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Measuring LCAs with flex joints and bends?

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Old 08-07-2017, 09:32 AM
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Just to expand on what Keeper10 and Jedg have already explained…..

When starting out I thought the whole caster/pinion angle was very confusing. I’d always read comments like this and it just didn’t set in. I found this picture to be the most helpful…and thinking about it in these terms (which, again have already been stated).



If your pinion angle was flat (0*), or parallel to the ground, then your caster is 6* because that is what is built in to your factory axle. For every degree you raise your pinion, caster is subsequently LOWERED by the same amount. Raise pinion 1*, and caster is now 5* (6* - 1* = 5*), and so on and so forth. I, like Keeper10, place an angle finder either on top of or below the pinion flange. If you have the factory flange, it offers a nice flat surface for the magnet to grab. The angle you read there is the pinion angle, and you then calculate the caster from that. If you are reading 3* pinion angle, then you subsequently have 3* caster. The caveat to this method is that you have to account for any slope in the surface the jeep is sitting on. If the surface has a 1* slope, you’ll obviously have to factor that in to the calculation when reading the pinion angle.

Also as pointed out by Keeper10, the eyelet on that joint is going to be misaligned when mounted. The eyelet on the axle side should be parallel with the eyelet on the frame side, and that is how you should measure it. That should make that process easier….and I suspect get you very close to where you should be. Or, do as Keeper10 suggest and just put angle finder on the pinion, with the help of a jack lift the pinion right to where you want it, test fit one of the arms to match. Then use that arm to make the other the same length. Install, done. The one problem with this is you can be only so exact with that cheap angle finder…..it’s def no precision machine, but gets you close. I’ve never had an issue using this method.

That rehashed a lot of previous info….but sometimes the pic helps in thinking about it. Maybe it helps someone in the future.
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Old 08-07-2017, 11:17 AM
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Originally Posted by resharp001 View Post
Just to expand on what Keeper10 and Jedg have already explained…..

When starting out I thought the whole caster/pinion angle was very confusing. I’d always read comments like this and it just didn’t set in. I found this picture to be the most helpful…and thinking about it in these terms (which, again have already been stated).



If your pinion angle was flat (0*), or parallel to the ground, then your caster is 6* because that is what is built in to your factory axle. For every degree you raise your pinion, caster is subsequently LOWERED by the same amount. Raise pinion 1*, and caster is now 5* (6* - 1* = 5*), and so on and so forth. I, like Keeper10, place an angle finder either on top of or below the pinion flange. If you have the factory flange, it offers a nice flat surface for the magnet to grab. The angle you read there is the pinion angle, and you then calculate the caster from that. If you are reading 3* pinion angle, then you subsequently have 3* caster. The caveat to this method is that you have to account for any slope in the surface the jeep is sitting on. If the surface has a 1* slope, you’ll obviously have to factor that in to the calculation when reading the pinion angle.

Also as pointed out by Keeper10, the eyelet on that joint is going to be misaligned when mounted. The eyelet on the axle side should be parallel with the eyelet on the frame side, and that is how you should measure it. That should make that process easier….and I suspect get you very close to where you should be. Or, do as Keeper10 suggest and just put angle finder on the pinion, with the help of a jack lift the pinion right to where you want it, test fit one of the arms to match. Then use that arm to make the other the same length. Install, done. The one problem with this is you can be only so exact with that cheap angle finder…..it’s def no precision machine, but gets you close. I’ve never had an issue using this method.

That rehashed a lot of previous info….but sometimes the pic helps in thinking about it. Maybe it helps someone in the future.
Now that is what I needed to see!!!

I understood that pinion angle + caster=6* What I didn't understand was 6* measured from what points and how to measure it, and what tool to use, to perform the measurement. That diagram is extremely helpful to clear that up. Now what tool do I need to buy?
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Old 08-07-2017, 11:30 AM
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Originally Posted by Rednroll View Post
Now what tool do I need to buy?
I just use a cheap angle finder similar to this:

https://www.amazon.com/Johnson-Level...s=angle+finder

Lowes/Home Depot should have em readily available. Sometimes it's a little difficult to read those cuz honestly....you're reading like 2* or so angle with it....all the while lying under the jeep trying to pinpoint a thin needle between narrow hashes on the dial. Again.....definitely not some computer calibrated laser, but gets you pretty close. Caster isn’t an exact science…..you just want to be in an acceptable range. After that it’s just kinda trial and error if you want to continue trying to dial in the best specs.

It becomes a little trickier if you don't have that factory pinion flange. In those situations you have to determine a good place to measure from.
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Old 08-07-2017, 02:32 PM
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Originally Posted by resharp001 View Post
I just use a cheap angle finder similar to this:

https://www.amazon.com/Johnson-Level...s=angle+finder

Lowes/Home Depot should have em readily available. Sometimes it's a little difficult to read those cuz honestly....you're reading like 2* or so angle with it....all the while lying under the jeep trying to pinpoint a thin needle between narrow hashes on the dial. Again.....definitely not some computer calibrated laser, but gets you pretty close. Caster isn’t an exact science…..you just want to be in an acceptable range. After that it’s just kinda trial and error if you want to continue trying to dial in the best specs.

It becomes a little trickier if you don't have that factory pinion flange. In those situations you have to determine a good place to measure from.
Perfect!!! I wish I understood and knew how to do this before pulling one of my lower arms off. That way I could have compared my measurements to the alignment shop.
Now that I understand what I need, and how to use it, I think I'm going to pay a visit to Harbor Freight. This digital one they have, seems like it will work perfect for this where I won't have to strain my eyes trying to read that needle where 6 degrees of measurement are all scrunched up into one area on the dial, and it looks a little smaller to fit in tight spaces.

Unless I'm mistaken, I'm also thinking this digital gauge might allow me to take any drive way slope variable out of the equation. Just thinking because it has a 0* calibration, that I could set it on top of one of my frame rails, calibrate that as being 0*, then take the pinion angle measurement.

It's $35, throw on one of their 20% off coupons, puts it at $28.
https://www.harborfreight.com/digita...uge-95998.html



Thanks for all your help resharp001. Like they say, pictures are worth a 1000 words and without the pictures of the tool and reference angle measurements, I'ld probably still be here scratching my head reading through posts trying to figure out how to take my own measurements, and trying to use a protractor or something like that.

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Old 08-07-2017, 03:05 PM
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And now that I understand what I'm looking for......it's time for another very educational video from my favorite Pabst Boys.


https://www.youtube.com/watch?v=t76BVhtBMnE
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Old 08-07-2017, 03:13 PM
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Originally Posted by Rednroll View Post
Thanks for all your help resharp001. Like they say, pictures are worth a 1000 words and without the pictures of the tool and reference angle measurements, I'ld probably still be here scratching my head reading through posts trying to figure out how to take my own measurements, and trying to use a protractor or something like that.
LOL. For sure. I'm visual as well....Weird how something that is rather simple can be pretty confusing when just reading. The digital is def the way to go. Had I thought about it much I would have opted to pay more for that myself.
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Old 08-07-2017, 03:31 PM
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You can also drop the DS at the pinion flange. Remove the 4 bolts, easy. Then put the angle right on the flange.
You can also use either of the two flat spots on the front of the axle housing. Nothing is exact so it's important to have the alignment checked. Then as previously mentioned you will know the difference (driveway vs Alignment rack)
So if you have pinion set to 2° but caster is 3° (like mine was), simply raise pinion to 3° or 4° to put you into stock range.
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Old 08-07-2017, 03:41 PM
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Originally Posted by Rednroll View Post
And now that I understand what I'm looking for......it's time for another very educational video from my favorite Pabst Boys. YouTube Link: https://www.youtube.com/watch?v=t76BVhtBMnE
Omg perfect video lol

A bike fork is usually the best way to explain caster. Usually its "imagine the fork straight up and down" .... paints a decent picture. But to actually see it done .. bravo.
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Old 08-07-2017, 03:54 PM
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Originally Posted by kjeeper10 View Post
Omg perfect video lol

A bike fork is usually the best way to explain caster. Usually its "imagine the fork straight up and down" .... paints a decent picture. But to actually see it done .. bravo.
I love those guys!!! Humorous and very informative!! I 1st ran across one of their videos trying to understand the need for a oil catch can on our JKs after reading about catch cans in the Mishimoto discussion thread. Mishimoto confused the heck out of me, where these guys gave me everything I needed to know in their hilarious video.

Blooooooooooooooow BYE!!!

https://www.youtube.com/watch?v=BmK3C0SuAjQ
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Old 08-07-2017, 04:01 PM
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Originally Posted by Rednroll View Post
And now that I understand what I'm looking for......it's time for another very educational video from my favorite Pabst Boys.


https://www.youtube.com/watch?v=t76BVhtBMnE
That's always a funny series of vids. The bike experiment really puts caster in to perspective. Honestly, caster has the to be the #1 misunderstood item when it comes to lifts, yet one of the most important concepts.
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