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Suspension Lift Basics

DebosDave'72

Bronco Guru
Joined
Nov 8, 2005
Messages
1,020
Loc.
Bozeman, MT
Basically in a suspenion lift you are increasing the distance between the axles and the frame of the vehicle. This allows for more articulation of the axles, and will allow room for bigger tires, which will give you greater ground clearance.

To understand the basics of a suspension lift, we need to look at all the parts involved. We need to look at how the axles are connected to the frame, and what we can do to increase the distance between them.

Front Suspension:

On the stock bronco the axle is attached at several places:
- Radius arms
- Coils
- Tracking bar
- Pitman arm
- Shocks
- Drive Line

The Radius Arms attach to the frame rear of the front axles, and to the axle via a "c-bushing" to wedges on the front axle.

The Coils are retained in cups attached to the axle and the frame

The Tracking bar connects to the passenger side of the axle, and to the frame on the drivers side.

The pitman arm attaches the steering via the drag link to the steering box.

The shocks attach to the radius arm and to the frame.

The front driveline connects to the front axle at the pinion and to the frame through the transfercase.

Rear Suspension:

There are only a couple things holding the axle to the frame in the rear:
- Leaf Springs
- Shocks
- Drive Line

The Leafs Springs are attached to one spot on the axle and two spots on the frame at each side.

The rear shocks are attached to the axle and the frame at one spot each for both sides.

The rear driveline is attached to the axle at the pinion and to the frame through the transfercase.

To address these components, there are the following options:

Coils - These are available in progressive rate, and linear rate, and available in various sizes according to the lift you are after (ie. 2-2 1/2", 3.5", 5.5").

- Linear - Coils are spaced evenly through the range of the spring. This provides a fairly consistent spring rate throughout the full travel of the spring.

- Progressive - Coils are wound tighter at the top of the spring. The result is that on compression the springs progressively get more stiff. On extension the opposite occurs. (The more they are extended the softer they become)

Radius Arms - There are extended radius arms available which help with articulation, and can be used from stock to any lift you can imagine. What needs to be addressed in a basic suspension lift is the "c-bushing" that is sandwiched between the axle and the radius arm. These come in different degrees to match the new angle of the radius arm to the frame.

Tracking Bar - There is a drop bracket available as well as an adjustable trac bar. The drop bracket will help retain the factory geometry for lifts 3.5" or more. The adjustable trac bar will help center the front axle under the frame. This has been used on lifts as small as 2", but generally speaking is only necessary on larger lifts. Also, the adjustable trac bar and the drop bracket are usually used in conjunction with each other.

Pitman Arm - The stock pitman arm is good for a lift of 2.5" after that, you need to look at a drop pitman arm. This will compensate for the lift, and keep the drag link in the proper geometry for steering.

Shocks - These need to be matched to your lift. They have variable rates of travel, but the stock shocks won't work for a lift over 2.5", and even then are pushing it.

Leaf Springs - The distance here can be increased by adding a block under the stock leafs, adding an add-a-leaf, or by completely replacing the leaf pack with a built in lift.

Drive Lines - The drivelines may need to be changed to offer more articulation. They are available in longer lengths and with longer splines to allow the driveline to articulate. The stock drivelines should not be an issue until getting into lifts of greater than 3.5"

There are various systems or kits available through the major bronco vendors, and there are many more custom options out there. Good luck with your lift, and I hope this helps your understanding!

If you have anything to add to this FAQ please respond below:
 
Last edited:

broncorican

Jr. Member
Joined
Jul 19, 2006
Messages
84
Loc.
Caguas, Puerto Rico
Hi Newbie question. My 74 has a 2.5" suspension lift. I recently installed an adjustable Trac Bar to align the axle under the body. How do I know it's correctly aligned? Does the Trac bar adjustment make a difference in the wheel alignment? I was told that the Trac bar would have an affect on my alignment since the Trac bar is connected to the chasi, which if not properly aligned would cause the rear axle not to be aligned with the front. I'm making any sense? Thanks!
Ed
 

Skiddy

Contributor
Bronco Guru
Joined
Oct 8, 2003
Messages
11,542
broncorican said:
Hi Newbie question. My 74 has a 2.5" suspension lift. I recently installed an adjustable Trac Bar to align the axle under the body. How do I know it's correctly aligned? Does the Trac bar adjustment make a difference in the wheel alignment? I was told that the Trac bar would have an affect on my alignment since the Trac bar is connected to the chasi, which if not properly aligned would cause the rear axle not to be aligned with the front. I'm making any sense? Thanks!
Ed
The trac bar will only affect the centering of the axle and nothing else. Just get it centered and should be good to go.
 

airman

Contributor
Bronco Guru
Joined
Nov 26, 2003
Messages
1,834
When centering mine I use the get it close method at first.

Shorten or lengthen the trac bar and attach so that the frame rails are evenly spaced between the c-cap ends of your radius arms. Stand back and squint your eyes a bit. Get it close. On your test drive (15-20 mph) hit the brakes hard with the wheels straight. Repeat a few times. If you pull one way that side has less axle sticking out (its been a while but I think thats right?). Adjust accordingly. May take a few tries. Just make sure you don't go fast until it is right or you may be suprised when you stop.

Ed, I think it may even be a good idea for you to feel what wrong feels like once to help you understand.

Skiddy can add to that or clean it up much better than me I'm sure. I would not be offended it it was deleted either. Not trying to steal. I think you did a great job.
 

broncorican

Jr. Member
Joined
Jul 19, 2006
Messages
84
Loc.
Caguas, Puerto Rico
airman, thanks for the input. I plan to try that as soon as I replace my break cylinder on the left side which was leaking. It's funny, but prior to installing the adjustable Trac bar, the front end was off to the right several inches. Remind you that it was lifted 2.5" without trac bar or drop bracked. It stopped okay when hitting the brakes. I replaced the Trac bar, re-sealed the power steering box and now a new problem. Again, it may be all related to a bad cylinder, I hope, lets see what happens. Thanks!
 

ace1204

Jr. Member
Joined
Apr 13, 2010
Messages
78
Loc.
Atlanta
Im looking at buying a bronco with a duff 3.5" suspension lift and 33's but the owner says it needs drop radius arm mounts to keep it from swaying as it does now when it drives. Does that sound correct?
 

NAK

Jr. Member
Joined
Jul 22, 2006
Messages
125
have the caster checked at an allignment shop. the front radius arm bushing may be worn or not of positive degree. you should be looking for at least +4 caster degrees if not more. i am going through the same with my bronco which has the Duff lift. if the radius arm bushing are a high degree then the next step is to drop the radius arms at frame using the brackets which is what the owner has suggested.
 

redpony

Sr. Member
Joined
Aug 9, 2004
Messages
738
Hi, I recently bought a 68 Bronco with this setup (3 1/2 ) lift. What concerns me on mine. Is that the radius arm drop brackets are only welded on one side. Not on both sides. It drives very nice! Just worried about safety. What is the right way to do this?
Thank you redpony
 

twnsig

New Member
Joined
Oct 23, 2011
Messages
2
I just took over my father's restoration and it's uncut.. I want to leave it un cut, but have a big question... can anyone tell me what are the biggest tires/wheels i can put on it and what lift size would get me there? ideally i'd like 33's
thanks for the help
 

dreg

New Member
Joined
Sep 2, 2011
Messages
17
Loc.
Winston-Salem
Is drive shaft extension required when lifting?

I purchased a 66 model with a 3.5" lift. I am now told that I should have the driveshaft extended to compensate for the increase in angle. My question is should this have been done originally? Are there any potential safety issues by continuing to use the original driveshaft?
 

MJG1094

New Member
Joined
Dec 28, 2012
Messages
3
Wandering now?

Hi, I have owned my '73 Bronco since '96. I have done a few things to it but it was a one owner truck when I bought it. I have rebuilt the 302 and the C4. I just recently installed new 2 1/2" coils and shocks on the front. My question and problem now is, before the springs and shocks, it drove very solid. I did install new trac bar bushings and a new adjustable draglink. Now the steering is better but the thing wants to wander all over the road. It's like the sterring is too sensitive if that makes sence. Am I missing something? Have I changed the camber of my front tires? How do I fix this issue?
 

Skiddy

Contributor
Bronco Guru
Joined
Oct 8, 2003
Messages
11,542
Hi, I have owned my '73 Bronco since '96. I have done a few things to it but it was a one owner truck when I bought it. I have rebuilt the 302 and the C4. I just recently installed new 2 1/2" coils and shocks on the front. My question and problem now is, before the springs and shocks, it drove very solid. I did install new trac bar bushings and a new adjustable draglink. Now the steering is better but the thing wants to wander all over the road. It's like the sterring is too sensitive if that makes sence. Am I missing something? Have I changed the camber of my front tires? How do I fix this issue?

i would check your tow in, it does cause a lot of wondering if not correct
 

MJG1094

New Member
Joined
Dec 28, 2012
Messages
3
i would check your tow in, it does cause a lot of wondering if not correct

Thanks, Now can you help me by explainng how thats done? My thoughts are that the front tires & wheels are not plumb. If thats "toe in" then I guess thats what its commonly called.Forgive me for sounding ignorant but I'm not that familiar with suspension mechanics.
 

Skiddy

Contributor
Bronco Guru
Joined
Oct 8, 2003
Messages
11,542
Thanks, Now can you help me by explainng how thats done? My thoughts are that the front tires & wheels are not plumb. If thats "toe in" then I guess thats what its commonly called.Forgive me for sounding ignorant but I'm not that familiar with suspension mechanics.

basically you want the front of wheel towed in more than the back. BC bronco's has a pretty good write up http://www.bcbroncos.com/techtips08.html
 

RCessna

New Member
Joined
Apr 27, 2013
Messages
5
Loc.
Waco
I have a 68 Half cab. The rear is sitting lower than the front, and I just want the best way to get it level and a little stiffer on the rear, for pulling my boat.
 

freshoil&pipes

New Member
Joined
Sep 24, 2013
Messages
2
Max uncut lift

I just took over my father's restoration and it's uncut.. I want to leave it un cut, but have a big question... can anyone tell me what are the biggest tires/wheels i can put on it and what lift size would get me there? ideally i'd like 33's
thanks for the help

Has there been an answer to this question and I just missed it?
 

Beresb

Newbie
Joined
Mar 9, 2020
Messages
6
Is there a way to determine the size of suspension lift already installed? I think mine has 5.5" but looking for a way to confirm for when I start to order new leafs and such.
 
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