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Old February 22nd, 2018, 10:43
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rockclimber rockclimber is offline
Join Date: Sep 2009
Location: San Diego
Posts: 5,073
Re: cav fab alpha 3 link, pics of install and any issues please?

Originally Posted by VAhasnoWAVES View Post
a 7/16" grade 8 bolt has a shear strength of over 13k pounds.
in a 4000lb rig traveling 50 mph how much force does a hard breaking event incurr on the upper?

IMO 7/16" is too small for a single upper.
I run 9/16" F-911s in my upper on my 3 link, which may be overkill, but the comfort factor is worth it.

and FWIW link bolts should only be loaded in tension, not in shear, ... but thats in a perfect world.

on a properly designed 3 link, there should be no fore/aft loading on the upper from terrain input. the lowers control the fore/aft location, thats why you need 2. all the upper is doing is controlling forces on the moment arm created by the upper link tower off the axle. as torque is applied, the pinion is driven down. under braking, the pinion is driven up. the upper lives in a state of tension and compression.
The only way to make that statement true would be to mount the lowers on the centerline of the axletube.

you cannot do that so the upper will always share some of the load of controlling the axle fore/aft. certainly the lowers see much larger forces in this regard because they are usually mounted closer to the centerline than the upper.

if either of the lowers fail on a 3 link, the system fails. bad things are going to happen if you lose one, regardless of placement of the upper link. even with a second upper link, the role of the upper links are is not the same as the lowers. can you maybe limp it back to the pits? sure. but if you continue to apply the same abuse that destroyed the lower, the uppers will surely fail. and lets be honest, very few people are pushing their cherokee that hard.
agreed 100%
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