Just completed an install of Ohlins DFV, Eibach F&R Sways, & Tarret front and rear drop links. I took the car out for a test run on a few deserted back roads and started getting violent vibrations through the steering wheel at speeds starting around 90-100mph and at 110 it was to the point it felt incredibly unsafe and I needed to back off.

I work in the wheel/tire industry so my first inclination was I had bent a wheel or flat spotted a tire with the car sitting over winter. I had everything road force balanced again just to make sure. Everything was in spec but we redid everything just to make sure. Went back out and re-tested - same vibration present.

We had issues with the front drop links (https://www.6speedonline.com/forums/...g-bending.html) on my install and ended up using lots of washers to get the clearence needed and having to install the bottom drop link on the inside of the swaybar (instead of on the outside like you're supposed to).

Whatever the issue is i'm 95% sure it's related to the suspension upgrade as this was not an issue prior to the install. Anyone have any ideas?

My (uneducated) theories:

• Front sway bar has no pre-load/tension so at high speeds it's allowing some side to side movement?
• The altered geometry of the droplink needed to get the proper clearence is not able to maintain it's integrity at higher speeds and more front end downforce (i have a RUF front bumper which really sucks the front end down at higher speeds)?

Anyone have any ideas?

 

i doubt its a sway bar issue. many drag racers unbolt their sway bars so they can have more weight trans ver. not a good idea for turning but on a straight away its done all the time. sounds like lug bolts rim out of spec or something not tightened down from the suspension install. go back to the beginning of what you added and check every nut and bolt

 

Alignment?

 

I would go get a good alignment from a place that knows suspensions well for porsches.

I had an alignment done and it they took 4-5 hours on it. Actually used a Porsche Dealership that everyone swears by for their builds here on Long Island.

 

Had a GT2 alignment done on it before I picked it up from the Porsche dealer here in town (that also did the entire install).

Hrmmm....

 

Whats the wheel and tire setup and when was the last time it was mounted and balanced?

 

Do they drive these effing things before and after a balance and alignment ?

 

19x8.5 19x12 ADV.1's with PSS's (245/35/19 and 305/30/19's). I had it re-road force mount and balanced on Saturday after the initial vibration was detected.

They had but to be honest they only did freeway speeds which it's not evident at all.

I'll double check and make sure they didn't put a conical seat lug bolt on the wheels somewhere or something.

 

Just confirmed i'm using ball seat lug bolts so that looks right.

 

The relationship between the front to rear ride height is off. It's like the front caster is too steep and making the front wheels shake from side to side at speed. It's called a head shake or tank slapper on a motorcycle. Death wobble on a lifted Jeep. If you raise the front or lower the rear a bit stability should return. Less caster is great for quick turn in but decreases high speed stability. More caster will be stable at speed but require a lot of effort to turn in quickly. Check your ride heights and rake.

 

Try removing the rims, then reinstalling them by hand and use a torque wrench and properly install each nut yourself. I had a similar issues once after having shop put on my rims on a different car, they used an impact gun like most tire places. Dunno if they put it on on too fast but it felt unbalanced, dismounted and remounted myself and it went away.

 

Which dealer ?