Technical Who's running parallel leaf and 4 bar triangulated rear suspension?

Having done this set up a couple of off topic vehicles I will say hemi joints suck! Bushings are the way to go. Rubber ones. Urethane sounds like a good idea but they wear quickly. Hemi joints are prone to wear and squeaks. Unless you can find some way to grease them and keep dirt out of them.
This is the entire reason Johnny joints were developed. Because hemi joints don't last, or have the resistance to impact required.

I know there are gonna be ten guys saying "I run heims and they are great" and they may work for fine for limited mileage on very clean roads.

 

Oh and one more thing,
There are loads of online calculators to properly set up a fourlink rear. Use one. A parallel link rear with a panhard is the way to go in my opinion. Get it right.

Roll steer, understeer and bumpsteer on the rear of a vehicle are both very real and dangerous as shit.

 

Heim joints actually allow less movement than a bushing.

Heim joints cannot deflect.

Most of the movement in the systems with bushings is torsional twist of the bushing, and deflection. That's what the bushings are for. They are not just isolators.

 

I prefer a Watts link.

 

Hi again
Art Morrison has a great web site and a lot of pdf files on all his frame and suspensions and the correct angles and placement of bars and shocks. You should take a look. I studied them and then built mine. When I was finished I shook the shit out of mine side ways and there was no movement to cause side ways movement in relationship with the frame. Just as good as a panhard bar. The upper limit of the diff is the frame bumpers and the lower is the end of the shocks, if either hits you need more travel or stronger springs. I'm sure you know that. There is not much travel needed in a model a.
Hope this helps and don't worry asking questions just get it right in your mind and then build it.
Regards
Dave

 

A watts link might be great on a car, I am used to stuff that has 14" of useable travel and 40" or so inches of flex, a panhard is the only thing that will work.

 

Well yeah, but most folks in the hot rod world don't need all that. A typical car uses a whole 5" of travel.

 

Very true. But gettting it right is getting it right. A lot of the steering and suspension systems I see on cars are very poorly designed.

 

Yup. That is absolutely true. I have been trying to stop myself from looking, as much as I can.

As an engineer, some things absolutely drive me nuts, and I need to learn how to let it go. I can't fix everyone's everything.

 

Ya no kidding.

 

Do a Triangulated 4 link setup, the TCI kits however nice end up costing more than the 4link and coil overs. plus they use 70's Dodge truck front springs which are a few hundred lbs too high of a spring rate for most applications. Used them on one 47-53 Chevy chassis and will never do it again they were stiff as hell and took 3 200+ lb guys jumping on them to get any real movement. the Triangulated 4 link keeps axle centered in chassis and gives plenty of travel 3-4" in most cases, plus you can get that and coil overs for roughly $400.00-$500.00 and the TCI kits are $600.00+ in most cases. If we do use leaf springs on one of our builds we use Ford Explorer leaf springs and remove the helper and 1 more spring to get perfect travel, plus the front brackets work perfectly, then we simply bore a hole in the frame and box it with 7ga, then we use DOM tubing and S10 Shackles for a very nice effective setup. If your interested in pics of both setups shoot me a PM and Ill email them to you so I don't clutter the website with giant pics.

 

Looks like the spring is outta the bucket on that XJ

 

Like DaveFriend answer - how much total travel did you end up with? Planning on 4 inch in my home built. Do search web & find sports car people do talk about angled links binding but never mention amount of travel. I can understand angled links would work for short travel but What is that in inchs?

 

If your suspension on a car is traveling more than 4" total from bottomed out to fully extended. This is the travel of most coil overs anyway. You must live somewhere that has unpaved roads and like giant cliffs you can fall off. We are in MN where the state flower is the road cone and most trucks we build have 3-4" of static ground clearance and have no issues. Only times you need more travel is if you have crazy speed bumps, in which case we do air ride, because we put everything in the weeds.

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Do you run any shackles off your springs front or rear? Seems you might need front but not rear

 

It is. This is before the far taller and softer springs went in.

It was a travel and articulation test.

 

Hi I think I bought 12 inch shocks. Installed them so I had the 3 inches up travel to the rubber frame bumper and down to the middle hole of three in the diff. bracket for the lower bar. That said I have 12 inches of travel.
Regards
Dave

 

Parallel leafs are cheaper, easier to install and ride very well when dialed in. Unless you want a crazy low ride height or air bags, there is no reason for the 4-link. I am building my first Triangulated 4-link in a '58 Buick. Lots of opportunities to get it wrong. Lots of geometry to consider.

 

I don't have shackles. It seemed pointless. Other setups I looked at such as old race cars didn't have shackles so I didn't. It just seemed like one more breaking point. I think a better quality spring would make a difference. Longer would help too. I'm going to rework it eventually anyway.


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Don't know exactly what you are looking to do with your car, how you want to drive it, and/or the theme you are after but ....

I am a bit old school so parallel leaf in the rear of 35-48 Ford cars is what I have always used. Sometimes the ride was too stiff, sometimes too soft but with adjustments like a nice rear sway bar and the right shocks, the taller old Fords with their heavy steel bodies handled pretty well. But, newer and more modern frame tech has changed things quite a bit and I am not up on that at all. I can tell you that with a dropped front axle, parallel leaves out back, a rear sway bar to stop the body roll in the corners, proper tire sizing, and the proper rim offsets, you will not be disappointed.

I have posted this pic of my old 40 coupe before but it's stance to me is perfect, it rode well, and it stood the test of time. The 40 pickup I am building has a very similar suspension setup and I might do some autocross with it.

 

Not just geometry ,but also load forces. Torque at the tyre footprint = thrust at the axle centreline.
If you 4 links the thrust is shared by upper and lower links [these are compression loads, but the uppers have torque reaction tension subtracted and the lowers have torque reaction compression added]

If you have arms AT the axle centreline [3rd gen Camaro] these will take All the thrust loads [compression] during acceleration and All the braking loads [tension]
Camaros use a torque arm and a panhard bar. But you can use a true triangle like a satchel link to do both these at once.
This triangle [if it meets together ] will become the true roll-centre. Lotus Cortinas have the triangle under the diff head to get a low roll-centre. This triangulated link is under compression during acceleration [pinion torque reaction] but the far greater loads of brake torque have tension loads on this link.

Brake torque on an axle housing is far greater than pinion torque reaction

 

Both are very effective centering devices, but the Watts is a considerably more complex design for, in the case of a typical street car, nominal gain.

The rearend shift from a Panhard setup as the suspension cycles can be effectively "zeroed" (not really, jusy 'close enough') out with a sufficiently long bar. I'd offer up some math for readers but I'm on a tiny phone at the moment.

Maybe @gimpyshotrods has some comparison numbers handy??? On a suspension cycling maybe 5-6" MAX full top to full bottom, and a Panhard bar whose ends are tucked just behind the axle ends, compared to a comparable Watts, and I suspect the difference in lateral shift of < 1/2" (that was a WAG).

Of course, a Watts link distributes its lateral movement in both directions, and if you can fit one large enough underneath a car, you can escape essentially all lateral shift by keeping the suspension cycle right at the center of the Watts cycle... but that requires a pretty large bell crank.

/words

Edit: Looks like @dumprat and @gimpyshotrods already discussed some of this above. Oops.