Vibration at speed

[kennyboy]

My C2 starts to vibrate at around 115mph and then goes away again at around 130mph. I can't tell where the vibration is coming from in terms of front or rear but it comes through the steering wheel and to a lesser extent, the whole car.

It's not really bad - in fact feels like wheels out of balance but it's annoying enough not to be able to cruise at them speeds.

I had new tyres fitted to the rear this week and had the fronts balanced at the same time and it hasn't improved at all...

Can anyone suggest what it might be?

 

[Sundeep]

odd that it settles up at higher speeds..

could be tyre pressure.... are you runnig the same tyres all the way around ?

 

[vic cohen]

Sounds from speeds like rear wheel balance ,comes in at 120mph. can feel like car shaking apart after short while....fronts abt 70 mph .........sounds daft but if u 've just had wheels off check all tight again ! If this doesnt work check u have the rigt 'n' numbers and correct inflations ,easier to do all that first .............if none of this works and tracking etc has been done recently get a thorough check .

 

[kennyboy]

Interesting....

I've just had 2 new rear tyres fitted and balanced - although on a machine that balances up to 100mph only, though aren't they all like this? got the tyres and balancing done by one of the national chains, not Porsche dealer.

The tyres fitted are exactly the tyres that were on the car when I bought it - i.e. pirreli pzero assymertric 255/40 zr 17 n2. not sure what the n2 means but is this ok?

Also noticed on the weekend that my front tyres are a different profile to the back ones I think they're 205/50's or 205/45's can't remember which now.... but when I saw that it scared me! can you confirm if this is normal?

Pressures are correct and as porsche recommends for the tyre size.

the shaking is the same with the new tyres as it was with the old ones where we very worn.....

 

[vic cohen]

In the ideal world all the n numbers should be the same ..............i am no expert here but if u have matching 'n' on same axle dont panic yet ..............tyres have been known to be balanced incorrectly before ,maybe worth checking if not someone used to dealing with Porkas etc ..........profiles may be different back and front i run on 285 30 18 rears and 235 40 18 fronts so as long as they re what the book says dont worry ,should nt affect vibration anyaway ,unless perhaps they were litterally dd tyres on same axle ! For sure they are unlikely to just bed in and ur using ur rubber up ,best bet go to someone Porsche and get it all checked if none of the above applies.

 

[kennyboy]

Nice one Maurice - I was hoping you'd have something to say on this one!

I'm hearing the same from rennlister's so as soon as I've sourced the nearest decent outfit to me in Leeds I'll be there to get it sorted.

So hoping Maurice gets some reply's to his 'oop north' request.

Just got a quote from local OPC for kinematic check and it's far too expensive for the time being.... do I really need the full works or would (proper) balancing do for now?

 

[vic cohen]

Oooerrrr,cupsports 285 30; rossos 265 30 ..............different car, may even have written it down wrong ! Need to look at car !!!!!!!!!!!!!!! Think i ll crawl away.................only wanted to confirm diff profiles back and front perfectly normal. Commuting in RSR today!

 

[kennyboy]

Thanks Maurice.... the bad news is that I am experiencing some pretty nervous handling - a lot different to my 993 C4 I had a few years back.

in fact on long, fast bends the rear seems all over the place - not in terms of oversteer but seems to shift left and right needing continual corrections - quite scary.
This was with 34 psi in the back tyres so have put them back up to 36 and will see what that does later this week.

I can see a kinematic coming on - do you know if the balancing will be done as part of this?
I think strasse of Leeds can do this now so hopefully much cheaper than OPC!

 

[vic cohen]

OK knickers out of twist ...........big boy runs 235/40/18 fronts as quoted rears in both cup and rosso[as u saw at Goodwood] are 285/30/18...........265/35/18 on rs/rsr
a first for me geting sizes right !

 

[38F3E1]

Narrow body 18s are 225/40 F, 265/35 R, wide body 285/30 R.

Maurice

Interested in this quote. I have a narrow body and I am running 10 inch 18s with 285/30 on the rear so far without problems. They came with the wheel which I got a good deal on (as in the tires were basically free but I didn't get a choice on the size). Knowing 265/35 are the size quoted in the drivers manual (although 285/30 are also quoted in the techquipment catalogue) should I change to 265/35?

Ian.

 

[vic cohen]

I believe [although u asked Maurice] its a matter of feel and what u want ..........with rolled arches the 285 fit the narrow body cars ,cost small amount extra,wear the same but overall feel is changed ,this include s the pressures u decide on ..............actual benefit limited ,when lets go u may be going that much quicker so it all happens faster......back to personal choice .........................Maurice is absolutely rigth on GT2 should be running 285/35 off to see what Michelin have ..........thanks M are u on comission!

 

[ajc]

Kenny

I had similar vibration symptoms on the Le Mans trip - settled down after 120 ish - I'll be keen to see how you get on with the geo checks. Does your car have spacers? - I remember hearing years ago that you need to balance your wheels on the car when these are fitted.

I'm near to Leeds, where did you get your new boots from? Good price? I want to stick with the PZeros and need some new fronts for my car which have worn the inside edges. I'm told that there is some -ve camber as part of the standard set up on the 2S ???

Cheers

Stan

 

[rjs993]

Gentlemen,

I have just posted a new topic only to come across this one which seems to talk to exactly the same symptoms i.e. vibration/shudder through the steering at high speed. Indeed it was on the Le Mans Classic trip and a blast around the circuit that this became evident. As with others with the same symptoms this comes in about 120mph but can disappear at lower or higher speeds. It gets worse under braking although does not seem to adversely effect the handling (cornering and roadholding at Le Mans was fantastic).

Mine is a C2S (wide body) running on standard 17" wheels.

Geometry was checked and adjusted within the last month.

Wheel balance or worn ball joint .... are my best guess? Although if the discs needed skimmed (there is some ridging around the circumference) could this cause a problem?

Let's keep this one running until we find a solution.

Cheers

Robert

 

[38F3E1]

ORIGINAL: vic cohen

OK knickers out of twist ...........big boy runs

Vic.

Are you the chap with the 993 with number plate B16 BOY I saw at PCT in Coventry a short while ago?

Ian.

 

[kennyboy]

Stan - I'm currently working in halifax so rang up charlie browns first and they quoted £138 each inc vat and fitting, valves and balancing. my tyres are pzero asymetrics 255/40 xr 17 n2 i.e. standard fare for C2 narrow body I believe.

they didn't have any in and I needed doing that day so rang up national tyres in the centre of halifax and they quoted £194 each!! I told them about charlie browns and they price matched! so I think I got a good deal eh!?

Stan - just noticed you've got a C2S, I have C2 so can't provide quote for your bigger boots.

Also I'm deffo gonna wait till the tyres have bedded in more before looking at a 4 wheel alignment etc. Looking at this thread a few of us are suffering from this so might be something else?

And Robert has had his alignment done recently...

 

[vic cohen]

Sorry thats another one! I own up to A 911 P GT;M33 RSR and M6 POR .................live just outside London ,St Albans 'ish

Was in a blue car at Silverstone last Wed

 

[Guest]

Have you checked that the wheels are running true? I had this problem and it was a slightly warped nearside rear......Robert

 

[Shane Hodges]

Kinematic toe .... I've heard about it, know it's important, but what EXACTLY is it.

Different to usual toe in/out ?

If someone could point me to a definition (or type it again) it would be much appreciated.

Ta.

ps Still currently having handling issues - I appears to have loose control arms (the ones that come off the stering rack and join the front wheels) - have a silly quote from local OPC which includes geo check so JZM might get my first bit of business.

 

[rjs993]

Shane,

You might want to consider a visit to Autostrasse in Coggeshall (Herts or Essex?). They are an independent but both the guys (Alan and Ken) are ex-Porsche trained and work exclusively on Porsche cars - but mostly 911's of one sort or another. They are helpful and know what they are about.

Just a thought.

Robert

 

[laura]

Kenny, if you're lookin for an alternative 'oop north' we have found Specialist Cars at Malton (a bit more 'up north' but we found it worth while) have been very helpful and knowledgeable. I don't know if they have a kinetic thingy but they set up our C2 and it is miles better since.
Good luck.