3 link ?

[Sandbed]

Just like the title say, ive got a 3 link questions.

Im currently finishing up the rear suspension on my 63 SS Nova.

Ive mini tubbed the rear 3" and made all the changes to the TCI 4-link needed to make it fit.

While im at it i would also like to make the 4-link interchangable into a 3-link. figured i would some what copy the Art Morrison idea and bring the 3 link off of the drive line loop.

Basically i have 2 question.

Should the upper 3 link be parallel to the lower two drag links?

How long should the upper link be.

Some where i remember reading that a good place to start would be 75% of the lower links lenght. In my case that would be approx 15" since the lower links are Approx 20".

i figured i would make it with as much adjustability as possible for tuning.

Any thoughts or help would be much appreciated!

[MrQuick]

yep, looks like you got it.


vince

[Bryce]

Upper link is typically not parrallel to the LCAs. There are suspension caluclators out there to determine you anti-squat, roll center, and roll axis angle. All of those are important to determine the handling characteristics of your car. Just welding on a third bar is the easy part. Plu syou need to figure out how much adjustment you want. How close can the mounting holes be so make adjustments, how does each hole change your geometry.

Sounds like a cool idea, just need to determine the geometry.

[Sandbed]

I was looking at doing that, but im not sure how to find my "Vehicles Center of Gravity". Atleast not without scales at my disposal. ANyone have any ideas on that? If i had that it would be easy to find my instant center and anti-squat.

I'm up for suggestions.

[Bryce]

Typically you can guesstimate the height of your Cg by using the cam centerline.

[cheapthrillz]

I was looking at doing that, but im not sure how to find my "Vehicles Center of Gravity". Atleast not without scales at my disposal. ANyone have any ideas on that? If i had that it would be easy to find my instant center and anti-squat.

I'm up for suggestions.

You might could try this...... might give you an idea lol. Just trying to help.

What you need:
Tire pressure gauge
measuring tape or ruler
2 pieces of cardboard with straight edges

What to do:
The car must be parked on a smooth surface like a garage floor. Put one piece of cardboard on the floor against the front "edge" and one against the rear "edge" of a tire. Push them tight against the tire, and make sure they are parallel to the tire edges and each other. Measure the distance between the 2 pieces of cardboard, in inches. Call this distance L.

Move one of the cardboards to the inside edge of the tire and the other one to the outside edge of the tire, again keeping them parallel. Measure the distance between the cardboards in inches. Call this distance W.

Measure the tire pressure in the tire, in pounds per square inch. Call it P.

Now multiply the 3 values, LxWxP. This will be the weight that the one tire is holding up. Repeat for the other 3 tires, and add all of them up to get the total weight of the car.

You can do this with metric units too, as long as you use metric for the distance and the pressure measurements.

Theory:
LxW gives you the area of a tire's contact patch. In english units, tire pressure gauges give you pounds per square inch of the air that is supporting the car. So when you multiply the area by the pressure, you get how many pounds that tire is supporting.

[BillyShope]

Upper link is typically not parrallel to the LCAs.

I had assumed he meant in plan view, but, if that's not the case, thanks for forcing a clarification.

He might profit from Pages 18, 22, 39, and 40 at my site.
http://www.racetec.cc/shope

[19,69camaro]

I know this is an old thread, but when are links considered too long. I dont plan on having a back seat so say if I have a 30" upper and 40" lower link using the 75% rule would this be a bad thing considering the materials used for the link tubes can handle the stress? I know a torque arm setup can suffer from braking lift if not set up right but I dont know if this applies to three links

[Bryce]

The link length will have diminishing returns. As you go longer you can have move suspension travel with less geometry change. But you will be adding weight. 40" is close to the length of a trophy truck suspension with 24" of travel. Brake hop is due to a really short Instant Center and high anti-squat values.

My 3-link will have 22" lowers and 13" upper and 50% A/S at ride height, at 2" of suspension compression I have 38% A/S just to give you an idea.

[19,69camaro]

Yeah that was the idea. To get geometry changes as minimal as I could get them. I figured since I wasnt going to be using the space might as well put it to good use. As for weight gain what is 2 to 4 more pounds of unsprung weight when compared to that of the 12 bolt Im running. As for instant center I dont see that being a problem I just didnt want the rearend to lift off like a non decoupled torque arm

[ArtosDracon]

Theoretically it wouldn't hurt anything in a 3-link, but it likely wouldn't be worth the effort over say a 30" lower bar and a 22-25" upper bar.

[Bryce]

Theoretically it wouldn't hurt anything in a 3-link, but it likely wouldn't be worth the effort over say a 30" lower bar and a 22-25" upper bar.

Thats what I was trying to say HA.