Shock purchasing & tuning strategy? W video
#2675328
07/07/19 08:35 PM
07/07/19 08:35 PM
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Joined: Jul 2007
Posts: 1,682 Philadelphia
radar
OP
top fuel
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OP
top fuel
Joined: Jul 2007
Posts: 1,682
Philadelphia
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Howdy Moparts! I built my 54 big block pickup out of stuff I could scrounge so the suspension is kinda oddball. The front is 1989 dakota 2wd with all new bushings & balljoints, no swaybar, and moog load handler coil springs. The rear is a 9.25 axle located by saggy A-body 6 leaf xhd springs. Ride height is set with helper airbags over the axle and wind up is controlled with slapper bars. With no air in the bags it sits just off the bumpstops. I usually run 25-30psi in them (individual schraeder valves) to get just a touch of rake for style and ground clearance. When I built it I threw some $15 monroe shocks spec’d for a stock ‘89 dakota, just to get rolling and keep it cheap. It cruises fine and there is no problem there, but they’re predictably not amazing. Here is a youtube link of a quick street launch- more of a rolling burnout. I used Imovie to repeat a zoom in on the launch- so first is actual speed, then slomo, then super slomo twice in a row so you have time to look at the front tire the first time and the rear tire the second time. https://youtu.be/IGzZB3f1A-8I only know enough to be dangerous concerning this stuff but what I’m seeing is the tires hit and the slapper bars give some chassis seperation and a tiny bit of nose lift, then it unloads the tire and I get a little rocking pourposing move going. Then into the rolling burnout it never hooks and steadily but barely carries a little weight off the front as it slips down the road. My next move is M&H ‘rod-19’ DOT drag radials and probably a shock absorber upgrade as well. Obviously there will never be a dead hook on the street but how can I use an adjustable shock to control what I got going on here? Easier extension and harder compression on both shocks? I don’t know how much looser I can get the front. I have an aluminum top end on my big block, 10” motor setback, and only 104” wheelbase plus a heavy 1” thick ironwood bed floor and the fuel cell & battery are behind the axle, so I do have some tricks up my sleeve already. Thanks for looking Radar
Last edited by radar; 07/07/19 08:40 PM.
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Re: Shock purchasing & tuning strategy? W video
[Re: radar]
#2675376
07/07/19 10:35 PM
07/07/19 10:35 PM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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If your gonna tune it.. it right.. pull those air bags and start at zero.. you have air bags.. you are doing the same thing with a few different items.. shocks are control the wind up or slow the rear end down.. if you want to do it right you need some weights first then you can look at the rest.. but from what I've read you wont want to do it EDIT you need a loose front end so you get the front lifting but a lot of work in the rear
Last edited by MR_P_BODY; 07/07/19 10:41 PM.
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Re: Shock purchasing & tuning strategy? W video
[Re: MR_P_BODY]
#2675391
07/07/19 11:40 PM
07/07/19 11:40 PM
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Joined: Jul 2007
Posts: 1,682 Philadelphia
radar
OP
top fuel
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OP
top fuel
Joined: Jul 2007
Posts: 1,682
Philadelphia
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Ok I’ll bite- I’m always down to try stuff of at least understand more. My original plan was just the XHD springs and slapper bars but after it sat for a while while building it the springs reminded me why I took them off my demon and went 002/003 springs. They sagged down after a few weeks. But in theory once the slappers rotate up and lock then the stiff short front segments should be acting like a ladder bar with a too-high instant center then the chassis is just held up by the airbags and movement is controlled by the shocks right?
I like the bags because they let me set ride height depending on what I’m trying to do. It can go from flat and a little too low to an almost cartoonish rake and the lower it sits the softer the spring rate. I figured that would be easier than guessing on leaf springs or coilovers and a 4-link that could hold stroker power is an expensive deal plus I didn’t know if I wanted parallel or triangulated.
So what do you mean pull the airbags? Aired down they do nothing and aired up I can haul a safe with an elephant in it so what’s not to love? They aren’t even that heavy.
Last edited by radar; 07/07/19 11:41 PM.
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Re: Shock purchasing & tuning strategy? W video
[Re: radar]
#2675417
07/08/19 02:14 AM
07/08/19 02:14 AM
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Joined: Aug 2003
Posts: 43,228 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,228
Bend,OR USA
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Ok I Aired down they do nothing and aired up I can haul a safe with an elephant in it so what’s not to love? They aren’t even that heavy. If they do nothing with no air in them what good are they With air in them they are not helping traction, are they You need to figure out what you want the MOST, traction or a comfortable ride and changing the looks of the truck to impress observers with the air bags
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Shock purchasing & tuning strategy? W video
[Re: radar]
#2675509
07/08/19 12:25 PM
07/08/19 12:25 PM
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Joined: Sep 2014
Posts: 4,457 Washington
madscientist
master
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master
Joined: Sep 2014
Posts: 4,457
Washington
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Well I don’t have a fancy air system with switches pumps and dumps, just two schraeder valves to set the ride height.
I don’t see how the bags are hurting me? To my thinking it’s just an adjustable spring rate? Shouldn’t the shocks control any bouncing? The reason I have them is I’m not 17 and trying to look cool with a 3” ride height. The bags let me set the rear with a little ground clearance. If I wanted to impress other people I would take them off and ride 1/2” off the bumpstops. They were an economical solution to the problem when I realized I needed stiffer springs. :
I’m not trying to say they are helping my launch- I just want to understand how they could hurt? Maybe if I have them set too high/hard the resulting stiff raked chassis would be harder to get weight transfer?
Here’s a shot from when I put the bags in- no air and 40psi
The shocks single purpose (for which you have the air bag if I'm following) is to control the motion of the axle/spring. Your bag doesn't do that.mit controls ride night. The shock doesn't do that. You can't have both. Either live with the air bags, or get rid of them and buy a good shock and live with one ride height.
Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
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Re: Shock purchasing & tuning strategy? W video
[Re: madscientist]
#2675563
07/08/19 01:51 PM
07/08/19 01:51 PM
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Joined: Jul 2007
Posts: 1,682 Philadelphia
radar
OP
top fuel
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OP
top fuel
Joined: Jul 2007
Posts: 1,682
Philadelphia
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The airbags are only there to add to the spring rate. The bottom bag brackets are curved to mate to the axle but not welded- they do maintain contact and don’t float around but don’t pull down or act as shock absorbers. I have conventional shocks using the top frame bracket from a dakota and ears welded to the axle tubes.
I have heard of people replacing shocks with airbags on IFS and not bothering to relocate the shocks (running without them) or running adjustable air shocks to lift a muscle car (getting a rock hard ride and eventually punching thru the top brackets). This is not that. I have my axle located with leaf springs but they’re saggy ones that lost arch after a year or so. The axle wind up is controlled by the short stiff front segment combined with the slapper bars, so under power the pinion angle is lifted to match the crankshaft angle.
Like I said I still have conventional shocks. I am not trying to get defensive and I think I understand the compromises I made with this setup but I want to learn the basics of rear shock tuning for traction.
My concept of how it works now is that since my leafs and slappers converge too close to the axle it is going to make my instant center too high, hitting the tires really hard. If they are triangulated in action they will act like a ladder bar but I would have pointed a ladder bar a bunch further up the chassis and probably a couple inches lower. So that isn’t ideal but I wasn’t willing to run a ladder bar on the street and end up constantly twist stressing the axle housing back and forth like a giant sway bar and I don’t have the know how or money to throw at doing a 4 link that could hold up to stroker torque. I never set up coilovers either and the choices are intimidating and expensive for trial and error.
Was all the ‘ditch the airbags’ talk because y’all thought I was running with no shocks? I have shocks they’re just stock replacement $15 blue ones that barely make the chassis not bounce a couple times after a bump. They work fine for cruising but I want to upgrade the shocks and want to understand more about where to start with settings.
From what I’ve learned on here and from books I want the shackles angled to separate the body upward on launch, pressing down on the tires. Check. I want the pinion rotation to stop with good driveline alignment and begin applying only forward and upward rotation with no oscillating wheel hop. Check. Then I want to hit the tires as hard as possible without spinning and keep them planted with as much weight transfer as I can muster. This is the area that needs work.
I figured the next obvious step was more and stickier rubber, and shocks to control the movement of the chassis relative to the suspension. I know the object in the front is to make it as easy as possible to lift the nose and to come back down slowly. There is only so much I can do with the dakota suspension without re-doing all the bushings etc but it’s all new and greased with decently light wheels, as much aluminum as I could get on the big block to replace iron, and the motor is moved back 10” too.
I have a much foggier idea of what you want the shocks to do in the rear. Is it the same as the front where you want soft extension and harder compression?
Thanks and sorry if I’m being hard headed I am still not understanding why helper bags are bad? How are they different than just making my leafs have a variable spring rate? In fact isn’t that a good thing if I can drop it down low for better weight transfer then air it up a few inches for a longer drive or something?
Radar
Last edited by radar; 07/08/19 01:52 PM.
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Re: Shock purchasing & tuning strategy? W video
[Re: radar]
#2675751
07/08/19 09:46 PM
07/08/19 09:46 PM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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Those rear shocks will never work.. the angle of them is all wrong.. I dont care if you had the best shocks on there.. remember the the rear is rolling upward.. if the springs are near right you wont need the slapper bars or the air bags
Last edited by MR_P_BODY; 07/08/19 09:47 PM.
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Re: Shock purchasing & tuning strategy? W video
[Re: radar]
#2675781
07/08/19 11:02 PM
07/08/19 11:02 PM
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Joined: Apr 2007
Posts: 871 WA 98043
thecarfarmer
super stock
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super stock
Joined: Apr 2007
Posts: 871
WA 98043
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First off, I have to say I really like the truck!
But, I would ask... Whiskey Tango Foxtrot was wrong with the original springs? Sat too high?
One thing about the A-body rear leafs is that the front section is short - really short.
Putting a slapper bar on that spring is going to try and lift the vehicle at the front spring eye of the rear spring. I would imagine that a system that would try and lift up the chassis at a point further forward would tend to lift the entire vehicle, instead of just picking the back end up. Hopefully putting a little more weight on the rear tires while it's lifting.
Unfortunately, my project has been stalled by a move across country, a career change, and a home purchase.
So, I'm gonna' have to subscribe to this thread and live vicariously...
Last edited by thecarfarmer; 07/08/19 11:03 PM.
Seduce the attractive, and charm the rest.
******
489 C.I.D., roller cam, aftermarket heads, tunnel ram, stock '54 Dodge rear axle assembly: which of these doesn't belong?
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Re: Shock purchasing & tuning strategy? W video
[Re: thecarfarmer]
#2675808
07/09/19 12:15 AM
07/09/19 12:15 AM
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Joined: Jul 2007
Posts: 1,682 Philadelphia
radar
OP
top fuel
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OP
top fuel
Joined: Jul 2007
Posts: 1,682
Philadelphia
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Hi Carfarmer! Thanks.
The original leaf spring setup had about 9” higher ride height plus it was equal length front and back sections of spring, not a short front segment like the SS springs. The Dakota came with an 8.25 axle and a really dinky spring pack with a super heavy overload leaf to keep it from flipping inside out. The reason I re-worked it was because I put a 512 motor in it and figured the 30 year old setup spec’d for a v6 driveline wouldn’t get er done. And I already had a set of 6 leaf xhd springs that I ran for a year on an a-body before switching to 002/003 leafs. Turns out I forgot they were already losing arch and sagging.
I also channeled the body down over the frame, shortened the frame a couple feet, boxed it, shortened the bed a foot, and set the motor 10” back into the firewall. Basically just got carried away working in my driveway last year and having fun. I already had the ‘54 and always wanted to build a stroker B engine.
I think you’re right- my instant center is too high and far back.
Last edited by radar; 07/09/19 12:16 AM.
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Re: Shock purchasing & tuning strategy? W video
[Re: radar]
#2675994
07/09/19 01:41 PM
07/09/19 01:41 PM
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Joined: Feb 2017
Posts: 566 Texas
RustyM
mopar
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mopar
Joined: Feb 2017
Posts: 566
Texas
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I agree with Mr P, your going to have to get the rear shocks into the right geometry- as they are, they will always be to slow to do anything effectively. Would also suggest a double adjustable front shock set pretty loose on extension. Might actually loosen it all the way up, see what you get from it, then start tightening it up until you have the right combination of front end travel and ride stability since your street driving. I don't think much is going to help until you resolve the shock geometry in the rear.
Just my opinion.
Last edited by RustyM; 07/09/19 01:43 PM.
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Re: Shock purchasing & tuning strategy? W video
[Re: RustyM]
#2675998
07/09/19 02:07 PM
07/09/19 02:07 PM
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Joined: Dec 2005
Posts: 11,611 Fulton County, PA
CMcAllister
Mr. Helpful
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Mr. Helpful
Joined: Dec 2005
Posts: 11,611
Fulton County, PA
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Shocks are useless mounted like that. Until the mounting is corrected, housing and crossmember, nothing will work right. The rest of it has potential. Air bags are an old trick on Stockers with coil springs. I don't know what benefit there would be on that set-up beyond covering up for dead springs or carrying a load of firewood without dragging the bumper. Swapping the slappers (I assume they're slappers) for a C-E Adjust-a-Link or Cal Tracs would be money well spent.
If the results don't match the theory, change the theory.
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Re: Shock purchasing & tuning strategy? W video
[Re: CMcAllister]
#2676211
07/10/19 11:23 AM
07/10/19 11:23 AM
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Joined: Jan 2005
Posts: 3,635 Oakland, MI
dizuster
master
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master
Joined: Jan 2005
Posts: 3,635
Oakland, MI
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I looked at the video (which was done nicely by the way), before I read anything. I thought to myself... "WOW... those rear shocks are WAY too loose".
Fast forwarding down to your picture... it's hard to say if the shock is too loose or too tight, but because of the steep angle it's making it "act" too loose.
Think of it this way. If the shock is straight up and down, the axle separation feels whatever force the shock puts on it. As you rotate the angle of the shock (in any direction... rearward, forward, inboard, outboard...) it begins to loose effective force on the angle. If you were to think of the extreme where the shock was mounted completely horizontal, it obviously wouldn't have any effect on the up/down vertical motion of the axle housing at all.
Because of the angle it's mounted at, the shock can't control the up/down housing movement during any kind of launch situation. It's unlikely any shock could/would be valved to fix this at the angle it's currently at, which is why guys are saying you need to fix that first before you do anything.
The A-body spring segment length is fine. That truck has a fairly short wheelbase, so it will work without issue... meaning don't worry about the instant center right now. Fix the shock location first, and that will help you a whole bunch with the traction.
Right now since the shock can't control the body separation, it basically uses up all of the travel right away, and then once it's out of travel it just spins the tires.
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