Coilovers/? - 986 Forum - The Community for Porsche Boxster & Cayman Owners

clb0099 · 05-21-2009, 08:25 PM

I had 19" brand new wheels mounted and balanced as well as installed on my 1997 Porsche boxster. After going on the highway and hitting 70 mph and above the steering wheel shakes violently. It use to shake with the stock wheels but was very little even not noticable . My question is I already bought coilovers which are not installed. I also bought brand new front wheel bearings . The question is a two fold one. First what the hell could it be making the steering wheel to shake like this... bearing? ball joint? tie rod? How would I test to see what it is? The second part of the question is how much it cost me to install coilovers exclude a car alignment?

Boxtaboy · 05-21-2009, 08:42 PM

You do realize that Porsche did not even offer 18 inch wheels as an option in 97? They beefed up the suspension in 98 to allow for 18s. Running 19s on a 97 model year car is really not recommended, but I'm not sure if that is the reason you are experiencing shaking at speed.

ekam · 05-21-2009, 08:44 PM

I say it's a wheel balancing job done poorly... that or you're using a set of cheap/replica wheels.

edevlin · 05-22-2009, 02:21 AM

Ditto on the possibility of poor balancing. Find a shop that uses a Hunter road force balancing machine and see if that helps. I bought my carrara lightweight aftermarket 18 inch rims with tires mounted, supposedly balanced. I also got vibration until I took them in and got them road force balanced.

Ed

clb0099 · 05-22-2009, 04:07 AM

Ekam... i got to disagree with you on the cheap comment. They are TechArt wheels almost 3k.... Also they put on my Porsche so not sure if that is the case. It happened on my stock 17s so i am not sure that it's a wheel problem at all instead I thing it's a tie rod or maybe a ball joint anyway of testing these myself to let me know.

j.fro · 05-22-2009, 04:56 AM

To check the front suspension components, jack up the front end and give each wheel a good shake. There should be no play at all. With both front wheels in the air and the steering wheel unlocked (key on but car NOT running), you should be able to move the front wheels through the entire turning arc. There should be a little resistance, and it should be uniform through the arc.
Check the tie rod ends to be sure that the lock nuts are tight.
Because you've experienced the problem with both sets of wheels, my guess is going to be alignment. Does the car pull to one side or the other at highway speeds? If the toe is very different from one side to the other it could cause this problem...and going to a larger diameter wheel may be exacerbating it. Did you have heavy wear on the inside edge of only one of your old tires?

clb0099 · 05-22-2009, 05:03 AM

Does not pull to one side at all. No extra wear on the old tires.. i am thinking you might be right as far as the nut on the tie rod

clb0099 · 05-22-2009, 05:31 AM

hey j.fro,

Going to sound like a dumb question but do you have paperwork on installing tie rods or what the nut looks like thatI am trying to tightening. I would go back the the porsche dealership but they will just try to find something to make up for a bad mounting and balancing job.

ramo80 · 05-22-2009, 05:36 AM

Some of it is here

http://gwl.rmsolo.org/hacks/suspension/

j.fro · 05-22-2009, 05:41 PM

The tie rod has a ball joint on the outside end, connecting to the bearing housing/brake mounting assembly. On the inside end, it threads into the arm that connects it to the steering gearing, and then goes through to the other wheel. The inside threaded part has a locknut, which may be loose. Hope that helps.

clb0099 · 05-22-2009, 07:09 PM

J.fro ,

how long would it be to install coilovers excluding and alignment?

j.fro · 05-23-2009, 01:57 AM

4-6 hours, depending on any "mechanical gremlins" that pop up. Funny thing, I'm doing a spring swap tomorrow for a client, which is almost the same job.

Sammy · 05-23-2009, 04:03 AM

Put my vote down for balancing. I have had multiple times where I just picked up the car from the shop (who used a Hunter machine) and there was still a shimmy at 70mph. I think if you sneeze on the wheels it throws them out of balance so I suggest taking the car back and getting them balanced until they get it right.

BTW-Both times it was on 18" wheels both OEM and aftermarket on my 2002 S.

RandallNeighbour · 05-23-2009, 03:04 PM

You can't rule out a bad tire either. I had a set of out-of-round Kumhos that could never be balanced properly, even on a Hunter 9700 series machine that put the heaviest part of the tire on the lightest part of the rim to minimize vibration.

I battled the same problem you're having for years on my 1997. Buying new rims helped a little, then replacing the bearings and coilovers and control arms helped more and now I have very very little vibration.