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How much travel can you get out of a leaf sprung suspension?
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How much travel can you get out of a leaf sprung suspension?
Hey guys Im a fabricator from southern MI. Im planning on starting another project. A solid axle swap in a '95 chevy 3/4 ton. I picked up a dana 44 for $20 from a buddy of mine that Im going to stuff under my truck. Although I am a fabricator I am not an engineer and doing a multi link coil over might be biting off more than I can chew for my first project. So I opted for a leaf spring setup. I was just curious how much wheel travel can be obtained, and how to go about getting the most. Its mainly a work truck but I do like to play a little too. Im not talking about Moab but it would be nice to cross a narrow ditch without teetering on opposite corners. Any tips are appreciated. Happy four wheeling
Generally the longer the spring the more travel you'll get.
My Suzuki (Samurai) has 43" long leaf springs and it gets almost 12" travel.
If you get a third of the length of the spring in travel you are doing well.
Shackle angle has a lot to do with the travel you'll get.
At rest you want the shackle to lay over at 50-45 degrees from horizontal, this will allow the spring to droop.
To gain angle on the shackle you can fit a slightly longer spring or move the chassis mounted shackle perch.
To make use of the extra travel you will need suitably longer shock absorbers with raised upper mounts and possibly bumpstop extensions as well.
My Suzuki (Samurai) has 43" long leaf springs and it gets almost 12" travel.
If you get a third of the length of the spring in travel you are doing well.
Shackle angle has a lot to do with the travel you'll get.
At rest you want the shackle to lay over at 50-45 degrees from horizontal, this will allow the spring to droop.
To gain angle on the shackle you can fit a slightly longer spring or move the chassis mounted shackle perch.
To make use of the extra travel you will need suitably longer shock absorbers with raised upper mounts and possibly bumpstop extensions as well.
cant add much more than what want33s has said, hes pretty much hit the nail on the head.
Another thing to consider is weight distribution, to get optimal flex it is good to have a bit of weight over the rear to force the leaves to work.
This is my leaf sprung cruiser. The suspension on it is nothing special, spring over conversion as it was sprung under originally and parabolic springs.
The potential for more flex than this is great, more weight in the rear and some nice longer springs.
Another thing to consider is weight distribution, to get optimal flex it is good to have a bit of weight over the rear to force the leaves to work.
This is my leaf sprung cruiser. The suspension on it is nothing special, spring over conversion as it was sprung under originally and parabolic springs.
The potential for more flex than this is great, more weight in the rear and some nice longer springs.
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Anything is possible at this point. Im working with a blank canvas, since the front clip needs replaced anyway Im taking it off for the conversion. I have a good one sitting in the barn waiting to be put on. I know what your saying about the shackle angle. With a rear mounted shackle I want it angled back about 50 degrees to allow maximum droop. I will be building my own shock hoops after I get the axle and springs mocked up but how do I determine how tall to build them? Lets say I get shocks that have 14" of travel that are 35 1/2 " extended and 21 1/2" compressed. Where do I want it at ride height? Do I want about 9" of droop with 5" of compression. 10" and 4", 7" and 7", etc. I have no idea at this point without actually compressing the spring untill the shackle hits the frame but thats months down the road. I havent even cleaned the garage yet to get my truck in there. 
another thing to add: I can ( and probably will) build my own shackles. A bit more travel can be obtained with a longer shackle but how long is too long? Obviously I can see some binding and twisting issues with the axle if the shackles are too long but how about 8" center to center is that too long? Or am I just thinking about this all wrong?
If wouldn't go any more than 50% longer shackle as the extra leverage on the top bushes will see the shackle bolts chew the bushes out VERY quickly and without a panhard rod you won't have any lateral stabilty.badbowtie wrote: A bit more travel can be obtained with a longer shackle but how long is too long?
My ZOOK.
I run the same springs on all four corners so my flex is same at both ends and you'll note the angle the body is laying over is approx half the front axle angle compared to the back....
This makes for a very stable and predictable ride.
Last edited by want33s on Tue Jan 26, 2010 9:59 pm, edited 1 time in total.
I knew u were going to reply like this,steel wrote:Z()LTAN wrote:uugh a flexy linked suspension setup will be much worse on the road lol
Yeah thats why every off-road racer, trophy truck, corr truck, rally raid and outback challenge style winch truck is running leaves.
C'mon man, i know you run leaves, but you have to admit theit limitations.
I think youll find every (decent) racer with linked suspension will run some serious torsional style sway bar system.
My point being, a "flexy" (as you put it) linked suspension system alone will not drive well on the road.
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Nah mate,, that's the beauty of a linked suspension, if the geometry is set up well, then things like excessive roll can be accounted for.
A well set-up link suspension will deal with alot of the vehicle dynamics, and leave the springs (whatever they may be,, even leaves) to control the ride.
Leaf springs have their place, but they are a bit 1880's.
Cheers Jason
A well set-up link suspension will deal with alot of the vehicle dynamics, and leave the springs (whatever they may be,, even leaves) to control the ride.
Leaf springs have their place, but they are a bit 1880's.
Cheers Jason
1880s or not, leaf springs are way cheaper, and yeah they may not have the flex of a coil over setup but I did mention that I WASNT taking my truck to Moab. This is a daily driver, a wood hauler, and a plow truck, which brings me to my next question. How well do those "slinkys" support the weight of a snow blade?
we dont do much in the way of snow blades in Aus .. plenty getting about with a decent bull bar and winch though.badbowtie wrote:1880s or not, leaf springs are way cheaper, and yeah they may not have the flex of a coil over setup but I did mention that I WASNT taking my truck to Moab. This is a daily driver, a wood hauler, and a plow truck, which brings me to my next question. How well do those "slinkys" support the weight of a snow blade?
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Hey mate, when you say slinkys, i guess you mean coils?, if so then, no they are not ideal for carrying weight like that ( although they could be made to work), but then a flexy leaf set up probably would'nt handle the weight either.
Sounds like you want a liked front end using airbags, would give you a set up that'd work reasonably well at both load carrying and articulation.
Does'nt have to be super $y if you scrounge some truck wreckers.
Having said all that, a well set up leaf spring suspension is probably the best option for a "work" truck like yours.
Sounds like you want a liked front end using airbags, would give you a set up that'd work reasonably well at both load carrying and articulation.
Does'nt have to be super $y if you scrounge some truck wreckers.
Having said all that, a well set up leaf spring suspension is probably the best option for a "work" truck like yours.
There's some issues here that need clearing up.
Travel refers to vertical axle movement. That's not the same as articulation. Articulation is diagonal axle movement, as in flex. It's possible to build suspension with very little travel and plenty of articulation. That depends on track width, spring spacing from the axle centreline and bumpstop location.
How much compression travel you "should" run is dependent on the range of load you carry and speed you want to travel offroad. Obviously, more compression equals a taller car and that compromises stability. Personally, I'd aim for about 70% droop 30% compression, but I like low cars.
Coil springs and flexy link suspensions can't carry load? Seen a unimog?
Any spring and any link configuration can be engineered for its application. The problem is when a wide range of applications is required. Take trophy trucks. In the late 80's, it wasn't unusual for these to be leaf sprung with massive 1/4 elliptic packs. In that application, there's some advantages to leaves set up that way, but they were a packaging nightmare. Trophy trucks are very very heavy, have massive travel, and absorb enormous loads, however, the load change from dry to fully fuelled is about 10%.... or like putting 180Kg in a hilux. That's easy to design a suspension for- any suspension- leaf, coil- whatever.
saying a flexy suspension can't handle, or that somehow controlling roll stiffness with a sway bar is invalid is missing the point. Suspension (should) be designed for it's application. Trophy trucks roll about like a boat at sea on tarmac because they aren't designed for a surface with that much traction, but get the design parameters right and it can be sweet - a range rover, in orginal, 205 tyred, non-swaybar form actually handles quite well on road for the amount of traction it has add tyre though, and they get ugly.
It all comes down to the design. Leaves have a number of advantages for heavy load carrying and a large load range. They are also self damping, and the self damping effect increases with payload (unlike coil cars) That's why the Boge hydromat was used on the Range rover - to support load without adding spring rate.
The big problem with getting big flex out of leaves is that the (normally) also locate the axle. The spring rate that allows good droop and a soft ride isn't normally enough rate to prevent massive axlewrap or braking windup. It certainly isn't going to support a large change in weight/load like a plow. We run our suzukis with as few as three leaves in the front, but boy, those springs wind up nothing on earth.
Leaves need weight on them to flex? That just means you have too much spring rate.
Badbowtie - there's some very good tech on Pirate4X4about getting chevy trucks to flex - they seem to flex very well. It really comes down to the longest leaves you can run and then pulling leaves out of the packs until you get the ride/height/load carrying capacity you require.
Steve.
Travel refers to vertical axle movement. That's not the same as articulation. Articulation is diagonal axle movement, as in flex. It's possible to build suspension with very little travel and plenty of articulation. That depends on track width, spring spacing from the axle centreline and bumpstop location.
How much compression travel you "should" run is dependent on the range of load you carry and speed you want to travel offroad. Obviously, more compression equals a taller car and that compromises stability. Personally, I'd aim for about 70% droop 30% compression, but I like low cars.
Coil springs and flexy link suspensions can't carry load? Seen a unimog?
Any spring and any link configuration can be engineered for its application. The problem is when a wide range of applications is required. Take trophy trucks. In the late 80's, it wasn't unusual for these to be leaf sprung with massive 1/4 elliptic packs. In that application, there's some advantages to leaves set up that way, but they were a packaging nightmare. Trophy trucks are very very heavy, have massive travel, and absorb enormous loads, however, the load change from dry to fully fuelled is about 10%.... or like putting 180Kg in a hilux. That's easy to design a suspension for- any suspension- leaf, coil- whatever.
saying a flexy suspension can't handle, or that somehow controlling roll stiffness with a sway bar is invalid is missing the point. Suspension (should) be designed for it's application. Trophy trucks roll about like a boat at sea on tarmac because they aren't designed for a surface with that much traction, but get the design parameters right and it can be sweet - a range rover, in orginal, 205 tyred, non-swaybar form actually handles quite well on road for the amount of traction it has add tyre though, and they get ugly.
It all comes down to the design. Leaves have a number of advantages for heavy load carrying and a large load range. They are also self damping, and the self damping effect increases with payload (unlike coil cars) That's why the Boge hydromat was used on the Range rover - to support load without adding spring rate.
The big problem with getting big flex out of leaves is that the (normally) also locate the axle. The spring rate that allows good droop and a soft ride isn't normally enough rate to prevent massive axlewrap or braking windup. It certainly isn't going to support a large change in weight/load like a plow. We run our suzukis with as few as three leaves in the front, but boy, those springs wind up nothing on earth.
Leaves need weight on them to flex? That just means you have too much spring rate.
Badbowtie - there's some very good tech on Pirate4X4about getting chevy trucks to flex - they seem to flex very well. It really comes down to the longest leaves you can run and then pulling leaves out of the packs until you get the ride/height/load carrying capacity you require.
Steve.
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