Hot potato: brake conversion – swapping a drum brake for a disc!

Hot potato: brake conversion - swapping a drum brake for a disc!

The drum brake is a relic of car brake technology. Until far into the 70ies it was standard for all cars. Nevertheless, a great deal of serious accidents of these cylinder capacity giants can be traced back to undersized and constructionally unfit drum brakes. Fortunately this soon changed.

Obsolete and undersized

Muscle cars with drum brakesEven the heavy horse-powered, US American muscle cars of the late 60ies often had this kind of brake – often with fatal consequences.

At that time, safety technology for passengers was still in its infancy.

Disadvantage of the drum brake

drum brake constructionAs its name already says, the drum brake consists of a rotating drum. Its interior contains two solidly embedded brake shoes. When braking, the brake shoes press against the inside of the brake drum. The developing friction causes the desired braking effect – in theory.
The main problem of the drum brakeThe main problem of the drum brake is its inability to adequately divert the developing friction heat. Protracted brake manoeuvres or emergency stops at high speed can cause the interior of the brake drum to overheat. The heat accumulation impairs the friction force between brake shoe and the drum interior, causing a braking effect loss between 50 – 100%.
Check the drum brake systemFurthermore, the encapsulated system is difficult to check. The condition of the brake drum’s interior cannot be determined from the outside.

  • Is the brake cylinder at the end of its tether?
  • Is the brake drum deteriorating?
  • Is a return spring broken?
  • Is the brake drum choking in its own abrasion dust?

To determine this, the wheel must be removed and the brake drum opened. Only then it is possible to see what is wrong with the brake.

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Disc brakes:
open, safe, accessible

Disc brake constructionTherefore, from the start the disc brake had an advantage over its drum counterpart. The disc is able to absorb stronger braking forces without any risk of overheating.

  • A brake disc is self-cleaning and self-cooling.
  • If wear or a defect occurs, the driver can see what is wrong with the brake even with the wheel still in place.
  • Nevertheless, the construction of the disc brake is complicated and its components heavier than those of the drum brake, making it more expensive.
  • For that reason, the conversion from drum brakes to disc brakes occurred only gradually.
  • For 25 years, the combination of disc brakes at the front and drum brakes on the rear axle remained standard. Not until halfway into the 90ies family and even compact cars gradually received disc brakes on all wheels.
  • For a long time, even sporty models like those of BMW hung on to the drum brake. Especially on versions with less than 100 HP economy prevailed, which is nowadays being taken advantage of by experienced mechanics.

Conversion from drum to disc
– wise and practical?

Conversion from drum brake to disc brakeTo be quite honest: swapping drum brakes for disc brakes only makes sense on rare occasions.

The brake system is specifically designed for the car in the construction facility. The traditional combination of disc brakes at the front and drum brakes at the rear, is generally more than adequate.

Nevertheless, a drum brake is what it is: a piece of outdated technology.
Disadvantage of the drum brakeThe drum brake has nothing in common with sportiness, dynamics or a progressive look. Striking details on all four brake discs like painted brake calipers and matching carbon or aluminium wheel hubs upgrade the progressive look of a car considerably. The conversion, however, is not that simple.

Information before installation

Inform MOT before installing the disc brakesThe main problem of this operation is the massive intervention in factory settings of a system. MOT inpectors do not like the look of it.

Therefore we strongly recommend to seek advice at a reliable inspection station. Investing a lot of money and time in order to be left with a car that is unfit for the road, is a hard and expensive lesson, although with a trick, the inspector’s approval can certainly and securely be won over.

Original rather than fancy

Disk barke and drum brake combinationInitially, conversion to disc brakes on all four wheels on family cars was reserved for models with high-performance engines. Cars with more than 150 HP had this feature at the start of the 90ies.

For an owner of a disc/drum combination this means: the rear axle of a model of the same series which is already equipped with disc brakes, is optimally suited for conversion.

All approved components are available in the right size. In addition to the conversion to the factory-type brake discs of the high-performance engine cars, everything which can be found for these models in the accessory catalogue is suitable.Brembo premium brake discs for a reduced price

A risk for the persistent

We conclude that conversion from drum brakes to disc brakes is a case for the hard-boiled fans of their own car.

why change the drum brake to disc brakeAll others are advised to leave the car in its original condition, sell it or purchase one that is equipped with four brake discs ex works. Everything else means the risk of investing a lot of time and money in a project which ultimately might have to be turned back.

Foto: aSuruwataRi, udaix, etraveler, anucha maneechote, Oleksandr Kostiuchenko, BELL KA PANG, Nixx Photography, Golubovy, Dmitry Kalinovsky, gyn9037 /

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