usctrojanGT3

Jacy, you should consider going with the stiffer spring set up that I have on my car....prevents the front tires from rolling over in heavy braking areas.

RocketGuy3

That's what air filters are for.

ShakeNBake

Got a response this AM. Their product guy says to run the R7 at higher pressure. 39-41 for best grip and least rolling resistance. He said to run it as high as possible, until you notice an obvious falloff. He noted that this is different than the previous generation.

ShakeNBake

That's the 100K question isn't it. It's certainly a much more intuitive driving car than a RS. There are two major downers on the GT4. 1) The steering - it has zero feedback. It feels a bit like you driving in mud when the car is sliding around - you know it's sliding because you can feel/see the yaw, or you are giving inputs that don't change any direction, but you have to assume why. The steering also lightens up at the limit - so it feels very much like steering in mud. In the 997 GT3, the texture of what the tires are doing is coming through and you know exactly what is going on by just the feel. Not there in the GT4 - and at the limit, it is missed - and I think that is why a lot of guys are shredding front tires - you don't witness the horror that you are putting them through, so you continue to torture them. There is a dilbert cartoon in there I think.

2) Power - while for another 30K BGB will fix some of this, it just does not have a special motor. It's a blah motor compared to a Mezger or S65. It just does not have the exhilarating top end that strokes the right nerve endings. It's a nice lump...but it's a lump. Not having experienced a track focused motor will make that comment seem a bit arrogant - but everything is a function of your experiences. It gets the job done, but that's it. The greatness of the car is the chassis and balance, not the motor. Porsche has saved the "status" of the GT3. It's also ironic that the GT4 shares more with a race car than the GT3 has in the last 3 years....but...

So in the end, I think the GT4 is plenty of fun, and plenty fast - but not what the RS was. It's half the cost and way cheaper to maintain....so I'll do this for a while until something that gets me more excited comes along. The 991.1 RS and GT3 don't do it, maybe the .2 will. If I win the lottery, I'd probably get a 996 cup car

I may go there soon

peterbigblock

Wow, that's higher than I've run them on my "similar" Boxster S (highly modified, I run with my friends' GT4s at MSR and COTA). Still, the R7 definitely likes more hot pressure than the R6; I typically run about 36 hot, will have to try out 39-40 and see how it feels. My car is about 250 lbs. lighter than a GT4.

How has the -3.5/-3.0 camber worked out? I run about -3.0/-2.6 and am going to experiment with higher settings in both cases as I also see the outsides scrubbing a bit -- though sometimes that's just good old-fashioned over driving on my part!

peterbigblock

One other thing to consider when choosing wheels is that 18" wheels will put down a longer contact patch (front to back) than a 19" or 20", all other things staying equal. That's why racing teams tend not to use bigger wheels. Just FWIW...

ShakeNBake

The pressure I was talking about was as read in the car (just to be clear). I was surprised as well, but to be honest now that I think about it, while the temperature profiles told me to drop the pressure, it was the tires at lower pressure that seemed to give way first. For example, the left rear was holding like glue in T2, T6, T14, T16-T18 and at 41psi in car, and the right rear was at 38-39, and breaking loose on every hairpin. Counter intuitive, but now that I have this guidance, I will play with higher pressures.

I will be trying -3.5 and -3 as soon as I get the car through the shop. I might need to add a thrust arm bushing in the rear, the wheel is already pushed back a bit towards the rear.

Rovman

Thanks for the explanation and details. Much appreciated.

First off I am surprised to hear about the high front tire wear issue with the GT4 as this is also an issue with the GT3???? Yet this makes sense to me as I know what you were driving before and know you are pushing the car a good bit. I think some folks who are not pushing as hard may not be encountering the issue you are seeing as they aren't there yet in speed and times to expose that issue. Hmmmm.

You made an excellent point that I had never thought of about the feel from the front and that possibly being the issue with the high front tire wear.

With both the GT3 and GT4 having these issue at first I thought maybe this was some Porsche chassis set up problem.

Like you, I feel like the 991 GT3 front end feel is numb compared to my 996 GT3. Since I do not have harness' in my car I figured perhaps that is the issue combined with the lack off feel. Thinking that maybe with harnesses , allowing me to gently hold the wheel I would Hopefully be able to perceive some feel from the front tires. This may not be reality... I also thought that maybe changing suspension parts and getting rid of rubber in the suspension should yield some feel as well. Not sure if this is reality and could be an expensive expirement for no gains other than a more consistent alignment when pushing the car (albeit a positive gain just not the one i was looking for).

hmmmm

surlynkid

Holy crap. Well no wonder I was rolling over on left front. I was 36 hot as I came into garage. I need to run higher.

ShakeNBake

I could not feel anything, gloves or not...harness, hoosier, cup2s, rain, dry, TWS, COTA....the technology just does not exist with this EPS stuff. I don't think it plays a huge roll in your speed, but it impacts your experience.

My theory on the tire issue is that Porsche has figured out how to find more front end grip, but it's still a strut design with the camber curve that comes with it - so with extreme body roll/wheel travel, it's moving all the weight onto the outside edge. To get a nice compliant street ride, they can't make the front roll too stiff, and without active roll bars, you kinda stuck with a front end that is too soft for the loads we're putting on it. I think Martin has it right, needs more spring...or extreme negative camber. If you could increase caster without tires rubbing, that might be helpful.


Yes, very different than R6s....and lots of misinformation out there given that the R7 is pretty new, and very different.

ShakeNBake

Mike, I'm trying out Ferrodo DS1.11 pads (with SRF fluid). This is my second set, first set on the GT4, and had used a set on my previous car. They do not last as long as a PFC08 - which is an enduro racing pad. They are close, but seems like 1 day less. On the positive side, two things. 1) Very easy on rotors. PFC08s beat up on rotors, and you get impressive cracking on new rotors within a day. I've already through one set of DS1.11, and no surface cracking on OEM rotors. 2) Consistent feel and easy to modulate. No matter how hot, the brake pedal works the same way corner after corner, lap after lap. PFCs would change in character a bit, sometime bitting more, and sometimes bitting less.

Overall I like them, and until something I don't like happens, I'll be using them. Apex is my crack dealer, prices are also reasonable as GT4/GT3 pads go.

Rovman

Man that is a bummer. I was hoping there was some room for improvement with a little bit of modding but it doesn't sound like it.

BBi already has a spring kit for the 991 GT3. Without giving away too many details about their kit and its purpose, they have said that the front spring rates are increased over stock yet they still work with the damping used on the electronic shocks. I suspect that is to remedy exactly what we are seeing with the GT3/4 cars when driven hard.

I think they were getting a GT4 to start product development on, perhaps they will have a solution soon?

usctrojanGT3

Front springs are WAY TOO SOFT. I was chewing up the outside of my front tires with -3.2 of camber and middle setting on the front sway car. The GT4 front springs are much softer than the ones on the GT3. Had my suspension guy installer 2x stiffer springs in the front and 1/3 stiffer springs in the rear and my tire wear has gotten better in the front.

Rovman

Hey that's sounds promising, thanks for sharing Martin...

I wish there was something we could do to bring back a little front end feel though. Can't have everything I guess....

ExMB

Any reason you did not go to PFC11s coming from PFC08s?