Which is weird because prior to lowering it drove like a cloud.

ok well forgot to also mention, I didn't align the car yet since the install, and my friend only removed the rear spacers and not the front as well. He said since the vibration can't be felt in the front, he didn't need to touch it ( today because it's the 4th and he had plans) so would that make a difference? Still having the front spaces on?

Im going to remove the front spacers later today.

 

Only if the Super Downs have lowered it so much that it's causing a vibration due to a very slight binding of the prop shaft.
Only another Super Down user would be able to indicate either way.
Given the speed it occurs at, could it just be a balance issue masquerading as a driveline issue? Balance issues usually only show up at higher speeds, unless they get really bad, then you start to feel them at lower speeds...but the balance would have to be out ridiculously to feel it at lower speeds.

 

i had a 13' Sonata turbo with similar issue. I installed coilovers, almost maxed the drop and it was crazy vibration because of the axel binding. Then then I was going to get rid of the car so I sold the coilovers and went stock, and issue was gone. It drove perfect again... ended up keeping the car and installed springs, was a decent drop and it vibrated a little because of the axel binding. Only on acceleration tho.

So im familiar with this type of issue if this is the cause. I'll deal with it, it's just unfortunate if it's too low for the axels to handle... in the end I guess the spacers was fine.

 

Also does AWD make a difference? I know a lot of models people have on here happen to be RWD.

 

It shouldn't make a difference.
And besides, the vibration is being felt through the seat, which indicates the rear is the issue, so the front driveline is not a factor, whether it's there or not.

 

And I'm sure if I went to Lexus about it they'll give me that "you have aftermarket suspension put in, we can't touch it" nonsense. Correct ? Lol

 

Before they blame the aftermarket parts, I hoped they would check the basics first.
Like...run the vehicle in the air on the hoist in drive and see if there is any abnormal runout from the wheels.
And road force balance all the wheels...or at least the rear.
At least then it would be an educated guess to say the driveline angle is causing the vibration, and therefore the springs are the issue.

 

Why don't you do your alignment first and see if the issue is still there instead of hunting in the dark.
You took out your suspension and put it back in it's guarantee your alignment is out of spec.
You should have done alignment right away after you installed lowering springs.
I remember someonehere had to replace his tires because he didn't do alignment after he lowered his car.
He listened to some of the forum members that alignment is not require after lowering the car and that costs him a set of tires.

 

First thing to note is that a misalignment is not going to cause a vibration.
And true an alignment is required with the amount of disassembly and reassembly involved in lowering a vehicle, but you also need time for the new parts to settle in.
Until normal driving (i.e. 2 trips a day times 5 days a week), I would probably wait 2 weeks then get an alignment done.
This will ensure the parts have settled in and no excessive damage would occur to the tires in that space of time either.

 

Misalignment can cause cars not going straight and vibration depends on the spec.
It already turned out the vibration is not cause by the spacers since he still having the vibration after he remove his spacers.
So that cause is already eliminated.
Second thing is there isn't much need to be settle just on lowering springs if everything is tighten up.
He got the vibration after he installed his lowering springs so now the most possible cause is his alignment.
Also misalignment is the 2nd easiest way of trouble shooting after the spacers.
I would start with the alignment now before anything.

 

Respectfully i will disagree with half your statement.
Misalignment will cause the vehicle to not go straight, but it will not cause a vibration, no matter the specs.
Vibration is caused by an imbalance of something...the alignment has no bearing on the balance of anything, rather the angles of the suspension components.
Agreed that removing the spacers did not cure the vibration, therefore they were not the cause.
Likely the lowering has created a driveline vibration due to the propeller shaft angle being changed.

In regards to the settling, there is two things that occur.
First, the spring being shorter than the stock means the ends of the springs will not terminate at the same point as the stock springs.
As the springs typically sit on rubber perches, top and bottom, an impression of the stock spring is made in those rubbers.
Typically you can get the bottom impression to align with the new springs, but commonly the top does not as the spring is shorter.
So part of the that settling will involve the new spring creating a new impression in the upper spring perch.
Secondly, the spring has been sitting in a box expanded since it was made until the time of install.
Once installed the spring is now compressed, but being expanded in a box for so long, it will resist that compression for a short time after being installed before it finally relaxes.
Between the two items settling you can get 1/4 inch lower after the final install, depending on the vehicle/spring...maybe even more sometimes.

To the original poster...clearly there is a differing opinion about the affect of the alignment. My suggestion is to speak to a tech at the dealer, or a shop that specializes in alignment and get their opinion.
I think from the posts above we already concluded it was a driveline vibration. Maybe a separate thread asking anyone with Superdowns installed if they have noticed any vibration may help to narrow down that it is a driveline vibration, and how they resolved it, if there was a solution.

 

Another factor that I came across after my coilover install is that being lower and stiffer means you feel more. Apparently one of my wheels was missing it's weights (the ones used to balance the wheel) they had probably fallen off during winter but I hadn't noticed until I lowered the car. Balancing the wheel fixed this issue. It's a simple fix but may be something you want to take a look at.

 

I also thought Of wheel balancing being an issue. However it is just weird when I'm between 70+ upon LIGHT acceleration the vibration is there. Once I cruise and let off the gas it's smooth. Only upon acceleration and it's only at those speeds. It's very weird.

Also since im moving to SoFlo next week I have an appointment for oil change at the dealer. I'll mention the issue. The service advisor I deal with is always cool, just hope the guy working on the car are just as cool about issues like this.

 

I had the exact same problem as you. Vibration only at certain speeds. It was because the hub-centric rings in the spacers. I have H&R on the front which are 1 piece, and I have Ichiba in the rear. The ichiba has the crappy hub centric ring that hardly fit. So I had my father make me new hub rings that fit correctly and all of the vibration's have gone away. Only reason I didn't mention this is because you said you removed the spacers and still have the issue.

 

Yeah nothing got better when I removed all the spacers. It just stayed with the same issue. Unfortunately