of those measurements positive caster, meaning the top of the knuckle is leaning towards the rear, relative to the centerline of the axle looking at it from the side?

The only way you could have gone from 1.8 degrees positive to 4.8 degrees positive is if the thick end of the shim was originally at the rear half of the spring pack, and it couldn't have been a very thick shim because you get 2x the machined degrees of the shim when you swap it end for end. A 1.5 degree shim is probably less than 1/2" thick at the thick end.
My OME YJ pack came with a 2 degree shim attached, like the OP's did. So, as I noted earlier...if he's getting 4.8, then he needs an additional 2 degrees. But rather than stack, he'll be best off with a single shim of the proper degree...that should be a 4 degree one based on his explanation.
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post #26 of 34 Old 04-24-2020, 08:59 PM
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I understand what he needs to do to get positive caster. What I don't understand was what the dummies at RRO suggested he do, because it's counter to what actually happens when you flip a shim around end for end. Thus the selection of the text that I selected to quote and respond to.
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post #27 of 34 Old 04-25-2020, 06:10 AM
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The OME springs that the OP bought are technically labeled *rear* YJ springs. They come with a 2 degree shim already installed to correct the rear pinion angle.

If these springs are used on the front, the pre-installed shims will be backwards, and need to be flipped 180 degrees. Even then, I found the 2 degree shims didn't provide enough castor. My numbers were almost identical to what the OP is getting, around 4.8 degrees, and my CJ still wandered and didn't return to center well. 4 degree shims put my castor to around 6.8 degrees, and now I'm very pleased with how it handles.

I hope that clears up any confusion.

Matt
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post #28 of 34 Old 04-25-2020, 11:54 AM
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Quote:
Originally Posted by Matt1981CJ7 View Post
The OME springs that the OP bought are technically labeled *rear* YJ springs. They come with a 2 degree shim already installed to correct the rear pinion angle.

If these springs are used on the front, the pre-installed shims will be backwards, and need to be flipped 180 degrees. Even then, I found the 2 degree shims didn't provide enough castor. My numbers were almost identical to what the OP is getting, around 4.8 degrees, and my CJ still wandered and didn't return to center well. 4 degree shims put my castor to around 6.8 degrees, and now I'm very pleased with how it handles.

I hope that clears up any confusion.

Matt
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post #29 of 34 Old 04-25-2020, 06:34 PM
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Perfect explanation Matt. The 1.8 he originally had must have been negative.
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post #30 of 34 Old 05-01-2020, 03:42 PM Thread Starter
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Hi All,

I appreciate all the replies and offered help. I know there have been differing opinions and I have continued to try and hunt down information.


I called Adams Driveshaft out of Nevada and spoke with their "angle" person and after I gave him my caster measurements he thought that the shim that was on there was a 1.5 degree shim and that a 3.5 degree shim would put me around 6.8 degrees, which is where I wanted the caster. After looking for a 3.5 degree steel shim I finally ended up calling Jack It, a suspension company out in Utah, and speaking with Tyler.

They were extremely helpful and said they would hunt down some info for me and see what they could come up with. He manged to contact ARB and verify that the shim that was on there when the springs shipped was a 1.5 degree shim. Unfortunately, Lift It doesn't sell a 3 degree or a 3.5 degree steel shim and locating one on the internet seems to be more difficult than it should be.

To update on some of the comments: my caster angles were all positive numbers. 1st measurement was 1.8 and after spinning shims 180 degrees it was 4.8. As one poster commented, "If you spun a shim around so that the thick end moved 180 degrees, the shim degree is half of the change in caster". So my 1.5 degree shim spun 180 degrees will give me 3 degrees caster change, which is consistent with my alignment shop measurements. It was also the consensus at Adams and Lift it. As mentioned already, Lift It confirmed the degree of shim with ARB. The poster who commented that the springs were intended for the rear is correct. They were all the OME CS036R (if I remember the number correctly).

I ended up calling Charlie out at Rocky Road Outfitters and they said they could cut me a pair of 3 degree shims and ship them out. Unfortunately, they only cut them in single degrees so i went with the 3 which should give me 6.3 degrees of caster. After I get it installed, I'll have the caster checked at my alignment shop and update from there. Hopefully, I can then relax a bit more at the wheel driving around instead of the CJ attempting to dart around, lol.

Thanks again for everyone's input. I do appreciate it.
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