4x4 drag truck 4 link

I'm working on a mud drags project, and I'm planning on 4 linking the rear axle with some short coilovers. I know a bit about 4 link suspensions, but its all related to rock crawling. My question to you other drag racing guys, is what antisquat value do you shoot for? Less or more than 100%? My guys would be somewhere around 90%, but that would be a COMPLETE guess.

welcome to the site GI ........ did some reading last night on rock crawling , because im a far cry expert on any suspension ....ck this out

The post below contains a lot of definitions and some explanations of what is going on with suspension whether it be a road car, drag car, off road car, or rock crawler, the physics are the same, but may need different applications.--

Right now I am working on my rock crawler, so in this post I will address some of those applications. It's been my experience that without enough anti-squat, the rear suspension will unload and loose traction, adversely with too much anti-squat, the rear suspension will drive under itself and bind. To adjust the amount of anti-squat, I put several holes for the upper links to bolt to. This allows you to fine tune your suspension. Non rock crawling applications, road cars, stock cars, and drag cars, will have several holes in the upper and lower link mounts on the chassis as well as the axle, to allow even more adjustment. This however, is not feasible on a rock crawler as the extra brackets hanging down would constantly get hung up. Another thing to consider with link placement is that as the suspension articulates the instant center will move, you can get a differing IC left and right which will cause the dropping tire to jack the chassis and not push the chassis over the rock.

Then there is bump steer. On a four link this is where the axle no longer remains perpendicular to the chassis, but begins to steer as the axle is compressed on one side and extended on the other. When you have four link front and rear, the effect is greatly exaggerated. Under chassis roll conditions, the front and rear axles steer together much like steering a skate board, so as you initiate a turn, and as the chassis rolls, it encounters gross over steer. While rock crawling this will cause crab walk. To reduce bump steer you need longer lower arms with less angle, say 5 to 10 degrees from the axle angled up to the chassis. I generally have the lower links as long as possible, but one drawback would be that the longer the links are, the more they can get in the way when setting up for an obstacle. There are trade-offs for almost everything.

With the roll center I like to keep it from moving around when the suspension cycles. Therefore I like to use a uniball, or large spherical bearing mounted to an "A" type upper link to keep it from moving as the axle articulates.

I don't like too much anti-dive with the front suspension as this will cause hop under power, and braking.

Last I remember checking we were somewhere a little north of the 100% range. Our rear actually seperates quite a bit compared to the others I see burying the rear fenders into the tires. A lot will depend on how much it weighs and where the weight is at. Start at 100% and you can go either way relatively easy

pirate4x4.com has a 4 link calculator in the General 4x4 section.

I already have the 4 link calculator. That doesn't help at all if you don't know what values you should be shooting for.

gijoe4500 wrote:I already have the 4 link calculator. That doesn't help at all if you don't know what values you should be shooting for.

you have any pics of this project ???

bruno wrote:

gijoe4500 wrote:I already have the 4 link calculator. That doesn't help at all if you don't know what values you should be shooting for.

you have any pics of this project ???

Nope. Right now, I've just got a pile of parts waiting to be put together.

gijoe4500 wrote:I already have the 4 link calculator. That doesn't help at all if you don't know what values you should be shooting for.

You're not gonna get a lot of answers or opinions without more info. Expected weight, wheelbase, horsepower? Things of that nature.

Gonna be a chopped up 80-96 bronco (still looking for the truck). 460/c6/bw1356. hoping to weigh in around 3600-4000 lbs. 8.8" or 9" rear with 3.55s and d44 TTB up front. Motor will be stock at this point. Gotta start saving up dollar dollar bills for a rebuild. Once rebuild is complete, it'll be somewhere around 450-500hp.

Definately do a 9" you will have a better axle. Why are you wanting to do a 4 link suspension? I ran over 700hp on a stock 89 chassis without any issues. Lots of serious work involved in the installation of a 4 link, and for 500 hp it probably isn't necessary.

schmitty wrote:Definately do a 9" you will have a better axle. Why are you wanting to do a 4 link suspension? I ran over 700hp on a stock 89 chassis without any issues. Lots of serious work involved in the installation of a 4 link, and for 500 hp it probably isn't necessary.

The actual installation of the 4 link isn't hard at all. I can do that in my sleep. The reason for wanting it, is easily tune-ability, and more room to grow. I guess I'll just need to build it, so I can tune for several different AS values, and see which one runs the best.

probably wouldn't do a 4-link either at that hp level and build. Most the time and places you would have to run in some of the upper or "pro" classes with the 4-link.

simpleman wrote:probably wouldn't do a 4-link either at that hp level and build. Most the time and places you would have to run in some of the upper or "pro" classes with the 4-link.

I'll be in the economy class, as long as I don't put aluminum heads on the motor or go about 466 cubes, or something like that.

Do you have access to the complete rules for the class you are wanting to be in, and can you post them. Sometimes these rules are a little ambiguous, and I'd hate to see you drop $1500 on a suspension unecessarily.

Here are the old set of rules that I have.

BODY

Any safe frame allowed
Must have sheet metal around driver's compartment
2 or 4 wheel drive allowed No wheelie bars allowed

ENGINE
OEM engine only (CID limit 474)
Headers allowed
OEM style intakes or equivelants
OEM ignition on 2 wheel drive , MSD 6 (only) on 4 wheel drives
No electronics accessories allowed -line lock or etc
Hydraulic cams only
OEM carburetor or equivelants
Must pull 15in of vacuum at 900 RPMS , MUST provide EASY test port
TRANSMISSION
NO 2 speeds
No working transbrake

FUEL
Gasoline, racing fuel or diesel allowed
NO nitrous oxide, butane or additives
NO alcohol allowed

GENERAL
NO paddle tires
Must have 3 working brakes

ALL GENERAL AND SAFETY RULE APPLY


On top of all that, is no aluminum heads.

Wow them are some wide open rules there now. I can see a couple places where one could rule the roost for sure for maybe a year before they either changed the rules or everyone got on the same page. Is this a bog style race, or is it side by side fast track?

schmitty wrote:Wow them are some wide open rules there now. I can see a couple places where one could rule the roost for sure for maybe a year before they either changed the rules or everyone got on the same page. Is this a bog style race, or is it side by side fast track?

Side by side fast track. And yes, they're pretty wide open rules. Also, the main reason why I'm looking at doing the suspension first, instead of putting that money into the engine, is because I already feel confident in my abilities to build the suspension. Just was un-sure what values to be shooting for. I'm still reading up on engine building (never built anything other than a small block chevy). Trying to decide how to go about building up my 460.


Here is some old in progress pics of the 3-link going under the front of my rock crawler.

are you serious about those jack stands

Rules are pretty wide open on the chassis side. Still wouldn't 4-link it. I'd spend that money on a new lift or jackstands or something.

no offense guys, but i was seeking an answer to a simple question. wasnt looking for whether or not i should do it, or whether or not i should buy a 2 post lift. truck is getting a 4 link, and the way it looks, i'll just have to play around with different antisquat values and figure it out myself. all i was seeking was a good starting point for dialing it in.

you are not going to get very far on this site being an a-hole.

There are some top notch mud drag guys on here who are eager to help and make the most of your money if you'd kindly help them help you. We also dont want to see your face smashed in when a jack stand falls.

With your build Id also be against a 4link. Karl Jetts (kjett) ladder bar/slider on a main leaf/coilover setup is pretty slick and works really well on a 700hp iron head 466. If class allowed Id be doing the exact same on mine. Im not sure if he has a build on here or not.


EDIT: heres a pic he posted of his setup.

Just saw this, whrere are you located? I might have to make a trip down to run with my little iron headed 466. I can "make it" pull the needed vacuum to get into the class rules


It's your truck, and your money. I can tell you my mono-leaf with sliders, ladderbars, and coilovers work REALLY well! Well enough that I can carry the front of the truck with no problems! To show you what a well tuned setup like mine can do:

https://s1200.photobucket.com/albums/bb331/old_blue1/?action=view&current=Karl9-10-11.mp4

im really confused ...do you want to drag race(mud/dirt) or rock crawl ???? two different suspension setups .....correct ???

Bruno,

You are correct in being 2 totally different setups. My mud drag truck is set up more like and asphalt drag truck vs. the days of the extreme jacked up to the sky 4x4's of the 80's. Rock crawling reauires tons of suspension travel, where mud drags need maybe 12" at most. My front barely has 12" of travel and most of that is downward.

4 link suspensions work on mud trucks, rock buggies, drag cars all the same. The difference is the setup - mud trucks and drag cars are actually very similar.

What hes essentially wanting to do is go full nuts crazy with the suspension while keeping the rest of the truck stock or basically as is with a 474 or less ci engine. Kinda like C heads on a junk yard block


EDIT: how can your fat fingers type faster than me?