Tires come up twice. Travel limiters?

With the new horsepower we have, after the car's front tires land after launch, they come back up again. Looking for everyone's suggestions in how to get that "bounce" out. Some have said travel limiters, some have said to adjust the double adjustable QA1's in the front. Some have said to adjust the coil overs in the rear (Currently single adjustable, not sure of brand). Some have said put QA1 double adjustables in the rear. What do you guys think? As it was explained to me, thinking of the front suspension in the sense of a pogo stick, travel limiters make sense. Thanks

do you have a video of the passes to post ?

A guy that has been helping me has them. I get him to email them to me and I'll email to you to post if you can. I haven't firgured out the posting of pics and videos yet . PM me your email. Thanks

soupbean wrote:A guy that has been helping me has them. I get him to email them to me and I'll email to you to post if you can. I haven't firgured out the posting of pics and videos yet . PM me your email. Thanks

will do , this way the suspension guru's can help you out

X2 on vids. I have an idea but would like to verify

X3 on posting good usable launch video. "Good & usable" video meaning the person filming the pass stands up-on the starting line behind the car (not shot from the stands) at an angle showing both the back of the car and the driver side of the car (somewhere around a 50/50 to 40/60 dr side-rear split).


Good video helps because it could be a number of things........

(A) It could be an unrestrained/uncontrolled inertia compression/rebound thing if the strut valving is adjusted too loose.

(B) Somewhat along the same "inertia" line of thinking if the wheelstand is now higher/too high vs before (if too much front suspension travel vs engine power), the increased "return to earth" energy/inertia could be causing the bounce.

(C) It could be the rear suspension suddenly unloading a given amount (for whatever reason) while the nose is still in the air causing a quicker front end "return to earth" and the resulting front bounce.

(D) Or a bunch of other possible causes.

Hey fellas, I'm still waiting on the email from the guy that has the good videos from back/side view of the car on launch so I can send them to Nick to post for viewing for your expert thoughts but in the mean time, does anyone have a link to instructions for adjusting these QA1 coil overs. Going for testing tomorrow night and would like to know what I can do if anything to get some help out of the front coil overs. Put some travel limiters on it last night and plan on playing with the rear coil overs tomorrow night and see what it does. Thanks

Oh and btw, the guy that has the videos says he was watching them today and the car barely squats in the rear and as soon as it does it rebounds quickly if that helps any.

here was my deal ........ pig rich , 63 jet in the plate , 3055s , no limiters

soupbean wrote:Oh and btw, the guy that has the videos says he was watching them today and the car barely squats in the rear and as soon as it does it rebounds quickly if that helps any.

It ain't transfering weight then effectively then. Does the body separate at all from the rear end?

And to add....problem isn't in the front either. At least from what you are telling us

yellowhorse7 wrote:

soupbean wrote:Oh and btw, the guy that has the videos says he was watching them today and the car barely squats in the rear and as soon as it does it rebounds quickly if that helps any.

It ain't transfering weight then effectively then. Does the body separate at all from the rear end?

Videos from last year with the smaller motor actually does appear that the distance between the rear fender and tire INCREASED during launch.

Has the car ever been measured and plotted? Where/what is the IC? Once I see video I can probably guess on the anti squat, rather to much or too little

bruno wrote:here was my deal ........ pig rich , 63 jet in the plate , 3055s , no limiters

Nice! What did you let off for?

yellowhorse7 wrote:Has the car ever been measured and plotted? Where/what is the IC? Once I see video I can probably guess on the anti squat, rather to much or too little

You lost my completely with all that verbage LOL! Hopefully I will have Bruno the video tonight and I'm sure you will probably find many issues

soupbean wrote:

yellowhorse7 wrote:

soupbean wrote:Oh and btw, the guy that has the videos says he was watching them today and the car barely squats in the rear and as soon as it does it rebounds quickly if that helps any.

It ain't transfering weight then effectively then. Does the body separate at all from the rear end?

Videos from last year with the smaller motor actually does appear that the distance between the rear fender and tire INCREASED during launch.

Too much A/S with too loose a separation setting and the front end lifts. As soon as the front suspension extends completely out you blow the tires off. Or if the track is on kill, you go up on the bumper. Long story short, your track was probably working well and the car dead hooked, you lifted, causing the front end to bounce. But again, need vids boss. I'll help if I can....

I gotcha and will get the vids to Bruno as soon as I get them. I don't lift, it doesn't get up that high, maybe a foot or foot and a half at most.

I just sent Nick a pretty good video from a launch at last saturdays race. This was a time trial run and we were leaving soft to stay within our 6.00 bracket. Left at 3400. Ran a 6.02 with 1.40 60ft. Notice the craziness going on with the front wheels.

Never mind Bruno! I fingered it out !

After watching this video more I don't think I needed travel limiters??? Doesn't look like much travel to me...

delete

It's almost impossible to see/fully understand what actions are actually really happening during the launch when viewed at real/full speed. It's not until the launch is viewed in super slow-mo, or frame by frame, that you get a much better idea of what is actually happening. Having good launch video is always "more gooder".


Rear separation vs rear squat:


Initial separation action ("initial hit") .....

Rear suspension separation action (rear housing C/L moving down-away from the car/frame/suspension) is the very first initial leveraging action/reaction (aka the "initial hit") that happens in a correctly setup drag car when engine torque/power is first released/applied to the rear suspension. This first initial action is what applies the first initial downward force to the rear housing & rims and starts to plant the slicks into the track surface.

The total amount (measured distance) of this initial rear suspension "separation" can be effected by the car's HP/TQ numbers, it's I/C placement, & how tight/loose the rear shock valving is. And the rear separation can be anywhere from a very, very large amount (like you see on some leafspring/slapper bar cars) to so microscopically small that it almost can't be seen, even in slow-mo video (like some high HP 4-link cars with super tight rear shock valving). Because of this some people mistakenly assume that an initial separation action might not be happening if they don't "see it" at full speed, but this first initial leveraging action is always there first to some degree. Initial separation/initial traction/initial sidewall wind-up has to happen first (no matter how big/small) before the resulting secondary nose lift/front-to-rear weight transfer action can begin to happen.



Secondary squat action ("recovery period")......

Because of how fast & violent a rear suspension's actions can be/appear during the launch when viewed at full speed, some people might see the slick sidewall wind-up action (and resulting body/housing/rim getting closer to the track surface) and mistakenly assume this downward movement as being the rear suspension/frame "squatting" over the housing (which it's not).

True rear suspension "squat" action (rear housing C/L moving up-into the car/frame/suspension) can be effected by the car's HP/TQ numbers, it's I/C placement, & how tight/loose the rear shock valving is (just like separation is). It usually doesn't really happen until (A) after the initial hit separation action has happened, (B) happens in concert with weigh transfer action already underway (as a secondary/continuation of extra downward force to enhance traction even further) after the launch is already under way (aka the "recovery period"). And just like the inital "separation" action, sometimes any secondary "squat" action that might be happening during the recovery period might be so small that it can't always be seen, even when viewed in slow-mo.

Total available engine torque/hp numbers "at launch" can further muddy the waters as to what is really happening during the launch since BOTH engine power AND suspension leverage work together at the same time to hit/plant/screw the slicks into the track surface. It's a balancing act between the two.



People will argue the "squat/anti-squat percentage" theory vs the "percentage of rise" theory, and which is best when setting up the rear suspension I/C placement. But truth be told in my opinion neither theory is really worth fighting over since neither theory takes into account the added effect the engine's at-launch power/torque numbers has on the rear suspension too. I have seen enough cars that did not do what the "squat/anti-squat theory" said they would do (squat vs not) because of the actual working HP/TQ numbers the car had to work with.

Thanks for the good info! So, what's your thought's on what you see from this launch? From your read, I would think my "initial hit" is ok but there doesn't seem to me to be much of a "recovery period".

After seeing the video.......

First off in my opinion the slick air pressure might be a tad too low since I can see sidewall wrinkles before the launch. Then there is approximately 1.5" to maybe 2" of rear suspension separation at the initial hit. Then as the slick sidewall first starts to wind-up and the car initially starts to move forward it's not a true 100% dead-hook, (but damn close) so there is some small amount of initial wheel speed. Then as the rear suspension reaches full separation/slick reaches full wind-up and the car begins to lift the nose a decent amount (start of the recovery period) there is almost zero rear suspension squat back up-into the car, maybe (maybe) only a half inch (1/2") the other direction. The controlled wheel speed/wheel slippage looks to be fairly consistent during the first 10-15 feet (no uncontrolled tire spin/shake). But beyond the 15-20 ft point I cant really see what is happening because of the increasing distance from the camera. As the wheelstand ends and the front bounce happens, the bounce doesn't really appear to upset/unload the rear suspension (but again it's hard to see 100% because of the distance at that point). The front bounce it's self might possibly just be from the strut valving being a little too loose (can't slow/control/dampen the front suspension compression-rebound action fast enough).

Also during the pass it does twitch to the left a small amount (left-launch initally maybe 5" over then continues to maybe 8-10" over). If track prep/roll-out difference/air pressure difference wasn't the cause of the left-launch, then the car might need a slight side-to-side preload adjustment to pull the launch back center.



But as a whole the pass does look pretty good in my opinion, it's not spinning or shaking it's nuts off. It looks to be a very usable baseline starting point to work from (and work back to if necessary) to play with different suspension adjustments.

That pass was 12 psi I believe in the tires. It does tend to pull to the left on nearly every launch. What would be your suggestions in trying?

As for the left-launch...........

If the slick's roll-out is the same, and you're sure the air pressure was the same side-to-side, and the housing is straight/square in the car, and you're sure nothing is bent in the rear suspension, then the stock suspension guys can usually adjust side-to-side preload with either the adjustable 4-link/control arm bars, or staggering the anti-roll link adjustments side vs side.

I hate using/adjusting/staggering the anti-roll adjustment (vs using a neutral adjustment) to control side-to-side preload numbers. Especially with aftermarket "true" drag 4-links because that's part of the 4-link's job, and not the anti-roll's job. But sometimes the stock suspension guys have to/are forced to use the anti-roll for preload because of how limited the stock suspension's adjustment window can sometimes be.



As for the wheelstand bounce/bounce.......

If the bounce/bounce is caused by the front suspension (and you have struts with adjustable valving to work with), the simplest thing to try is just go track testing & play with the strut valving from pass to pass and see what happens. A little more involved, but could still be something to try is to install travel limiters & play with suspension travel and the strut valving at the same time.

If the front bounce/bounce is actually caused from the rear suspension suddenly unloading (while the nose is still in the air) and causing a spin-hook-spin-hook effect to happen repeatedly unloading/loading the rear suspension, then playing with the air pressure & shock valving is probably something to try.