Prospective 981 GT4 Owners Discussion Forum.

[Dave_T]

O

itsybitsy said:

The yellow pec gt4 is a pre production model that has been heavily used for the last couple of months and once people get there cars ie mrD will be singing the cars brakes praises!
Out of the box the CR and spyder brakes were not exceptional !

The braking performance of most cars is tyre limited, unless the brakes are so weak as to be unable to lock the wheels. I would be very surprised if there is much difference in overall stopping distance between PCCBs and steels. I've species PCCBs on mine

[PorscheGT4]

berty37 said:

So why then if as you question that the GT4 is not in the same league as the Cayman R(which it isn't) at what £45k where they have always been incidentally why then at £20k less than a base Gt4 is it not being lifted out of sight... The market decides these things.
You know I am not saying for a moment that they were ever going to do away with the Cayman I was just pointing out Porsche Cayman I was just saying that for a pretty much lacklustre model in sales terms the GT4 is the first Cayman that has got people genuinely excited.

the R speced up with PCCB , leather PSE etc was about £68k , not sure what a £45k comment comes from, that's just a 4 year old 2nd hand value !

the GT4 did not get people excited imo it was the 3.8 engine figure and imo it brings not much to the car as a whole esp with bigger in speed gears on those 20" wheels.

You can make a R a better car for fun if you wish for less money imo, if you want grip and lap times oem then a GT4 will always win, but if you want laps times a 991 GT3 will always win !

Depends what you want, I think 90% of people just wanted a Cayman with a 3.8.

[berty37]

PorscheGT4 said:

the R speced up with PCCB , leather PSE etc was about £68k , not sure what a £45k comment comes from, that's just a 4 year old 2nd hand value !

the GT4 did not get people excited imo it was the 3.8 engine figure and imo it brings not much to the car as a whole esp with bigger in speed gears on those 20" wheels.

You can make a R a better car for fun if you wish for less money imo, if you want grip and lap times oem then a GT4 will always win, but if you want laps times a 991 GT3 will always win !

Depends what you want, I think 90% of people just wanted a Cayman with a 3.8.

I am pointing out that a car that you think is one of Porsche's best has never made money or attracted a premium.
No point going down the road of you can make an R do this and that by doing this and that to it ... You can do most things to most cars to get them to drive how you want.
Not sure I agree with your last statement either.... The pure fact it had Andreas Preuninger all over it and has got a GT badge I think is enough.

[PorscheGT4]

making money does not make a car a good car.

I have also not said anywhere the GT4 is a bad car, I even said it's like a Cayman R + 20% and plus 50% of grip if I remember ;-)

What it's not is leagues ahead of the game. It's a bloody good car though, but now with all that grip it's like it needs 430BHp not 380 ;-)

[berty37]

PorscheGT4 said:

making money does not make a car a good car.

I have also not said anywhere the GT4 is a bad car, I even said it's like a Cayman R + 20% and plus 50% of grip if I remember ;-)

What it's not is leagues ahead of the game. It's a bloody good car though, but now with all that grip it's like it needs 430BHp not 380 ;-)

I agree 100% with you on the first statement. It does show you the basics of supply and demand what people are prepared to pay though.

[PPPPPP]

PorscheGT4 said:

making money does not make a car a good car.

I have also not said anywhere the GT4 is a bad car, I even said it's like a Cayman R + 20% and plus 50% of grip if I remember ;-)

What it's not is leagues ahead of the game. It's a bloody good car though, but now with all that grip it's like it needs 430BHp not 380 ;-)

So will you attempt to increase the power/shorten gearing on your GT4 to meet with your needs, as you have tweaked the CR & the Spyder. Or just flip the car?

[HokumPokum]

I personally just can't justify PCCB.
there is only 1 serious guy "ChrisW" who uses his cayman hard that has PCCB.


He may be right in that with SICOM, we no longer fear the astronomical costs associated with replacement PCCB, but for me the certainty in steel and the size of the OEM calipers and 390mm disc means I'm just a pad change away from an awesome brake.

NB: you now need to remove the caliper to change pads..........how can they be so dumb????!!!

[PorscheGT4]

PPPPPP said:

So will you attempt to increase the power/shorten gearing on your GT4 to meet with your needs, as you have tweaked the CR & the Spyder. Or just flip the car?

selling it, it will never feel as good as the Spyder and I am happy with that car for my fun car but prob not till Spring 2016.

I will go for another brand for my normal car for a year or so and see what happens. ie some thing with a bit of real poke.

I might put it up for a silly price as it's an early car and see if any fools can be parted with big money :-)
I won't be trying to sell it, but no harm in a daft priced advert.

[av185]

PorscheGT4 said:

I might put it up for a silly price as it's an early car and see if any fools can be parted with big money :-)
I won't be trying to sell it, but no harm in a daft priced advert.

I see a reasonable specced lwbucketed 2k miler at £99750 Spring 2016...........

[J-P]

PorscheGT4 said:

PPPPPP said:

So will you attempt to increase the power/shorten gearing on your GT4 to meet with your needs, as you have tweaked the CR & the Spyder. Or just flip the car?

selling it, it will never feel as good as the Spyder and I am happy with that car for my fun car but prob not till Spring 2016.

I will go for another brand for my normal car for a year or so and see what happens. ie some thing with a bit of real poke.

I might put it up for a silly price as it's an early car and see if any fools can be parted with big money :-)
I won't be trying to sell it, but no harm in a daft priced advert.

Interesting, will you keep the R or get rid of that and the GT4 in favour of something else? Mac 570s perhaps?

[Scooty100]

PorscheGT4 said:

selling it, it will never feel as good as the Spyder and I am happy with that car for my fun car but prob not till Spring 2016.

I will go for another brand for my normal car for a year or so and see what happens. ie some thing with a bit of real poke.

I might put it up for a silly price as it's an early car and see if any fools can be parted with big money :-)
I won't be trying to sell it, but no harm in a daft priced advert.

Demon , you're a fan of the spyder so did you not consider the new spyder over a gt4?

[fioran0]

PorscheGT4 said:

I think the issue with the GT4 is the MASSIVE increase in wheel/tyre combo weight. tyres alone weight 6lbs more a corner on the back, I would say 20" wheels weigh another 3 lbs

so cira 10lbs added to the rear per corner in rotating mass !!! and say 6 lbs at the front !

all of that you have to stop rotating and you also have to start accelerating ! add that to loner gears and it's no faster than my cars I own, and imo stops SLOWER !!!

shame Porsche went to 20" wheels on the 981 again adds to the higher speed in each gear !

that 3.8 is all but cancled out adding in both issues !

Is that MASSIVE though?
Assuming you ball parking is correct and its 10lbs per corner rear and 6lbs per corner front. (BTW I see 4lbs per rear tyre, 2lbs per front tyre assuming both cars on Cup 2s in OEM sizes)
Thats 32lbs total, or ~14.5kg.
Assume a ballpark 1.8 equivalent static mass multiplier and that becomes 26.1 kgs in practice (though not on the scales since at rest mass is just mass).

So 26.1kgs of additional weight introduced over 19” equivalents in tyre and wheel while in motion and 14.5kg when loaded up on a scale.
The cars EC weight is 1415kg.
Those numbers for wheels and tyres don’t look all that massive when viewed in that context. 1% change in total static weight when switching between 19s and 20s and Acceleration is simply Force/Mass.

I know we have been through this many times also; but stopping is tyre friction limited and mass doesn’t factor into the equation to calculate deceleration.
Stopping distance is simply a function of speed and tyre mu (grip). More speed or less grip equals longer stopping distance, less speed or more grip equals shorter stopping distance.
Where mass matters is in kinetic energy, which the brakes convert into heat. The heavier the car and the more stops that one does, the more total heat will be generated. Depending on cooling etc, a lighter car could have an advantage eventually if heat build up were become so great as to prevent brake function.

[keep it lit]

fioran0 said:

PorscheGT4 said:

I think the issue with the GT4 is the MASSIVE increase in wheel/tyre combo weight. tyres alone weight 6lbs more a corner on the back, I would say 20" wheels weigh another 3 lbs

so cira 10lbs added to the rear per corner in rotating mass !!! and say 6 lbs at the front !

all of that you have to stop rotating and you also have to start accelerating ! add that to loner gears and it's no faster than my cars I own, and imo stops SLOWER !!!

shame Porsche went to 20" wheels on the 981 again adds to the higher speed in each gear !

that 3.8 is all but cancled out adding in both issues !

Is that MASSIVE though?
Assuming you ball parking is correct and its 10lbs per corner rear and 6lbs per corner front. (BTW I see 4lbs per rear tyre, 2lbs per front tyre assuming both cars on Cup 2s in OEM sizes)
Thats 32lbs total, or ~14.5kg.
Assume a ballpark 1.8 equivalent static mass multiplier and that becomes 26.1 kgs in practice (though not on the scales since at rest mass is just mass).

So 26.1kgs of additional weight introduced over 19” equivalents in tyre and wheel while in motion and 14.5kg when loaded up on a scale.
The cars EC weight is 1415kg.
Those numbers for wheels and tyres don’t look all that massive when viewed in that context. 1% change in total static weight when switching between 19s and 20s and Acceleration is simply Force/Mass.

I know we have been through this many times also; but stopping is tyre friction limited and mass doesn’t factor into the equation to calculate deceleration.
Stopping distance is simply a function of speed and tyre mu (grip). More speed or less grip equals longer stopping distance, less speed or more grip equals shorter stopping distance.
Where mass matters is in kinetic energy, which the brakes convert into heat. The heavier the car and the more stops that one does, the more total heat will be generated. Depending on cooling etc, a lighter car could have an advantage eventually if heat build up were become so great as to prevent brake function.

tut spoilsport ... I preferred the baloney above lol ;-)

[paralla]

It's six pages since anyone mentioned the colour of the paint, wheels, wing supports or stitching.

Are we loosing focus?

[fioran0]

keep it lit said:

tut spoilsport ... I preferred the baloney above lol ;-)

haha. I bet!

PorscheGT4 said:

all of that you have to stop rotating and you also have to start accelerating ! add that to loner gears and it's no faster than my cars I own, and imo stops SLOWER !!!

that 3.8 is all but cancled out !

Again for the wider info. Acceleration versus speed plots for the Cayman R and the GT4. Corrected for weight, tyre/wheel sizes etc etc. The only factor not inlcuded in either plot is drag.
The higher up the line, the more acceleration.
I didnt optimise the GT4 plot to further illustrate why it's not looking optimal to shift at redline in the GT4 either. Once there are dyno plots from cars in the wild, this can be refined. At the moment its using the factory dyno plot info.

[PorscheGT4]

My Spyder is over a full second quicker In a 3rd gear pull over my R I am using that as my bum benchmark drives.

I am still saying the GT4 is like these cars +20% people are missing out that quote ;-) it's just not moved the game on much to give it a wow factor, in fact after 2.5 hours in the thing I was quite board.
on a fast track the GT4 grip advantage would muller a Spyder or a Cayman and for some that's enough.

ALso if you are talking weight lets not forget the 350mm CCB on my Spyder only weigh 10 lbs a corner the GT4 are 15 lbs and 13.3 lbs, and the steels are 27lbs/24lbs

So total rotating mass is another 15 lbs off vs GT4, and steels 63lbs lighter on top of the wheel tyre combo.

It all adds up and my car weighs over 100kg less.

Brakes are NOT all about the tyre in the first 30/40mph mph or so, as there is NO way you can lock a wheel on a car with that rotating mass at 70mph. I proved this on my R vs my Spyder when we chatted about it last time, the R was way off the stopping distance of my Spyder.

I take it you ride bikes, most people do, spin a mountain bike wheel and then a road bike wheel and try and stop them with your hand, you can stop the road wheel very easy where the MB wheel will prob bend your finger off.
mass of the bike at that point makes no difference, we are just trying to stop a rotating wheel.

how about a modded 370Dyno plt vs the GT4 that would be interesting.

Edited by PorscheGT4 on Monday 10th August 21:19

Edited by PorscheGT4 on Monday 10th August 21:22

[PorscheGT4]

Scooty100 said:

Demon , you're a fan of the spyder so did you not consider the new spyder over a gt4?

nope. no adjustment on the Spyder and it weighs more than my old car, but still with a roof you have to get out the car and run round twice to take off, add the longer speeds and the faker steering and it had no appeal over the old One.
My R is also going.

[isaldiri]

fioran0 said:

I know we have been through this many times also; but stopping is tyre friction limited and mass doesn’t factor into the equation to calculate deceleration.
Stopping distance is simply a function of speed and tyre mu (grip). More speed or less grip equals longer stopping distance, less speed or more grip equals shorter stopping distance.
Where mass matters is in kinetic energy, which the brakes convert into heat. The heavier the car and the more stops that one does, the more total heat will be generated. Depending on cooling etc, a lighter car could have an advantage eventually if heat build up were become so great as to prevent brake function.

Out of topic but a bit of a question i had asked in the RS thread previous and would hope you might be able to shed some light on this.

A friend of mine has told me some people who should know (engineer for a gt3 team) that the 918's e-motor braking is able to help the car brake better than through pure tyre grip and has quoted the sport auto supertest results where the 918 recorded a decently better 200-0kmh braking number over the 991 gt3rs despite being ~150kg heavier and where both cars are running identically sized Cup2s. he was likewise told the hybrid GT3-R porsche ran at the ring a few years ago likewise had a decent braking advantage over the non hybrid RSRs....

Does this sound plausible at all as it's completely at odds with anything i have ever read on braking dynamics or anything I personally was told by reasonably experienced people.....?

[ChrisW.]

HokumPokum said:

I personally just can't justify PCCB.
there is only 1 serious guy "ChrisW" who uses his cayman hard that has PCCB.


He may be right in that with SICOM, we no longer fear the astronomical costs associated with replacement PCCB, but for me the certainty in steel and the size of the OEM calipers and 390mm disc means I'm just a pad change away from an awesome brake.

NB: you now need to remove the caliper to change pads..........how can they be so dumb????!!!

Take a look


http://www.pistonheads.com/gassing/topic.asp?h=0&a...

[Scooty100]

PorscheGT4 said:

nope. no adjustment on the Spyder and it weighs more than my old car, but still with a roof you have to get out the car and run round twice to take off, add the longer speeds and the faker steering and it had no appeal over the old One.
My R is also going.

Kind of interesting of all the Pork you've had including 911 you'd sell them all and keep the older spyder . Can see the logic in that you find your driving Nivana and stick with it.

Been looking at them myself