Centre Gravity Visit 9th March

[Motorhead]

ORIGINAL: Buddy It will effectively be a tutorial on suspension, tyres and related items in fact Chris has requested that we have a poll of whatever modifications people have envisaged having to their suspension set ups and so if all of you are interested in an expert view on what mods you are considering he will give his opinion of the benefit or if of no benefit they may be. So if you will please add your lists to the thread.

Kevan, Since my Cayman is under the Porsche extended warranty, effectively this precludes any unauthorised suspension components/set-ups but I would be interested to hear from Chris what, if anything, can be done within the production suspension tolerances set by Porsche to change the car's handling characteristics. In his experience is the choice of tyres significant? Rather a tall order perhaps but, just as a matter of interest, given a free choice I'd like to know if there is just one thing that can be done to change radically how the car behaves. Jeff

 

[Buddy]

Dave, glad to have you along, as an engineer and speaking with Chris I feel I have a lot to learn but then engineering is a very wide field and Chris is a specialist but I found him most interesting to talk to. Jeff, Chris asked me for a list of the mod's people had considered or were considering along with anyone who has any problems with the handling of their car, if for instance someone has a car which pulls one way on certain road features such as white lines, tramlines on ruts, becomes unstable under heavy braking or whatever else someone comes up with. For most people envisaging toe in on two axles seems a lot to imagine but suspension action and effect relevant to alignment has to be considered through the full range of suspension movement and considering the loads involved. Chris did say that anyone hoping for measurements to be taken must have a full fuel tank ( tank weight being a variable ) but if someone has a particular problem please let me know in order that he can decide which will benefit the demonstration. I for one am looking forward to the day which will be starting about 10am and he expects it to last past 3pm ( 8pm is latest kick out but hopefully we can allow him off earlier ) anyone who cannot afford so much time is still welcome as he says if they just get some information sorted in their minds it is better than none and he would like a group who can talk in an educated manner using correct terminology etc. Choice and even age of tyres is significant, when I was there he had a 993 on the lift and due to age the front tyres had hardened which effectively meant there was an imbalance between effective springing and damping of the two axles ( he can measure the spring/rebound capability of the tyres ). He also has a way of testing the dampers by operational frequency as he described from seasick to what I would call vomit comet![:'(][:'(][:'(][&o] It should prove a most interesting day so get a good nights sleep beforehand.

 

[Buddy]

Ok, I've put together a starter list of points which may be raised on the day of Cayman Handling mods for consideration. If anyone has anything they wish to add please post a reply on the forum. For discussion: in old cars with rigid rear axles the front wheels often had positive camber said to be for straight line stability, not so today what brought about the change? Anti roll bar upgrades Lowered suspension Stiffer springs Adjustable shocks Upgraded Fixed rate shocks Advantages or not of PASM Castor angle maxed up +/- Camber front rear changes advantages/disadvantages Wheel changes with tyres, ( 18”- 19” or vice versa) Tyre brand differences for case stiffness Compound variations across brands and consideration of aging on the compounds for low mileage “garage queens”

 

[GT4RSWirral]

Hi all Looking forward to this, is anyone travelling down from the northwest region on the 9th March? Alun

 

[Buddy]

I spoke with CG this afternoon and one thing Chris wants everyone to know is that the workshop is not very warm and advises that since the concrete floor tends to be very cold that we should all make sure that we wear warm socks and footwear even warm hats if that's where we feel the chill! Like any garage type workshop the ceiling is high due to having car lifts in it so the heat rises. Otherwise, they are looking forward to our visit and will be expecting us there for 10am and I'm told that there is a neighbouring cafe if you want a hot breakfast beforehand.[] Apparently they are now so busy that they are booked up through March. Chris is asking if anyone has a particular handling problem and he will discuss and probably take the measurements to carry out some investigation. But please try to let me know beforehand and also try to be among the first to arrive.[8|]

 

[GT4RSWirral]

Hi Kevan Can you give me the address for Centre Gravity? Alun

 

[Buddy]

Certainly Alun, they are based close to the A5 at :- Center Gravity Limited Academy workshop, Unit 2, Plot 14 Brindley Close, Holly Lane Industrial Estate Warwickshire, CV9 2GA 01827 718800 It's at the back of an industrial estate outside Atherstone and quite easy to find.

 

[MrDemon]

Can I pop along also Fancy asking questions about rss lower control arms for my Spyder. And he relation between front and Rear camber

 

[Buddy]

No problem, so far I think there will be room.

 

[Buddy]

Please remember that the garage is pretty cold and dress for outside temperatures without wind chill, not too bad for bikers and outdoor types as they will know very well what to wear to keep warm. Chris says that feet particularly feel the cold due to the concrete floor so please be aware of this. I'm not sure what time we will be finishing as it depends on the questions raised etc but the norm is 4-6 hours. Has anyone got a suspension/handling problem which we can get checked out? Understeer, oversteer, pulling to either side, odd cornering characteristics? Let me know and I'll send the info to Chris.

 

[Motorhead]

Kevan, just a thought but I presume that Chris will be covering after-market alternatives (Bilstein?) to the PASM dampers which could be due for renewal on some of the older Caymans. It would be interesting if we could get an older PASM-equipped car on his damper test rig to check damper functionality after 50k+ miles, but I doubt that there'll be time. Jeff

 

[Buddy]

I think Chris may be able to check several or maybe everyone's dampers depending on numbers attending, which could be interesting. Particularly if your in the driving seat when he turns it up!! He certainly rates the Cayman very highly and his wife Jayne drives a Boxster ( like a Cayman but with a tent where the roof should be ).[][]

 

[Buddy]

The CG visit took place today and although we only had 8 people attending it was felt by all that it was highly beneficial to those who attended. Chris is a font of all knowledge where suspension systems are involved and the equipment he uses so skillfully is to a very high standard, Peter who works with Chris is also extremely knowledgable and since there were only 8 of us they divided us into two groups one with each of them ( Chris's wife Jayne looked after catering, different for her as she usually also has logistics to contend with ). All questions raised were dealt with very well and we all felt that there is only one point of contact for suspension issues in future, CG. Chris and Peter have a large capability in modifying the suspension and they are most attentive in their adjustments not working only to limits but equallising the settings across the car in order that the set up is set side to side. They evaluate the effects of differing toe in, camber etc to achieve optimum handling for each owner's style of driving. We all got "crib" sheets of what changes can cause understeer/oversteer tyre pressures, spring rates etc and as I was first to arrive my car went onto the lift for measurement, A couple of things were outside limits by a very small amount but since Chris sets a car up for an individual's preferences I felt lucky to see that for the way I like to drive, mine is close to spot on. No bad for a 51,000 miler. Jayne was also telling me that they do have some good deals from the OPC and pass these on to their customers and so for the std of work carried out they can give a good price. In short if you have any detailed questions I would say to give them a call, for general queries start a new thread and those who attended today will try to help. You missed a good visit.[]

 

[BrianJ]

That was a brilliant visit. The friendliness, quality, knowledge and hospitality of Chris, Pete and Jayne was fantastic. It was great to understand more about the construction of the suspension and steering components on our cars, how and why they wear, the impact on handling and how they have developed from 986 to the current models. Many thanks for organising - very much appreciated and enjoyed.

 

[chrisH]

Kevin, It would be interesting to learn what Chris had to say about rear tyre wear, especially as out of alignment is blamed to be the cause whereas it seems from his checking of your car that there was nothing wrong with it. I think it's purely a question of which make of tyres you get when the car is built and therefore have to replace with to keep the warranty valid. In my case my car has Pirellis and from what I can conclude they just wear out quicker (9000 miles) than Michelins and Bridgestones. The new 981s all seem to be coming through with Pirellis too unfortunately for me.[] Chris

 

[Buddy]

Chris, It is a fact that some tyre brands and even compounds from one maker will wear at differing rates, it's been gone over many times on different areas of the forum but of the approved tyres which were until recently Michelin PS2's, Continental Contisports and Bridgestone RE050 the Conti's were generally found to have the least longevity with the other two being relatively close on their wear rates. Weight balance does have some bearing on the rear tyre wear rate as does the RWD, Chris counted the weight distribution as 45%rearto 55%front and of course the fact we are driving the rear tyres make them wear quicker. Not so badly as for a FWD car with any amount of power where the fronts will wear 2-3 times faster than the rears but on those you can swap end to end and prolong the longevity. Having said all of the above, apparently the newer Michelin Supersports are said to give better grip than PS2's and last longer, it's such a pity that as yet they are not N rated, maybe in a year or two? I have had my Gen1 for 5 1/2 years and in that time have had the three approved tyres fitted as I said earlier the Continentals wore very quickly, especially at the rear, the type of driving I did on the Michelins did include a lot of distance cruising so it wsn't that surprising that the rears were only a little more worn than the fronts when I changed the full set and again on the Bridgestones I have noticed that the rears are very slightly lower than the fronts, I will however be hoping to replace the present tyres with the same type next time around. They do seem to have good feel, wear and grip but it could be down to my driving, local road surfaces and using them through the summer more than the winter. Town driving with lots of turning, accelerating and braking will increase the wear rate due to more friction loads. So, you can see that type of driving does have an effect on wear rates, also, as Chris said today Bridgstone tyres have the stiffest sidewalls of the approved tyres which means that there is less deflection in the tyre carcase. For the launch last week the OPC asked to borrow my car as an example of an early Cayman S and so I refitted my summer wheels and tyres, I was not surprised to find they were a harder ride the difference between 18" & 19" but as Chris pointed out stiffer sidewalls too. To further complicate matters, over the winter I fitted a set of 18" wheels with Michelin Alpin M&S tyres, wear rate is minimal all around, wet grip incredibly high cutting through standing water at speed with no tugging to either side but while being Porsche Approved N rated, they are rated to a lower speed than the summer tyres. A soft grippy tyre with low wear not what we are used to at all. When N rated tyres are plentiful it s usually ok to state a preference but then, who is currently producing 20" tyres? It may only be Pirelli!

 

[Motorhead]

As Kevan has said, a very interesting and informative day at CG. They came across as a small but very focused and professional outfit. Chris' enthusiasm and expertise in this field are second-to-none and he has succeeded in passing on his knowledge to his very capable assistant Peter. Many thanks to them and to Jayne for hosting us and thanks also to Kevan for organising the event. It was good to meet up with fellow Caymanites. Jeff PS: I think that it would be good if Chris invested in a workshop space heater - I was frozen at the end of the day despite being clad for winter..!

 

[Motorhead]

Paul made an interesting comment regarding tyre sourcing. They had a customer whose car was handling very strangely despite the geo set-up being spot-on. The tyres were all from the same manufacturer and had identical N-ratings but they found that the two fronts were manufactured in different countries and therefore were likely to be slightly different rubber mixes. So if you're forced to replace a single tyre on an axle, it'll pay to check that the supplier is replacing like with like. On an unrelated matter, we were also told of a customer whose PASM-eqipped car was proving undriveable, even for a local daily drive to the garden centre. I think that he'd been to several PCs who'd failed to address the problem - no PIWIS faults were found. Chris drove the car over a local grating and diagnosed that the front dampers were locked in Sport mode..! I think he said that this was confirmed by putting the car on their damper test rig. The result....one very satisfied customer. Unfortunately, due to computer/rig gremlins, we were unable to witness the machine in action yesterday. Jeff

 

[Buddy]

It's also necessary to ensure the tyre ages are reasonably close, when I was there a few weeks ago they had a 993 on the lift which had it's tyres paired across the axles but there was a problem because one pair was several years older than the other pair resulting in a difference in flexibility of approximately 30%, tyres harden as they age due to losing some of their elements, the ones which you can smell when they are enclosed. When exposed to the outdoor atmosphere these aromatic components of the rubber compound escape even faster due to atmospheric and UV exposure. Since they are the elements which define the compound for grip and flexibility it can mean a difference in the grip and even corner spring rate not dissimilar to stiffening the suspension at one end of the car, of course if we then consider replacing a single tyre of an old set with a new item than that will be like having a softer shock/spring assembly. Tyre manufacturers generally say that tyres should be changed every 4 years due to the aging effects but taking it that cars used regularly will wear tyres far quicker than that even changing one or two from the same factory should not be a problem for most owners but most owners will usually change tyres as axle sets to equalise wear. Porsche state if memories serve correctly, that tyre wear should not differ by more than 3mm on any axle.