Brake upgrade for non-S

[pecivil]

so Jim, according to that line of thinking, the reason they put even LARGER brakes on the 911 S and the 911 turbo, is because they are heavier, and it has nothing to do with horsepower? I can't imagine that the Boxster S weighs too much over the standard model. Certainly not enough to justify larger brakes.

But, Hey maybe you are right, and Porsche only puts on bigger brakes to charge more $$$ and for the "bling" factor.

But somehow, I doubt it.

[MNBoxster]

Originally Posted by pecivil

so Jim, according to that line of thinking, the reason they put even LARGER brakes on the 911 S and the 911 turbo, is because they are heavier, and it has nothing to do with horsepower? I can't imagine that the Boxster S weighs too much over the standard model. Certainly not enough to justify larger brakes.

But, Hey maybe you are right, and Porsche only puts on bigger brakes to charge more $$$ and for the "bling" factor.

But somehow, I doubt it.

Hi,

Yes, Horsepower has absolutely nothing to do with how a car stops. You can have 1000 Horsepower on a Boxster and assuming the weight hasn't changed, it will still stop in the same distance with the same brakes as a stock 200HP one. If you're braking from 60 MPH you're braking from 60 MPH, it's the same whether you reached that 60 MPH in 3 seconds or 10 seconds, you are still braking from 60MPH...

Happy Motoring!... Jim'99

[pecivil]

of course hp has nothing to do with how a car stops....

but it has a LOT to do with how fast the car is going when it tries to stop, 'eh?

so as a cars TOP speed increases, the braking capacity needs to increase to be able to stop in a reasonable distance, correct?

so if my boxster, or twin turbo 911, or whatever stops from 60mph, yes the same brakes will work just dandy

However if my boxster is stopping from 150mph, BUT my 911 twin turbo is stopping from 185mph, then we need better brakes on the turbo, if it is to slow down in the same distance as the boxster. The key is stopping in the same (or lesser) distance.

Stopping DISTANCE is the key here, Jim. I could easily stop my twin turbo with my stock boxster brakes, cept it may take a bit longer to do it.

so, what we end up with is:

a higher hp car needs bigger brakes

exactly what I said in the beginning, and exactly what car makers tend to do with their sports cars.

[MNBoxster]

Originally Posted by pecivil

of course hp has nothing to do with how a car stops....

but it has a LOT to do with how fast the car is going when it tries to stop, 'eh?

so as a cars TOP speed increases, the braking capacity needs to increase to be able to stop in a reasonable distance, correct?

so if my boxster, or twin turbo 911, or whatever stops from 60mph, yes the same brakes will work just dandy

However if my boxster is stopping from 150mph, BUT my 911 twin turbo is stopping from 185mph, then we need better brakes on the turbo, if it is to slow down in the same distance as the boxster. The key is stopping in the same (or lesser) distance.

Stopping DISTANCE is the key here, Jim. I could easily stop my twin turbo with my stock boxster brakes, cept it may take a bit longer to do it.

so, what we end up with is:

a higher hp car needs bigger brakes

exactly what I said in the beginning, and exactly what car makers tend to do with their sports cars.

Hi,

Again, HP has nothing to do (relatively speaking) with the top speed of a car, it has to do with how fast you attain that top speed. Most cars are aerodynamically limited, not power limited, to how fast they can go. You're never gonna hit 150 MPH in a Boxster unless the Top is Up anyway.

Your arguement about the Boxster at 150 MPH vs the TT at 185 MPH is illogical, you're comparing apples to oranges.

For a street driven Boxster, how often (if ever) do you go 150MPH or even 100MPH? And, assuming there are times which you do, how often are you gonna need to panic Brake at that speed? And who says that the Brake upgrade will be sufficient?

The differences in Stopping Distance are really negligible, less than 10% between the two Brake setups. Given the cost and such, I just don't believe it's worth it. I think most doing the upgrade are going for the Bling of it all and justifying it with arguements like yours.

The value to the Brake upgrade is on the Track where the smaller Brakes will fade more readily. On the Street, where you don't have a constant application of the Brakes without a cooling period in-between, they don't offer that much advantage...

Happy Motoring!... Jim'99

[Paul]

Hey, I agree with Jim on this one, except the part about horsepower and top speed a 2001 Boxster and 2001 996 have the same front end (therefore the same drag) , guess which one goes faster?

[MNBoxster]

Originally Posted by Paul

Hey, I agree with Jim on this one, except the part about horsepower and top speed a 2001 Boxster and 2001 996 have the same front end (therefore the same drag) , guess which one goes faster?

Hi,

I know what you're saying, but Frontal Area is just one component of Drag. The 911 (especially the coupe) is cleaner in overall drag than the Boxster. Yes, I agree, HP allows the 911 to exceed the Boxster purely because of the power which is available to overcome the drag which is the square of the car's speed. But, it's also more efficient. Put the same 3.4L into the Boxster and you won't match the 911's Top Speed, you'd need even more HP to do that, 100 HP more by my calculations...

Happy Motoring!... Jim'99

[Paul]

BTW my major at Penn State was Aerospace engineering, want to talk about Reynolds number, stagnation pressure, force equations for deformable bodies???

0.29 - Porsche Boxster, 2005
0.29 - Chevrolet Corvette, 2005
0.29 - Mazda RX-7 FC3S Aero Package, 1986-91
0.29 - Lancia Dedra, 1990-1998
0.29 - Honda Accord Hybrid, 2005
0.29 - Lotus Elite, 1958
0.29 - Mercedes-Benz W203 C-Class Coupe, 2001 - 2007
0.28 - Toyota Camry and sister model Lexus ES, 2005
0.28 - Porsche 997, 2004


.29 for a boxster, .28 for a 997?????

[Tool Pants]

Originally Posted by Paul

Hey, I agree with Jim on this one, except the part about horsepower and top speed a 2001 Boxster and 2001 996 have the same front end (therefore the same drag) , guess which one goes faster?

Boy, this is an oldie that came back to life.

I think the one that Porsche wants to go faster is the one that Porsche charges more money for.

[insite]

Originally Posted by MNBoxster

Again, HP has nothing to do (relatively speaking) with the top speed of a car, it has to do with how fast you attain that top speed. Most cars are aerodynamically limited, not power limited, to how fast they can go. You're never gonna hit 150 MPH in a Boxster unless the Top is Up anyway.

cars are drag-limited at a given power output. terminal velocity is reached when the power required to overcome drag for a given vehicle equals the maximum power output of the motor. for a vehicle of a given frontal area and cd, increasing the power output will increase the top speed capability.

Originally Posted by MNBoxster

The value to the Brake upgrade is on the Track where the smaller Brakes will fade more readily. On the Street, where you don't have a constant application of the Brakes without a cooling period in-between, they don't offer that much advantage...

agreed. pecivil's point, however, is still valid for track scenarios. a higher HP car will see higher average speeds around a track (given equal chassis). accordingly, the kinetic energy the brakes will have to shed increases. this will increase heat. as a brake system essentially changes kinetic energy to thermal energy, the job of a brake rotor is to get rid of that heat, hence the larger system. on the road, this makes almost no difference. on the track, it makes a LOT of difference.

[MNBoxster]

Originally Posted by insite

cars are drag-limited at a given power output. terminal velocity is reached when the power required to overcome drag for a given vehicle equals the maximum power output of the motor. for a vehicle of a given frontal area and cd, increasing the power output will increase the top speed capability.







agreed. pecivil's point, however, is still valid for track scenarios. a higher HP car will see higher average speeds around a track (given equal chassis). accordingly, the kinetic energy the brakes will have to shed increases. this will increase heat. as a brake system essentially changes kinetic energy to thermal energy, the job of a brake rotor is to get rid of that heat, hence the larger system. on the road, this makes almost no difference. on the track, it makes a LOT of difference.

Hi,

No disagreement here...

Happy Motoring!... Jim'99

[porsche986spyder]

Originally Posted by pecivil

of course hp has nothing to do with how a car stops....

but it has a LOT to do with how fast the car is going when it tries to stop, 'eh?

so as a cars TOP speed increases, the braking capacity needs to increase to be able to stop in a reasonable distance, correct?

so if my boxster, or twin turbo 911, or whatever stops from 60mph, yes the same brakes will work just dandy

However if my boxster is stopping from 150mph, BUT my 911 twin turbo is stopping from 185mph, then we need better brakes on the turbo, if it is to slow down in the same distance as the boxster. The key is stopping in the same (or lesser) distance.

Stopping DISTANCE is the key here, Jim. I could easily stop my twin turbo with my stock boxster brakes, cept it may take a bit longer to do it.

so, what we end up with is:

a higher hp car needs bigger brakes

exactly what I said in the beginning, and exactly what car makers tend to do with their sports cars.

Yes, he is right. Jim I have to disagree with you on this one.