Thread: Beam Suffering

Basically you want the moment of the suspension locating devices (roll center) to be close to the c of g. In the b14 case the rear c of g is right about axle level thus keeping the roll center close reduces the roll couple (which is the distance between the c of g and roll center). On cars that don't have good trailing arms (like a live axle rwd with leaf springs) a watts link works wonders over a panhard bar bc that axle moves all over the place. The only problem we really have is the roll couple being too big thus for the b14 a panhard tends to be a better choice. Plus it's much easier to fabricate

Another little update on overall suspension. I'm really loving the ES bushings and the Addco on fully stiff. The road NVH only slightly increased, but the car control is amazing. I took the same downhill s turn, wasn't trying to go fast (trunk had a brand new battery for the B15) and cake in the car (don't want to damage the cake you know!)

I hit 45mph and didn't even notice it. It felt smooth and like I was going the 25mph speed limit. I asked the wife if she remembers when I took that turn and it felt like the car was gonna flip over, well I am going about the same MPH.

TheSam call it right:








It was stupid easy. I was able to press them in with my bare hands. It's either because P11 holes are bigger, or rear bushings need some play.



That's actually how I was considering building a Watts setup. The thing is, after reading 2JR's thread to the end, I saw that they still went back to a Panhard since it was a lot simpler and the benefits where neglectable.




This is why I would also consider mounting the watt's on the beam. But then you run into ground clearance issues.




I have a Stillen bar on my B15, I was very tempted to remove it and try it on the P11. Though it sounds like it's a few inches short. Interesting enough the Stillen doesn't even attach to the back of the beam, it's way infront of it.



Look at were the Watt's is mounted at on the body itself. That's what determines the roll center. If you can get a watt's real low this would fix the issue, but then you start having ground clearance issues with the arms.

Amazing what happens when you stiffen the end that is not doing a damn thing in a corner, isn't it? (I am referring to the rear end but of course)

Remove front sway bar end link, naow. Don't replace bushings, just remove an end link and push the car. I still have yet to do that on my car!!!!!

IRS > Beams

Okay. I think I'm getting it. The higher the end links the more it wants to rotate (roll) the chassis. Which in turn unloads the inside tire. Less rubber on the road = less grip.

boss

You are almost there Hank.

Think of it like this,

Picture the side of the car

Now picture a point about 4" off the ground at the front axle and a point about 12" off the ground at the rear axle.

Now draw a line between those points.

That is the axis that the body of the car wants to roll around as it goes through the corner.

Now imagine how that car looks from the back end as it rolls around that line.

Yes, a tire that is not in contact with the road offers no traction, but that is not really what is happening in this case. It is actually just the opposite. Because of the angle of that imaginary line, the car ends up placing a tremendous amount of load on the outside front tire. Becasue of this, the outside front tire will reach and exceed its limit sooner as it is being forced to do more work. Then your car goes plowing straight off the track!

Now picture the same car but with the point at the rear axle at the same 4" off the ground. Perhaps even 3.5" off of the ground.

Now how does the car look when it is going around the turn?

Let me just say from personal experience that it is a big difference.

The 4" and 12" numbers I gave are for an example only. I do not know where the actual roll centers for the B-14 are located. I just wanted to give a simple example of what a difference lowering the rear roll center can make.

12" is correct for the rear. Here is what 2JR said. They obviously have a modified LCA to get -2" up front.



I would even say, if we can lower the roll center of the SRL link, it would be sufficient enough imo.

I notcied something else while putting in a B15 link on my car this week. the SRL has on over-center point as it sweeps through the range of motion. Meaning that there is a kinid of natural center location and as you go up or down from there it swings the axle and eventually induces bind. I would think with enough spring or swaybar you could mitigate that effect, but it's still there. The other thing worth noting is that if you're lower (or higher) than stock height, you're already locked to one side of the SRL and it seems to make it tougher to move it past the over-center position.

Either way the PHB set up would be the best fix for this. Making the SRL adjustable to deal with that would be way more trouble than it's worth.

i've already bought an adjustable srl for the panhard and it wasn't difficult to fit and allows you to re centre everything at whatever your chosen ride height

I really don't see how the adjustable dog bone really does anything. If you don't change the length of the entire assembly, it's still going to bind when it goes past center while on its arc travel.

For those that are lost, I'm referring to the main SRL attachment point on the beam, not the dog bone attachment point.