boqueron

Coming back home from my third track day in the first month of GT3 ownership on a bumpy road, the CAR NEARLY THROWED ME OUT OF THE ROAD when passing a bump. I repeat: THE CAR. I know that it is not politically correct to say such thinks in a GT3 forum but...

I would like to know if other GT3 owners have experienced the same problem !?

Since that has happened before, I am extremely careful on bumpy roads which, unfortunately,are fairly abundant in Spain.

I have tried to analyze were and how it happens, here is the result..:

When driving through bumps on a straight line I have no special problems. The car jumps with "reasonable" manners. Nothing specially dangerous, if you pay attention to your steering wheel. If it happens with some shifted weight ( i.e. overtaking a car on a corner of the road) and the car takes a large bump which affects more than 1 weel, it jumps and SUDDENLY seems to shift and accelerate in the same direction where the steering wheel was aiming. If you are in this situation when pushing strongly the trottle it becomes even more FRIGHTENING and DANGEROUS. All this can be kept under control at a speed up to 85 mph and becomes extremely hazardous when going at speed of more than 110 mph.

I discussed this matter with another GT3 owner ( the only one ) that was on the track. This guy was coming back from Germany and was going next week to SPA Francorchamps ( French Track) . He had his car aligned and set in Germany by the same people - he claimed - that developed in Porsche the GT3 suspension... He told me that the GT3 is not conceived for spanish roads and that it has happened to him to appear in another LANE (!!!) after a bump !!!. As a mater of fact, he was taking the car to the track on a truck !!

Not so long ago I posted a topic with the same problem https://rennlist.com/forums/996-gt2-gt3-forum/264209-dangerous-street-handling-tyres.html

I have, again, to thank all of the Rennlisters that gave me their advise.

NJ-GT kindly advised me to look for my rear toe. He also took the time to explain the mods that he had done with his suspension. Problem is that I do not feel, yet, happy with the idea of expending 9.000 $ + to solve a problem that, from my very particular point of view,, should not be there...


Sweanders advised me to look for the bump stops

Bob Rouleau told me that it was, probably, a mater of too stiff setting of the sway bars...for the road.

I re-checked my alignments, changed tyres to Pilot S2. I did not change my sway bars settings ...as I bought this car mainly for tracking..!

If this is a characteristic of the car it will be an extraordinary surprise. This car is sold as a ROAD car that is specially adapted to tracks. NOTHING (or less) ELSE.

I hope that something is wrong and can be fixed... And that you can help me...

I am waiting your comments .. At the end, if this car can not be driven at more than 85mph on public , bumpy, roads, Porsche would have invented the best system to force me to maintain legal speeds....

Nordschleife

Hi

Its summer, bring your car to Germany, take it to Manthey, Ruf or TechArt and have them duplicate the situation. There are plenty of mountainous roads the car can be checked on. Then take their recommendation.

Its impossible to perform remote diagnostics without seeing the patient. Unfortunately, real Porsche experise is a bit short in Spain and France. On the plus side there are lots of lovely things to see and places to eat on the way betweeen Spain and Southern Germany.

You are right not to go out and spend a lot of money on suspension parts before a real expert has checked everything. Without seeing the car, its all guesswork. However, remember that the GT3 makes a very successfull rally and hillclimb car, it is developed on a track with some awesome bumps, it gets driven flatout round Namibia, South Africa, the Arizona Desert, the Rockies and across Australia, it can handle it.

R+C

GreigM

What you are describing I have also experienced to some degree as the roads around my part of the world are very twisty and bumpy. In all honesty my 2.7 boxster is a quicker and more capable a to b car on these sorts of roads unless you are willing to take big risks. The GT3 is not good on some twisty, bumpy european roads - I'm not saying that it can't be driven quickly here, just that it is a lot of hard work to keep it under control and specifically when lanes are no wider than the car. To be honest these are not the kind of roads GT3s are built for - far better with a TT or even something like a boxster which has suspension much more capable of damping the bumps and a set up suited to these roads.

However, take the GT3 to a smooth piece of tarmac or a race track and it is a different story - I tend to find most roads in Germany superb due to the quality of the tarmac and width of the roads (and a similar story in the USA) and the setup of the car is much more suited to these roads and given the car is built in Germany and one main market is the USA its understandable that they develop for these kind of roads and not the poor quality we get here in Scotland and with you in Spain.

But, I believe there are things you can do, but you need to decide on your primary reason for the car - I have had my car set up changed to a purely "road" focus in the past and that helps significantly, but given I use it for track (going to SPA/nurburgring in a few weeks) I have kept what many describe as a "fast road/track" - which means its not so good on very bumpy roads, but excellent everywhere else.

I've also found that my previous "street" tyres (Pirelli Pzero assimettrico) were IMHO very poor - when dry weather I tend to leave my track tyres on (Dunlop SSR) as apart from superior grip these are far more comfortable on bumpy roads (perhaps due to softer sidewalls?) - or it may be because the sizes have changed (I use 245/265 front/rear instead of the factory prescribed 225/285).

Changing the sway bar (anti roll bar) settings is a very simple job and only takes about an hour - so easily done before or at a track, so no excuse for not trying this, however I don't think it will be the "cure" you are looking for.

The last thing I would say is that I don't know how long you've had your car, but I feel it takes 6 to 9 months minimum to properly understand the feel and adapt yourself to driving the GT3 - it is not your normal 911 - I found that after about a year of ownership I realised that I was getting much quicker on the kinds of roads you are describing, by learning to understand the incredible amount of feedback available from the steering wheel, reacting to it correctly (not over-reacting) and learning to read the road ahead better, anticipating what will unsettle the car and preparing the car for it.....its not an entirely natural way of driving but very rewarding in the GT3 once you get used to it.

DanH

There may be nothing unique about what your car is doing. Mine is fairly hard work at high speed on poor quality roads too. For me I think it is largely the car and how it feedsback (I have a fast road/track setup), but also how relaxed I am behind the wheel. I do look at what the road is like before initiating an overtake, and certainly wouldn't do it on a bumpy corner for the reasons you outline.

If you do take the car over to Manthey for their dampers, let me know how it works out as they are something I've considered, but its a lot of money to spend when I don't really know what the results will be.

The other option of course is to flip your 996 GT3 for a 997 GT3 which seems to be being recognised as much better on the road. I'm not sure how you strike a great balance between track and road usage on a 996 GT3, its always going to be compromised somewhere (as with any other car trying this trick). Perhaps they have cracked it with the 997 (although the odd review does state it has had the setup softened for track, so it may not be quite as deft in that environment).

Nordschleife

Dan
Your car has softer springs than the Euro GT3 MkII

boqueron

Nordschleife,

Is it Dan's car that carries softer springs or it happens with all the UK cars ?

DanH

I've heard that bandied about, but it doesn't tie up with a comment by Preuninger in the Excellence magazine article on the RS (reprinted in total 911). He claims the springs went from 40N/mm to 45N/mm, but at the same time were swapped to progressive, which might explain what is a possible misconception. It also states the dampers are a tad stiffer too to go with the springs, as well as stiffer sidewalls in the Corsas, so that total affect is about 10-15% stiffer in bump & rebound.

I've heard it suggested that the Manthey setup improves dynamics on both road and track, but for me it would be a rather expensive experiment!

One thing I've noted when jacking the car up, is the absence of much droop. Is this a side affect of the lowering, as I've never seen a road car with so little before.

I'm actually reasonably happy with my car on the road. I can make very adequate progress even on bumpy roads, it just requires getting into the right mental groove (I don't tend to go at 110mph though). I had my setup done by JZ Machtech who are Manthey's UK agents (hence me pondering Manthey dampers).

boqueron

Nordschleife,

Is it with the standart suspension as it comes from the shop ? If this is so , I am totally convinced that something is wrong with mine. I have raced rallies ( many years ago, I have to admit ) and would not survive ( no joking at all ) with my present car.

I am seriously considering to follow your advise and go to Germany to check it.

boqueron

If this is the "normal" limitation then, my car is normal . On bumpy roads, until 150 km/h ( 90 mph) I can drive and talk. From there up to 165 km/h (100 mph) I can drive and listen. From there...I can barely drive.. and pray not to find a strong bump on a bend when overtaking..
Totally different on good highways were I can speed without limits. ( Anyhow, I tend not to speak too much with any car over 100 mph , I am rather cautious..)

boqueron

Greig M

One month ownership... I perfectly understand what you are saying. As a mater of fact I am doing my best in order to keep IN the track and not OUT.. I have decided to re-learn to drive and I am convinced that this is the ideal car. The only thing is that I like to experiment on a track and not in the road..

Thanks very much for your advise,

Harry

DanH

Well it sounds similar to mine then. I don't really have any desire to go beyond about 100mph on poor roads. To be honest, I've had other cars with more compliant, but still competent, road setups and they weren't a whole heap of fun beyond those speeds on that type of road either. They reacted slightly differently but the whole car would still lurch on big bumps in the road. Not much good given the roads are often narrow.


p.s. you used the HTML tag to do a QUOTE. It isn't very readable

Nordschleife

No its with modified suspension that it rallies and hill climbs, but the fundementals are there. The engine position is great for driving across rivers.

R+C

Nordschleife

It depends which car the RS is being compared to. US GT3 or European or British (I think the Brtis gor one slightly softer sprung to cope with the roads).

It can be very misleading to compare a car to North American specified car, lots of things are different.

R+C

DanH

Didn't realise they respecced the dampers in different territories. I'd be surprised if the UK GT3 had been changed though as C16 is meant to be identical as far as I've ever heard. I can see why they might change things for the US though. Preformed concrete highways with those little joints every few metres are bad enough in a flabby road car.

I don't really know much about suspension dynamics. Are the poor road issues largely due to a lack of suspension travel? Would boosting the ride height help, or would new dampers+springs then be necessary too? Presumably a GT3 could be setup to ride as well as a turbo on the road, but then it would wallow like a turbo on track.

Kiko

Hola Boqueron!

What you mention fits into the "bumpsteer" symptoms perfectly but since your car has OEM suspension and you did the alignment at a good Porsche dealer (please confirm this) I guess the car needs a close inspection to suspension components (visually inspecting the bumpstops) but specially the bushings and a shock absorber test just to make sure you don't have a defective or damaged shock absorber since this behaviour happens when a shock bottoms out.

P.S. Congrats on your track record (road cars) in Jerez!!!