Spring Arc After Shackle Upgrade?

[Howard70]

Hello:

I've just upgraded the rear shackles on our Tacoma Doublecab with Daystar 1.5" greasable units (they look fairly similar to the Downeys). The new shackles provided the expected lift but they also seem to have flattened the springs. Is this normal? I sort of expected to maintain the previous arc of the springs.

While I'd like to sneak this post through without specifying the springs I suspect someone will ask. So... the springs are stock. Not for long as we're planning new rear springs as soon as we have a better idea of weight, etc.

Thanks for any insight.

Howard L. Snell
1987 4runner
2004 Tacoma Doublecab

 

[Scott Brady]

Howard,

That is pretty common, as the leverage point has changed on the trailing end of the spring. I.E., the longer shackle has more leverage on the spring pack aft of the axle. Forward of the axle, the arc should be the same.

I noticed the same thing on my Deavers, though only slightly.

Longer shackles do have many advantages, including the lift, better articulation (due to the leverage and greater negative arc allowed). Of course they can also fatigue springs faster (negative arc), and the travel is likely limited by the shock anyways.

I guess in summary, long, thick leaf packs on top of the axle with minimal arc and a longer shackle is just about the best performing leaf configuration.

 

[Ursidae69]

Hey Howard, glad you made it to the forum. :victory:

 

[seth_js]

Make sure the aren't going to far into negative arch on compression now. If they are, run a longer bumpstop. Also re-measure your shock lengths.

 

[BogusBlake]

I guess in summary, long, thick leaf packs on top of the axle with minimal arc and a longer shackle is just about the best performing leaf configuration.

I second that.
Also, a longer shackle will help with droop because the end of the shackle will travel a longer arc for the same angular movement than a shorter shackle.
If you're worried about it, fix your shackle angle by moving the upper mount forward a little. Marlin and Trailgear both sell upper shackle hangers that can easilly be welded on after cutting the stock ones off. Do that after you get your new springs though :sombrero:

 

[Howard70]

Thanks!

Hey -

Thanks for all the input. It turns out that I redid the install today. Last night I wasn't convinced that I could get the large metal bushings that surround the rubber bushings out of the spring eyes. Leaving those in meant that the new bushings provided with the shackles wouldn't fit and the shackles wouldn't accept stock metal inserts inside the stock rubber bushings.

Thus I spent way too much time trimming down a set of bushings left over from a rear spring project on the 4runner until they I could press them into the metal bushings in the spring eyes. Of course, once I pressed them in the diameter of the bolt how was reduced by the squeeze and the bolts could only be inserted with a lot of pressure. So when the whole thing was done, the shackles didn't articulate well and I think that contributed to the more-than-expected deformation of the spring.

This morning we removed the shackles from the springs and used a combination of hammers, chisels, and gear pullers to remove the metal bushings. Once we used the set of bushings provided with the shackles, the shackles moved more freely and aritculation seems better.

The Tacoma now has 2" lift in front provided by mounting Tundra springs and about 1 inch in the rear from the shackles. Today we also mounted the Bilstein 5100's in the rear, added a longer brake line, bleed the brake lines, modifieid the spare tire braces to accept a larger spare, and put the 255/85/16 BFG Mud Terrains on. Tomorrow is alignment day!

Thanks again,

Howard Snell