Rear end bouncing after shock change? Updated 9-30-2012

Posted By: 540CUDA

Rear end bouncing after shock change? Updated 9-30-2012 - 09/22/12 04:34 PM

I had a leaking rear single adjustable QA1 shock so I replaced both rears. The new shocks have more adj clicks so I was guessing at the setting. The old shocks were at set at 9 (1-15 clicks) I set the new ones up at 11 out of 18. Now the car keeps bouncing in the rear pretty much all the way down the track, which is very noticeable in the video but it just felt like I was loosing traction during the run. Are they just set up to hard? It also shot to the right on launch slightly so a little more preload on the right ladder bar is in order, yes?
Opinions please.

Posted By: Jeremiah

Re: Rear end bouncing after shock change? - 09/22/12 04:43 PM

I would guess that if the car is bouncing the shock is too loose? If I tighten up the shocks on my car too much it will blow the tires off. If I set them too loose the weight transfer overcomes the shocks and the car will do strange things (not want to go straight, feel spongy, etc.) This is a four speed car and I don't know that much about this stuff so take it with a grain of salt.

Perhaps the shock was too stiff and causing the car to bounce on the tire? What does the vid show?

Posted By: Cab_Burge

Re: Rear end bouncing after shock change? - 09/22/12 05:48 PM

The only set of single adjustable QA1 I had where fronts, they where 90/10 on extension and the compression was what was adjusted by the knob, not the extension

What are your ratio

on the extension?

Posted By: Dyno1

Re: Rear end bouncing after shock change? - 09/22/12 05:54 PM

I would guess that the shocks are to soft. What brand shock did you replace the QA1's with? Dyno

Posted By: Jeremiah

Re: Rear end bouncing after shock change? - 09/22/12 07:56 PM

Quote:

The only set of single adjustable QA1 I had where fronts, they where 90/10 on extension and the compression was what was adjusted by the nob, not the extension What are your ratio on the extension?

Not trying to be smart but how can they be 90/10 if we are talking about extension? I am not following.

I was looking at some other QA1 shocks that were here in the shop and had some concerns and the tech at QA1 (nice guy, very smart) told me to install the shocks and tune them on click at a time in the front until the front end stayed up long enough to get the car moving/weight transfer. He said keep the rear in the middle setting during that test. The next step was to tighten up the shocks in the rear until the car started to loose traction off the line. Those were instructions for a base line on a new set of shocks. This is for a leaf spring car.

I have talked to several guys with ladder bar or four link cars that have not had much success with single adjustable shocks and prefer double adjustable. That is not my direct experience just hearsay.

Posted By: Jeremiah

Re: Rear end bouncing after shock change? - 09/22/12 07:58 PM

Quote:

I had a leaking rear single adjustable QA1 shock so I replaced both rears. The new shocks have more adj clicks so I was guessing at the setting. The old shocks were at set at 9 (1-15 clicks) I set the new ones up at 11 out of 18. Now the car keeps bouncing in the rear pretty much all the way down the track, which is very noticeable in the video but it just felt like I was loosing traction during the run. Are they just set up to hard? It also shot to the right on launch slightly so a little more preload on the right ladder bar is in order, yes?
Opinions please.

Question : Is there a reason why you did not have the QA1's rebuilt? I think there is a place in sac that is a QA1 authorized rebuilder with a shock dyno, etc. If you want the number it's floating around my shop somewhere.

Posted By: MR_P_BODY

Re: Rear end bouncing after shock change? - 09/22/12 08:04 PM

First I would wonder if the shock is bottomed out
going down the track or if its topped out(put a tie
rap on it to see whats happening)... with the different
shocks its loading differently so thats why its going
to the right... correct the shock issue first and the
loading might be right again

Posted By: 540CUDA

Re: Rear end bouncing after shock change? - 09/23/12 12:43 AM

Thanks for the replies guys, It was easier to get QA1 shocks than a kit,plus I can use them on my truck later. Theyre not bottoming out, but that had crossed my mind. I should have mentioned I completely rebuilt the rear end housing and brackets so it was a baseline adjustment that got me to this point-zero preload and then one flat on the right side. I guess it needs more preload to go straight. And after looking at the pics and videos Im killing the tires at the line with 7psi, so multiple issues I guess. I'll post some pics when I can.

Posted By: JAKE68

Re: Rear end bouncing after shock change? - 09/23/12 01:23 AM

Reading between the lines you have a caltrac system????? If that is the case then that is not the right shock. That shock cannot control that system enough.

Posted By: Jeremiah

Re: Rear end bouncing after shock change? - 09/23/12 04:35 PM

Quote:

Reading between the lines you have a caltrac system????? If that is the case then that is not the right shock. That shock cannot control that system enough.

What would be a good rear shock on an application such as this?

Posted By: MR_P_BODY

Re: Rear end bouncing after shock change? - 09/23/12 04:59 PM

Quote:

Thanks for the replies guys, It was easier to get QA1 shocks than a kit,plus I can use them on my truck later. Theyre not bottoming out, but that had crossed my mind. I should have mentioned I completely rebuilt the rear end housing and brackets so it was a baseline adjustment that got me to this point-zero preload and then one flat on the right side. I guess it needs more preload to go straight. And after looking at the pics and videos Im killing the tires at the line with 7psi, so multiple issues I guess. I'll post some pics when I can.

At 7# tire pressure thats no where near enough...
I run 7# and I'm alot lighter than yours(assuming
its the one in your sig comment) and if thats the
car those shocks might not be enough... as Gary(Jakes)
stated... they work with the leafs but just enough
but now add the leverage of the caltracs and I dont
think its enough..... JMO
EDIT
Try your new shocks near the max setting on extension

Posted By: JAKE68

Re: Rear end bouncing after shock change? - 09/23/12 10:11 PM

Either the calvert shock or a step up would be a afco dbl adjustable.

Posted By: 540CUDA

Re: Rear end bouncing after shock change? - 09/24/12 03:49 PM

Its a ladder bar system that went 1.30 on the old QA1 shocks. It just started the bounce with the new untuned QA1's. Next weekend I'll try more tire pressure and preload and stiffen the shocks if it needs it after that.

Posted By: JAKE68

Re: Rear end bouncing after shock change? - 09/24/12 04:10 PM

Now with more info I have another question.Did you change anything on the front end? Ya you should be at least what it was before!!!!

Posted By: 540CUDA

Re: Rear end bouncing after shock change? - 09/30/12 07:10 PM

http://www.youtube.com/watch?v=0CQHLzN_lHE&feature=channel&list=UL
Video of the bouncing last weekend. I made some runs yesterday after adding more preload,softened the rear shocks, upped the tires to 9psi and went up 2 jet sizes. It responded with a 9.30 at 145.13. Launches are straight and no more pogo action. Video of that run soon to come.

Posted By: 540CUDA

Re: Rear end bouncing after shock change? - 10/01/12 11:40 PM

9.30 145.13 run http://youtu.be/yr7hzWzcEIM

Posted By: sshemi

Re: Rear end bouncing after shock change? - 10/02/12 07:50 AM

Qa1 can handle caltracs.
They get super hard when adjusted.
I have never set mine any harder than halfway.