Advices to Setup Double Adjustment Shocks (Updated)

Hi Folks,

Finally I could test my new set of Viking DA Shocks that I installed in my car. These shocks already improve my 60ft from 1.58 to 1.54 but I'm still having tire bouncing on the start.

I'm using this setup on the Shocks:

Front: Compression = 12, Rebound 2.
Rear: Compression = 4, Rebound 12.

My car is an A Body, 3300lbs Small Block with 464WHP, Footbrake, 4500 Stall Converter, Hoosiers 28x10.5, 4.56 Gear, Leaf Springs with Assassin Traction Bars.

I'm sending two videos of the start... So if someone could see that and can support me to fix this issue will be great.

https://www.youtube.com/watch?v=kpsFBEn8U4A

https://www.youtube.com/watch?v=ErDPMz66wkw





Thanks,

Diego Reis

Stiffen the extension and the compression.

If compression is going down and rebound is extending the shocks I would stiffen up the front shocks on compression and loosen up the extension some more, probably the same on the rear
Have you check the rear spring rear shackle angles with the suspension unloaded with the wheels off the ground and no weight on the rear tires by having jack stands under the frames yet? If no do that and see what angle you have on the rear shackles
If they hang straight down or are angled towards the front end you need to think about fixing that

Shackles looks like fine but I'm plannig change them for Sliders ASAP...

Suspension Loaded



Suspension Unloaded


Another thing that I'm looking is Traction Bars angle. I'm running with lower holes mounted front/rear and I understand that I'm having a very agressive rear tires hitting on the ground with this combination because front of the bar is higher them rear and when I leave the brake and car launch, loading suspension this angle change a lot hitting tires on the ground so hard as you can see on these picture that I posted above...

So, make sense or don't?

Thanks

Looking at the 1st video, the car plants the tire fine then it bounces back up in the car. To get rid of that hop, tighten the compression on the rear from a 4 to a 7. that should keep the tire planted.


Joe

It looks like the front is running out of travel and offloading the rears. I probably have 20 - 30 videos of mine doing the same. If you can, lower the front to get as much travel as possible - set the front shock rebound (extension) to full loose and start making passes. Tighten the rebound 10% each pass until the 60 foot times start to fall off.

I tried to sort out the rear first and didn't make any progress until I added travel and started tightening the front. I now have 5" of travel in the front with standard valved Dual Adjustable AFCO's and already ran out of rebound adjustment, but went from 1.48 60's to 1.41's. They are currently getting revalved with stiffer valving.

Also make sure your rear shocks are long enough by unbolting the shocks and letting the rear hang. The shocks should be an inch or two longer than the distance between the upper and bottom mounts when suspended.

Make only one change at a time.

Looks like it extends/separates way too much to me. Tighten, if you have any more adjustment, the extension. The compression could be set in whatever the middle is to start.

Personally I like to start with everything, front, and rear tight hoping it'll spin, then loosening up only what it takes to get the best 60.

Me thinks the rear shackles are going past center(straight up and down) when it leaves and that will make the rear unload causing the hopping
Is there any way you can video the back of the car by the rear springs, Go Pro camera maybe, to see if that is happening or not?
I've seen that same problem on more than one A body drag car

Guys, I really appreciate all advices that everyone gave me. I'll make some changes based on your advices and post all improvements here.

Thanks a lot!

As DT pointed out start stiff and go from there. Depends on track conditions what will make it happy. Looks like it is separating to much to me as well and I would follow his way. Tighten the extension start with compression in the middle...

Diego
That is such a cool looking A Body. I have never seen a South American A Body before. They should have offered that style here. They would have sold a lot more A Bodies. I LIKE IT!

Thanks ScatPack! I really like the body and details of Brazilian Chargers. Basically the body is the same them 68' Darts with some changes in details...

Folks, I measured front end travel this weekend and had 4.2" of travel... So I reworked the suspension bumpers that was blocking my front end travel and lowered front of car 1/2" and now I've 5". I know that the golden rule is do not change more than one thing per time but I'm thinking in tight rear shocks extension from 12 to 18 to start.

Jully 22, 23 will have an event and I will can test my last adjustments...

Thanks Guys!

As I posted in another topic, my car has made his best ET so far. I could drop 60ft from 1.54 to 1.50 based on advices that I received from everyone on this topic.

The problem with tire boucing is almost solved but the car still boucing tires on start. I'm thinking that rear separation is too much as Al Alguire told me before and you can see at picture attached. I have put extra clamps on front segment of leaf springs but I think that's not enough. Maybe time to change for Calvert Mono Leafs!

I started with last configuration that I ran on the rear, 12 rebound and 4 compression and ran at 1.51. So I tighten the rebound for 14 and compression to 5 and 60ft droped to 1.50. I just could made only three passes and don't had time enough to work more on suspension. If I had time I'll tighten more rear shocks but I couldn't.

I'm sending below a video from my GoPro camera that I installed under the car. Sorry for the quality but was darken when I made the video.

Advices will be great again..

https://youtu.be/FqMf1UC3lVs

It looks to me like.. your settings are still way too loose.. and yes the monoleaf is the way to go it also helps get rid of weight. On compression you should be. Almost full tight... and on extension somewhere in the middle.. if the track is greasy you can loosen extension up for some extra hit... the front end looks way to stiff.. do you have aftermarket a arms.. the Freer you can get the front end the better the car will work

I'm talking with Calvert tech support right now about monoleaf. This should be my next upgrade. I agree with you about front too stiff. I'm running on Rebound 2 and Compression 12 and I lowered front of the car to have more front end travel. currently Front end travel is 5" and still looks too stiff.

About control arms I'm still using OEM arms and torsion bars too.

Any recomendation of wich control arms to use?

That looks good to me
There is always more in it as we get brighter and hungrier for more speed and quicker ET

I have the early qa1 upper control arms on my car they don't make that version anymore.. at least so I think.. I think Hotchkiss make some nice upper control arms kind of spendy you might take a look..

I have been eyeballing these...seem reasonable. Anybody using them?

http://www.magnumforce.com/magnumstore/shop/item.aspx?itemid=13

As Shiloh pointed out to many people overlook the front end and just how tight many of them are. Not talking about the shocks them selves per se' just the suspension in general. As for the rear shock keep tightening the extension til it spins Soften the rebound as much as it will tolerate as well for now. Generally speaking the extension controls the hit or plant of the tire and the rebound how well or long it plants the tire..

With the numbers you are talking are you referring to how far from stiff or from soft they are?? Just to clarify

Viking shocks that I'm using have a total of 19 positions (18 clicks plus a zero position) of adjustment per knob. Position zero is the softest setting and is found by turning the knob counterclockwise until the positive stop is located. Position 18 is the stiffest setting.

Just to clarify the things for me also, When you tell me shock extension... extension = compression?

This is the tunning and adjustments that Viking recomends for inital setup for cars under 600HP (my case)...

Front: 12 - 18 compression; 0 - 4 rebound
Rear: 0 - 4 compression; 4 - 10 rebound

I tried start with 4 on compression and 8 on rebound for the rear and was terrible. boucing like a wild horse. lol....

So I keep 4 on compression and change rebound to 12 on the rear... Works better but still boucing...

On the last race I changed the compression from 4 to 5 and rebound from 12 to 14 on the rear and works still better, dropping my 60ft from 1.54 to 1.50 but still boucing on the start.

Yeah to many options on nomenclature for sure. I refer to stuff as extension and compression most the time. But depending on my mood might say bump and rebound, or combine them So I confuse myself frequently.

So you are saying your numbers are from softest setting correct?

Yes on the Vikings smaller is softer. I'm surprised by how much dampening there is in these shocks. With the most compression I can't compress the shock at all.

Paying attention to this as I just purchased Shilo's rear DA Viking Crusaders and will get fronts soon so all ears here..........

I think you'll be so happy you'll be buying fronts too.

Not racing till I get fronts................

Thanks Shiloh! I'll take look at hotchkiss arms for sure. Do you think that for street use I can run with eyeballing or bushing on arms?

Watching the video made by Gopro camera and looking to diferential angle during the start I can see too much angle and I was seeing yesterday under my car the pinion angle. I measured in relation to the ground and found this numbers:

Driveshaft angle: + 1.2°
Pinion Angle (measured in the pinion yoke): + 1.8° nose up.

Could be this part of my problem or don't make sense?

I would not have a problem using behind joint style a arms on the street.. that was kind of why I thought of Hotchkiss.. their stuff seems to be very durable.. anything you can do up front is a plus maybe do some aftermarket strut rods get the front end working absolutely as free as possible.. and then control the motion with the shock

Concerning pinion angle if you can post some pictures of what you're looking at.. this is my opinion only.. on a street driven car you need enough downward pinion angle to get a good rotation on the needle bearings.. and ideally you want it to come two as close to straight as possible at wide open throttle.. if you could get the GoPro down there on a pass and see how much movement you have.. you could tune for that movement.. some people feel there's a magic number but I think every car will need something a little different.. because of weight and horsepower.. this is what I have found worked on my car

As to pinion angle UP is definitely not the way you want the yoke orientation....

This is a horrible pass but you can see how much movement as well as rotation is in the rear end housing myself I run about 7 degrees down. your car may only want 2.3.or4. https://youtu.be/gQEzZ2Xjzw0

Are you talking about the strut rods with heims on one end?

Thanks for your help.
Don

I was reading in Moparts Tech pages about pinion angle and 3° nose down is a good start point but I agree with you. Each car has a different setup. I started the installation of 4° pinion shims last night and I will finish tonight. After installed I will take some pictures of the angles and will post tomorrow here. It is possible see at video posted before that I had a large positive angle on WOT. Definitely this is not a good thing.

I have finished installation of pinion shims and take two pictures. One of pinion yoke and other of driveshaft.

Pìnion angle has 3.7° nose down right now.

Sorry about the pictures quality, I'm very bad photographer...

I'm assuming that you are checking the pinion angle at ride height. If so if I am reading this correctly it looks like you're pretty close..

Yes man! I did check at ride height. Looks better right now. Thanks for your advices Shiloh

Way better place to be than you had...Not that it will necessarily show anything on the track the parts will be way happier now

Yes I agree that looks better now. Next race will be probably in march. Lets see if changes will be effect. Thanks for everything Guerdon. I will keep everyone informed...

I have a friend here in Brazil that is seeling same then your... Anyone already use and can give opinion about that?

Thanks