Handling dynamics off after subframe reinforcement? Tips and advice needed

[MTiz]

Hi guys, I'm looking for advice on how to dial in my suspension after my subframe reinforcement. For reference, I got all new OEM bushings in the rear, as well as two poly (80 Weight) diff bushings, as well as cracks welded and plates put in.

The rear feels the phenomenal, perfect amount of stiffness for a road car. But the problem I'm having is that it doesn't feel like it matches the front-- the front feels floaty in comparison. I have KW V2's all-around in seemingly good condition, as well as new tie rods, sway bar links, OEM control arms, and a fresh alignment. At high rates of speed, it feels unstable/floaty, and around the turns, the DSC light keeps flashing and it feels like the rear wants to do a 180.

What could I do to get the front to match the rear in stiffness? Is it possible my KW shocks need a rebuild? Or should I look into some stiffer bushings in the front, or maybe a thicker sway bar? What do you guys think?

[FBloggs]

I would:
1, check the alignment.
2, check tire pressures.
3, check the torque of the fasteners.
4, evaluate the valving of the dampers.

[Arith2]

Check your sway bars and mounting points. A loose sway bar can definitely cause this. What's the spec sheet for your alignment? Any spacers or aftermarket wheels? What tires and what age? Were all bushings torqued under load and not in the air? Did you get a tire rotation unknowingly?

[MTiz]

Check your sway bars and mounting points. A loose sway bar can definitely cause this. What's the spec sheet for your alignment? Any spacers or aftermarket wheels? What tires and what age? Were all bushings torqued under load and not in the air? Did you get a tire rotation unknowingly?

- Will post the alignment spec sheet below
- OEM Style 67 19's with 15mm spacer in the front and 12mm spacer in the rear.
- Front tires are a year and a half old with good tread. Rear tires are brand new. Hankook Ventus V12 in stock sizes
- What do you mean by torqued under load and not in the air? All of the new bushings were installed with RAC and Diff removed from the car if that helps.
- For the tire rotation, I highly doubt it. The new rears were just mounted and balanced by my indy and I doubt it was that.

EDIT: After reading my alignment sheet it says 41 psi in the front and 48psi in the rear after the alignment. That is way too high, isn't it?

[stephen]

EDIT: After reading my alignment sheet it says 41 psi in the front and 48psi in the rear after the alignment. That is way too high, isn't it?

That sounds way too high imo. Try somewhere in the low-mid 30s.

[Arith2]

- Will post the alignment spec sheet below
- OEM Style 67 19's with 15mm spacer in the front and 12mm spacer in the rear.
- Front tires are a year and a half old with good tread. Rear tires are brand new. Hankook Ventus V12 in stock sizes
- What do you mean by torqued under load and not in the air? All of the new bushings were installed with RAC and Diff removed from the car if that helps.
- For the tire rotation, I highly doubt it. The new rears were just mounted and balanced by my indy and I doubt it was that.

EDIT: After reading my alignment sheet it says 41 psi in the front and 48psi in the rear after the alignment. That is way too high, isn't it?

I keep my tires at 41 and 48 so no. If you do 100mph, there's a warning on the door that says put it at that. I have tracked my tire wear and it has been very even. If you don't do 100+, stick to lower pressures. It's not pressures for the track, but the street.

Bushings need to be preloaded before torquing them. They need to be in the position they will normally be at when the car is sitting in your garage everyday. If you torque them in the air, they are not preloaded. When you lower the car, the suspension and the weight of the vehicle twists and loads the bushing creating a constant massive load on the bushing. So now all the rubber bushings are twisted and tweaked when they are only meant to do when there's compression of the suspension.

Try setting pressure to 33 and 35 like the door says. Your camber is quite high which may not be the cause but is absolutely a contributing factor. Those specs are intended for a car with 150lbs in both front seats, 150lbs in the back seat, a full gas tank, and 40lbs in the trunk.

[MTiz]

Dropped the tire pressures. Made a small impact but it still feels way looser in the front than it does in the rear. Thinking about going with a sticker front sway bar, any thoughts on that?

[01SG]

I do not think a bigger front bar will solve your problem. That is like buying new struts because the control arms are shot; it is not addressing the actual problem. The car should handle excellent with a completely stock suspension. I have solid subframe bushings and do not experience the problem you have.

Whatever it is, the bar will not be the answer.

That alignment does not look great. Having more camber in the rear than the front may contribute to your problem. That is also too much toe-in on both ends, especially in back. Other than that, it seems like you replaced most things. Maybe engine mounts?

[FBloggs]

That camber in the rear is nothing out of the ordinary for lowered cars.
The rest of the alignment spec is ok...when static.
If the front control arms have worn balljoints, a good alignment tech would know, but a jobsworth may not.
If the front control arms are good, then the struts may be blown.
KW are reputed to be on the stiff side, so a floaty front end is telling.

[MTiz]

The motor mounts were done last year with the rod bearings.

That camber in the rear is nothing out of the ordinary for lowered cars.
The rest of the alignment spec is ok...when static.
If the front control arms have worn balljoints, a good alignment tech would know, but a jobsworth may not.
If the front control arms are good, then the struts may be blown.
KW are reputed to be on the stiff side, so a floaty front end is telling.

Is there any way to tell if the shocks are blown besides just guessing and replacing them? They aren't leaking and visually still look fine. And they only have 20k miles on them so I'd expect them to last longer.

Edit: I also want to stress that the front doesn't feel sloppy, it feels the same as it always has. It's just that the rear is so much stiffer now that it doesn't match and doesn't feel great.

[MTiz]

Someone gave me an interesting piece of advice yesterday. It may be possible that I need to adjust the dampening settings on my coilovers-- specifically in the rear. Could it be possible that now that there is extra weight in the rear as well as fresh bushings, the previous settings are too high, making it overly stiff and wanting to kick out around the turns?

Heading out of the country so haven't been able to test it out yet, but it sounds plausible in my head.

[01SG]

Sounds like a logical step to take before spending any money.

Also, the alignment may not be part of the problem, but toe-in is slightly over the already conservative factory spec in front. It is also a full twenty-five percent too much in the back. The general idea with camber is to have more in the front than the rear.

[Casa de Mesa]

That's not a lot of toe.

Toe in will make the car more resistant to changing direction. Zero toe or toe out will make the car darty.

The dartiness you're experiencing might be due to the toe. Camber isn't excessive so you could just be feeling a twitchy feeling correlated to toe. But it's not that much of a change from your pre-alignment specs so not sure what's up with that.

Also, 41 and 48 psi cold could be causing some of what you're feeling. Like others have said, drop the pressures and give it a go.

EDIT: I misread your alignment from my phone. You're total toe F/R is 0.26/0.40 (I misread as 0.026 and 0.040 from my phone). I went to find my car's alignment spec (below pic) on my laptop when I noticed my mistake. I'd drop the tire pressures and try that first.

[MTiz]

Fixed it! Turning up the dampening settings on my front coilovers immediately fixed my handling issues. I can take turns hard again without DSC flashing out of control and the back doesn't feel like it wants to do a 180 when I turn.

I'm going to go for another alignment as it still pulls to the left quite a bit. Should I add more camber to the right? I'd imagine that because the left and right side don't have the same amount of camber, that's why it would pull.

Thanks everyone for the helpful advice and suggestions.

[FBloggs]

So the car felt like the two struts were blown? Interesting for the driver lol.
The rear end was trying to faithfully emulate the sloppy front...as it should typically do.