Tom Stephens:Our upcoming programs have aggressive mass targets
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I dispute the fact that the G8 GT has 'decent' brakes. They might be OK for a few straight line stops but they are far from decent if they are used for circuit work over a few laps. That's why HSV have monster stoppers under their 19/20" inch wheels... because they are 'race' spec brakes... like a lot of performance production cars these days and they maintain their braking performance under almost any street/race application.
I'm not sure the E39 BMW M5's brakes are any good if used for more than a few laps around a circuit, either. The E39 M5 is nigh on Camaro's weight but it isn't fair comparison because we're talking last generation's cars, not today's cars. Case in point, I'm sure 17" wheels and 11" brake rotors are good specs for a 3300 lb car but we don't build 3300 lb performance cars anymore. For the same reasons, we don't put small wheels/brakes under heavy performance cars. Anyway, moot point regarding the E39... so let's talk today's M5.
Having made my point, I can't understand how GM decided to go with 12" rotors on the current CTS-V (4200 lbs)?
I guess the term 'decent brakes' is relative as we're talking both street and race applications. GM generally always leave room for engine enhancements and I'm glad they also took a similar view with brake wheel/brake specs upgrades for Camaro... even if some believe it's overkill.
I'm not sure the E39 BMW M5's brakes are any good if used for more than a few laps around a circuit, either. The E39 M5 is nigh on Camaro's weight but it isn't fair comparison because we're talking last generation's cars, not today's cars. Case in point, I'm sure 17" wheels and 11" brake rotors are good specs for a 3300 lb car but we don't build 3300 lb performance cars anymore. For the same reasons, we don't put small wheels/brakes under heavy performance cars. Anyway, moot point regarding the E39... so let's talk today's M5.
Having made my point, I can't understand how GM decided to go with 12" rotors on the current CTS-V (4200 lbs)?
I guess the term 'decent brakes' is relative as we're talking both street and race applications. GM generally always leave room for engine enhancements and I'm glad they also took a similar view with brake wheel/brake specs upgrades for Camaro... even if some believe it's overkill.
I would say my Magnum R/T has decent brakes and 18in wheels too (13.6in front rotors, 12.6 in back). Are they up to track duty? No, but they're up to task of bringing the 4300lbs whale to a stop in everday traffic. Most of the LX guys that complain about the brakes go with a better pad compound and that seems to make a significant difference. With Brembo becoming the supplier of choice for performance applications of late, I'm betting that they could design a rotor and caliper that would be able to more than meet the requirements needed.
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I dispute the fact that the G8 GT has 'decent' brakes. They might be OK for a few straight line stops but they are far from decent if they are used for circuit work over a few laps. That's why HSV have monster stoppers under their 19/20" inch wheels... because they are 'race' spec brakes... like a lot of performance production cars these days and they maintain their braking performance under almost any street/race application.
I'm not sure the E39 BMW M5's brakes are any good if used for more than a few laps around a circuit, either. The E39 M5 is nigh on Camaro's weight but it isn't fair comparison because we're talking last generation's cars, not today's cars. Case in point, I'm sure 17" wheels and 11" brake rotors are good specs for a 3300 lb car but we don't build 3300 lb performance cars anymore. For the same reasons, we don't put small wheels/brakes under heavy performance cars. Anyway, moot point regarding the E39... so let's talk today's M5.
Having made my point, I can't understand how GM decided to go with 12" rotors on the current CTS-V (4200 lbs)?
I guess the term 'decent brakes' is relative as we're talking both street and race applications. GM generally always leave room for engine enhancements and I'm glad they also took a similar view with brake wheel/brake specs upgrades for Camaro... even if some believe it's overkill.
I'm not sure the E39 BMW M5's brakes are any good if used for more than a few laps around a circuit, either. The E39 M5 is nigh on Camaro's weight but it isn't fair comparison because we're talking last generation's cars, not today's cars. Case in point, I'm sure 17" wheels and 11" brake rotors are good specs for a 3300 lb car but we don't build 3300 lb performance cars anymore. For the same reasons, we don't put small wheels/brakes under heavy performance cars. Anyway, moot point regarding the E39... so let's talk today's M5.
Having made my point, I can't understand how GM decided to go with 12" rotors on the current CTS-V (4200 lbs)?
I guess the term 'decent brakes' is relative as we're talking both street and race applications. GM generally always leave room for engine enhancements and I'm glad they also took a similar view with brake wheel/brake specs upgrades for Camaro... even if some believe it's overkill.
I do realize that some people do race big heavy sedans as lots of Impala SS folks have been doing it for more than a dozen years. But 99.9% of the time these cars are street cars only. For street duty the OEM brakes on these cars are better than average. If anybody is seriously going to track their car, they are going to upgrade the brakes 2nd, right after the tires.
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Originally Posted by SSBaby
that M5 developed 400 bhp compared to today's M5 which produces 500bhp!
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Trust me, I like badass brakes as much as the next guy - actually, probably more than most. My point was, that high mass creates it's own associated costs. I'm betting that the more expensive Brembos weren't the first choice for the SS. I'm betting the less expensive Delco, (or whoever supplies them), brakes just weren't up to the task of meeting performance targets on a two ton car. So enter the higher cost brakes.
FWIW, Motorweek tested the V6 Camaro vs. the Hyundai Genesis coupe and the Camaro smoked the Genesis in braking. Isn't your statement more of a "guess" anyway?
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From: Chicagoland IL
I didn't watch that one. What did they say?
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Don't forget, the 20" wheels allow bigger brake rotors. I'd rather have additional weight due to bigger brakes than have a heavy-ish car with smaller wheels and under-specced brakes.
It has as much to do about engineering as it has to do with design. HSVs use big wheels because they need exceptional braking power given the mass and performance of their vehicles!
To save a few kilograms by opting on smaller wheels seems like illogical idea. Weight savings should not compromise solid engineering.
It has as much to do about engineering as it has to do with design. HSVs use big wheels because they need exceptional braking power given the mass and performance of their vehicles!
To save a few kilograms by opting on smaller wheels seems like illogical idea. Weight savings should not compromise solid engineering.
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HSV use 19" to accommodate 365mm rotors (14.5") but the wheels can be optioned up to 20". Given we are referring to relatively heavy performance cars, it makes complete sense to make the wheel/brake combo designed for future upgrades.
Now if we had to take your train of thought, upgrading your brakes on Camaro with 18" wheels would require a completely new wheel and brake combo.
Now, imagine if you had to throw out your engine if you needed more power?
EDIT: the Bentley Continental GT has 420 x 40 mm rotors for reference. Point being that heavy cars NEED capable brakes.
Last edited by SSbaby; Aug 31, 2009 at 06:21 PM.
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I can engage the ABS / lock the 315/35-17 Hoosier A6s on the front of my car using nothing more than upgraded street pads (Hawk HP+). The very same brake hardware (but with different pads) is competitively road raced in several different classes / organizations. The braking system I am referring to is nothing special or hugely sized. In fact, it is the very same hardware found on every stock '98 - '02 Camaro and Firebird.
If I can lock BIG competition tires with such equipment and the road racers can make do with only additional ducting, why the hell would anyone need brakes larger than what would fit inside of an 18 inch wheel?
Lastly, the NASCAR boys seem to have few problems road racing and short track racing 800+ hp / ~3500 lb cars with brakes that fit inside 15 inch wheels.
Last edited by Chewbacca; Aug 31, 2009 at 07:33 PM.
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You mean upgrade beyond the Brembos that are on the car now? For the love of God, why? Bling? And upgrade to what, the 15.5 inch ZR1 carbon-ceramics? Again, why?
I can engage the ABS / lock the 315/35-17 Hoosier A6s on the front of my car using nothing more than upgraded street pads (Hawk HP+). The very same brake hardware (but with different pads) is competitively road raced in several different classes / organizations. The braking system I am referring to is nothing special or hugely sized. In fact, it is the very same hardware found on every stock '98 - '02 Camaro and Firebird.
If I can lock BIG competition tires with such equipment and the road racers can make do with only additional ducting, why the hell would anyone need brakes larger than what would fit inside of an 18 inch wheel?
Lastly, the NASCAR boys seem to have few problems road racing and short track racing 800+ hp / ~3500 lb cars with brakes that fit inside 15 inch wheels.
I can engage the ABS / lock the 315/35-17 Hoosier A6s on the front of my car using nothing more than upgraded street pads (Hawk HP+). The very same brake hardware (but with different pads) is competitively road raced in several different classes / organizations. The braking system I am referring to is nothing special or hugely sized. In fact, it is the very same hardware found on every stock '98 - '02 Camaro and Firebird.
If I can lock BIG competition tires with such equipment and the road racers can make do with only additional ducting, why the hell would anyone need brakes larger than what would fit inside of an 18 inch wheel?
Lastly, the NASCAR boys seem to have few problems road racing and short track racing 800+ hp / ~3500 lb cars with brakes that fit inside 15 inch wheels.
Why do we go racing? Why do cars get heavier? Why do wheels get bigger? Why do brakes get bigger? It's for design and engineering reasons, I would say... and there is always room under any wheel for bigger brakes on production cars. Are you against progress?
NASCAR? You can't be serious. Yes, I know you are only joking about the brakes on NASCARs. Please tell me you are joking!!!
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For sure.
Pretty early on, the Camaro's developers knew that they wouldn't even come close to their weight targets. NOT. EVEN. COME. CLOSE. But, old CAFE targets were a cake walk, and GM Powertrain could pull the fat out of the fire for performance and fuel economy. Yes, we now have a released, saleable product - but as we've seen from all the reviews - one that falls short in certain aspects of it's dynamics, etc.
Pretty early on, the Camaro's developers knew that they wouldn't even come close to their weight targets. NOT. EVEN. COME. CLOSE. But, old CAFE targets were a cake walk, and GM Powertrain could pull the fat out of the fire for performance and fuel economy. Yes, we now have a released, saleable product - but as we've seen from all the reviews - one that falls short in certain aspects of it's dynamics, etc.
You can see why they missed the weight target. If GM had done like Hyundai and gone for a 300hp V6 as the top model, is there any reason they couldn't have matched the Genesis coupe at a little under 3500 (for the 6M at least)?
If you compare F4 to F5, you add capability to handle another 200hp and tq, you add to the wheelbase, you add to body rigidity, you add IRS designed for dragstrip launches, a differential designed to survive same, you add half a dozen airbags, you add stability control, 17" ==> 20" wheels, etc. Every one of those features adds weight (we can argue how much, but we'd all agree more than zero).
They did pretty well adding only 350 pounds or so.
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No, of course a greater thermal heat sink, swept area and leverage are benefits, but there is also the rule of diminishing returns you are not considering.
Additionally, you fail to consider the marketing factor. For example, C6 engineers have quietly admitted at some club gatherings that the factory non-ZR1 drilled rotors were... wait for it.... a marketing driven decision and NOT an engineering one.
I am no fan of NASCAR but their brake tech is outstanding. In fact there have multiple write ups in Racecar Engineering magazine ( http://www.racecar-engineering.com/) regarding exactly that.
Still not convinced? Well, the Australian V8 Supercar series seems to do quite well with 14.8 inch (376mm) rotors inside 17 inch wheels.
And before you go on about clearance issues related OEM durability and servicing, let me point out that my truck has huge twin piston calipers placed close enough to the wheel that one would be hard pressed to insert a paper clip in the space available.
In conclusion, huge ridiculous wheels are not required for world class braking and are simply a styling / marketing choice.
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Essentially. They complained about it feeling big and heavy, though they liked the engine.