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pancobalt
Spa-Francorchamps


Joined: 02 May 2015
Posts: 282
Location: surrey


PostPosted: Mon Feb 05, 2018 5:05 pm    Post subject: new tyres vs new shocks vs ? Reply with quote

Hello all

Some advice please. My front end has started floating ( skitish ), every bump is felt through the steering wheel and car handles quite badly. Car has done 79k miles

no diagnostic faults found with the PASM and no PASM error messages on dash . No punctures . Tyre pressures fine.

However , front Michelin PS2 tyres have 3mm tread remaining and perished side walls

front shocks and springs removed from the car for inspection. Springs are fine.

front Top mounts and bearings and bump stop dont look clever so they are being replaced. Shock absorbers however show no signs of leaking and when one pushes down on the piston there is good resistance and return .

Would new tyres be a remedy ?

Would new shocks be a remedy ?

Just some thoughts and experiences sought really .

£457 for a genuine Porsche shock absorber is a sting , especially if not necessary !?

Thank you for your help as always.
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Robertb
Long Beach


Joined: 01 Sep 2003
Posts: 6530
Location: South Oxfordshire

2002 Porsche 996 Carrera 4S

PostPosted: Mon Feb 05, 2018 5:32 pm    Post subject: Reply with quote

I would start with the tyres, seeing as they don't have a lot of tread (particularly on a light front end like a 911) and are perishing. Decent new tyres can make a surprising difference.

Worn shocks could, theoretically at least, cause a skittish feel as the rebound would not keep the wheel on the ground as well as they might over bumps.

I've read of mythical testing rigs in German Porsche dealers, which can assess if shocks are performing as they should. Anyone know of anything similar in the UK?
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Magic919
Montreal


Joined: 05 Jun 2013
Posts: 607
Location: Berkshire


PostPosted: Mon Feb 05, 2018 5:45 pm    Post subject: Reply with quote

I expect Center Gravity can test the shocks.
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MJA911
Magny-Cours


Joined: 10 Dec 2013
Posts: 2603
Location: Berkshire

2006 Porsche 997 GT3

PostPosted: Mon Feb 05, 2018 5:54 pm    Post subject: Reply with quote

They certainly can, they have a machine specifically for that job, car stands on pads in the floor which vibrate and produces as graph that tells them all they need to know about the shock absorbers. I'd back them and their process to ascertain what's going on with your car and take the guesswork out of how to optimise it.
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Porschekit
Hockenheim


Joined: 12 Aug 2014
Posts: 702
Location: North East UK


PostPosted: Mon Feb 05, 2018 5:55 pm    Post subject: Reply with quote

March 2017 I had the same feeling on my 2009 997.1 C4S. Very floaty on the front at high speed.
Paid a visit to Centre Gravity who confirmed that the shocks and tyres were fine (even though my fronts were well worn to 3mm and feathery on the edges but still legal)

They adjusted the camber and toe set ups on my geometry, from the Porsche standard (i.e. set up with under-steer for any driver and to avoid them putting it into a hedge) to what I wanted, which was upright, no camber , no toe.

The difference is very noticeable and she now runs on rails. Well worth the £325 for four hours work. I watched the whole procedure and was guided through all the changes as they made them Thumb
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T8
General
General


Joined: 29 Jun 2010
Posts: 13881
Location: Kent


PostPosted: Mon Feb 05, 2018 6:42 pm    Post subject: Reply with quote

Replacing the tyres would definitely be the place to start. 3mm tread OR perished side walls would give sub-optimal handling. Both would be awful.

Also, when you say "tyre pressures fine" what pressures are you running. Question
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pancobalt
Spa-Francorchamps


Joined: 02 May 2015
Posts: 282
Location: surrey


PostPosted: Mon Feb 05, 2018 6:44 pm    Post subject: Reply with quote

Thank you all for your help. I shall pay a visit to centre gravity in due course.

Porschekit - during your floaty period , did you feel every bump , even at low speeds , like me ?

In sport mode , one expects a hard, no comfort ride. But in normal pasm , my ride is still harsh , hard and bone shakingly terrible Dont know
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pancobalt
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Joined: 02 May 2015
Posts: 282
Location: surrey


PostPosted: Mon Feb 05, 2018 6:46 pm    Post subject: Reply with quote

T8 wrote:
Replacing the tyres would definitely be the place to start. 3mm tread OR perished side walls would give sub-optimal handling. Both would be awful.

Also, when you say "tyre pressures fine" what pressures are you running. Question


M ps2 all round 34psi front 40 psi rear
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T8
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Joined: 29 Jun 2010
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PostPosted: Mon Feb 05, 2018 6:47 pm    Post subject: Reply with quote

Reading your post from a couple of weeks ago when you found your pressures were 20 front and 30 rear I suspect you've fubared your tyres and need to replace all four.

=> http://911uk.com/viewtopic.php?t=125199&start=0&postdays=0&postorder=asc&highlight=
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pancobalt
Spa-Francorchamps


Joined: 02 May 2015
Posts: 282
Location: surrey


PostPosted: Mon Feb 05, 2018 7:26 pm    Post subject: Reply with quote

Yes T8, i suspect i may have wrecked my own tyres . !

But the rear tyres are not perished . Hopefully it will just be the fronts i replace.

perishing , punctures ,low tread ,old age , are the the obvious signs of unwell tyres -

But are there methods of testing the integrety of the tyre walls and metal bands within ?
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T8
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PostPosted: Tue Feb 06, 2018 12:45 am    Post subject: Reply with quote

I've no idea but if you've run them for any length of time at only 30 psi I suspect that they aren't very good.

I'd certainly replace them before replacing any suspension components.
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MJA911
Magny-Cours


Joined: 10 Dec 2013
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Location: Berkshire

2006 Porsche 997 GT3

PostPosted: Tue Feb 06, 2018 1:41 am    Post subject: Reply with quote

Tend to agree, going for a roadtune at Center Gravity is always a good thing, but with those fronts at 3mm and maybe a few years old, replacing them is a no-brainer, then see where you are on the way the car handles.
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maldren
Hockenheim


Joined: 07 Oct 2016
Posts: 719



PostPosted: Tue Feb 06, 2018 9:22 am    Post subject: Reply with quote

How old are your tyres (check the manufacturing date on the sidewall). They really shouldn't be perished unless they are old. 6 years should be the limit, especially for high performance cars.
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2003 996.2 C2 Coupe Arctic Silver
 
  
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wasz
Indianapolis


Joined: 28 Dec 2012
Posts: 2397


1999 Porsche 996 Carrera 2

PostPosted: Tue Feb 06, 2018 10:24 am    Post subject: Reply with quote

As said any tyre over 5 years old bin it - they do go hard in UV light and if there are cracks, well they have gone hard already!

Replace any worn bushings.

Get it aligned on a laser rig or at a trusted motorsports type place.

Should be back to normal Thumb
 
  
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krispe
Monza


Joined: 05 Feb 2014
Posts: 215
Location: Northampton


PostPosted: Tue Feb 06, 2018 10:47 am    Post subject: Reply with quote

Just had my front end redone, new gt3 lower arms, new top mounts, new Bilstein B4 PASM shocks (much cheaper than Porsche) and the difference is amazing. All the knocks and play have gone and the B4 Damptornics ride much better. Original shocks were on 60k miles but 13 years old and driven over good knows how many speed bumps, pot holes plus a half a dozen trackdays. Just need to refresh the rear now. The B4's were about £260 each plus VAT. and identical to the Porsche (bilstein) shocks removed from the car. I spent ages trying to decide between, B4, B6 B8, B16 and even Ohlins shocks, but decided I like the way my car handles already (it has Eibach springs and H&R rollbars) and it's also my daily so decided against coilovers and even the stiffer B6,B8 shocks. Definatley feel I made the right choice for me, now feels like a new car thumbsup
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Porschekit
Hockenheim


Joined: 12 Aug 2014
Posts: 702
Location: North East UK


PostPosted: Tue Feb 06, 2018 1:15 pm    Post subject: Reply with quote

Pancobalt: To answer your question, no I did not experience a hard ride when the front end was floaty,and before the Centre gravity work. It was fine at motorway speeds and below, just a little loose at higher speeds and making me not confident to push.
Once adjusted I got that connection with the road confidence back. Hope you get sorted, but I agree, new rubber all round first would be the way to go before having the geometry work done. Thumb
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pancobalt
Spa-Francorchamps


Joined: 02 May 2015
Posts: 282
Location: surrey


PostPosted: Tue Feb 06, 2018 5:39 pm    Post subject: Reply with quote

Thank you porschekit. And thank you to all. Your kind advice and wisdom is much appreciated.

Rears are 4 years old. The vendor replaced them for me when i bought the car in feb 2015. So they have been on the car for 3 years. I recall the date stamp on the rears being xx14.

6mm tread left and no perishing on rears.

As for the fronts, they are very old. Maybe 2012 , cant remember and the car is not with me at present.

Anyway im getting x 2 new front michelin ps2's next week for sure. I have also taken the decision to refit my old front shocks as they look and feel ok on the bench . If they were leaking i would defo replace them.

Will keep you all updated . On my journey through the school of 997 handling f*ckness, i have learnt ( the hard way )

1. Check tyre pressures weekly.
2. Check condition of tyres.
3. Then launch into removing the suspension !

Sad
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pancobalt
Spa-Francorchamps


Joined: 02 May 2015
Posts: 282
Location: surrey


PostPosted: Wed Feb 14, 2018 6:32 pm    Post subject: Reply with quote

So today , both june 2013 knackered michelin ps2 front tyres replaced with brand new august 2017 m ps2.

Massive improvement in handling, drive and feel . 2 weeks to bed 'em in then its full geometry at the end of the month.

Thank you all again for all your advice and kind help.
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James M-S
Nürburgring


Joined: 11 Apr 2017
Posts: 469
Location: Derby

2009 Porsche 997 Carrera 2

PostPosted: Wed Feb 14, 2018 10:56 pm    Post subject: Reply with quote

pancobalt wrote:


Rears are 4 years old. The vendor replaced them for me when i bought the car in feb 2015. So they have been on the car for 3 years. I recall the date stamp on the rears being xx14.

6mm tread left and no perishing on rears

Sad


You’ve had a 911 three years and still have 6mm on the rears!!!
Surprised Surprised
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pancobalt
Spa-Francorchamps


Joined: 02 May 2015
Posts: 282
Location: surrey


PostPosted: Thu Feb 15, 2018 5:28 pm    Post subject: Reply with quote

You’ve had a 911 three years and still have 6mm on the rears!!!
Surprised Surprised[/quote]

Yes , only done 8000 miles in 3 yrs and no track days
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