Thread: Four Link Specifics Required

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Further to my introductory post in the "Members Sign in Forum", I require some specific information about four link setups for my project.

The car will be primarily for street use, and I don't really have any intentions of drag racing. Just your regular old spirited drive or cruise to events and shows etc. I'm hoping to achieve a well handling car with a comfortable ride.

I'm thinking that the best kind would be the parallel four link, with two pairs of links one on either axle, one link above, and one link below the axle, like this:

http://i231.photobucket.com/albums/e...g?t=1201738124

This means, I would cut out two long sections of the floor up to the crossmember, and brackets would be welded to that crossmember for the links to swing off. Something like this.

http://i231.photobucket.com/albums/e...g?t=1201738705

Also, what would be the best way to locate the setup laterally? I was thinking a long panhard bar, attached virtually central on the axle housing, and extending on and angle and mounting to the opposite chassis rail, like this one here:

http://i270.photobucket.com/albums/j.../RearSusp6.jpg

Now for a coilover question. I had thought of running a cross brace between the two rear rails of the car above the rear axle, and having the coilovers mount to them, as well as central on the axle housing. Is it best to have the colovers angled, or straight up and down?

There is not a lot of kick up in the rear of the car, so I'm not sure if that theory will be successful, I may have to mount the coilovers in the original rear shock absorber tower, which will mean it will need to be made bigger. Like this:

http://i231.photobucket.com/albums/e...g?t=1201738980

Also, if I were to sucessfully mount the coilovers to the central, rear side of the axle housing, would I still be able to run a panhard bar? It would mean that I need to make a bracket off the axle that extends past the coilovers, and then run the panhard bar from there to the opposite chassis rail.

Anyway, I hope some of that is understandable, I think I've basically blurted out my theories, and want somebody to tell me whether I'm on the right track!

Hmm, a 289 in a Cortina should be very interesting.!!!! The parallel 4 bars work great, another option to consider would be a triangulated 4 bar. Your plan for the parallel 4 bar would work fine!

For the street, the coilovers work best if angled in from the bottom to the top at an angle between 25 to 28 degrees. Some manufacturer's suggest their coilovers mount at 30 degrees.... Mounting the coilovers vertically leads to a harsh ride and is best left to the drag cars... If it were my choice, I'd go with the new crossmember and the coilovers angled in.

A panhard bar is the easiest solution to control lateral movement. The mounting height on the rear end housing can also be raised and moved forward so that the panhard bar is forward of the coilovers and above the housing. Also, the nearer you can have the panhard bar to parallel with the ground at ride height, the better off you are.

I would say you are on track, if you have any other questions, ask away!!!

Ditto. You can buy your four link bars in custom made lengths, and even get the bracketry that joins them to the frame. We are right in the middle of installing a fourbar setup in my kid's '29 right now. We are using quarter eliptic springs, but coil overs would be even easier. A panhard bar is going to be used also . We have to still make and install tube cross members, one of which will support the shocks.

Here are a couple of pictures of our installation that might help somewhat. One source for components is Auto Weld in Pennsylvania, among many others.

Don

You may not have to cut your floor if you run both upper and lower bars below the center of the axle.

Take note of the upper bar placement as pertains to axle center:
http://i49.photobucket.com/albums/f2...tarRRTsize.jpg


Here's an undercar pic that just barely shows the axle bracket.
http://i49.photobucket.com/albums/f2...2BrakeLine.jpg

Said bracket is a Chris Alston ladder bar axle bracket with the top front cut off at an angle and a new hole drilled a bit lower.

Bars are home-made, 1" x .120 wall DOM tubing with helicoil threads.
1" x .156 wall directly threaded may have been better, but the .120 wall tubing is working fine.
The roadster has a very torquey (about 530# torque) 462" Buick engine.

The four bars are parallel in both the side view and the top view.
There is a long panhard bar in front of the rear axle.

Recommendations I've read for using a 4 bar on the street say to run them parallel horizontally and vertically.
This is not drag racing practice, but it works quite well on the street.

The car handles well, especially so on twisting mountain roads - much to the dismay of a few sporty type cars - and has good highway and in-town manners.

An experienced at drag racing friend noted that the car squatted a touch on take off.
That's normally an indication of less than optimum traction when accelerating, but in actual use the car launches fairly well.
Running 8" tread width street tires at the drag strip the roadster can keep up on the launch and pull some of the dedicated drag racing door slammers with big slicks in 2nd gear.

I have another roadster under construction, a 31 A on a 32 frame.
This one has a Chris Alston ChassisWorks 4 link under it and has quite a bit of adjustability so I can run the links parallel or set up for a better "Instant Center" for drag racing use.
The bars are similar height-wise to the ones in your first photo, but I didn't have to cut the floorboard.

Pics of that if you wish.

Dunno why the pics won't come up.

Perhaps PhotoBucket is having a problem.

They work when you click on them.

Thanks guys, that's some great information. C9x, that's a good point, I could run the links below the axle, I did not think of that. However, that would mean they are visible below the floor of the car, which is something I'm not a fan of, both aesthetically, and in the sense that things can hit any low hanging components. It would not be easy to tuck them away either, because the car was originally only intended to be a four cylinder, there's not a lot of space under the car to tuck exhausts away, and things like these parallel links.

I think cutting the two small sections out of the floor is good. They're not ovverly huge portions of the floor, and will be pannelled over and strengthened again anyway, and I'm probably not going to fit a back seat, due to the cage etc, so there are no real issues there.

Is there an effective way to prevent squat with a parallel four bar system? I know it is very difficult. It's not a huge issue for me, because it's going to be a street car, but as I think I've said, spirited driving is not out of the question.

I'd definitely like to see pics of the suspension setup on the A. As well as photos of the panahrd bar setup on the Roadster too if possible.

Thanks again guys, very helpful info!

You can get some of the squat out by playing with bar lengths and pinion angle, and a bit more with springs and shock valving.... Squat is not the ultimate way too hook a car up, but lots of time with a parallel 4 bar it works the best.... With the bars being equal length and parallel, sometimes it's just something you have to live with... On a drag car, with an unequal length non-parallel 4 bar you can make it do anything you want....but with all their adjustability it's almost too much hassle on the street.... Just another of those compromise things we have to live with on the street.....

Yeah, being a street car, I think I can live with a little squat. It's a small price to pay for all the otehr benfits of a link setup really isn't it?

A couple more questions just out of sheer interest really. Firstly, in regards to ladder bar type link setups, what are the differences, advantages, or disadvantages of the ladder bar over the parallel four link? I know the ladder bar is more widely used on drag cars. I have a bit of an idea, but would like further clarification.

Also, what kind of bushes are best for the parallel four link setup, in the rod ends and bracketry and such? I've always liked Nolathane in suspension, but from what I have been reading, it's not so good in a link setup, as it does not allow as much free movement, and can cause binding. Is this correct, or a bit of an old wives tale. From my experience, Nolathane does take a reasonable amount of driving miles to settle in a bit.

This thread is great, it's really given me a lot more confidence that the setup will work and work well. I always get the impression that there is some sort of great mystery or technique to a successful four link system, particularly when talking to those who are quite experienced and in the know. But I'm always of the belief that anything is possible, and a little hard work is nothing if it gets you the desired end result

I much prefer the urethene bushed ends on the street. The heim joints are a bit much for the street, hard to keep clean and lubed and just plain noisy and rattly. IMO best left for the drag cars.

Ladder bars work fine on the street, just subject to binding up a bit more then a 4 link. I've ran them on the street, just have to remember what you have on the rear when you start playing on a curvy road! They will tend to build a bit of push into the front end if you get back on the power a bit soon...

I don't have any pics that show the 32s panhard bar.
It goes from left inside frame rail to as far to the right side of the rear axle it could go and is in front of the rear axle.
Since it has to go forward a touch compared to some cars the axle end is mounted much like the bottom end of a coilover with a coilover mount upside down and a 1" bushing to space it out like the bottom of a coilover.

The 31 on 32 rails car is a roadster as well.
It runs a transverse leaf spring on the rear and due to 'packaging' problems the panhard is behind the rear axle and shorter than I like, but it should work ok.
If you look close at the pic you'll see the left side bushing welded into the rear crossmember and a short bit of the panhard bar.
http://i49.photobucket.com/albums/f2...hassisview.jpg

You may be wondering why the panhard since it has a transverse leaf spring.
We had a long discussion on the HAMB a couple years back and since the car was originally slated to be a dry lakes car a panhard would add a little steering accuracy at speed since the rear spring would swing on the shackles a bit.
A lot of guys run sans panhard on the street with a transverse sprung car, but since I make these at home it didn't take long to knock one out.

This pic shows how the rear axle was set up.
http://i49.photobucket.com/albums/f2...uspension2.jpg

The 4 link you see is a ChrisAlstonChassisworks kit.
http://i49.photobucket.com/albums/f2...trear4link.jpg

A drag racing piece made from 1 1/4" OD tubing which is overkill for a street car, but it should work ok.
Couple of nice things about the kit is, it's adjustable for instant center and all that, but right now the links are parallel.
First thing up after the car is running - and probably smoking those skinny tires is to bring the top bar down one notch in front and perhaps the bottom bar up one notch. (Both roadsters run torquey 462" Buicks.)
Shouldn't be a problem on the street adjusted like that.

If you get a pencil and a string, swing the arcs and measure the difference it isn't very much at all . . . which means the pinion angle changes only a very minor degree and is not the end of the world like some of the evangelical style preaching guys do about differing arcs.

Another nice thing about the ChrisAlston links is the style of polyurethane bushing they use.
It looks like a cross between a Heim joint and a street rod poly bushing.
They have a website and there should be a pic to show that.
I believe they make that type bushing in smaller sizes as well.

The 32 does pretty good far as traction goes, large and soft rear tires with an 8"+ tread.
Probably better than the hard slicks from back in the day.

http://i49.photobucket.com/albums/f2.../JanKlatt1.jpg

Sorry about the pics.
All the information is there on the word processing program I use as well as on the edit screen here at CHR.

I posted an article yesterday and they all came through ok.

????

This is a great article have a quick question dose any body have a picture of a non equal lenght 4 bar set up Dose the short bar go on top? And where do you start in other words dose bottom bar go parallel and top bar go at a higher angle. also can I get shorter bars of equal length and make this setup into a equal lenght 4 bar set up with out changing mounts? sorry to get your thread off track just seemed to fit here since you where talking about 4 bar suspension.

Have a look at this thread---It may help a lot.---Brian

http://www.clubhotrod.com/forums/sho...rod-frame.html

Thanks Brian I am sure it will have alot of reading to do

Originally Posted by mark craig

This is a great article have a quick question dose any body have a picture of a non equal lenght 4 bar set up Dose the short bar go on top? And where do you start in other words dose bottom bar go parallel and top bar go at a higher angle. also can I get shorter bars of equal length and make this setup into a equal lenght 4 bar set up with out changing mounts? sorry to get your thread off track just seemed to fit here since you where talking about 4 bar suspension.

Unequal length 4 bars are entirely different on their geometry and how the settings can be changed to react to track conditions. The shorter bar is always on the top but the mount holes are drilled in the mount plates on an arc that follows the angle of the bars so you can change bar holes on either the front or rear mounts and change what the chassis is doing..... Sound confusing? Well, unequal length four bars are somewhat confusing until you spend some time studying their geometry and how bar mount positions change what the chassis is doing.... The Doorslammers Chassis Book is probably one of the most complete and thorough books on the science of bar adjustments.

Can't really see where the unequal length 4 bar setup would do much on the street unless you just want the "eye candy" effect.... Even at the track I have seen many both new and experienced drag racers dial their traction and hook up right out of the car by making the wrong adjustments!!!!!

IMO for street or dual purpose machines, either the parallel or triangulated four bar is the way to go. The unequal length 4 bars would be best left for the race only cars... They will work on the street and can be set up with polyurethene bushings, just a lot of hassle for the little bit of advantage they would ever give if the bars were occasionally adjusted to match the ever changing conditions on the street!!!!