Bumpy Ride in Sport suspension mode

**Man In Black (MIB)** · 27-08-2013, 05:08 PM

UPDATE: Camber was actually fine. Both front electronic height sensors now replaced. No luck though.

Getting a local Porsche mechanic and suspension specialist to do a proper wheel balance to see what effect that has.

Problem most notable on smooth roads at about 80kph in Sport mode. If not wheels or suspension then could be a diff issue.

Will report back.

**Man In Black (MIB)** · 23-12-2013, 02:38 PM

Solved.

After much investigation (and new rear Shocks and rear diff end dampener) turns out it was a flat spotted tyre. Only one. That's why it didn't vibrate through the steering.

Flat spotted meant an up and down movement not a left right vibration (which you would normally feel through the steering). This is why the chassis control could control it in comfort but transferred the movement to the car's chassis in the less compliant sport mode. Effect was only felt around 80 and 100 and would go away when the tyres were hot.

Took it to a tyre/wheel expert in Mitchell in the ACT who pretty well diagnosed it from my description. We then ran them up on the balancing machine and one stood out (visually) as not being quite round.

No explanation for the flat spot. Could have been tyres where hot and I parked one tyre in cold water which changed its shape.

Anyway, real happy it's not the car's fault. Pretty annoyed with Jax at Fyshwick who I took it to 6moths ago for a balance and rotate and to find out what the problem might be. They should have seen the flat spot and reported it to me.

**Grah22** · 24-12-2013, 01:32 PM

Good to know it's fixed.
Strange you had no feel for the flat spot through the steering though...

**Man In Black (MIB)** · 26-12-2013, 11:15 AM

Shock absorbers were taking all the load so it wouldn't transfer through the steering. Left right movement/vibration would have been sent down the shaft and then to the wheel.

Certainly speaks volumes for the chassis control that it could hide it in comfort mode.

**kam** · 02-01-2014, 09:17 AM

takes a while to get a flat spot ?

as in, parked in the same spot for a couple weeks, not overnight...

**seangti** · 24-01-2014, 12:27 PM

Originally Posted by Man In Black (MIB)

Anyway, real happy it's not the car's fault. Pretty annoyed with Jax at Fyshwick who I took it to 6moths ago for a balance and rotate and to find out what the problem might be. They should have seen the flat spot and reported it to me.

That's not a fair summation to blame a workshop that touched it 6 months. Add driving, temp change, braking, etc, will turn a small blemish of 6months ago into a much larger one now.