tv

Compared to the 1 lap only special qualifying tires that Senna used to take out to get his pole position, I don't believe any current tires come close in terms of extreme grip. F1 backed off a lot since the mid 80's to make things safer. BMW engines had 1200hp then.

dprantl

Argh, you will never get it.



Dan
'91 928GT S/C 475hp/460lb.ft

tv

All I know is that rotors and pads stop cars, tires only do so if they are leaving smoke and marks.





page 152
http://books.google.com/books?id=9pF...brakes&f=false

hacker-pschorr

I'm waiting for you to tell everyone you are swapping out the 4-piston Brembo's on your GT for 78-81 calipers & rotors. Much lighter and I could lock-up my front tires at any speed before upgrading (or did I downgrade) to S brakes.

All of your reasoning has convinced me smaller is better, might as well go with the absolute cheapest setup to maintain.

dprantl

If all I cared about was one-time stopping distance from 60-0, then hell yes. Slowing down to 55mph from 160mph multiple times, not so much

Dan
'91 928GT S/C 475hp/460lb.ft

tv

As to Tire technology - F1 grooved tires NOT as good as mid-80's gumball slicks, yet braking performance improved. Braking Technology really improved. And regarding rotor size, 1 F1 team actually had a 2 rotor design once.




Banned! Slicks
15 March 2007 by Keith Collantine

Christian Klien, Red Bull-Ferrari, Monza, 2006, tyreGrooved tyres – surely the greatest anachronism in Formula 1 today?

No other major open wheel racing series uses them – not the Champ Car World Series, Indy Racing League, GP2, World Series by Renault, A1 Grand Prix – none of them.

In F1, of course, slick tyres have been banned for nearly a decade. Might we soon see their return?

The development and introduction of different tyre technologies is difficult to trace across the motor racing spectrum, including Formula 1.

One thing can be said with certainty – slick tyres originated in the world of drag racing in American in the 1950s. Dragster drivers noticed their treaded tyres became quicker when the grooves wore away, and this soon led to the development of dedicated racing slicks.

Attuning the idea to the tougher demands of circuit racing, with the challenges of corners and far greater distances chief among the problems, took some time. It was not until the early 1970s that slick tyres became a part of Formula 1.

That too had an American influence as the Goodyear and Firestone brands had out-spent Dunlop, squeezing them out of Formula 1. Firestone brought slicks for its teams to use at the 1971 Spanish Grand Prix at the Montjuich Park street circuit. They quickly became de rigeur for dry-weather racing.

The arrival of slicks followed several years of the tread patterns on Formula 1 tyres becoming increasingly fainter and more spread apart – it was almost an evolutionary process.

The same cannot be said for the manner in which slick tyres fell out of use in Formula 1 – that was a swift, decisive blow by the sport’s governing body with the specific intention of reducing cornering speeds.

FIA President Max Mosley had taken many great steps to reduce car performance in the wake of the tragedies of 1994. But when Bridgestone entered F1 in 1997 and a new tyre war began lap times were slashed as cornering speeds went through the roof.

Desperate to contain the escalating speeds Mosley devised new regulations for 1998. Chief among which was inhibiting tyre performance by putting three grooves in the front tyres and four in the rears.

This succeeded in containing speeds in two ways:

Jacques Villeneuve, Williams, Suzuka, 1998First, the tyres indeed proved slower. However, developments in other areas meant that Mika Hakkinen’s pole position time at the opening race at Melbourne in 1998 was only 0.7s slower than Jacques Villeneuve’s had been twelve months earlier on slicks. Nonetheless, without grooves, Hakkinen’s time would have been whole seconds quicker.

Second, it ended the tyre war, as Goodyear left F1 after 1998, unhappy with the grooved tyre regulations. They were not the only ones – reigning champions Villeneuve was just one of many critics of the tyres, although he was surely the most vehement.

Groove tyres ultimately proved to be a limited means of controlling cornering speeds.





Slick tyres were banned in F1 after the 1997 season as the FIA tried to constrain escalating cornering speeds by imposing the use of grooved tyres. Jerez is the last circuit at which an F1 race on slick tyres was held.

Hilton

Ah, the internet argument domain.. where people can choose the evidence that supports their position whilst ignoring all else.

What about other factors that will affect braking:
Vehicle weight vs. centre of gravity
Tire contact patch size/shape (and thus tire pressures, tire tread, lateral shear characteristics of the tire materials)
Amount of downforce provided by aero (still relevant to road cars)
Resolution/reaction speed of electronics and mechanical actuators (i.e. ABS)

Carl Fausett

If you measure performance brakes against a single 60-0 stop or panic stop you will miss the point.

The greater thermal mass is for repeated hard stops without brake fade.
The increase in effective radius is for higher torque against the rotors inertia without exhausting the driver.

If you measure the performance of your brakes based on a single panic stop - then you dont need them.
But don't track those brakes and wonder why the brakes fade awayand your leg gets exhausted.

tv

This is just impressive stuff from an F1 website;

http://www.f1technical.net/articles/2

Brake system

In physical terms we can state that energy is the capacity of a physical system to do work. When a car comes down a straight line at 300 km/h or more, it possesses lots of kinetic (movement) energy. Due to the fact that energy does not get lost, but can instead only be converted one form into another, the only way to slow down the car is to convert the kinetic energy into another form. Brakes as we know them both in race cars and road cars convert this movement energy to heat.

Formula One cars must sometimes decelerate in a matter of seconds from 350 km/h to about 70 km/h. During such heavy braking, the temperature of the brake rotor and pads can warm up from 400°C to more than 1000°C. These 1000°C occurs at the very end of the braking, and is approximately the highest temperature a carbon brake disc (as they are used in F1, and limited to 28mm thickness and 278mm diameter by the FIA) can take.
Applying carbon brakes

A mere 4 seconds is the amount of time it takes for a Formula One car to go from 300 km/h to a complete halt. At 200 km/h, a Formula One contender requires just 2.9 seconds to stop completely, a process that will have been accomplished over 65 m. At 100 km/h, these values are just as mind-blowing 1.4 seconds and 17 meters! Under these heavy braking periods, a driver is subjected to a horizontal deceleration of close to 5.4G.


62 -0 in under 60 feet

Carl Fausett

tv - gorgeous picture in post 61

Nobody has asked me, but our rotors are 32mm in section, same as all 928 and 993 Rotors accept 78-79 US. The section of course increase thermal mass, but also increases unsprung weight and rotational inertia. 32mm seems to be a happy compromise that Porsche and Brembo like to use on cars that weigh about what we weigh.

Imo000

I fully agree with you. Most street driven cars only see emergency stopping on single occasions. At that occasion, if you can continuously keep the tires right at limit of locking up, for the entire duration of the emergency stop, then it doesn't matter if you have a single piston, small rotor or a jumbo six piston setup. Unless you track the car, you will never see the benefit of larger brakes on a 928.

What Ive noticed with the factory set up 4 piston calipers (S4-up) is that it takes less force from you foot to get the wheels to the edge of lock up than on the single piston setup. This gives a false sense that the brakes are better, when in reality, they are both equaly good for emergency stops.

Carl Fausett

On a typical F1 car that weighs what - 1600 lbs?

Increase the weight of the car,and you need a larger effective radius, more thermal mass, and higher hydrailuc gains between the master and the calipers. And I think F1 cars have manual brakes - no power assist.

Good info, tv! Thanks for posting it.

tv

You can have all the factors you want but the bottom line in stopping is about heat dissipation. Cross-dilled with vents is better than solid, Larger is better than smaller, and Carbon Ceramic is better than steel for all stopping.

Given the same car, whether F1 or a station wagon, every braking situation will be shorter with the larger, vented discs, even better with Ceramic.




NOT my Opinion, IT IS SCIENCE FACT. ( I just read )

Imo000

And here's your problem........"I just read"

Reading it is not enough if you don't understand what it means and what situation it describes.

dprantl

I agree 100% with the above. I was simply stating that for a street driven car, upgrading to bigger brakes from stock S4 or GTS brakes will be of limited value since the largest stress on the brakes is going to be mostly from a single 60-0 panic stop. In such a situation, upgrading from stock S4 brakes will not help (unless you have a seriously withered right leg or something). Oh, and I say mostly because not everyone goes in the fast group on the SITM fun ride But even at that time while following another supercharged 928, at no point did I experience brake fade and ABS intervened towards the end of the run just like at the beginning. Pretty much what you stated in your first post, for the street this brake upgrade would be for looks with >17" wheels.

Dan
'91 928GT S/C 475hp/460lb.ft