This may or may not be a problem with the braking system!
Vibration when braking
The vast majority of drivers and mechanics stereotypically associate vibrations during braking with wear of brake discs. Experts from Rotinger agree that this is the probable cause, but remind that there are several others. Here is a short guide on how to properly diagnose and eliminate vibrations during braking.
The topic of vibrations felt when braking comes up very often during the holiday season. The point is that during gentle, urban driving for short distances, they may not be noticeable. They usually manifest themselves when braking with a loaded car on the highway. These are usually vibrations of the steering wheel and pulsation of the brake pedal. Steering wheel vibrations may also occur with increased energy and spread to the entire car.
The key factors for the manifestation of this phenomenon are:
- starting braking from a specific, high speed
- car load
- extended continuous braking time, which translates into a significant increase in the temperature of the braking system.
First of all, before starting any work, it is worth checking the thickness of the brake discs. If it is below the minimum limit or dangerously close to it, the discs must be replaced without fail.
Loss of parallelism parameters of the brake disc
The cause of vibrations during braking may, of course, be the popular “brake disc runout”. During braking, when the pads press against it, the deformed disc forces the brake caliper to move. The driver most often perceives this as a pulsation of the brake pedal. In this case, the quality of the disc can be verified very easily – just check the disc surface (its axial runout) using a dial indicator. It should be taken into account that two more factors may be responsible for the disturbing result: incorrect seating of the disc on the hub (the brake disc was installed without prior cleaning of the contact surface) or damage to the hub itself.
If the brake disc is deformed, it can be repaired by turning it. However, remember not to reduce the thickness of the brake disc below the permissible minimum as a result of processing. To make sure the thickness of the disc after processing is correct, measure it and compare the result with the minimum thickness specified by the manufacturer.
Brake disc overheating
The fact that measurement with a dial gauge does not reveal any irregularities does not mean that the dial is in perfect condition. It may happen that the disc has been locally overheated. The friction coefficient changes in overheated areas of the brake disc surface. This has a huge impact on the operation of the brake pad, which slips or slows down on individual sections of the disc during braking. This process will also be felt by the driver as vibrations.
Looseness in the suspension
When inspecting the braking system to look for the causes of vibrations during braking, do not forget to check the condition of the suspension. It turns out that looseness in the cars wishbones and steering rods can also cause vibrations during braking or increase their intensity.
Causes of brake disc damage
Before replacing the brake discs with new ones, it is worth answering the question what caused the wear of the old parts. Among the most popular reasons we can point out: Intensive, extreme use, careless installation of discs, failure of braking system components, worn brake pads, improperly selected rims.
To make your new brake discs last as long as possible, make sure that the brake pads are also replaced along with the discs.
Please note: always after driving with intensive use of the brakes, drive at least one kilometer to allow the brake discs to cool down evenly around the entire circumference. Otherwise, the “hidden” part within the brake caliper cools differently than the rest of the part.
Discs should only be installed on a functioning braking system. This is not only about the proper operation of the brake calipers working with the mounted discs, but also about the condition of the brakes on the other axle. Remember that although the car brakes mainly from the front, a faulty rear braking system leads to overload of the front brakes, especially if the car is loaded.
During repairs, remember to carefully clean the contact surfaces of the hubs and discs. A properly mounted brake disc must fit perfectly to the hub – do not forget to clean any rust deposits.
Finally, there’s the matter of rims. In addition to their aesthetic role, they also have the task of properly dissipating temperature from the braking system. Factory designs are specially tested for this purpose. Installing other rims may disturb the heat balance and contribute to overheating of brake discs and pads.
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