Need suspension help

Laga

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Three years ago when I did all the mods on my 05, one of them was installing the Ford racing suspension pack from AM. This lowered the car 1”. Now, the back end is sagging and hitting the bump stops. Yes, they are shorter than stock to accommodate the lowering. This tends to happen after the car is completely warmed up. There is only 7-8K miles on the springs and shocks and the car is not a DD. It only goes to shows and track days. In fact, the sagging started after the last track day on 6-1. I just tested it. I sat on the trunk ledge while the wife watched the bump stops and they are definitely hitting. Do I replace shocks, springs, or both?
 

Laga

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Cut the bump stops.
Technically, they’ve all ready been cut, being shorter than stock. If springs support the car, and the car is hitting the shorter bump stops for the first time in three years, I’d say the springs need a good inspection or replacing.
 

Juice

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The big question is why the springs sagged in a short time/low miles.
 

Laga

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That’s why I’m asking for help. Could the springs or shocks been damaged at the track day?
 

Juice

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I would think a bad batch of springs. Manufacture defect. 8k is low miles, even with track use IMO.
 

07 Boss

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That’s why I’m asking for help. Could the springs or shocks been damaged at the track day?

Shocks won’t have anything to do with ride height. Either your springs are sagging, which I kinda have a hard time believing, or something shifted or is binding. The only thing I can think of might be the bottom spring perch on the axle but that seems like a reach. Maybe take another 1/2 off the bump stop or go on a diet.
 

Pentalab

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Three years ago when I did all the mods on my 05, one of them was installing the Ford racing suspension pack from AM. This lowered the car 1”. Now, the back end is sagging and hitting the bump stops. Yes, they are shorter than stock to accommodate the lowering. This tends to happen after the car is completely warmed up. There is only 7-8K miles on the springs and shocks and the car is not a DD. It only goes to shows and track days. In fact, the sagging started after the last track day on 6-1. I just tested it. I sat on the trunk ledge while the wife watched the bump stops and they are definitely hitting. Do I replace shocks, springs, or both?

I'm lowered 1.25" with rear roush springs + shocks (Roush supplied new, shorter bump stops) . I'm no where close to the bump stops. I only weigh 150 lbs, and sitting on the trunk ledge, and it barely deflects...with a full tank of gas too...and a lot of misc junk in the trunk. Repeat your test, sitting on the trunk ledge, but get your wife /helper to look at the springs on both sides. See if they are bound up tight. The spring perch top and bottom may be the issue, but I find that hard to believe.

You may well have one / both defective springs.
 

Laga

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I’ll check that first chance I get. What should be normal travel or space between top of bump stops and body? I’ve got 1.5” with empty truck on flat ground.
 

Juice

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Just a guesstimate here, but with Rousch springs I have about 2" to the uncut bump stops.
 

Laga

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Finally had a chance to change both springs and shocks. I went with Roush lowing springs and Strange adjustable shocks. The Roush springs claim to lower car 1/2” from stock. The existing Ford Racing springs lowered the car 1”. This turned out pretty close with the car being 1/4” higher after swap. The Ford Racing springs were 5/8” taller than Roush when off the car, yet the car sat 1/4” lower with them. I didn’t touch bump stops and car no longer bottoms out and rides much better.
 

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