Nurburgring - new lap record for a sham road car
Discussion
Not sure about that,, are you going to 19" so that you have the room for massive brakes?
I would have thought 18" would have been enough of a step up and nearly every decent tyre has a good size range in the 18".
I have to hand it to you for pushing the envelope with the Mclaren, when I last had the opportunity to see one up close last year the 17" wheels and gold Brembos did remind me a little of a Subaru Sti...no disrespect meant but clearly technology has moved on at least one big step.
I would have thought 18" would have been enough of a step up and nearly every decent tyre has a good size range in the 18".
I have to hand it to you for pushing the envelope with the Mclaren, when I last had the opportunity to see one up close last year the 17" wheels and gold Brembos did remind me a little of a Subaru Sti...no disrespect meant but clearly technology has moved on at least one big step.
Actually I prefer the look of tall sidewalls, which remind me of so many gorgeous race cars from the past.
The reasons for 19s relate to why the car needs different tyres in the first place.
They are that both pairs of tyres are too flexible laterally and that the rear tyres particularly need to be stiffer in order induce more below-the-limit understeer.
Then you look at what tyres actually exist that would fit the car, be the correct width, have the correct rolling diameter, have the right sort of tread pattern, and have a sufficient speed rating. This narrows down your choices very sharply.
On top of these considerations, I wanted a tyre that I knew would still be in production ten or twenty years from now.
Without boring you with all the details, the two kinds of tyres that I seriously thought about were the Bridgestones designed for the Enzo (Pirelli now do something similar for the MC12), which are 19 front and rear, and the Michelins for the CGT (19/20). It appeared to be pretty much of a tossup between the two, but I thought that 20" rear wheels would look OTT on the car so I opted for 19s. I may still have BBS do a set of 20" rears to experiment further.
Other things are not equal, but if they were, the main differences between 18 and 19 would be, as you say, more space for rotors with the 19s, but with a weight penalty.
Rotational weight is the absolute worst, so I keep looking for ways to minimise it (recently a PHer pointed me towards a British wheelmaker, which may prove fruitful). You get some more rotational weight with the larger wheels, although the difference obviously depends on how light your wheel design is, as well as the tyre construction.
I don't think that the extra space for brakes is necessary. To wit, the ceramic brakes on a GT3 fit inside 18s, the GT3 weighs about 200kg more than the F1, and that size rotor is more than sufficient for the Porsche. Yes the F1 may have to stop from higher speeds, but not several times in succession, and since the F1 brakes need to be pulling back considerably less weight, I wouldn't be worried about the stopping capacity of the Porsche ceramics. In fact I can imagine using rotors for 18s inside the 19s in order to keep the weight down. We'll see.
The reasons for 19s relate to why the car needs different tyres in the first place.
They are that both pairs of tyres are too flexible laterally and that the rear tyres particularly need to be stiffer in order induce more below-the-limit understeer.
Then you look at what tyres actually exist that would fit the car, be the correct width, have the correct rolling diameter, have the right sort of tread pattern, and have a sufficient speed rating. This narrows down your choices very sharply.
On top of these considerations, I wanted a tyre that I knew would still be in production ten or twenty years from now.
Without boring you with all the details, the two kinds of tyres that I seriously thought about were the Bridgestones designed for the Enzo (Pirelli now do something similar for the MC12), which are 19 front and rear, and the Michelins for the CGT (19/20). It appeared to be pretty much of a tossup between the two, but I thought that 20" rear wheels would look OTT on the car so I opted for 19s. I may still have BBS do a set of 20" rears to experiment further.
Other things are not equal, but if they were, the main differences between 18 and 19 would be, as you say, more space for rotors with the 19s, but with a weight penalty.
Rotational weight is the absolute worst, so I keep looking for ways to minimise it (recently a PHer pointed me towards a British wheelmaker, which may prove fruitful). You get some more rotational weight with the larger wheels, although the difference obviously depends on how light your wheel design is, as well as the tyre construction.
I don't think that the extra space for brakes is necessary. To wit, the ceramic brakes on a GT3 fit inside 18s, the GT3 weighs about 200kg more than the F1, and that size rotor is more than sufficient for the Porsche. Yes the F1 may have to stop from higher speeds, but not several times in succession, and since the F1 brakes need to be pulling back considerably less weight, I wouldn't be worried about the stopping capacity of the Porsche ceramics. In fact I can imagine using rotors for 18s inside the 19s in order to keep the weight down. We'll see.
Thanks for the explanation, so are you comfortable with the pccb2 composition?
Maybe the 200kg advantage is the answer, but from where I sit a pccb equipped Gt3/RS is worth less than a steel braked car because you know you are going to have to flex the plastic to get the thing through a hard session of trackdays.
As an aside I had one of the last Gt3RS on order (with steel brakes)...I reluctantly cancelled when I realised I would probably have to sell my 993 RS.
Not trying to be a hero....just could't do it...market prices would suggest I was on the money
Maybe the 200kg advantage is the answer, but from where I sit a pccb equipped Gt3/RS is worth less than a steel braked car because you know you are going to have to flex the plastic to get the thing through a hard session of trackdays.
As an aside I had one of the last Gt3RS on order (with steel brakes)...I reluctantly cancelled when I realised I would probably have to sell my 993 RS.
Not trying to be a hero....just could't do it...market prices would suggest I was on the money
I am not in the least worried about the Porsche (Brembo, I believe) ceramics.
This year I have done 100ish laps of the 'Ring on a set in a GT3 and they're fine. I've also done about 30 laps in a CGT and again no probs whatsoever.
The 2005 GT3 Cup car comes with ceramics as part of the new formula and I'm unaware of any inherent problems with them.
As I am not on the verge of making a change there is plenty of time to get more information, and, as indicated, for competing developments in other systems. But so far as I am concerned the ceramics are fine and would be the conservative option.
This year I have done 100ish laps of the 'Ring on a set in a GT3 and they're fine. I've also done about 30 laps in a CGT and again no probs whatsoever.
The 2005 GT3 Cup car comes with ceramics as part of the new formula and I'm unaware of any inherent problems with them.
As I am not on the verge of making a change there is plenty of time to get more information, and, as indicated, for competing developments in other systems. But so far as I am concerned the ceramics are fine and would be the conservative option.
flemke said:
R2TR,
For brakes, there are three possibilities of which I am aware:
- the carbon-ceramics that are now in their third generation and fairly well sorted. I reckon that I would save about 1.5kg/wheel relative to what's on the car now, maybe 2. This would be the simplest option.
- the Delphi "dual-rotor" system which is like a pair of bike rotors and one caliper with maybe an inch of space between them (the rotors), which are scheduled to be in production next year, and
- a system that is being developed by a chap I know which consists of solid carbon pads and rotors which have a special treatment to get over the low-temp coefficient of friction problem.
As the last two options have some promise, but I would be crazy to use either until it is more developed, it may make sense to be patient, despite the fact that by this point I am very impatient.
nords,
The car looks the same as it has done (pictures of which have been on PH a few times) except that at the moment it is bearing 19" BBS two-piece wheels which, with their gold centres and polished ally rims, look pretty awful.
Flemke
Surely the Carbon Ceramic option would be the choice if your impatience gets the better of you? Given it has undergone the most development and has now been proved successful on the road.
I can see the wheels are a little fussy for the simple elegant lines of the Mclaren, im assuming the new wheels will be an exact replica (in terms of design) of the originals?
Regards
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