Reverse 4-link question

[BigMatt]

I want to get the triangulated 4-link for my 96 Toyota Tacoma. I' ll be using an 8" step-notch with airbags mounted on top of the axle. There is no room for upper-bars because of the gas tank. Even though I have seen many mini-trucks with reverse upper-bars, The " no no no" in the catalog keeps me from doing it.

So, what about mounting reverse upper and lower bars? I have seen this done also. It wouldn' t cause the extreme pinion angle problem, but I' m sure you' ll be able to tell me if its a good idea. I' m a detailed person, so don' t be afraid to get technical.

[darren@ridetech.com]

Yea but under breaking conditions instead of planting the axle it will lift. It' s not a a good idea. I would consider ditching the tank and getting a fuel cell.

[threeimpalas]

The driveshaft yoke will also want to pull out of the suspension at travel positions other than center. That' s not a good thing.

[BigMatt]

Threeimpalas, Are you sure? I thought the yoke pulling out of the transmission was caused by running the upper and lower bars in different directions causing an extreme pinion angle problem. Could anyone recomend a good book I could find at Barnes & Noble about suspension geometry? I would like to be more informed before I start picking a setup.

[threeimpalas]

It will still tend to pull out due to the arc of travel that the rear axle goes through. On a regular 4 link it travels in a ) shape - with the front of the car on the left - while on a reverse setup with both upper and lower arms reversed, it' d travel in a ( type arc.

The pinion angle will remain the same throughout the arc if you run equal length parallel bars. Unequal length bars will change the pinion angle slightly throughout the arc. If you were to run a reverse setup, unequal length bars would be even more hazardous than doing a just a reverse setup with equal length parallel bars. Running the lowers forward and the uppers backward causes even bigger problems.

[BigMatt]

Here' s the deal, I don' t want to relocate the gastank and worrie about plumbing all the lines and making a new filler hole and filling the old one. So, there' s no room to run a tri-link the right way. I might be able to fit parallel bars on the outside of the frame, but does the panhard bar have to run parallel to the axle tube? I don' t think there will be enough room to do this with the bag mounts I' ll be using. So, would it hurt if it went from an angle from the axle to the frame, kinda like running the forward bars of a tri-link reversed except its just one bar instead of two. If someone could give me a measurement of the amount the bars & bracket stick out from the frame, I could see if there' s enough room to even do this. Is AirRide ever gonna make a Road-Grater for the Tacoma fans?

Here' s what I was talking about...I couldn' t insert the pic, so just click the link. It' s a hand-drawing of what my setup would be like.

http://www.geocities.com/nitrocustom/draw.htm

Big Matt........ heres the deal.... reversing any part of a four link throws the geometry out to lunch. It doesnt matter if it is two bars or all four bars. With two bars rearward and one forward you will find that you have excesive pinion angle variable. That is caused from the front links and rear links swinging in two converging arcs. This type of set up also does nothing for instant center or roll center. It also places load on the frame where it was never intended to see load. Now running all of the bars in reverse will end up putting the instant center of the vehicle several feet behind the vehicle ( not a good scenario ) not only that but your axle and your driveshaft are starting to pivot in to converging arcs. On a four link all four bars need to be run forward to the center of the chassis. Now it is possible that on a triangulated four link that you angle the upper bars the opposite direction. Instead of running the from the frame rail in to the center of the rear end, you will fabricat a new crossmember and attach the two upper bars centered on the crossmember and run them out towards the end of the axle tubes. This little trick will help clear most gas tanks. Now on a parallel you are going to want 4-5" from the framerail to the tire in order to have anough room to clear the bars. In the image you posted you have the panhard bar running at to great of an angle. ideally your panhard bar is going to run parallel with the axle tube both in height and laterally within tha chassis.

Tony....

[BigMatt]

Thanks for all the help tony, that answers all my questions.