TTORA Forum banner

1 - 20 of 292 Posts

·
Registered
Joined
·
206 Posts
Discussion Starter #1 (Edited)
So Alpha_nett and I are working on a little project but I have decided we could use some information from people who have tried different things on their trucks. Right now we only know results from what Alpha_nett has done on his truck so I would love to hear what other combinations yielded as far as performance goes.

We are attempting to nail down what exactly makes or breaks the rear leaf setup of a truck. What shackle to spring angles you can get away with as well as shackle length and separation.

So here is what I would like from you guys!!! If you have installed some long travel leafs in the back of your truck (doesn't even matter what year/kind) I would like these things:

1) Distance from front leaf eye (where it bolts to the frame) to the point where the shackle mounts to the frame. The straight line connecting them.
2) Shackle length
3) Vertical separate between the where the front eye mounts to the frame and where the shackle mounts to the frame.
4) Which spring you are using F67, 50T etc...
5) If you can Some spring dimensions: eye-eye distance when unloaded, arch when unloaded (from the imaginary line connecting the two eyes to the tallest part of the arch), eye-eye when flat.
we don't need em for the F67 and 50T since we know those already.
6) THE IMPORTANT PART!!! How does the rear of the truck work for you? The hard part here is going to be resisting the urge to say, 'works awesome!', or 'handles great!'. We need to know things like if the truck was good over small bumps (rocks), big bumps(whoops), jumps. How did adding weight to the back of the truck help or hurt? Was the rear too stiff? Too soft? Bottoms out easily? Was bouncy? etc...
7) toss in any other juicy information like info on your shocks and stuff, it all helps.
8) of course a picture!

What do you get out of this? Well you can feel good about your self for helping others out AND a pretty picture like this:

52.5 separation (eye to shackle mount)
F67
10" shackle
19" vertical separation (just a random guess!!!!)

Except it'll have your numbers in it and if you want I can change it so you can know what to expect if you are designing a new setup or changing your existing one.

Show me what you got!
 

·
Registered
Joined
·
523 Posts
Matt Helton ran F67 on his truck. His magic number between shackles to front hanger was 52.5" and he ran a 12" shackle.

http://www.myspace.com/video/dezertvideos/2006-mdr-class-1450-points-champion-matt-helton/24088743
The "Magic" part of suspension is exactly what we are aiming to destroy. Felixre7 can come back and show you the travel numbers that a 52.5" spread of frame mounts and 12" shackles will give.

Maybe limiting up travel is within the desires of Matt Helton in that he achieves a specified ride quality; however, we just don't know at this point. This infomation is precisely what we are looking to find out. It would be great if Matt Helton could expand on this. His opinion would be very helpful.

Off the top of my head, from the data we have already collected and my own truck, I can tell you that the 52.5" and 12" setup will limit up travel with the f67s. I know this from exact numbers that Felixre7 can give, and because my previous suspension was exactly the same (which I thought rode like garbage for my off road needs of chasing Score with heavier loads, mild off roading with no load, and street DDing).

That setup handled stiff and choppy on the street; sagged way too much while chasing and gave me very limited up travel so I bottomed out on even the smallest whoops; and on the street with no load in town it was too stiff. However, going fast on the highways at 80 it handled very nice and all the bumps in the road were floated across. In straight single jumps (in baja mostly) it seemed to take the compression well without a load. multiple jumps (or whoops) it did not perform to my liking.

I believe that the f67 leaf springs are of great quality and provide a progressive rate that can create a superior ride. However, to utilize what these springs have, the proper setup is needed. At this point, I am fully convinced that the 52.5" spread of frame mounts and 12" shackle is not that setup.
 

·
Registered
Joined
·
3,205 Posts
Bump. I need some education.:)
 

·
Registered
Joined
·
68 Posts
That is some great info!!! I think you are on to something here. So It looks like most of the trucks out there (including mine) have limited up travel and even negative spring arch at bump because we cant chop our frame aft the shackle? I also see that your shackel mounts have been moved up and wont fit between the bed like more common set-ups?
 

·
Registered
Joined
·
206 Posts
Discussion Starter #6 (Edited)
Matt Helton ran F67 on his truck. His magic number between shackles to front hanger was 52.5" and he ran a 12" shackle.

http://www.myspace.com/video/dezertvideos/2006-mdr-class-1450-points-champion-matt-helton/24088743
Exactly what Alpha_nett said. If you could get us some more information about the setup we could determine what made it work so well for him. It is possible the vertical separation makes the difference in that particular combination. We honestly have no idea what the ideal shackle-to-leaf angle range is or how much vertical separation affects ride quality. It does affect the travel though.

Also that picture i posted up there is with:
52.5 separation (eye to shackle mount)
F67
10" shackle
19" vertical separation (just a random guess!!!!)

compared to what most people run:
52.5 separation
F67
12" shackle
19" vertical separation (just a random guess!!!!)



Pros:
More linear spring rate, allows for a more consistent rate over the whole of the travel
Can be made to fit most trucks
Puts the rear end at the appropriate ride height to match most front LT kits

Cons:
Decreased travel


THEN we have our guy Alpha_netts setup:
52.5
F67
9" shackle
19" vertical separation

interesting fact: the spring does NOT hit the shackle mount just comes very very close

This is as far I can tell from screwing around with all the numbers this is nearly the best TRAVEL numbers that can be achieved with a spring of the same dimensions as an F67. It should also be noted i have NO idea what his vertical separation is :D i just made a random guess and optimized. You can see proof the up travel is maximized because the Horizontal wheel movement has been minimized (you convert it into up travel by angling the spring further forward) and is very close to zero.

Pros:
largest travel possible

Cons:
Progressive spring rate that gets softer as it compresses. not good for anything!
Doesn't fit in most trucks (frame cutting/bed clearance)
Rear ride height is severely cut

And just so I'm not one of the couch racers I want to hear from people's experience if some one says their truck does awesome I want to find out why. Our final test can be my truck which is soon to get some F67s in the back upon my return to the states. I'll use every ones suggestions and the math to set it up and then go do some testing! :D
 

·
Registered
Joined
·
523 Posts
That is some great info!!! I think you are on to something here. So It looks like most of the trucks out there (including mine) have limited up travel and even negative spring arch at bump because we cant chop our frame aft the shackle? I also see that your shackel mounts have been moved up and wont fit between the bed like more common set-ups?
My shackle mounts WILL fit under a stock location bed, barely:)
At full compression the shackle becomes parallel with the frame, roughly.

best pic I have, sorry.

Now, I have heard some talk about having the shackle become parallel with the frame as bad. So, that became one of the points of research. I think that idea got mixed up with the shackle becoming parallel with the datum line of the leaf, which is potentially bad/breaking some rule of physics like two things in one place at the same time or something like that.

Felixre7 is killing it with the info!

with that, I have an idea...
 

·
Registered
Joined
·
523 Posts
Terms

This list is a collection of some of the stuff Felixre7 and I have been working with. Lets make this list of terms communal. if you have something to add(or edit), PM me and I will edit the post. that way we can keep the clutter down on this thread.

Leaf Springs- Sometimes referred to as a semi-elliptical spring. The center of the arc provides location for the axle, while tie holes are provided at either end for attaching to the vehicle body. For very heavy vehicles, a leaf spring can be made from several leaves stacked on top of each other in several layers, often with progressively shorter leaves. Leaf springs can serve locating and to some extent damping as well as springing functions. While the interleaf friction provides a damping action, it is not well controlled and results in stiction in the motion of the suspension. For this reason manufacturers have experimented with mono-leaf springs. (http://en.wikipedia.org/wiki/Leaf_spring)

main leaf- the primary leaf in a pack that has the spring eyes on either end.

progressive leaf pack- leaf pack that has a progressive rate at which it compresses.

Spring Rate- in the simplest sense, is a measurement of the load required to compress the spring a given distance. In other words, it is a gauge of spring strength and flexibility. "X" amount of rate is required to support "X" amount of weight. Rate, and rate curve, is influenced by several factors including: material grade and thickness, individual leaf plate length, leaf end configuration and interleaf friction.

Arch-The free arch of a leaf spring is correctly measured by drawing a line (Datum line) through each leaf eye center and then measuring (perpendicular) from the datum line to the spring surface at the centering pin. The spring should be lying on its side in the free state whenever it is measured. When experimenting with different arches you can expect the following effects on handling. If the center is lower than the ends it is called positive arch. If the center is higher than the ends the arch is negative.

Inactive Length-The central portion of a leaf spring that is prevented from flexing by the U-plate.

Shackle- a short swinging arm. The shackle takes up the tendency of the leaf spring to elongate when compressed and thus makes for softer springiness.

spring arch- distance from the datum line to the center of the spring.

Datum line- the imaginary line between the spring eyes. the distance of the datum will change under load as the leaf flattens out.

Full Droop- maximum extension of the suspension.

Full Jounce- maximum compression of the suspension.

Ride Height- height at which the vehicle sits while supporting its own weight.

Moment Center Height- The proper way to determine the moment center height for a leaf-spring system is to measure the height of the two eyes from the ground, add them, and divide by two. This method has been proven to be true and accurate through the use of dynamic simulation software.

Travel- is when both wheels move up or down together in the same direction.

Usable Travel- the travel in which a vehicle actually has with all the limited factors in effect.

Articulation- is when both wheels move up and down in opposing directions.

Usable Articulation - the articulation in which a vehicle actually has with all the limited factors in effect.

Vertical RC- Felixre7, you gotta help me on these ones still????

Horizontal RC-
 

·
Registered
Joined
·
206 Posts
Discussion Starter #9 (Edited)
Fine I admit it i'm bored as hell in the sandbox. Here are some more scenarios:

Looks like I was WAY wrong when saying the 9" shackle gave the most travel:

49.5" separation
F67
12" shackle
16" vertical separation

Things to note about this setup:
it is going to be softer than the 9" are the beginning of the cycle because of the decreased shackle to spring angle at droop


but you can fit a 9" shackle under the frame with minimal cutting:

52.5" separation
F67
9" shackle
13" vertical separation

Things to pay attention to (other than travel):
1) The longer the shackle gets the more prone the axle is to moving left and right under corning loads. It is just inherently more unstable. This is the same when reducing the eye to shackle separation distance, that is required for longer shackles.

2) Horizontal wheel travel:
This is actually a good thing as it gives the system more 'time' to react to stuff it encounters at high speeds. It just can't get too out of control or you will start pulling drive shafts apart. Also if the axle travels straight up with NO back motion the distance between the fixed point on the drive shaft axle is going to decrease.

3) seems to be the ideal separation number (to maximize travel) for a spring with a given flat length X and shackle of length S is:
X-S= separation

4) longer shackles will give more travel, when placed in the correct location, just slapping a longer shackle on an existing setup will NOT give more travel. But don't forget point number 1. They will also decrease the shackle's angle and range of travel, see 5 for the implications.

5) Those jounce and droop angles you see in the pictures are the angles between the invisible line that connects the two eyes of the leaf and the shackle's center line. This is the tricky part. according to all sources as the shackle rotates backwards (decreasing the angle) the spring rate goes up. This is true but has a marginal effect at best. The movement of the shackle itself in our case (long travel trucks) is by FAR the dominate factor in this case and as such the systems spring rate goes DOWN as the shackle rotates rearward (decreasing angle). Also means limiting the angle the shackle sweeps is helpful as it keeps the spring rate from dropping off too much.

If you needed proof:
front facing:


rear facing like ours:


Same leaf, same load, same shackle. The 2nd one moves MUCH further. This holds true for angles closer to and further away from 90 as well (trust me i tested them out).

as a side note this is why the 05+ Tacomas have an inverted shackle it provides the opposite effect of a normal shackle. A positive progressive spring rate in the rear making for a MUCH better ride.
 

·
Registered
Joined
·
408 Posts
I'm interested in this one too so bump... Once I get Jprich's truck back in my hands I'll get you guys some preliminary numbers on what we did on it. As far as ride quality though, how can you address that when the shock is playing probably the majority factor in that. On my truck when I first set it up it rode like a brick. Then I reduced the compression valving and sped up the rebound and got it to come alive. Has anyone pointed this thread towards Helton's direction to see what he knows off memory?

I can post pictures of my setup on my pickup but it's gone now and is sitting on links. I was running Helton's numbers for the frame pivots but think my shackles were 1/2" longer or shorter then his, I honestly can't remember off hand.

That said... Helton did run his shocks outside the frame rail and know it should function better the more outboard your shocks are mounted.

Full droop on mine all said and done.





Interesting picture showing how they load... This is with them sitting on the bumps when the rear of the truck was VERY heavily loaded...








Here's the setup we did on Jprich's truck that we will be racing. Like I said, I can get you numbers and stuff eventually once I get the truck back. As far as ride quality, I believe it bucks in the rear right now but there's been no shock valving done at all that I know of...

The leafs right now are all pro's baja setup. We're going to start off with these and see how they do since we already have them.













 

·
Registered
Joined
·
408 Posts
BTW, reason I'm interested in this is we're racing the truck in class 2000 which is pretty open up front but leaf spring in the rear. The truck is having a front end built that should own the rear end so the leaf setup is going to be the limiting factor in the suspension on the truck imo. We are running 3" bypass shocks but still, getting every little bit out of the leafs plus hopefully setting them up to where they survive the races and hopefully maybe reduce prep costs would be nice. I know Helton was having Deaver service his leafs between virtually every race.
 

·
Registered
Joined
·
325 Posts
I messed up a bit. Helton had an H70 pack not a F67 pack. It had more arch then the standard F67 which gave him more bump travel. After he parted his truck he sold the pack to my friends who prevously ran the F67. After they put it on their truck you can notice it sat higher in the rear.


suspension rear/manufacturer-62" DEAVER RACE PACKS on 12" TC shackles/hangers with 2.5x18" racerunner tripple bypasses and 4" racerunner airbumps. *wheel travel is 19.5" - I pulled that from his racer profile from dezertrangers.

Also Khris pointed out a very important factor which is the shocks. Valving is key.
 

·
Registered
Joined
·
963 Posts
Here is my old setup
90 comp/70 reb
Beat up F67/Allpro 50t
Eye to eye= 52.56"
Vertical Seperation = unknown
12" shackle

Bump:

Droop

Overview

Travel (taken at droop with the tape starting at the bump pad)


Review: I really liked the setup. The allpros increased my ride hieght and had no complains from then

Current Setup
90 comp/70 reb
Allpro 50t
Eye to eye = 52.625
Vertical Seperation = need to measure
12" shackle

Bump


Droop (it's the only pic I have haha)

Overview

Travel = 17" too but i dont have a pic

Review: rides a lot more rough. I'm not sure what's causing it but it's a relatively new setup so it just might need some shock tuning.

The only main 2 differences between the setups are 1) the bump location. New setup bumps several inches higher 2) on my current setup my truck weighs significantly more.
 

·
Registered
Joined
·
206 Posts
Discussion Starter #15
something in the model is off if your're only getting 13" of travel. it looks like the spring arch may be off. on mine the shackle is almost vertical at droop as well
alrighty i'm glad some one brought that up! I thought for a second I was going to be able to sneak it by. I can tell you with 100% certainty that the travel WOULD be the same in real life if the springs were the same configuration and location.

Here are the things that can throw off real life travel compared to the model:

1) Full droop isn't really full droop. In the model i have the spring in the position as if it just came right out of the box. With the axle, driveshaft, wheels, tires hanging on it it will pull the spring much further down than i am showing here. ESPECIALLY if you are only using the main leaf from the pack while you are doing the measurements and the axle is hanging on it.

2) Taking the travel measurement:
A) if you only lift one side of the truck up to measure the travel the distance out past the leaf will travel further than the leaf itself
B) negative arch, if people are getting a little two happy when jacking up one or both sides you could probably snag another 1" or two by putting it into negative arch without even noticing.

SO this model is great for ideal conditions where there is no extra weight on the spring and the twist of the axle isn't talked about. In answer to your question NO, you can NOT predict the travel of a setup with 100% certainty. What you can do, which is arguably more important, is compare setups to each other with ALL other things being equal. Hell when you put it on your truck the distances won't be the exact same, the springs will sag, and our measurements are going to be a little off.

So the important part is really the ability to compare setups apples to apples without any kind of outside interference. I promise you the numbers don't lie, they just represent a simplified situation. It should still be more than good enough to make some excellent predictions. It's better than installing 10 different shackles in different places at least :D.
 

·
Registered
Joined
·
206 Posts
Discussion Starter #16
I'm interested in this one too so bump... Once I get Jprich's truck back in my hands I'll get you guys some preliminary numbers on what we did on it. As far as ride quality though, how can you address that when the shock is playing probably the majority factor in that. On my truck when I first set it up it rode like a brick. Then I reduced the compression valving and sped up the rebound and got it to come alive. Has anyone pointed this thread towards Helton's direction to see what he knows off memory?

I can post pictures of my setup on my pickup but it's gone now and is sitting on links. I was running Helton's numbers for the frame pivots but think my shackles were 1/2" longer or shorter then his, I honestly can't remember off hand.

That said... Helton did run his shocks outside the frame rail and know it should function better the more outboard your shocks are mounted.

Full droop on mine all said and done.

Interesting picture showing how they load... This is with them sitting on the bumps when the rear of the truck was VERY heavily loaded...

Here's the setup we did on Jprich's truck that we will be racing. Like I said, I can get you numbers and stuff eventually once I get the truck back. As far as ride quality, I believe it bucks in the rear right now but there's been no shock valving done at all that I know of...

The leafs right now are all pro's baja setup. We're going to start off with these and see how they do since we already have them.
GOD you guys are calling me out on all kinds of good stuff. So once again let me admit how right you are. YES valving plays a HUGE part in the rear of leafs. As i mentioned before they are inherently shitty! Who wants springs that get softer as they compress! The answer is no one. The solution, is some thought put into the spring setup and lots of time tuning some great shocks.

To be honest I am fully of the opinion that you can slap any old leafs on the back of the truck with some almost random setup and make the thing kick ass with great shocks and tuning. But that isn't the goal here. If you want things to last and win races you want every thing as well dialed in as possible . Nice shocks and setup on a shitty leaf design is just band-aiding a broken arm if you ask me.

Now as for what i'm asking for, I really can't go asking people what valving they were using or did they change it, etc. etc. because it is information very few people are probably going to have and honestly wouldn't do us much good as people run SO MANY shock/spring combos. But this is why we need as much information from as many people as possible! If we can find trends in the info that correlate with certain leaf setups we should be able to determine some numbers like the range a shackle should operate in along with ideal shackle to eye separation given a shackle length.

You mentioned shocks being mounted further out making them better. This is true when only one side is moving up or down. honestly if the whole axle moved up and down at the same time you could have them both in the middle and it wouldn't make any difference (jumps).
nifty fact if you were to mount the top of the shock further in toward the center line of the truck it would perform better when only one wheel is moving and worse when both are moving as their transmission angles are worse then.
But yes the further out the better like you said but the more important concept is that you would like to use as much of the shocks travel as possible (by moving it out you allow it to move MORE when only one wheel is compressed). The more oil moves around inside of it the better the valving/bypasses can control the piston. No oil movement no damping.
SO heat issues aside you could use a rocker and 10" shock to control 20" of travel and it would work fine as long as you use the whole stroke of the 10" shock. Oh and it'll need some pretty friggin stiff valving in it too but it'll work just as well, until it overheats and explodes that is :D.
 

·
Registered
Joined
·
206 Posts
Discussion Starter #17
Here is my old setup
90 comp/70 reb
Beat up F67/Allpro 50t
Eye to eye= 52.56"
Vertical Seperation = unknown
12" shackle

Bump:
Droop
Overview
Travel (taken at droop with the tape starting at the bump pad)

Review: I really liked the setup. The allpros increased my ride hieght and had no complains from then

Current Setup
90 comp/70 reb
Allpro 50t
Eye to eye = 52.625
Vertical Seperation = need to measure
12" shackle

Bump
Droop (it's the only pic I have haha)
Overview
Travel = 17" too but i dont have a pic

Review: rides a lot more rough. I'm not sure what's causing it but it's a relatively new setup so it just might need some shock tuning.

The only main 2 differences between the setups are 1) the bump location. New setup bumps several inches higher 2) on my current setup my truck weighs significantly more.
Sounds like you and most every one in this thread so far should be checking out the first picture in post 6. That is the one with your 52.5 magic separation number and 12" shackle. Since i have yet to get a good vertical separation number it'll have to do for now. You can see you are loosing a significant amount of travel and would actually gain a lot if you moved down to a 9" shackle. But you are definitely going to have to change some bypass settings or valving as the springs will be softer at the end of their travel.

probably just needs shock tuning since the 50T pack is the exact same as the f67 just stiffer. but moving the shackle mount forward should help too. and give more travel.
 

·
Registered
Joined
·
408 Posts
I'm not going to pretend to be a pro and you're putting way more effort into this then I probably ever would so I'll commend you on that and once I have time (aka not at work) I'll read thru the whole thread rather then just the first paragraph and looking at the pictures and diagrams. LOL

But that said... As far as leafs are concerned... I'm of the mind set that I want the softest spring I can to support the vehicle but I want/tend to like my ride height about mid travel if not a little above mid travel. In the rear I like to have more droop then bump in a perfect world. Reason being, I want the axle to fall into the holes and I want the leaf to unload and help slam the rear into those holes. I'll control the compression with the shock but I want the spring to over power the shock on rebound. A lot of the time people will tell me that this will lead to it bucking hard in the rear. My reply is if you're truck is bucking and you know it's not packing, chances are you actually need more compression cause it's blowing thru the travel. Sure, you can have too much compression but that's usually noticable cause the ride all around and on small stuff will be rough too.

Say you're on a 62" spring, it's not unheard of by anymeans to have 18" of vertical travel. Personally, 8 up & 10 down is what I'd be shooting for and I'd be running a hydro bump. Start with a 4" and if you find you're smacking it all the time shorten it up.

Now this setup isn't what everyone likes and everyone has their own opinion. Who's right? No fricken clue!!! But personally I prefer a spring with A LOT of free arch in it that actually has quite a bit of sag meaning a low spring rate.

Jprich's truck above isn't my "ideal" setup but it's what we're starting with no matter what. The rear is getting bumps and it's actually sitting a little lower then it is in those pictures now with the rest of the weight on it and some use.

Unfortunately I can't give you answers now cause I'm A LONG ways from testing on the truck but hopefully come late summer and into fall I'll be able to get the front dialed in to the point where we have to start massaging the rear to get all we can out of it.



My challenge is going to be to get that rear end to keep up with this front end that's in the making. Shocks shouldn't be an issue!!! LOL It's going to be a matter of tuning which I'm planning to spend A LOT of time out there doing myself first hand learning as I go...



 

·
Registered
Joined
·
408 Posts
Funny part is I'm planning on putting more work into his truck then my own! I want his truck to hang with mine that's linked now! At least that's my goal!!! I took a few short cuts here and there on mine that I'm not taking on his. Considering what Jprich has supplied me with to work with and put on that truck I really think it's an achievable goal but I know the hardest part is going to be getting the rear of the truck to work. It might not even be achievable with those leafs but that's where we're starting and we'll figure it out as we go. If we find a magic setup we'll let you know I know I'm not afraid to share info and I doubt he is either... Some people act like their shocks and suspension is national security and I find that really funny.
 

·
Registered
Joined
·
206 Posts
Discussion Starter #20
Well to be honest CAD makes a little bit of work look like i put a lot of work into it. Now i just change numbers and every thing updates itself automagically.

Another very interesting thing I learned in my time designing suspension for race cars. There is no perfect suspension design, and any one who says there is clearly has no idea what they are talking about. Spend 10 minutes in a suspension design book and you will quickly see it is impossible to get the best of every thing.

now that being said you can optimized a suspension setup for a given number of variables/conditions. Those conditions are much easier to define on a road car or race car. Off road trucks pretty much throw it out the window though. We expect them to be able to deal with any thing we throw at them. Huge jumps, whoops, rocks, slow turns, fast turns, silt, rocks, gravel, sand and every thing in between. moral of the story, do what works for your style and what fits the course you are driving on that weekend.

lemme know what the dimensions on his leaf setup are when you get the truck so we can toss that into the mix. I'm sure we can get an excellent leaf setup to play with a linked truck.
 
1 - 20 of 292 Posts
Top