A new twin-disc brake from the supplier’s labs could mean twice as much stopping power.
2003-10-20)

Tucked away on the Frankfurt Auto Show stand of Delphi, the former AC-Delco operation, was a display whose small size failed to signal a development the company describes as "the first significant change in base braking technology since the first volume application of disc brakes more than 50 years ago." The words are those of Chris Baylis, director of engineering at Delphi's Innovation Center in Leamington, England, where the new system has been perfected and is being prepared for manufacture.

The secret of what Delphi calls the "Maximum Torque Brake" is that it replaces the single disc of conventional brakes with two discs, giving four contact surfaces instead of two. The result is up to 1.7 times the torque output of a conventional single disc system of the same effective diameter in a more compact and more efficiently cooled configuration.

Delphi says it believes the new technology will help solve many of the challenges currently faced by braking engineers. Based on a twin floating disc architecture with a single piston, the Maximum Torque Brake provides a high specific torque capability, with substantial improvements in thermal management that can lead to benefits in weight, packaging and NVH (noise, vibration and harshness).

The guts

Improved thermal management provides engineers with many options for enhancing other aspects of the braking system. By greatly increasing opportunities to optimise the combination of disc size, pedal travel, booster size and friction material, Delphi says the Maximum Torque Brake will allow the feel, cost and performance of the system to be precisely matched to market requirements.

For example, with four pad surfaces, Maximum Torque Brake requires approximately half the apply pressure of a conventional disc brake. This could be utilized to significantly downsize the vacuum booster or to reduce the pedal effort and travel. A downsized booster could reduce weight by up to 1 kg (2.2 lb) and provide more premium under-hood space to improve packaging flexibility. Alternatively, disc diameter could be reduced by up to 25 mm (1 inch), allowing smaller wheels (which can generate a substantial cost saving), higher aspect ratio tires (important for off-road vehicles) and a significant reduction in unsprung weight.

The superior thermal management of Maximum Torque Brake, and its minimal generation of Disc Thickness Variation (DTV, caused by the discs wearing unevenly) also provides excellent NVH performance. This, according to Delphi, helps to solve the potentially significant problem of noise-related warranty claims, which surveys show is a major consumer issue in the U.S. and the cause of significant warranty costs. "Because the discs are floating on the hub, their contact with the pads is always even. Maximum Torque Brake doesn't have the wear issues or the tolerance stack-up that can cause judder and squeal in conventional systems," says Baylis.

Other benefits of the system include reduced brake fade and, due to the reduced apply pressure, shorter stopping distances in the event of a vacuum failure - a homologation requirement that can be increasingly challenging to meet using conventional, highly-boosted systems. Delphi's claims for the performance of the system are borne out by testing to the independent AMS standards (conceived by the German magazine Auto Motor und Sport) using a BMW X5 fitted with the system. In the 12-stop test, which is increasingly seen as a European standard, the vehicle demonstrated an exceptional "no fade" performance.

Delphi's testing indicates that in a typical high-performance SUV application, Maximum Torque Brake will remove the need for several brake system specifications, reduce the maximum operating temperature by more than 100°C, improve refinement and offer either reduced pedal travel, by up to 25 mm (due to the reduced volume of fluid required for actuation), or booster downsizing by around 40 mm. Total vehicle weight saving could be as much as 7 kg (15.4 lb), depending on system specification and the level of integration.

The system has completed more than 1.5 million test kilometres in 20 vehicles to help ensure that it will continue to perform to specification in any terrain or usage pattern, throughout a vehicle's life. Two fully-engineered implementations have been shown to vehicle manufacturers: one fitted to a Ford Fiesta, a typical B-segment small European car, the other on a BMW X5, a large high-performance SUV. The former has the piston integrated within the suspension knuckle, while the latter demonstrates a stand-alone piston architecture that could be implemented as part of a mid-life model upgrade.

TCC's representative was among the first journalists to test the new system, driving examples of the Fiesta and the X5 with both their original equipment braking systems and the Maximum Torque brakes. In normal road use, braking efficiency is difficult to judge subjectively, and in both normal braking and panic stops all four cars were totally satisfactory. In terms of the numbers, without a fully-instrumented road-test setup, one has to accept Delphi's word that the system is superior.

There was one situation, however, in which the Maximum Torque-equipped vehicles were markedly different, and this was true of both the small 1.4-litre Fiesta and the large 4.2-litre X5. In simple check braking, such as when one leaves a car park and approaches the road, using the brakes gently in order to make sure the road is clear, the Maximum Torque system gave a sharper and more definite response. Without being jerky or snatching, the twin discs had a positive feel that gave confidence in the brakes. It was the only time that the twin system made itself felt, but it was definitely noticeable and gave the driver confidence that the system was in fact more efficient than the conventional single disc.

With an extensive road-testing program completed, Delphi is now working on productionizing the system and has a prototype build layout installed at its Leamington center. Chris Baylis is upbeat about the potential: "With Maximum Torque Brake," he says, "we have a production-ready product that will allow Delphi's customers to introduce a true 21st-century solution for vehicle braking." Delphi says that discussions with vehicle manufacturers are progressing well and that the system could be in production by 2006.

Source: http://www.thecarconnection.com/index.asp?article=6530

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My guess is dual vented are next?

Haasman

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'03 E320 Wagon-Sold
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'65 911 Coupe (#302580)

there is another manufacturer that created a single-rotor brake, but with brake pads all along the the 360 degrees of the rotor, much like a clutch.

i remember also seeing this tested in racing, on a Porsche 911.

i just don't remember the brand of the brakes, though ...

Is there a single brake pad in between the two rotors, or are there two?

I was hoping the picture would show that a bit better. I'd like to see how the caliper assembly works...

Otherwise, looks cool!