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Is this going to be a hard core rock crawling rig and do you care much about your approach angle?
 

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Discussion Starter #22
Not a hardcore anything, it will get crawled, asked to go fast over rough terrain and be comfortable enough on the road for my wife to drive. Why are you asking about approach?
 

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Leafs just don't off the best approach angle set ups. I was going to suggest a coil or coil-over upfront, but leafs would be great for the direction you are going with your build. Going through Deaver would also be my first choice. Cheers
 

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whats the planned wheel base? If its long why not a shackle reversal.. that way when hitting rough stuff at high speed the wheel can go back and up instead of needed to go forward and up.

I agree with you though leafs up front and links in the back.. i've been thinking about changing mine from links in front to leafs with shackle reversal. I think it would be great for crawling still and help in the high speed stuff
 

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I have a CJ7 with custom Alcan’s up front with a shackle reversal and a 4 link in the rear with rear TJ coils. Been running it for 8 years now. Works great for crawling and the go fast stuff but I only have a H.O. 4.0 on propane.

I really like leafs in the front links in the back. It side hills great and doesn't have a lot of body roll on high speed corners.
 

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Discussion Starter #26
Leafs just don't off the best approach angle set ups. I was going to suggest a coil or coil-over upfront, but leafs would be great for the direction you are going with your build. Going through Deaver would also be my first choice. Cheers
At this point in time (which really means nothing) I'm planning on links and coilovers. Approach angle is one factor, overall strength another, and easier placement of steering components to make room for uptravel is the primary. It's hard to have a mid-steer or low steer setup on sprung over leafs. I plan to keep the frame mostly intact and on previous versions I had to cut most of the frame out to clear the drag link and panhard.

whats the planned wheel base? If its long why not a shackle reversal.. that way when hitting rough stuff at high speed the wheel can go back and up instead of needed to go forward and up.

I agree with you though leafs up front and links in the back.. i've been thinking about changing mine from links in front to leafs with shackle reversal. I think it would be great for crawling still and help in the high speed stuff
In my first post I said 102"- 110" and am still planning around this ballpark number. The big decision at this time is keeping the tub stock, running a 102" WB and stepping down to 37's or stretch the frame/ tub, stretch the wheelbase even to as much as 112" and run a 40-42" tire. The shackle in front idea had nothing to do with extra wheelbase, especially with how the slider is setup. I'll get into the "why" a bit further down.

Below is the pm that I got. I'll never claim to be an expert at anything, but am happy to share my experiences, decisions and reasons for doing what I do, because I do put a fair amount of thought into this crap.

ISDTBower said:
Anyhow, this has probably been covered on pirate as to where the shackles should be, but I usually like the leafs to pull from the hard end when gassing it. You don't push a hoop into the spring. If I still go with this thought,...then.

When on the gas the front pinion will go down.

For spring over the hard point should be in the front and the slider in the back. You are trying to pull the front of the spring straight...and the rear portion is trying to hoop, but will more than likely slide back instead of bend. Having the hard in the front also helps when hauling A.

In my mind, I see the axle forces and direction of travel are the same for both spring over and under. The tires are trying to pull forward regardless, but the leverage on the spring is different for spring under/ over the way I see it. On my previous buggy (and the intent on the frame shown above) was to get the axle to pull from the fixed end when climbing hills. With a shackle reversal, given ample traction I have seen the axle walk out from underneath the rig (using the shackle travel). Shackle in front causes the axle to pull the vehicle from the rear fixed mount. My experience with this came after attempting a climb and coming down at full throttle. The axle pulled out from underneath the rig to get into the last inch of travel on a 13" driveline. The torque mushroomed the collar out and failed.

There are two options for spring under. For crawling, I like the slider in the front, as you are pulling on the spring from the rear. If you are a deswert racer and not putting real torque on the front axle then run the hard mount in the front so the axle can kick back on hitting something hard.

I agree for purely charging hard, rear shackle makes sense and for the same reason that IFS setups are raked. This allows the wheel to travel in the direction of the forces are acting on it, while the suspension is reacting to those forces, it provides more "give"

Have you understood different? I would like to hear other opinions, and right now too lazy to search, as the reply would probably be 20 years ago.. Been watching this stuff since the 70's and the rigs that bounced kind of went against that thinking...

I like leafs myself...just everyone is pushing me to newer stuff on a new build. Coolstuff. Ben

I think leafs are great, simple and have their place on most trail rigs. I've said more than once that if people were willing to spend the same amount of time and less money on their leaf sprung suspension, they wouldn't think they "need" links. Most people aren't willing to spend money on a good, custom leaf setup from Deaver, or Alcan and good shocks to go with them becuase it does begin to approach the cost of going to links and coilovers.

Here's the setup on my previous beater buggy:









After looking around a fair bit, I found a lot of mention of better geometry #'s if the shackle end of the spring is higher than the fixed portion. I do not know if that only pertains to forward shackle or would apply to all, but it is very difficult (damn near impossible) on a front suspension to get the shackle point higher with a shackle reversal. For OEM reference, consider super duty fronts (forward shackle, mounted high) and pretty much every OEM rear setup has the shackle higher than the forward mount (rear shackle).

A big operational downfall of the front shackle for rock crawling is your shackle and spring are sitting out there and would be the first point of contact in many cases. The slider fixes that by protecting the spring within the slider mechanism. Another consideration is shackle flop. After two back flips on back door in the beater rig, I noticed I had bent all 4 pieces of my 3/8" ruff stuff shackles. I've also seen many cases where the shackles and bushings cause the axle to shift under the vehicle from either steering forces or obstacles/ terrain. Again the slider eliminates this. The last and maybe one of the more important attributes for the slider (from a competitive aspect) is that it creates a more consistent and linear spring rate. It causes the spring to move in one consistent direction and the spring is the only thing holding the vehicle up. With a shackled suspension the angle and length of the shackle all play a roll in how the forces are applied to the spring via leverage. This can make tuning more difficult and attention does need to be paid to your shackle length and position.
 

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Great discussion. All good points, and thinking now more about the thrust.

I am thinking that a leaf suspension designer would want either front mounting points higher to give kick to the axle when it hits something. That makes it much easier on the driver and the spring. Not sure about leafs but kick also gives antidive on IFS and antisquat on IRS...and can give front LIFT on acceleration.

I think we are on somewhat the same page that Spring-Under is the proper way to leaf spring a crawler (Other than clearance). In the front axle , you want to pull the jeep along with the solid mount in the back (agreed). From the rotational torque of the axle tube (pinion down), there are less forces from a bottom spring trying to reverse and bow the spring packs. As the pinion wants to rotate down it is wanting to bow the back section of the spring, but it is also trying to pull the frame mount forward and down. This helps to keep it straight-neutral (until you hit a BF rock at speed and the top leaf bends under compression in the back). The front part of the spring wants to reverse, but it can't because of the spring pack or military wrap doing it's other job. It wanting to lift the front mount. But if it is shackled, that lift will be absorbed by the shackel moving forward and minimize lift to the front (on a climb). You have to make the decision how fast and hard you are going to hit something to move the spring under solid mount to the front to get some more kick and a good solid "link.". We would suffer frame lift, and wheel hop as the front part of the spring can really reverse and push if we got that desert runner in the steep rocks... Cool? Just my thinking.

So lets look at what happens with Spring-Over in the front. I am constantly reminded by several OLD Moab Jeepers that never went spring-over or hard front until winching down became popular. I didn't experience it but they all said that it lifted the front end too much and they would go over, or it would skip sideways.

With spring-over in the front the pinion still goes down on axle torque. (The resistance to that is the only reason you go forward)

With the hard end in the rear the rotational force wants to put more of a bow in the rear of the spring pushing and pulling it apart. At some point it will reach equilibrium and start to pull (wheel hop possible). The front of the spring wants to lift and reverse also but the shackle takes most of it. So I guess this is not too much different than spring-under, except that it is way easier to bow the rear of the spring and probably why front spring packs have more clamps in the rear (to keep the rear top leaf from bowing/bending). If you made the top leaf thick, there would go your soft ride. True also for spring under. Now hit that rock under acceleration, and bending the rear becomes real easy. The forces are compounded. All-in-all a compromise for ground clearance.

Now for my somewhat changed thinking on S-O hard mount in the front.
My reasoning here was to take those hits, and the front of the spring on accel would want to straighten as it was pushing on the forward frame. But, the bending and pulling-the-pack-apart of the rear section might actually be worse as the shackle would let it happen. The shackle would also negate any pull down so the front would be very free to lift. Again compromises.

OK Wilson. No beer or campfire talk. I had to go through this just like 1000's of Jeepers before this to really know why we are both going to work harder to go links or IFS (as of today). Thanks for bringing me back to the pushing and pulling against the hard mount. I was only thinking about the instant the throttle is hit, and not when the spring maxes it's flex to provide drive. It's only money.....Link:$$ IFS:$$$$$$

Welcoming comments from all. Are there any leaf spring mfgs, designers or guru's out there that can shed more light on this? Or point us to a tech article. I know this is just the basics and could even have that wrong.....

Thanks for letting us steal your thread for awhile, but the posted subject was too perfect for a real discussion that I probably have missed in the past.
 

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Sure you can haul ass with leafs and they offer good road manners and affordable suspension, etc.
The downsides to having leafs are:
-approach angles
-axle wrap
-leaf breakage in the field sucks
-shorter lifespan than coils
-unpredictability
-noisier:flipoff2:
 

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Discussion Starter #29
Sure you can haul ass with leafs and they offer good road manners and affordable suspension, etc.
The downsides to having leafs are:
-approach angles
-axle wrap
-leaf breakage in the field sucks
-shorter lifespan than coils
-unpredictability
-noisier:flipoff2:
I don't know the sliders on my coilovers were pretty damn noisey, the creaking in the heims while crawling took some getting used to as well.... But yes, ultimately stronger and bottom line more tunable and more easily tuned by the average user. :flipoff2:
 

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not to argue but here are my thoughts.


Sure you can haul ass with leafs and they offer good road manners and affordable suspension, etc.
The downsides to having leafs are:
-approach angles
with 40-42 inch tires and shackle reversal , offset centerpin and mounting the spring hanger high you can get a pretty decent approach angle
-axle wrap
link the rear , anti wrap bar front, anti wrap spring in your alcan leaf pack, and suspension winch with some thought into where it mounts and what way it pulls you wont have much wrap

-leaf breakage in the field sucks

so does breaking a 3/4 inch heim like everyone thinks is big enough and having your axle move 2 feet and breaking the shafts on your coilovers , driveline ect

-shorter lifespan than coils
alcans hold up well and mix in junk yard leafs
-unpredictability
not sure where your going with that?
-noisier:flipoff2:
coilovers and clanky joints can be pretty loud

not saying leafs are better
but I think they a well designed leaf set up can work very well

look at george breakall 70 years old.. simple truck simple leaf suspension 37s and he does very well

george
George Breakall- Chile Challenge Tabasco Twister 2/2011 - YouTube

Breakall on Crap Shoot - YouTube

jeff.. leafs front bigger tires.. links rear
Bad Buggy Roll Over on Crap Chute Farmington New Mexico - YouTube


george
George Breakall, Potato Salad Hill, Most Difficult Line, 1984 Toyota, April 2009, Moab - YouTube

curtis
Potato Salad Hill 2010 - Buggy Rolls and Catches Fire! - YouTube

i know this isn't that good of a comparison and there are too many variables I'm just saying leafs can work well


that being said all the cool guys have 4 links front and rear with 18 inch tripple rate coilovers and quadruple bypass shocks..so if you don't do that your rig sucks.. So i'm keeping my links
 

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not to argue but here are my thoughts.
not saying leafs are better
but I think they a well designed leaf set up can work very well
Good discussion and I agree with some of your points. A smart man once told me; 'A leaf spring is like a paper clip, you can only bend it so many times before it breaks'. :D

I'm also of the mindset that if I have to design anti-wrap bars, custom shackle mounts, and pay for custom leafs..........I might as well link the rig! Most guys I wheel with all have similar heims/bolts and we can normally weld a link back together if it breaks(super rare), or borrow a heim. Kinda hard to do this with leafs.

as far as unpredictability: have you ever side-hilled very far in a leaf sprung rig? It can get more unpredictable than a 3-Link set up with crappy air shocks.
 

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wilson let me know and I will delete my post if it was too much of a hijack
Thanks for taking the time to find and post those. Build, Tires, Line, Driver? Probably all. Articulation on George' looked all of 10". There is a school of thought that lifting a tire on solid rock with lockers is not all bad. It transfers the weiight-traction forces to the other one(s) that, may have/has better footing. I survived with that for several years until wheelbase and 33's left me home. It was predictable....

I have not proven it, but I see movement toward big Sway Bars and Softer Springs for dual sport-KOH buggies. The sway bar makes the suspension responsive and predictable, the softer springs make straight ahead fast running-climbing able to absorb the bumps and jumps...and shocks trying to solve fewer issues....until you consider IFS (but most are running big bars in the linked rears.) Not everyone...just noticing trends. With soft leafs comes a link of some sort??
 

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Good discussion and I agree with some of your points. A smart man once told me; 'A leaf spring is like a paper clip, you can only bend it so many times before it breaks'. :D

I'm also of the mindset that if I have to design anti-wrap bars, custom shackle mounts, and pay for custom leafs..........I might as well link the rig! Most guys I wheel with all have similar heims/bolts and we can normally weld a link back together if it breaks(super rare), or borrow a heim. Kinda hard to do this with leafs.

as far as unpredictability: have you ever side-hilled very far in a leaf sprung rig? It can get more unpredictable than a 3-Link set up with crappy air shocks.

paper clip comparison is great! and your right about designing anti wrap bars and dropping big money into leafs. i was not saying its a better route i just think people dont give leafs any credit

i guess it is easier to carry a heim or even link then a spare leaf pack

my leafs were not as un predictable as my airshocks but i had horrible panhard angle




george has alcan leafs front and rear. the front pack uses some factory toyota rears to get a better approach angle. anti wrap springs with no anti wrap bars or suspension winches. the 37 inch red labels help alot but i've seem him on 35 inch km2s crawl just like there reds. He's a good drive and really knows how to pick a line. I think the biggest factor is he knows his truck!



big sway bars and softer springs seems like a good theory to me! also i'm not sure why more trail rigs that are on air shocks are only running rear sway bars.. If you had to pick wouldn't a front sway bar help the most??

I assume its packaging issues. Also i have more travel in the rear why limit it or put extra stress on the sway bar when you could put it up front ?


That being said I have never had a sway bar but hopefully someday i'll be rich :p


Thanks for taking time to explain things this is a good thread. I'm 22 years old and just trying to learn more but some people are to cool to share knowledge
 

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Good discussion and I agree with some of your points. A smart man once told me; 'A leaf spring is like a paper clip, you can only bend it so many times before it breaks'. :D.
He wasn't that smart. Leaf springs will last an extremely long time as long as they are being used within their elastic limits. Coils wear out and break too. The difference is that they are only controlling ride height, not locating the axle. But links break, too.
 

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Not sure how relevant this will be but I read lots of familiar words, leafs vs coils, FJ40, SOA/SUA, shackle reversal, go-fast, etc and thought I would pitch my two cents in:

Cholistan Jeep Rally 2012 - Evo vs Jevo - Part I - YouTube

Its a friend's Mitsubishi Pajero Evolution (on 31s with King triple bypasses and KING coils) against our Toyota FJ40 Concordia 1UZ V8 (on 33s with thick stock leaf spring packs SUA, stock shackles, 8 mismatched racho/bilstein shocks, front & rear anti sway bars): Effectively the best coils vs the worst leafs!Kinda pointless to compare the time owing to multiple variables (mostly one sided) but hopefully worth sharing the experience!

I think about linking the front, but can't figure a way to increase uptravel without major surgery and will probably end up doing a shackle reversal with some half decent shocks that I can afford.
 

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I thought I would add this thread to this because it discusses leaf wander. Panhard rods, rigid shackels, and Holbrook Springs that are flexy (longer) on one side. Also some info coming on Wagoneer springs that were used for short course go-fast, and kind of dumped for linked rock crawling and eventually KOH....We will see where it goes for those working with leafs...and running within their capability?

http://www.pirate4x4.com/forum/showthread.php?t=1071231
 

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I have been watching this thread for a while, time to chime in. In no way am I an expert, just someone who has tried a few things in the absence of any real knowledge!
I race offroad in the UK in the leafsprung class, my truck has a 102" w/b, spring under with parabolic leafs all round. I have been racing for 7 years and have developed the truck from standard to what is now a purpose built leafer. I have 11" travel at the front and 12" at the rear on Fox 2" resis. The truck is stable at 75mph on forestry tracks, once I finish the engine swap I will find out how stable it is at a higher speed. At the moment it is front shackle, I am converting it to rear shackle as I am changing the axles to cope with the extra power. I am not running the sort of power you guys are (180hp) however the truck weighs in at 2200lb max so springs are light. fronts are 288lb/inch, rears are 185lb/inch. At these spring rates the ride is good but a hard hit will bottom out the suspension. Earlier in the development of my truck I tried a lot higher spring rate to prevent the suspension bottoming out, this worked to a degree but was hard on my back and the rest of the truck.
I calculated spring rates based on 2/3 bump travel and 1/3 rebound, this will give a max hit of 3g, to be fast this needs to be 4-5g meaning that some progression of spring rate is needed (or as I tried in the past a high initial spring rate that means the low amplitude bumps hurt)
In the end I fitted 4" hydraulic bumps and rated them to provide adequate progression, perhaps not what they are usually used for but I knew no better, tried it and was happy with the result. With limited power I do not suffer from axle tramp however I feel that stability could be improved with better location of both axles. It is noticeable that you have to "take up the slack" in the rear when setting it up for fast corners and mid corner bumps require correction. The slack in the front is not that noticeable when driving, however when parked you can see how much the chassis moves relative to the springs/axle when turning.
By way of explanation parabolic springs are tapered along their length, each leaf is separated by steel or rubber pads reducing interleaf friction.
I am watching this thread with interest hoping to pick up some tips.
 

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i'm running a SUA CJ7 built for the sand. I am using 2.5" wide, YJ 3.5" soft ride springs with a shackle reversal up front and Currie boomerang shackles on all 4 corners. I used 7" MORE spring perches in the rear to fight axle wrap and I built a single traction bar mounted 4" from the center line of the axle (as close as I could get it) and the opposite end is mounted to a shackle with a 2.5" poly bushing on the crossmember and a 1 1/4" forged HEIM with high misalignment spacers on the trac bar end. My jeep is roughly 3200 lbs. and I'm running a 400 horse V8. Even with the HEAVY 35" Toyo MT 10ply tires, there is absolutely zero axle wrap on the asphalt when doing burnouts or hard street launches. Even in the sand with 33x16" paddles, ZERO axle wrap. It flexes a lot better than I had thought it would (10"+) in the rear. It flies over whoops and rough stuff, but that's mostly due to the FOX piggyback bypass shocks up front and FOX comp. adjustable res. shocks in the back. I'm very confident that it will take 200 more HP with the same results and I will see when I get the nitrous kit. I'd like to jump it more, but i'm running 4" poly bumps and you can feel it.
Just tossing my $.02 in as it's similar in theory to what you are looking to do.
 
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