Having what I deem a shock adjustment issue. The car is a 2008 Dodge Stratus built by Don Ness race cars. Johnny Gray ran it 4 races I believe in pro stock that year. Well now my Dad owns it, & Im trying to help get the shocks adjusted right. This car has the Koni Electric shocks with the 2 knob Yellow Box & Ness air sweeps on the shock themselves. I am going to upload a racepak run so you can see what it's doing. Looking at video frame by frame the car plants the tire then you can see the car lift back up which unloads the tire I think. This occurs about .3 into the run. Just looking for some direction as to what to adjust 1st. Looking at the accel G meter it looks like the car is porpusing a little bitThis message has been edited. Last edited by: MorgretNation,
This message has been edited. Last edited by: MorgretNation,
I would start by taking some starting line rebound away. It is grabbing the tire to much that will make it do that.
So You mean stiffin extension a little ?
Your going to want to soften rebound.
Extension is rebound and bump is compression
To my understanding the rebound (extension) would need to be loosened (to the negative) this will essentially cause more chassis separation and keep the car from hitting the tire as hard
To me it looks like it is hitting the tire too hard.
Making a more drastic move that would cause more separation would be to take the top 4-link Bar and go up one hole
If looking for expert advice I would contact Shane with competitive suspension solutions
I run Penske Shocks and was schooled on them by my contact there (Eric Davis).
The first movement on any car is going to be extension, but unless you get into the $18k inerters your shocks are going to be able to control that initial movement because it's too quick (the shock travel velocity is too high).
The second movement is when the car squats, the weight is transferring back and this is where shock adjustments start to help(Compression or bump). generally speaking the compression adjustment is good for the first .25-.6 second or so of the run. if you have too much wheel speed at this point you want to loosen the compression/bump and if you don't have enough wheel speed you will want to tighten it.
The 3rd movement is when the shock/spring starts to extend again. you're basically deciding how quickly the allow some of the weight to transfer back forward. if you have too much wheel speed from .4 - 1 second or so you will want to loosen the extension/rebound and if you don't have enough wheel speed you should tighten it.
Remember, if you have nitrogen or CO2 assisted shocks the pressure in those will affect both your shock adjustments, but it will affect compression/bump more. Also, always start at full tight and adjust from there. you number of clicks should be how far you are away from full tight. Never go to full tight either. the internals of a shock are a needle valve in their simplest for and how tight or loose the adjustment is equates to how far the needle is from closing off the orifice. if you are full tight there will be no fluid moving at all and the shock won't function correctly.
i wasn't able to watch the movie, but from the look if the graph i would tighten the extension/rebound. i'm not sure how many clicks of adjustment you have, but i would make a decent move and see how it works (for example i have 50 clicks of extension and i would go 6 clicks or so). i would also consider loosening the compress a small move, but you may want to see how much the other adjustment helps/hurts before you do that.
also, how much air pressure are you running in those tires? it really looks like you're hammering them.
Should this say, if you have too much wheel speed the extension should be tightened to keep weight on the back tires and if not enough wheel speed loosened to let weight transfer forward?
Koni electrics don't have nitrogen pressure so that is out.
If you tighten rebound in this circumstance you will make that driveshaft worse. Tightening it will roll over the tire harder.
You said it above that it he is working in the third movement. In extension (rebound) so why not loosen the rebound up and free the tire up?
If this is an old Pro Stock car, how has its original chassis setup been modified to fit your combo? Night and day differences here! You will need to do more than change the shock settings!
Next, you got them, so post them, shock travel graphs and Accel graph.
How much power does this combo have now?
Need much more info
I will post that stuff Tomorrow. We are both going to the same race so I get his laptop. As far as I know they have not changed the setup. Now the people they bought the car from may have done that. I don’t know. Car now has 1000+ hp now. Car weighs 2300 runs 4.8’s in average air
No, i believe i have it correct, at least for how my car works/how i adjust my shocks.
the car should still be accelerating pretty hard at this point (probably only 1/2 way to 60 ft or so) so the weight isn't going to start transferring back to the front for a little while. what you're controlling at this point is how much the rear will be pushed back down by the spring. the more you let it push back down (the looser the extension is) the more traction/less wheel speed you'll have. if you you tighten the extension it will slow down the springs pushing the rear back down and give you less traction/more wheel speed.
Weather prevented any runs this weekend. Here is the same log with the shocks & accel meter turned on.
This message has been edited. Last edited by: MorgretNation,
I'm by means no expert as my s10 is a turd BUT i have friends with fast door cars. I couldn't get the video to work but going by the pic above it appears to be crushing the tires and not touching the wheelie bars. Is it possible that the wheelie bars need to be adjusted lower?
Loosen extension, tighten compression for wheel speed.
yup, i still agree that extension needs to be loosened
If the car is still crushing the tire after extension is loosened then you may need to take the top 4-link bar up 1 hole
In laymen's terms they'll be delaying the car rocking back by loosening the rebound and tightening the compression, it's using up the tire now. The tire will stay round with a little speed. They can look in the groove behind the car after the car leaves to guage progress by the tire tracks it leaves.
This message has been edited. Last edited by: Mike Rietow,
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