The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > General Truck Forums > Suspension

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 06-14-2014, 01:32 AM   #1
siggyfreud
Registered User
 
siggyfreud's Avatar
 
Join Date: Jun 2012
Location: Portland
Posts: 1,330
How do lowering shackles work?

Might be a dumb question, but how do lowering shackles work? It's been awhile since I had my leafs together it's hard to envision how they operate. Do they just let one side of the leaf swing up higher? When ordering them, so I just need one pair, or a pair for the front and back?

When I took my rear apart everything was so rusted together I plasma'd a lot of the shackles and parts to get it apart, and now I'm trying to figure out what I need to get it all back together.
siggyfreud is offline   Reply With Quote
Old 06-14-2014, 01:39 AM   #2
Captainfab
60-66 Nut

 
Join Date: Mar 2007
Location: Coeur d'Alene, Idaho
Posts: 23,252
Re: How do lowering shackles work?

You only need one pair since there are only shackles at the rear of the springs. The longer shackles when mounted in tension will lower the body of the truck by aprox 1/2 of the increased length of the shackle. IE: a 2" longer shackle will lower the rear aprox 1".
__________________
Power Steering Box Adapter Plates For Sale HERE
Power Brake Booster Adapter Brackets For Sale '63-'66 HERE and '67-'72 HERE and '60-'62 HERE and "60-'62 with clutch HERE
Rear Disc Brake Brackets For Sale. Impala SS calipers HERE Camaro Calipers HERE D52 Calipers HERE 6 Lug HERE
Hydroboost Mounting Plates HERE

Last edited by Captainfab; 06-14-2014 at 01:57 AM.
Captainfab is offline   Reply With Quote
Old 06-14-2014, 01:45 AM   #3
markeb01
Senior Enthusiast
 
markeb01's Avatar
 
Join Date: Feb 2007
Location: Spokane Valley, WA
Posts: 8,356
Re: How do lowering shackles work?

Typically leaf springs are mounted on a solid pivot on one end, the other end has a shackle mount. The purpose of the shackle is to allow the spring to grow or shrink in length when encountering bumps or holes in the road surface. If both ends were mounted solid, a leaf spring could not move up and down.

Lowering or raising shackles use the same principle, depending on whether the eye of the spring is mounted above or below the other end of the shackle. If the spring eye is below the bracket (like early Camaros, etc) installing long shackles will jack the rear end way up in the air. This was very popular back in the 70's to fit tires on the rear that were too big for the car.

If the spring eye is above the bracket, adding long shackles will drop the rear end of the vehicle (by raising the end of the spring up closer to the chassis). The problem with long lowering or raising shackles (in addition to clearance issues), is they often adversely affect handling because the rear end is allowed to sway back and forth on the shackle plates, effectively steering the vehicle undesirably.
__________________
My Build Thread: http://67-72chevytrucks.com/vboard/s...d.php?t=444502
markeb01 is offline   Reply With Quote
Old 06-14-2014, 02:16 AM   #4
siggyfreud
Registered User
 
siggyfreud's Avatar
 
Join Date: Jun 2012
Location: Portland
Posts: 1,330
Re: How do lowering shackles work?

Great info, thanks guys!

So Mark, based on what you said would it be advisable to do drop leafs as opposed to longer shackles in regards to keeping the handling solid? Leafs are about 6-7x the price as shackles, but if it's the right way to do it then . . .
siggyfreud is offline   Reply With Quote
Old 06-14-2014, 02:21 AM   #5
markeb01
Senior Enthusiast
 
markeb01's Avatar
 
Join Date: Feb 2007
Location: Spokane Valley, WA
Posts: 8,356
Re: How do lowering shackles work?

Depending on how you use the truck, you might get the same result by just removing a couple of leaves. I did that on my 46 Ford front spring to arrive at the ride height I wanted.

And you don't necessarily need to get new springs either. Older spring shops can re-arch (or flatten) your existing springs for a lot less than the cost of new ones. It's been many years since I needed those services, but it was easy and cheap compared to new springs.

Personally I'm not a fan of long shackles for the reasons noted earlier.
__________________
My Build Thread: http://67-72chevytrucks.com/vboard/s...d.php?t=444502
markeb01 is offline   Reply With Quote
Old 06-14-2014, 11:30 PM   #6
Captainfab
60-66 Nut

 
Join Date: Mar 2007
Location: Coeur d'Alene, Idaho
Posts: 23,252
Re: How do lowering shackles work?

Keep in mind that removing leafs to lower the ride height will result in a softer spring that will be more susceptible to spring wrap.
__________________
Power Steering Box Adapter Plates For Sale HERE
Power Brake Booster Adapter Brackets For Sale '63-'66 HERE and '67-'72 HERE and '60-'62 HERE and "60-'62 with clutch HERE
Rear Disc Brake Brackets For Sale. Impala SS calipers HERE Camaro Calipers HERE D52 Calipers HERE 6 Lug HERE
Hydroboost Mounting Plates HERE

Last edited by Captainfab; 06-14-2014 at 11:36 PM.
Captainfab is offline   Reply With Quote
Old 06-16-2014, 08:56 AM   #7
fleetsidelarry
Senior Car Nut
 
fleetsidelarry's Avatar
 
Join Date: Jan 2008
Location: shellman bluff, GA
Posts: 1,411
Re: How do lowering shackles work?

siggy, have you thought about blocks, i.e. lowering blocks? a 2" block will give you a 2" drop. you can even use a combination of blocks and longer shackles. and an anti-sway bar will help with handling
__________________
Larry
fleetsidelarry is offline   Reply With Quote
Old 06-16-2014, 09:54 AM   #8
siggyfreud
Registered User
 
siggyfreud's Avatar
 
Join Date: Jun 2012
Location: Portland
Posts: 1,330
Re: How do lowering shackles work?

Thought about it, but I've also read it can lead to bad wrap/hop. It sounds like the best way is going to be lowering springs. I'll probably load it up with the old springs, see how I like the overall height, and then adjust accordingly.
siggyfreud is offline   Reply With Quote
Old 06-16-2014, 05:40 PM   #9
SCOTI
Registered User
 
SCOTI's Avatar
 
Join Date: Apr 2001
Location: DALLAS,TX
Posts: 22,066
Re: How do lowering shackles work?

Quote:
Originally Posted by fleetsidelarry View Post
siggy, have you thought about blocks, i.e. lowering blocks? a 2" block will give you a 2" drop. you can even use a combination of blocks and longer shackles. and an anti-sway bar will help with handling
Blocks only work if the rear end is flipped vs OE truck position (housing under the leafs). How much drop is desired here?
__________________
67SWB-B.B.RetroRod
64SWB-Recycle
89CCDually-Driver/Tow Truck
99CCSWB Driver
All Fleetsides
@rattlecankustoms in IG

Building a small, high rpm engine with the perfect bore, stroke and rod ratio is very impressive.
It's like a highly skilled Morrocan sword fighter with a Damascus Steel Scimitar.....

Cubic inches is like Indiana Jones with a cheap pistol.
SCOTI is offline   Reply With Quote
Old 06-16-2014, 09:57 PM   #10
fleetsidelarry
Senior Car Nut
 
fleetsidelarry's Avatar
 
Join Date: Jan 2008
Location: shellman bluff, GA
Posts: 1,411
Re: How do lowering shackles work?

I was thinking the housing was above the spring on these older trucks.
__________________
Larry

Last edited by fleetsidelarry; 06-16-2014 at 10:19 PM.
fleetsidelarry is offline   Reply With Quote
Reply

Bookmarks


Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 11:56 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright 1997-2022 67-72chevytrucks.com