I have just cured an annoying shimmying problem which started with my L405 recently and wanted to signal it up in case it helped anyone else.

Short version of the story:
ContiSilent acoustic tyre foam separated from the tyre carcuss causing an inconsistent shimmy.

Longer version for those who are intereseted:
At a previous tyre change I opted to try the 'silent" tyres with the acoustic foam in them and was impressed with the results, I went for Conti Silent's because the car had 2 Conti's on at the time. The improvement in cabin noise was impressive, sit I have insisted on them since.

Recently the car developed a pronounced shimmy, shudder, kind or out of balance issue from the rear which was shod with a pair of ContiSilents with a manufacture date in 2018.

The shimmy was annoying and also variable, sometime almost non existent, sometimes very pronounced. It did not feel like a balance issue because it could be felt from 30mph to 70+mph at different times and got consistently worse as the speeds rose.

I checked for tyre damage and had the rear wheels rebalanced then fitted the spare one side and the best of the other two tyres on the other. The issue changed but persisted so I guessed I might be onto something having checked the proposal shaft centre bearing whilst the car was in the air (all ok).

When having the two rear tyres replaced the problem became obvious. The acoustic foam had completely separated from both the tyres and free to move around which was obviously causing the problem.

Morel of the story, at least have someone pop the tyre off the rim and investigate this before going down the expensive route of wasting money elsewhere if you get an inconsistent wheel wobble which is speed related and not a balance issue.

Hope it helps!
David 2016 (L405) Autobiography in Black with Ivory - for ULEZ
2014 (L405) VSE in Black with Ivory
2011 (L322) VSE in Black with Ivory
2005 (3.2 V6) Porsche Cayenne in Black with Savanna
1999 (P38) VSE in Burgundy (?) with Sand

Photo of one offending item - oops will try again! 2016 (L405) Autobiography in Black with Ivory - for ULEZ
2014 (L405) VSE in Black with Ivory
2011 (L322) VSE in Black with Ivory
2005 (3.2 V6) Porsche Cayenne in Black with Savanna
1999 (P38) VSE in Burgundy (?) with Sand

Last edited by 160dmb on 21st Jun 2023 7:39am. Edited 2 times in total

Photo of one offending item

Click image to enlarge

Thanks for the info, what tyres have you replaced them with..?? Pete
__________________________________________________
2014 L405 Autobiography SDV8 4.4 Loire Blue Ebony interior
-Click here for Thread-
2012 L322 Autobiography 5.0 Supercharged Ipanema Sand Sold
2011 L322 Vogue SE 4.4 TDV8 Baltic Blue. Sold
2002 L322 Vogue 4.4 V8 Epson Green (Fatty Offroader) Sold
-Click here for Project Fatty off roader-

I had already bought two Conti's to keep them matched on the vehicle and across the axles.
Probably wouldn't have if I had known what I know now!

I called Conti technical this morning and they knew exactly what I was going to say and even asked "is the internal foam yellowish in colour?". The later Foam is apparently thicker and grey and does not suffer the same fate.

Continental are collecting the tyres and will inspect them and make a compensation payment but I doubt that will be generous as the tyres are being changed because they are due for replacement and Conti will say they are finished anyway but that does not compensate for the past discomfort or time, money or effort I have been through to solve.

Truth is I really hadn't considered that the acoustic foam could be the issue

Hey ho, the joys of car ownership!  2016 (L405) Autobiography in Black with Ivory - for ULEZ
2014 (L405) VSE in Black with Ivory
2011 (L322) VSE in Black with Ivory
2005 (3.2 V6) Porsche Cayenne in Black with Savanna
1999 (P38) VSE in Burgundy (?) with Sand

Yes, sounds like you are unlikely to get much compensation but at least you have got to the bottom of it..  Pete
__________________________________________________
2014 L405 Autobiography SDV8 4.4 Loire Blue Ebony interior
-Click here for Thread-
2012 L322 Autobiography 5.0 Supercharged Ipanema Sand Sold
2011 L322 Vogue SE 4.4 TDV8 Baltic Blue. Sold
2002 L322 Vogue 4.4 V8 Epson Green (Fatty Offroader) Sold
-Click here for Project Fatty off roader-