Handling Eradict & unpredictable. Help!!

[Bbarfoot14]

So I recently got some new wheels and tires (NT555 G2 265/35/20 & 295/35/20) on 20x10/11 wheels. I also swapped some new springs into my GC coilover setup with a higher spring rate (525lb) to be able to run it lower and increase handling on those back roads. At this point I have double checked every bolts torque spec involved with the wheels and suspension setup including my top mounted camber/caster bolts. So we can rule that out. I do have the front dampening set to the max to allow for the low setup so a harsher ride isn't unexpected especially on these roads.
But the issue is not the harshness of the bumps but more so the unpredictability as the wheel randomly moves, driving on the highway requires full attention and 2 hands on the wheels.
At this point here is the only thing I can think of in terms of a solution.
1. Bump-Steer Kit (the car is fairly low, with the bad NE roads this seems to be something that could cause trouble)
2. Soft tires + smaller tire + 20 inch wheel (This setup seems conducive to feeling everything on the road. Maybe that adds to it, but I had 20s with 275/35 last season on Sportlines and it was great. Granted, those were NT05's all around which i assume is a firmer tire)

Beyond that I'm not sure what it can be, any input would be greatly appreciated! Thanks

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[xXANCHORMONXx]

Sounds like you didn't get an alignment

 

[qtrracer]

x2. Lowering the front causes more negative camber. More negative camber changes the old toe setting to more toe-out. Too much toe-out makes the car unstable at speed. You may also be experiencing tramlining just from the design and width of the front tires.

 

[Bbarfoot14]

I thought that as well, I guess I should have mentioned that I got an alignment and it didn't really help. The front camber is -1.5 and toe is within stock spec so that wasn't it either.

 

[qtrracer]

Maybe you're tramlining then. But given the description of the problem, sounds like alignment/worn components. By the way, I never did like my GC C/Os, nor the Koni SAs they came with. Springs they recommended were too soft which meant I had to have the height set a max up and mx rebound up front (mid in the rear). Ride was too harsh, hit the bump-stops a lot. Car handled pretty well but the cost of ride quality and adjustability was too high.

 

[Bbarfoot14]

Maybe you're tramlining then. But given the description of the problem, sounds like alignment/worn components. By the way, I never did like my GC C/Os, nor the Koni SAs they came with. Springs they recommended were too soft which meant I had to have the height set a max up and mx rebound up front (mid in the rear). Ride was too harsh, hit the bump-stops a lot. Car handled pretty well but the cost of ride quality and adjustability was too high.

After looking up the definition of tramlining it's exactly what's going on with me, it's always a ridge in the road or something else that takes the wheel towards it. Why is it so noticeable now and how can it be reduced?

 

[xXANCHORMONXx]

Are you slammed?

 

[Bbarfoot14]

Are you slammed?

I wouldn't say slammed, I havnt rubbed but yes it's low. I may actually bring it up a few notches in front.

 

[BmacIL]

After looking up the definition of tramlining it's exactly what's going on with me, it's always a ridge in the road or something else that takes the wheel towards it. Why is it so noticeable now and how can it be reduced?

What's your front wheel offset? That plus the camber are the biggest things. What are your front spring rates?

 

[Bbarfoot14]

What's your front wheel offset? That plus the camber are the biggest things. What are your front spring rates?

20x10 35mm which is a pretty common size for the s550 community. Only -1.5 camber in front which isn't too bad and the spring rates are 525lb

 

[Bartly]

How about that topic where you are supposed to tighten some of the arm joints with the weight of the vehicle on the springs so the bushings aren't under tension when at ride height? Sorry if naive, never replaced springs on a car so not sure if you had to disconnect the arms, but it's important on my Jeep.

 

[BmacIL]

20x10 35mm which is a pretty common size for the s550 community. Only -1.5 camber in front which isn't too bad and the spring rates are 525lb

That's a very stiff spring for street use. Do you competitively autocross? That would be the only time you'd need or want something that stiff. Mine wheels are +35 and 9.5" wide, and I get quite a bit more tramlining than stock as well, just from the wheel change. The stiffness of the springs is heavily exacerbating all the behaviors of the car. I would chop that rate in half at the least, probably closer to 200-225 lb/in. The rears you want in the 800-900 lb/in range for stock location, and about 400-600 lb/in if it's a coilover spring/damper setup.

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