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Rear suspension issue after lowering

Volta

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Hi everyone

I recently lowered my PP1 on Steeda Progressive springs. At the same time, we did new wheels (LMR SP2 staggered set) and Nitto NT555 G2 in 285/35r19 and 305/35r19. For reference, too- this is a new car to me and my first S550. I had one Mustang long ago, but it was a 5.0 LX Fox Body.

Anyways- the car feels great- it's more planted, sharp, and of course looks the part. Thing is, I have noticed one new characteristic that bugs me. It's more obvious while turning left. Say I'm on a long sweeping left hand corner, foot on gas, car feels great until I let off the gas. When I let off, I get this loose, disconnected feeling from the rear end. It sort of sways to the outside of the corner. It's not a sharp or dangerous snap or anything, it just feels like what a bad bushing might feel like. It's not like the car is going to fall apart either- it's a small movement overall. Maybe it's just the character of a lowerered but otherwise stock S550. Oh, and it does it while coasting and turning right too, just doesn't feel as pronounced.

I have noticed one thing- and I didn't know about this until we (my friend and I who installed the springs) were done, but the rear subframe is shifted ever so slightly to the left side now. You can tell just by looking at the rear of the car and paying close attention. The left side tire is just a little more flush than the right. We loosened the 4 main bolts to be able to drop the rear springs out. I already have the Steeda centering kit on order, but maybe this is related? I feel like it has to be.

I'd appreciate any and all input on this. I'd really like to know where to look or know if I'm thinking too hard about this.

(Picture for your time)

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StangTime

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Do you have the Steeda rear cradle lock-out bushings? The ones that lock the IRS to frame? I would do these at the same time you do the alignment bushings. Your loose caboose will be gone after that.

P.S. your car looks badass!
 

K4fxd

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Looks like a lot of camber on that rear tire. Did you get an alignment after installing the springs? The alignment bushings will center the cradle.

It sounds like the IRS moving. Try the IRS braces if it still feels off after fixing the alignment.
 

NightmareMoon

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That's the first question - did you get an alignment after lowering.

Also, did you "clock the bushings" after lowering the car.

There are some other things, but lets focus on those first.
 

Buldawg76

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It's very likely that the rear subframe shifted some from you loosening the bolts to install the rear springs so an alignment is definitely in order after you install the centering bushing and I also recommend the bushing lockout kit as well at the same time. Then have a 4 wheel alignment done and you should be good to go.

BD
 

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It's pretty common for the subframe to move when lowering these cars. I tried installing the same steeda centering sleeves and that didn't help on mine I had to re lower the subframe on each side. Something to look into to stiffen up the subframe are the steeda braces, that might help with that disconnected feeling you are experiencing.
 

GrabberBargeCaptain

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Steeda sells those centering dowels for the rear subframe which I recommend.

This wouldn't make your car handle funny like what you're describing though, you might want to post your alignment numbers (you got an alignment, right?)
 
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Volta

Volta

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Hey guys, thanks for the comments and help. Sorry for the late response.

We did an alignment after install, and we got it within spec as much as we could. We did notice a front camber difference between L and R which I found very strange. (-2.1 L and -1.4 R) My friend did the fronts and I think maybe he didn't clock the strut mounts correctly (notch pointed inwards). It's on our to-do list at the moment. If checking and clocking the strut mounts doesn't solve it I will be counting on camber plates to do the trick.

That issue aside, I think that clocking the bushings will be the first thing we do. How the install went down was this- we had the car on a 2 post lift here at our work. Loosened the 4 main subframe bolts to give us some room. Loosened a few of the lower control arm bolts, disconnected one of the arms. We pryed the spring out of the perch, popped the new one it, clocked the spring correctly in the rubber, and then used one of those threaded pole jacks to put some pressure on the control arms so we could torque what we loosened. Torqued everything in the air. Lowered the car down.

After reading here I now see the errors we made. This has been a learning experience!

Sidenote- the symptoms of the rear bushings needing this process done all seem to fit mine. I sort of expected the rear to sit a little lower than it does currently, plus the floaty feeling.. this must be it...? Look at the rake the car has right now. Doesn't seem quite right. Looks cool, but I expected a little more level.

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Buldawg76

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Do you have a printout of the alignment specs you had so we can see the exact numbers for front and rear.

BD
 
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Volta

Volta

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I don't, we didn't print it out. When I get it back in to the shop next week I will get that for you.
 

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NightmareMoon

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Hey guys, thanks for the comments and help. Sorry for the late response.

We did an alignment after install, and we got it within spec as much as we could. We did notice a front camber difference between L and R which I found very strange. (-2.1 L and -1.4 R) My friend did the fronts and I think maybe he didn't clock the strut mounts correctly (notch pointed inwards). It's on our to-do list at the moment. If checking and clocking the strut mounts doesn't solve it I will be counting on camber plates to do the trick.

That issue aside, I think that clocking the bushings will be the first thing we do. How the install went down was this- we had the car on a 2 post lift here at our work. Loosened the 4 main subframe bolts to give us some room. Loosened a few of the lower control arm bolts, disconnected one of the arms. We pryed the spring out of the perch, popped the new one it, clocked the spring correctly in the rubber, and then used one of those threaded pole jacks to put some pressure on the control arms so we could torque what we loosened. Torqued everything in the air. Lowered the car down.

After reading here I now see the errors we made. This has been a learning experience!

Sidenote- the symptoms of the rear bushings needing this process done all seem to fit mine. I sort of expected the rear to sit a little lower than it does currently, plus the floaty feeling.. this must be it...? Look at the rake the car has right now. Doesn't seem quite right. Looks cool, but I expected a little more level.

unnamed-24.jpg
Right, clock the bushings first and see how it drives.

You've changed a lot.. Those progressive springs are going to react differently than the springs you had before, and your tire choice isn't exactly a lot of people's favorite tire. Its a budget tire, and it might not be reacting like your used to a tire to reacting.

When you're in a sweeper and then lift, the rear will raise and lighten and grip is removed from the back of the car. The car will be more likely to rotate on you and might even get sideways. The closer you are to the limits of the tire, you really can get into territory where lifting in a corner is dangerous and one needs to learn to be very careful and smooth with the inputs when you're close to the limit like that. Your new tires, stagger, and springs are changing those dynamics and you may have some recalibration to do as a driver.

I'll say that progressive springs are often frowned because they're not as predictable from a handling perspective. Also those 555G tires are not as good as many other summer tires so you may be getting to their limits sooner than you expected. In general when you lower and stiffen the car you're more likely to be making it more reactive to shifts in weight (like lifting in a corner). So there's a lot going on here. If you didn't trim or swap in shorter bumpstops, they could be getting more involved now too. But all that said, hopefully clocking the bushings fixes your issue.
 
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Volta

Volta

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Thank you for the extremely informative and thorough response. I will start with the bushings as you suggested and re-evaluate. Once these tires wear out I think I will step up to the PS4S, but the price on the Nittos was too good to ignore as I was getting wheels and springs at the same time. I do honestly like the feel of the tire, it's quiet and has plenty of grip for the way I drive. But I have driven on PS4S and realize they're basically as good as it gets for a street tire..
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