4 link info

ORV design and fab

ORV design and fab

Well-Known Member
Joined
Jul 11, 2009
Location
Raleigh area, NC
Getting ready to build my rear 4 link on my Toyota. So what is a good starting point with roll axis and center axis etc? How far forward does my vertical links need to insect?

How long do y'all recommend my links be? I've looked at 40" on my lowers and 29" for my uppers.
Is this too long? I've thought about lowering my lengths cause of my 14" of travel?

I'm only upper triangulating my links. My lowers will have a little triangulation but not a lot

I know the basics. Uppers should be 70% of lowers,
There Should be at least 8" of vertical separation at axle end?
Link vertical intersection should be in front of vehicle. But how far is ok?

And how much anti squat do you recommend? I've heard 100%-80% but I think 100% would be ideal??????? Does that seem right?

Ultimately what is an ideal set of numbers to try for for a good 4 link to work in all varieties of wheeling?


I am really at a point were I'm getting ready to chop my chassis off in the rear and going to start tack my links in place and can build my brackets anywhere I need to to make it good. This is my first linking project and I have done a lot of research. I couldn't make it double triangulated but I am going to run 2 pieces of 2"x4" tubing on the inside of my chassis for my lower links to set the front brackets anywhere I need to. To raise if need be and bring the lower links inside more for the triangulation on the lowers.( just can't bring the lower links inside like 6" away cause of my driveshaft. )

I'm running 14" airshocks

Here's some calculated numbers I've built so far.

Give me some info that worked for y'all?
 
What has worked for me and multiple friends/customers. But let me say that I am no expert compared to many on here.

Lower links length (in inches) should be near the tire diameter (in inches)
Uppers 75-80% the length of the lowers.
Frame end separation should be 75% the separation at the axle. Generally 6" and 8" work frame side vs axle side.
Make the lowers as flat as possible and it'll climb better than steep angled ones

Honestly, there are so many different factors that come into play with link suspensions it is hard to say ________ works for every setup.

Good luck!
 
From reading threads on pirate, I am going to shoot for almost no squat when I link my rear (100% anti squat in the 4link calc). There were guys that were complaining that anything with 85% AS or less led to wheel hop on steep obstacles with high traction, like Moab. On the other side there were others that hated their designs which had around 120% AS and said that the suspension did not settle down on climbs. There is much more to doing links than just anti squat but it is a big component.

This article helped me figure out what to shoot for.
http://www.fourwheeler.com/how-to/suspension-brakes/131-0307-four-link-suspension-part-2/

Xtreme 4x4 also did a nice segment on links
http://www.powerblocktv.com/episode/XT2009-07/suspension-101-rock-racing#.VA0L5ktbTwI

I'm a newb when it comes to links so I may be completely off. Hopefully someone will call me out if I am :D
 
Set up a few, and there are the numbers I shoot for.

60-80% anti squat make upper frame mount adjustable. Using the calculator it's not hard to design these into the layout.

0-1% roll axis angle.

Instant center as far in front of front axle as you can, with mounts still being practical to your frame.

A couple of things I shoot for.
1) get upper links as high up and as horizontal as possible and practical at ride height.
2) get both uppers and lowers as long as you can practically
3) figure out you link lengths in 4 link calculator and use the travel function to check pinion change. Keep that below 6, degrees total change, the less the better.
4) make sure your total triangulation is more than 40 degrees.

As you lay it out, you may find the lower links at axle need to be on top of housing and upper links are way higher than what can fit your rig practically. So keep going back and forth between calculator and your rig till you find the best compromise, while still having proper geometry.

My yj is currently set up this way as well as my dads k30/s10 hybrid. Both work very well for the time money invested. I'm using all of my 14" coilovers, and his truck cycles around 20" of useable travel.

Don't focus too much on what pirate says, spend more time getting what you find in the calculator to work on your frame. Generally they will be close to that 70% rule, but it's more important to build something without much bind, and that won't blow the driveshaft or ujoints out from too much pinion change.

The last note. Make sure you anti squat and roll axis angle do not change much as the axle moves from rh to bump/droop. This is the hard part. So start with getting numbers right at RH, then move small increments to get them to work right during travel.

A hint, when you make upper frame mount adjustable. Those holes will most likely offset some front to rear as well as offsetting vertically.
 
ImageUploadedByTapatalk1410178157.798492.jpg


I like locating both frame points on plate to be welded to the frame, it makes the welding and fab time under the vehicle much faster. It takes more time at the fab table but to me is worth it in the long run. Just locate the two plates on the frame and weld them on , and add crossmembers.
 
I wish my roll axis was closer to zero. Sometimes you get it as close as you can with what is physically possible. I couldn't be more happy with the AS results. upper link is flat
4link.jpg
 
Mac5005 is dead on.. (IMO)

60-80% Is great; if you want high anti-squat, stick to 80-85%, that should be a cap. Too much anti-squat really limits your rig over steep obstacles, ive seen a lot of rigs become unstable. A slightly lower anti-squat will dampin your torque through the suspension, BUT she'll hug the rocks a bit more. And even at 80%, don't worry, you'll feel it when you put the skinny down.


Also, locating both lower and upper mounts as one piece helps keep everything a bit more accurate. (I built my entire 4 link as one piece outside of the vehicle and then put it into position)


Also, if your using the calculator (which you should). Watch how it acts as you change a link position just 1 inch. Depending on what your changing, percentages can jump an obnoxious amount. So, "close enough" measurements may not be close enough.... Anyway, just measure, double check, if anything changes, put it back in the model and see what happens. Try to be as accurate as possible.

Hope this helps.
 
I did all that research and bashed my head on an anvil 50 times. ...then i made ALL 8 links exact same size ( 36" eye to eye ), made axle brackets, made lower frame brackets (both uppers and lowers triangulated front and rear ). I then spread all the uppers as far as i could on chassis, attached adjustable uppers in rear and fixed on front, (this in turn "shortened" the uppers as viewed from the side profile). 6 & 9" separation top and bottom, front and rears. At ride height all my uppers are parallel to ground and rears have less than a 10 degree (depending on ride height) angle from ground. Also to note all the uppers are mounted on axle centerline from top and lowers are fore/aft of centerline, helping to aid in pinion angle throughout travel.
This was my first link job (and last to date ) and works great. Very neutral in all aspects. ... no body roll, no squat, near zero lift or torque twist, good pinion angle through travel on 16" ori's, great traction when pointed at the sky. A professional builder may run the numbers and say it's junk....I've never ran them and don't care. Works great for me. ...wouldn't change a thing.
 
Post up some screen shots of what you are getting in the calculator and let's see if we can tweak them. I don't mind running everything in the calculator to try to fine tune it. Movement of the location points even 1/2" will drastically change the geometry, most of the time.

Also what is a range of applicable measurements that fit your frame.
Ie: ( 22-24" height on lower link frame mount, 27-30" height on upper link frame mount, 19" to axle tube center line, cog height, link separation range on axle, and frame, etc. )

Post it up and we will be glad to help.


Nothing against just building the links, and not running them in the calculator, my preference is to know what the geometry is, and how it works, so I can compare it with others on the trail to see how a/s affects how a rig climbs, or how roll axis affects the rig leaning or rear steer.
 
mcutler, you ever punch your finished numbers into a calc? The reason I asked is cause my first build, I tried so hard to get good numbers with approx. measurements from my buggy. Then I went out and realized there was a few points of interest that would not be obtained due to layout restrictions...anyway, tweaked my measurements to fit, then went back onto the computer and punched in the new numbers... and wa-la, the numbers were even better than my ideal numbers originally lol. So you could possibly have good numbers!
 
Never have. Pulled up the Calc a few times but never when close enough to buggy to input accurate measurements. Wouldn't know a good set of numbers from a bad set any way lol. I'm afraid if i do, in my tinkering nature, i would get a decent number and screw the whole she - bang trying for that perfect set up. It's worked flawlessly for near 4 years. Same u joints and dshafts since first test ride at gmp, have never pulled the spares from the mounts. I'm still curious but. ...Ain't broke don't fix it. ...
 
ORV design and fab said:
Did you notice it rise when acceleration. 125% of anti squat is a lot. How do you like it?
Click to expand...
no squat or hop. I think it has settled some which makes the numbers even better. The point is once you take measurements for where you want the mounts you can decide on whether to compromise for better numbers with small changes. Separation at the axle is important too. Everybody wants long, flat lower links but there comes a point when you're giving up too much ground clearance. Its a compromise. Also you need to consider if you plan on running bigger tires in the future. Run the numbers with both sizes. This was helpful except for the water in the front tires crap:
http://www.azrockcrawler.com/_images/tech/2007/6-27-074link/4linksurvey.html
 
DMiller said:
Mac5005 is dead on.. (IMO)

60-80% Is great; if you want high anti-squat, stick to 80-85%, that should be a cap. Too much anti-squat really limits your rig over steep obstacles, ive seen a lot of rigs become unstable. A slightly lower anti-squat will dampin your torque through the suspension, BUT she'll hug the rocks a bit more. And even at 80%, don't worry, you'll feel it when you put the skinny down.


Also, locating both lower and upper mounts as one piece helps keep everything a bit more accurate. (I built my entire 4 link as one piece outside of the vehicle and then put it into position)


Also, if your using the calculator (which you should). Watch how it acts as you change a link position just 1 inch. Depending on what your changing, percentages can jump an obnoxious amount. So, "close enough" measurements may not be close enough.... Anyway, just measure, double check, if anything changes, put it back in the model and see what happens. Try to be as accurate as possible.

Hope this helps.
Click to expand...
100 or more AS helps short wheelbase rigs do steeper climbs than they could otherwise do. I feel like my little POS has proved that.
 
lol, it always comes down to a matter of opinion as well which every online discussion under the sun will show. The best thing to do is drill each mount with 1 additional hole top and bottom just to give you some adjustment, id throw all possibilities in the calc just to be sure these additional options will be giving you enough variety of possibilities. Then all you have to do is find a rock and tune.

why is running water in the front tires crap?
 
mcutler said:
I did all that research and bashed my head on an anvil 50 times. ...then i made ALL 8 links exact same size ( 36" eye to eye ), made axle brackets, made lower frame brackets (both uppers and lowers triangulated front and rear ). I then spread all the uppers as far as i could on chassis, attached adjustable uppers in rear and fixed on front, (this in turn "shortened" the uppers as viewed from the side profile). 6 & 9" separation top and bottom, front and rears. At ride height all my uppers are parallel to ground and rears have less than a 10 degree (depending on ride height) angle from ground. Also to note all the uppers are mounted on axle centerline from top and lowers are fore/aft of centerline, helping to aid in pinion angle throughout travel.
This was my first link job (and last to date ) and works great. Very neutral in all aspects. ... no body roll, no squat, near zero lift or torque twist, good pinion angle through travel on 16" ori's, great traction when pointed at the sky. A professional builder may run the numbers and say it's junk....I've never ran them and don't care. Works great for me. ...wouldn't change a thing.
Click to expand...
I did exactly the same things. Never used a calculator and mine works pretty good I think. I've not adjusted anything on my suspension since I put it together except my ORIs. You can talk to all the builders in the world and you get a different story every time.I just took all their common points into consideration and applied them.
I'm sure mine could be better but its a 100 times better than what I used to have.
 
ORV design and fab said:
Pretty crazy ny tires are 4 different heights. I pumped all tires to 12 psi. 37 boggers are 34"-35". All have the same tread. Sorry for the rabbit trail.
Click to expand...

hahaha, that's why I like you so much Jonathan.

I know there's a lot of info to pick around in this thread, but your instant center looks to high to me. I would say level it out in between, or maybe even lower because your driving style needs traction, using the tires that are at bump when your articulated. I didn't see this thread til you called but, since I've seen you drive, that is what I would do. Get the instant center closer to digging. Get the pinion angle situated the best it can be throughout it's travel, and tune those new air shocks you got.

The whole thing about the upper links being a percentage shorter or longer has everything to do with the instant center, and the pinion angle. Get this stuff figured out and you should get away with running some pretty crappy u-joints
 
My uppers on the samurai are actually a little longer than the lowers which when the axle droops it makes the pinion point up towards the tcase instead of the uppers being shorter which would point the pinion to the ground the more the axle drooped.
 
Dynamite Design said:
hahaha, that's why I like you so much Jonathan.

I know there's a lot of info to pick around in this thread, but your instant center looks to high to me. I would say level it out in between, or maybe even lower because your driving style needs traction, using the tires that are at bump when your articulated. I didn't see this thread til you called but, since I've seen you drive, that is what I would do. Get the instant center closer to digging. Get the pinion angle situated the best it can be throughout it's travel, and tune those new air shocks you got.

The whole thing about the upper links being a percentage shorter or longer has everything to do with the instant center, and the pinion angle. Get this stuff figured out and you should get away with running some pretty crappy u-joints
Click to expand...
O I've gotten my instant center to about 25". I'm wondering if I can do better. My lower links are going to have to be mounted on top of my axle tube to be that low as well. Do I need to figure mother way to lower my instant center?
 
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