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View Full Version : Tuning the BOUNCE out of lowering leaf springs??



Austin97C1500
05-13-2014, 04:13 AM
I've posted a little history on my truck in my build thread, but a quick refresh on suspension. The front has 2" drop spindles and 3" springs with tubular uppers and Qa1 single adjustables. The rear has 4" drop springs and drop shackles combined with drop shackle mounts, and Qa1 single adjustable shocks. Since acquiring the truck I have C notched it which made a big improvement in ride as well as the Qa1 shocks. I also added an addco rear anti sway bar that is 1" diameter. I have played with the shocks a little bit but I still have some bounce. I started out pretty aggressive at 12 clicks. I still had some what of an undesirable ride, so I have backed of to 8 clicks and still have some bounce. My original thinking was slow everything down with the shocks by slowing the rebound. I don't mind a firm ride after all, its kinda what I signed up for. Any how this weekend I loaded up an Artic cat 650 H1 atv in the back of the truck and the rear squatted pretty low, probably 3" or so. Well with some preload via atv, the truck actually road down the hiway with no bounce. So now I'm thinking by increasing the preload I increased the effective spring rate and improved my ride. I originally thought the springs were stiff but now I'm thinking maybe not so much. Since I'm not going to ride 600 lbs in the back of the truck all the time just to have good ride quality where do I go from here? I would like to think I can tune the bounce out with the shocks, but which way I go? My gut says go more aggressive, maybe 16 clicks?? I can see the future probably holds a 4 link and coil overs but for now, any suggestions or advise would be appreciated.

bdiamond
05-13-2014, 05:26 PM
I think its a function of the shackle pointing up with virtually no angle to it. As the spring gets weight on it, it flattens. The spring tries to swing the shackle around(down) then gravity works against it by trying to keep the shackle vertical. I think mine does the same exact thing as yours, not a bounce but more of an annoying oscillation? I have no hard engineering, but I think that if you moved the rear hanger back an inch or so it would stop the shake.

Austin97C1500
05-14-2014, 04:22 AM
I definitely need to take a look at that. In fact, there is something odd going on with the shackles because I can lay on the ground under the truck and push up on the frame and it the chassis acts like its pivoting funny around the shackle. It's very odd none the less.

snopro
05-14-2014, 05:47 AM
You could try using a leaf spring slider box set up and get rid of the shackles all together.

Austin97C1500
05-14-2014, 11:43 AM
You could try using a leaf spring slider box set up and get rid of the shackles all together.

I'm digging that idea. Speedway on Ebay has them for Camaros for something like $58 that are bearing style. They should prove to be super smooth plus I can play with rear ride height a little bit since I'll have to fabricate mounts. They also look way cooler than shackles!! My Dad has a 79 Z28 so I'll have to measure his spring width and see if these will work. Lot's of others out there to be bought.

bdiamond
05-14-2014, 11:58 AM
Theres a Lightning website that has pretty good writeups on shackle braces and installing sliders on his truck. I don't remember the name but I'll post up what it is when I get home

http://www.timskelton.com/lightning/index.htm

Austin97C1500
05-16-2014, 04:15 AM
Okay.... slider boxes it will be. I figure if I'm gonna pull the bed and go through the trouble to move the shackle mounts I might as well take it to the next level. I'm gonna get the slider boxes in and start fabricating mounts. Got an Idea in mind on mounts, just got to put it to paper (cad). My springs sit above the top of the frame at current ride height and I don't want to lift the truck when I do this. Shouldn't be a problem though. The tough part is the springs sitting outboard of the frame so the sliders are hanging of the top side of the frame so it has to be strong.

snopro
05-16-2014, 04:34 AM
Looking forward to seeing what you come up with

Austin97C1500
05-16-2014, 06:48 PM
I have been thinking about slider box location and a strong enough mount since it will be attached to the top of the chassis. I got to thinking though if I were to flip the axle ( it still resides on the bottom), I could lower the slider boxes to a height that would have them end up mounting nearer the bottom of the chassis and it would be less concerning that the mount would bend do to a big hit. This has me wondering are there any performance advantages to the axle being mounted on top of the leafs. After all, most performance muscle cars with rear leafs had the axle mounted on top the leaf springs. Any one with any thoughts on this? I know if nothing else I'll have more room for ride height adjustment. As it sits I can't go any lower without modding the bed just behind the fenders.

bdiamond
05-16-2014, 09:18 PM
You can get brake hop if you lower the rear eye or raise the front eye too much. How about doing the flip, but ditching the drop springs/shackle in favor of a worked over stock pair of springs. You could bracket the slider somewhere around the center of the frame and shorten or lose leafs until it sat right. If you trim the rear half and leave the front alone it should be tons better than the drop jobs in the axle wrap department.

Austin97C1500
05-19-2014, 08:33 AM
You can get brake hop if you lower the rear eye or raise the front eye too much. How about doing the flip, but ditching the drop springs/shackle in favor of a worked over stock pair of springs. You could bracket the slider somewhere around the center of the frame and shorten or lose leafs until it sat right. If you trim the rear half and leave the front alone it should be tons better than the drop jobs in the axle wrap department.

Well, the lowering springs were on it when I purchased the truck. They are dual leafs and not a monoleaf so it actually doesn't suffer from axle wrap.... At least not to the point you feel wheel hop. Of course I'm still running a stock 305. I will have to measure the difference in spring eye location and get the difference and see If I have room to play with it. Rear eye at least 9" above the front eye seems to be the rule of thumb for performance. Still haven't found a definitive answer on axle on top or bottom. I don't have to flip the axle, but if I do I'm thinking of making the spring slider mount's so I can use aluminum spacers to adjust the ride height. I'm gonna pull the truck in the shop on level concrete and get a measurement this afternoon and I'll know if flipping the axle will work out or not.