Diagnosing Weird Steering Vibration

I wanted to wait to post this thread until I got a new set of tires on the car. To paint the whole picture, when I bought the car, it had sat for a while and developed flat spots on the tires. It gave the car a freeway steering wheel shake. These spots didn't go away, and I wanted new wheels anyways so I hunted on ******** until I found a set with well-used MPSS mounted. The driving certainly improved, but the steering shake still remains, albeit it happens at a higher mph than on the old tires (70+mph vs 55+mph). It recently developed an issue where the vibration intensifies during 70+ to 60 mph braking under moderate to hard braking. Under 60-0mph braking, there is no evidence of shuddering whatsoever. I don't even hear a sound during low speeds, either in braking or coasting. Weirdly enough, I don't feel it in my *** either lol. I mean to say, the chassis doesn't shake, nor do the tires seem to transmit the shudder into chassis movement, but the vibration is intense. The brake pedal doesn't shudder. This leads me to think that it is the rotors. BUT! If it were the rotors, then I would feel the warping at all speeds under braking AND through the brake pedal, wouldn't I? So cliff notes: - Steering wheels vibrates during freeway speeds, methinks tires. - Replaced tires (with used tires), vibration still there, just higher mph - During braking from freeway speeds, vibration intensifies, then stops completely from 60ish to 0mph. - No evidence of braking shudder through chassis nor brake pedal It could be that I have the same flat spots on the new set and have not eliminated tires as a variable completely, it IS bad rotors but the symptoms on Porsches are different than other cars, or something else entirely. Does anyone know of a different root cause of shaking aside from the above? Thanks.

I recently got a used 2005 Boxster 'S' and it made me nervous at 70+. First thing I did was have the wheel balance done. Second thing was replace the Inner Tie Rods. They clearly had a 1/8 clicking/looseness. Then I got aligned by the best. He set me up enjoyable driving at highway speeds and took a little camber out of the rear for tire wear. Now all that exists is a little something around 60 and I bet it is the All Seasons I'm riding on. I also replace several other suspension components. Car drives amazing, truly a joy. Nothing like new Tie Rods and a spot on alignment. BTW I could not tell they were worn until I had removed the Inners.

What about it made you nervous at 70+? I'm perfectly content with how it handles at 90mph. Shaking aside, it feels hunkered down. However, it does click some times when turning 90 degrees at parking lot speeds, especially when transitioning from one surface to another e.g. concrete to asphalt. Good point on the alignment. I was going to wait until I put a new set of tires on my new set of wheels, but maybe it's time.

When I got it it had got worse with higher speeds. Around 55 it would shake real bad sometime and then just go away. I had one wheel that a weight had fallen off and once I had them re-balance the 55mph issue went away. Since I have a tiny bit occasionally at 60ish I'm guess from the previous experience it might be the all seasons or flat spots that then go away after warm up. I've had 4 boxsters and I just love this one now, turn ins are quick and I like that rock solid feel on the highway, it reminds me of a Cayman R I used to drive, that was my standard for how a porsche can feel on the highway. Oh and I have over 100k miles...so I knew it likely needed work.

Oh and regards to the 90degree parking lot skipping of tires. THIS IS NORMAL . Should be lots of threads on this.

So I just jacked up one side of the car and shook the wheel on the horizontal axis (3 and 9 o'clock). It has play at about 1/4in. There should be no play with 1 wheel on the ground and one up in the air, correct?

This can't be good . Could be the ball joint on the tie rod where it connects to hub.

You obviously have issues with your front suspension. With that much play you should be able to notice when moving the wheel where the gap is coming from. In your place I would check everything - ball joints, tie rods, stabilizer bar links etc. I'd replace in pairs. If you are not comfortable doing this by yourself find good independent. Front suspension issues could be dangerous and IMO are not to be taken lightly.

I agree, hence the thread. Do you know of a method to check the lower control arm & ball joints vs the tie rods?

UPDATE: I had a chance to work on the car last week. On a weekday night, I put her up on stands and marinated the outers in AeroKroil. The outers came off with little fuss but I realized I was going to be in a world of hurt for the inners. Just no space to work. I admitted defeat, and rang up West End here in SoCal the next day. They were able to accommodate me yesterday. It drives sooo much better now. It still has a small amount of steering wheel vibration, but Darin kindly pointed out the brake rotors as the source of the issue. I also did not have an discernible play in the rods. It was the rod ends that were loose. If you can move the ends about the ball, it's time for them to go. Would like to recommend West End. They take their time with you. I just wish I asked for more front camber!