zero index birdcage

[King1]

My main point was I see a lot of people outsmarting themselves chasing load numbers Etc the mechanics of the racecar haven't changed fundamentals of it are the same we just go about achieving what we need a different way now if you understand a lot of this stuff you can look back at your old setups and kind of start to understand why you had to do certain things because of what we know now and how those changes affected other corners

I hear what you're saying. I think we're all smarter than we used to be and take a piece to the track that is a little more dialed in than it used to be.

I drop the LF out a little more if I need the RR to do a little more work in the center

And i take LR droop out just to control roll steer a little better.

I hadn't tried it til the guy I get info from tested with me once. I went from cranking wedge in a car and rolling the tool box out, to making small adjustments and not working near as hard. But that's why I source my info because I'm simply not smart enough nor do I have the time or resources to test or make educated guesses.

[Kromulous]

Thanks King1, i was thinking along the same lines with LF and LR, but i always like to check my thoughts about what affects what.

Anyway, i agree with the small adjustments. I am in the process of learning spring rubbers etc, and after sitting with my spring smasher and adding in and taking out rubbers and packers you can make some big changes, and with minimal work. After this last couple weeks where i dialed the car completely out, i am going to change my approach, to small adjustments etc.

[Nesmith14b]

@RaceEngineer. Why do you suppose a nearly cammed over birdcage kills speed? On the LR, the solution might be to raise the lower bar on the frame, or lengthen the lower, or index the birdcage back at ride height, to decrease upper bar angle at full droop. But what do those changes accomplish?

[RaceEngineer]

@RaceEngineer. Why do you suppose a nearly cammed over birdcage kills speed? On the LR, the solution might be to raise the lower bar on the frame, or lengthen the lower, or index the birdcage back at ride height, to decrease upper bar angle at full droop. But what do those changes accomplish?

The system has little to no compliance. The spring cannot function. The shock cannot function. That is bad for maintaining traction over bumps. You can rock the cage back to compensate.

[Nesmith14b]

Thanks. Now you have me thinking...

[brett4]

what would your guys opinion be on just moving the left rear lower bar forward on zero index plate and leaving the top bar alone??? so on the birdcage with the car on the ground to top bar would be at 12 o'clock and the bottom would be at 7 o'clock.

[Kromulous]

I believe it would almost index away from the spring, the further it traveled down, it would be a small amount, maybe even zero indexing. If the bars are perfectly parallel, i think it would index away from the spring.

[brett4]

I agree just wondering all your opinions..

[ukydude]

It would not index away from the spring. Moving the bottom rod forward and keeping it the same distance from axle centerline will not change indexing all that much but it will change how much load that bar carries and how the car lifts and falls.

[Kromulous]

Ok, more or less loading? and how so on the lifting and falling?

Interested in this, something i have never done before.

[billetbirdcage]

Ok, more or less loading? and how so on the lifting and falling?

Interested in this, something i have never done before.

Too lazy to figure out just moving the lower bar only but this will give you an idea:

if you take a std cage set up with 25* LRU and 9* LRL and let it travel till the upper bar reaches 45.7* and compare that to the bars moved 1" each forward/backwards the difference isn't much (granted drawn in CAD and only looking at the LR cage movement not the whole rear end movement which will be exaggerated at the LR wheel):

Both set to 45.7* of LRU bar angle at drop

STD: 4.89" of drop at cage
2.587" of Steer
12.384 degrees of index

Bars moved 1 back and 1 forward: 4.999" of drop
2.646 of steer
11.356 degrees of index

Difference of .060 drop and .100 steer.

[powerslide]

what would your guys opinion be on just moving the left rear lower bar forward on zero index plate and leaving the top bar alone??? so on the birdcage with the car on the ground to top bar would be at 12 o'clock and the bottom would be at 7 o'clock.

Could you create similar effect by indexing the birdcage back instead of forward?

[ukydude]

If you want to alter indexing you need to work on your combination of upper and lower bar angles/lengths. Placement on the birdcage has more to do with load and timing. Moving the top back and bottom forward have different effects and both have advantages and disadvantages. I can tell you exactly how and why but I would suggest just trying out different configurations. Something that looks great on paper might be excellent for driver A but terrible for driver B. And yes you can index the cage back and that will have a similar effect of moving top back and bottom forward but now you have altered the shock mount location and the spring's input/resistance will also be altered.

[Kromulous]

More steer, and less indexing, might be worthwhile. I have run the top bar back 1" but not the bottom bar.

[7uptruckracer]

So I see these “zero Index” cages they almost look like the old school where we had a few series of holes. Is that how to zero index? Which some say here is good or bad or run longer upper bars and shorter lowers if we have the corresponding holes on the 4 link brackets? I’m trying to do this on a mod ALSO SECONDLY is it true if you run the zero index being CAM over isn’t a problem you have guys running much steeper angle in the LRU?