PDA

View Full Version : Birdcage drop?



Kromulous
07-27-2015, 03:53 PM
Drop to the shock mount, from the axle CL, what does it influence?

I notice alot of mounting options, and have never moved them LOL.

Thinking out loud, i would say it would have an influence on how fast or slow the indexing of the birdcage is applied to the spring, as well as the amount of leverage the indexing has on the spring, and the overall amount of indexing into the spring (short lever arm)?

Would it be good, in the very slick to reduce the drop on the RR birdcage?

Thanks, Krom.

Matt49
07-27-2015, 04:40 PM
The further the shock mount is away from the axle CL, the greater the motion ratio of a given birdcage indexing. So a shock that moves X inches with 15 degrees of birdcage indexing at 4" from CL will move >X inches with 15 degrees of birdcage indexing at 6" from CL.
So for very slick conditions, if you want more side bite, you should actually move the drop further down (away) from the CL (and obviously put ride height back where it was). And on the LR, same thing, except moving it further away will give you more initial forward bite.
Not an adjustment I've ever attempted at the race track though...
I set the shock drop so that my shocks are in there optimal stroke during on-track travel.
So I'm making sure that the LR isn't topping out at full extension of the LR (chain catching first) but I don't go any closer to CL than that.
And I make sure that the RR isn't going to bottom out at what I would consider full compression of the RR (that's another discussion) but then I don't go any further from CL than that.
How much drop that equates to will depend on your shocks, chassis, birdcages, etc.

Kromulous
07-27-2015, 09:37 PM
Thanks Matt49, that provides clarity.

And another question lol, the car seems stiff on the RR and we can't keep the RR from dominating coming off the corner, so the car is throttle loose. I was thinking to much indexing, 225 RR spring thou. J-bar real low as well.

Gonna work on bar angles and not sure what else lol

billetbirdcage
07-27-2015, 10:56 PM
Keep in mind there are 2 directions you can alter the shock mount to axle centerline, most only think in "Y" (up and down) and you have "X" also.

Kromulous
07-28-2015, 07:52 AM
So moving in the X direction, leans the shock / spring FWD or AFT maybe adding some progression to the travel?

MBR Performance
07-28-2015, 05:26 PM
Just drop your RR top rod if you're getting to much RR drive.

25drtrkr
07-28-2015, 08:08 PM
Keep in mind there are 2 directions you can alter the shock mount to axle centerline, most only think in "Y" (up and down) and you have "X" also.

That is a forgotten adj. It was one of our "go to's" on a Smack car.