Fuel saving is an issue since October 1973. But even 43 years later cars are constructed in a way that an economic mode of driving risks rotten brakes.
(deutsche Fassung)
Naturally German cars are troubled in particular. As German cars are meant to be driven without Speeding limit, their Brakes are oversized and easily underused.
Historical background:
Since 100 Years car brakes are cooled by airflow. Frederick W. Lanchester invented the predecessor of today’s Disk brake (see GB190123500.) He invented the cooling of engine and brake by airflow (see GB190009983.)
Since Lanchester’s days cars turned faster and heavier. Instead of one central brake at Lanchester’s time, there is one brake at every wheel, and the brakes are very exposed to the environment. Thus dirt and water can do harm to the brakes surfaces.
Until October 1973 that was OK. Fuel was cheap. An economic mode of driving was out of question. Frequent use of brakes would grind their surfaces and abrade dirt and corrosion.
But today an economic mode of driving and fuel prices are an issue. Today manufacturers instructions tell the driver not to apply the brakes and coast instead whenever possible. But if drivers comply with these instructions, their brakes may corrode and finally fail.
Most of todays cars have diskbrakes made of steel. All of them have trouble to cope with the extremely antagonistic need of cooling the brakes and protecting them from dirt and corrosion. In patent offices‘ databases one may find thousands of proposals to cope with these antagonistic needs. DIN 15434 defines the dimensioning of brakes and believe me: If a car is driven under worth-case conditions, brakes must absorbe more energy and the brake disks will turn hotter then you can imagine!
So the rotten brakes issue is not a problem of volkswagen in particular. But it is a problem of my own car, a WV Polo TDI BlueMotion. By march 2014 I had to pay hundreds of Euros to replace all diskbrakes as they were rotten due to underusage. So I sent a letter to Volkswagen by 30 march, 2014. I confronted them with the concept that their cars should be fit for purpose. I still assume the purpose of a WV Polo TDI BlueMotion is to be driven as teached by the instructions.
Unfortunately, I observed that VW Chairman Poetsch turned to fight mode when I as an outsider offered unsolicited advice.
Poetschs refusal of a productive communication led to a situation where my political blog comprises far more car related content then I intended.
There is one reasoning I hope Volkswagen will unterstand one day:
Volkswagen’s BlueMotion cars are among the best fuel savers worldwide. It makes sense to assume that many of them are bought by people who are used to an economic mode of driving.
Ignorance of buyers motivations led to failure: The Polo BlueMotion was quitely phased out. (Adieu BlueMotion, in german only)
