What happens if the brake pads are overheated, the magazine has already told (see ЗР, 1998, No. 7). And how do the wheels feel?

Maxim SACHKOV, Alexander BUDKIN

Recall the summary of that article. An attempt to make twenty consecutive acceleration-braking cycles from 120 km / h to a complete stop on the VAZ 2109 3, among other troubles, led to the brake pads being heated to 170-370 ° C (depending on the material from which they are made) . A sophisticated form of bullying helped us compare the capabilities of the pads. Now let's see what happens to the disks. There is no need to torment the machine for this anymore - heating the parts to the required temperature will be ensured by the inertial dynamometer SNT-NAMI, on which braking is simulated at a speed of 100 km / h at a fluid pressure of 50 kgf / cm2 in the system. After reaching 400 ° C - natural cooling to room temperature.

There are six applicants: four “foreigners” and two “Russians” (see photo). The honor of the country is protected by “native” (Togliatti) discs and products of an unknown domestic manufacturer, purchased at the largest car market in Moscow. The competition included a mandatory program - a test for compliance with the VAZ 2108 -3501070 drawing and demonstrations - a test of the disc's ability to maintain its normal state after strong heating. There are three main controlled parameters: deviation of working surfaces from flatness, their non-parallelism to each other and runout. The last parameter will determine how hard the brake disc will hit the block during its rotation, trying to push it away from itself. Separately - checking the hardness of the work surface.

The results are logical and at the same time unexpected. Of course, we guessed that nameless discs would be worse than the "native", but not so much! The hardness values ​​measured at four points of one “market” disk are from 166 to 182 Brinell units (with a norm of at least 190). Even if this is forgiven (many “foreigners” did not fit the VAZ standard in hardness), the matter is still bad: the non-parallelism of the working surfaces on one of the two unidentified disks exceeded the norm by more than two times. The hardness test result of Togliatti is from 209 to 226 HB. The “native” disc not only met the norm, but also turned out to be the best in this category. Everything would be fine, but the range of values ​​is a bit big - 17 units. It turns out that different parts of the part differ markedly in the structure of the metal, which affects the tendency to warpage. So, the beating of a VAZ sample after heating increased ten (!) Times (for an unknown - the result is the same). In the QH disk, for example, the beating after heating did not change at all, while in the Brembo it increased only threefold. ATE warping was noticeable, but for other reasons. To improve the braking properties in wet weather, less noise and the ability to visually control the degree of wear on the working surface of this disk, special grooves are made. And the areas in which the thickness of the metal changes, when heated, according to the laws of physics, warp more.

Of course, overheated disks are not required to meet the requirements of the drawing, but if you still check, it turns out that only Brembo fits into them. If you close your eyes to firmness, the company will become more representative - it will also include QH and Brady. About the rest has already been said. But it’s better not to overheat even the leaders of the test, and if you happen to drive them into the colors of the rush, do not spare money for a replacement.

Manufacturer Brembo

Price 600 rub.

Meet all requirements even after overheating. The minimum spread of hardness values ​​for one disk. Working surfaces are processed by grinding.

Manufacturer QH

Price 600 rub.

The only ones whose heartbeat did not change after overheating. Some do not reach the VAZ standards in terms of hardness. Work surfaces are finished by turning.

Manufacturer VAZ, Tolyatti

Price 360 ​​rub.

New discs fully comply with factory requirements. After overheating, two of the three control parameters “sailed away”. The biggest hardness. Working surfaces are processed by grinding.

Manufacturer Bradi

Price 750 rub.

Two of the three parameters did not change after overheating. No runout was detected in the new disk (within the accuracy of measurements). Hardness on the border of requirements, but with a wide range of values. Work surfaces are finished by turning.

Manufacturer ATE, Power disk

Price 880 rub.

Special grooves are designed to improve braking properties in wet weather, reduce noise and provide visual control over the degree of wear. Work surfaces are finished by turning.

Manufacturer Unknown

(no marking).

Price 250 rub.

One of the two new discs has a large non-parallel surfaces. After heating, two parameters “floated away”. Given the extremely low hardness - a failure.