LR Drop

[musolino21]

Just want to check… Is it a common adjustment to reduce LR drop length for qualifying in tacky conditions? If so, would reducing the overall chain limiter length a 0.25” or more be preferred?

[MasterSbilt_Racer]

Limiting overall limiter length vs what other means? I feel like I'm missing part of the question.

[musolino21]

I watched a video of a qualifying session that broke a track record. In the video I noticed the RF nose isn’t down as far as when you see the nose being sealed to the track when the track has slicked off. I’m curious if there are adjustments to shorten left rear chain limiter length that would reduce lr drive for heavy conditions? As it would give the visual of less lr hike and the RF nose not being down tight.

[MasterSbilt_Racer]

You could make that adjustment and likely get the results you seek. A higher rr would also result in a higher rf.

I've known of teams also being successful reducing hike when it gets slick to remove steer. Obviously that wasn't the only adjustment.

[billetbirdcage]

Couple things to keep in mind on chain length: depending where you are on the curve of the arc of the 4 link when your stopping travel while you may be limiting hike (IE wedge) you are also reducing steer. So if your chain is long enough that it's stopping at the very end of the arc before it overcenters or is going forward as much or more then it's going up on the chassis, shorting it can tighten a car. Meaning sure you removed 1/4" of hike (wedge) but removed 1/2" of steer, the loss of steer will tighten the car more then the removable of the hike loosens the car for a net of being tighter.

While you never really know what all teams are doing, I'm pretty confident is saying in general. . . "NO, most do not shorten chain for qualifying"

[billetbirdcage]

As far as seeing the RF being down less: Depending where you are seeing this (IE on corner entry or after they are back hard on the gas), there could be a number of factors to why your seeing that.

1. More RR load/rate so the RR is carrying some of the load the RF would normally be carrying so it travels less.
2. More RR bar angle so RR raises more picking up RF
3. Using way way more HP which will pick the RF up when heavy. I can easily see over an inch difference in upward travel of the RF in telemetry from a heavy track to a slick one if you don't adjust the rebound on the RF when slick.
4. May have reduced J bar rake which would push down on RF as hard.
5. May have added rate or shims to RF to not bottom out RF with the high speed of a tacky track thus less travel

[musolino21]

You could make that adjustment and likely get the results you seek. A higher rr would also result in a higher rf.

I've known of teams also being successful reducing hike when it gets slick to remove steer. Obviously that wasn't the only adjustment.

Thank you for your input. We make adjustments in preparation for heavy tracks, particularly Lernerville where it can provide a lot of bite early and then slick off. Was wondering if messing with the limiter was in the playbook.

[musolino21]

Couple things to keep in mind on chain length: depending where you are on the curve of the arc of the 4 link when your stopping travel while you may be limiting hike (IE wedge) you are also reducing steer. So if your chain is long enough that it's stopping at the very end of the arc before it overcenters or is going forward as much or more then it's going up on the chassis, shorting it can tighten a car. Meaning sure you removed 1/4" of hike (wedge) but removed 1/2" of steer, the loss of steer will tighten the car more then the removable of the hike loosens the car for a net of being tighter.

While you never really know what all teams are doing, I'm pretty confident is saying in general. . . "NO, most do not shorten chain for qualifying"

Thank you for your info. I had the assumption of rear steer playing a role, just wasn’t sure which played a bigger part.

[MasterSbilt_Racer]

The knowing of the outcome of steer vs load is often hard to know ahead of time, unless you've tried it and kept the variables the same. It's very situation specific, as Billet pointed out.