what is BRAKE JUDDER?
Brake judder is the vibration felt through the steering wheel and suspension when the braking
Judder It can vary from a barely noticeable vibration to a violent judder. It is typically experienced either through the brake pedal or steering wheel judder.
Take care when installing your new discs
Take care when installing the brake discs as any warpage to the discs caused by poor-fitting practices will not be covered by any warranty. Failure to document the disc run-out prior to using the vehicle on the road will also result in warranty claims being rejected.
Use a DTI mounted to the strut and measure the run-out on the front and rear surfaces of the discs. This process should be recorded via video for future reference. Sweep a full 360 of the disc avoiding the pattern on the braking surface on the inside and outside of the discs. If run-out is more than 0.1mm then try mounting cleaning the hub sufaces again and/or trying the disc in a different position on the hub.
None of our products are covered by any warranty when used for track or racing as discs and pads can easily be pushed beyond their intended operating parameters. EBC Race pads RP-1 or RP-X are not road legal.
Patterned discs
When braking, all patterned discs tend to make some noise.
A small popping noise is normal, as this is the sound of the pad going over the slots/holes. C-Hook patterned discs are typically the quieter option for minimal NVH during normal driving.
Grooved discs tend to be the louder out of the options we offer.
Drilled discs can over time crack if driven hard frequently, if this is your intention we would recommend C-hook, Grooved or Dimpled discs.
CAUSE 1: HUB AND/OR DISC RUN-OUT
Check for rust or dirt on the wheel hub surface
WHY? Rust or dirt causes poor contact between the disc and hub.
THE SOLUTION: Dismantle the disc and clean both surfaces to remove rust and other pollutants.
Check whether the hub contact surface has been distorted by excessive tightening torque
WHY? Using overly severe tightening torque on the positioning screw leads to vibrations throughout the brake application.
THE SOLUTION: Replace the discs, avoiding excessive tightening torque.
Check for distortion of the hub itself
WHY? Although rare, it’s possible for hubs to warp. Bolting a disc to a warped hub will always result in brake vibration. The same will happen if any rust from the hub surface is not removed before fitting the disc.
THE SOLUTION: After fitting a disc, always check for disc run-out using a dial gauge. If the run-out is out of tolerance, re-fit the disc in an alternative position until the run-out is within tolerance. If run-out still remains out of tolerance, hub maintenance is required.
Check whether the alloy wheels have been fitted correctly
WHY? A common cause of disc run-out in recent years is the incorrect fitment of ‘one-size-fits-all’ alloy wheels. As the same wheel is used for multiple hub types and sizes, installers are using location spacers on the wheel spigots. If the spacer is lost or damaged, the wheel cannot be correctly centred.
THE SOLUTION: Place the run-out gauge on the back of the disc while fitting the wheel, and measure the run-out. The gauge will only show run-out once the wheel is fitted and tightened, and it may be necessary to change the wheel.
Failure to check and document discs run out will invalidate any claims for warranty replacements
CAUSE 2: SEVERE DISC OVERHEATING & DISTORTION
Any severe temperature increase can cause the disc metal to distort in different areas of the disc.
These ‘hot spots’ cause intermittent contact between the pad and disc and that results in judder. To help you identify if this is the case, here are some symptoms and solutions:
Check for any signs of brake abuse
WHY? Brake abuse is the most common reason for overheating. Discs are designed to cool rapidly between brake applications. But when the brakes are applied intensely in quick succession – e.g. during alpine driving – the discs don’t get enough time to dissipate the heat.
THE SOLUTION: Blue spots on the disc surface are a good indication of overheating. Discs that show blue spots and/or a darker colour in some areas cannot recover and should ALWAYS be replaced, together with the brake pads.
Check the quality of the brake pads
WHY? Poor quality brake pads can overheat very easily, especially during heavy braking. The excessive heat from the pads can cause the discs to overheat, resulting in disc warping.
THE SOLUTION: Again, look for blue spots on the disc surface. ALWAYS replace the brake pads and discs when you do see blue spots on the disc.
SF-Tuning LTD is happy to recommend good quality pads and will help you choose the correct compound depending on your vehicle's power and intended use.
None of our products are covered by any warranty when used for track or racing as discs and pads can easily be pushed beyond their intended operating parameters.
Failure to allow discs and pads to cool sufficiently risks damage to your brake system
Burning up the discs and pads by taking them beyond their intended operating temperature will result in brake fade. This will also invalidate any warranty claims.
CAUSE 3: DISC THICKNESS VARIATION (DTV)
DTV is the variation in thickness around the disc surface.
For effective braking, the disc should have the same thickness throughout. If there is an uneven friction surface, the brake pad loses and regains contact with the disc(s) as it turns. And that’s what causes brake judder. To help you identify if this is the case, here are some symptoms and solutions:
Check the brakes have been properly bedded in
WHY? To get the best performance from your brakes, it’s essential to follow the bedding-in procedure. By applying only moderate pressure on the brake pedal during the first few applications, an even layer of friction material is transferred from the pads to the disc. Mating the surfaces this way improves safety and prevents DTV-related judder.
THE SOLUTION: Prevention is better than cure. Each time you fit new brake pads, you should avoid hard braking for the first 500 miles. When poor bedding-in has resulted in slight DTV, it may be sufficient to bed in the brakes once again. If this does not re-align the disc surfaces, the discs may need to be skimmed or replace both the brake pads and discs.
Check for dirt or corrosion on the disc surface
WHY? During braking, some of the brake pad’s friction material transfers to the disc however with poorer quality brake pads, the deposits of friction material can stick to the disc unevenly, changing the disc’s thickness and parallelism.
To avoid excess deposits, avoid holding the brake on when you come to a hard stop.
THE SOLUTION: If there’s only minimal DTV, it may be sufficient to remove the deposits using a brush or sandpaper and road test the brakes. If this has not re-aligned the surfaces, the discs may need to be skimmed or replace both the brake pads and discs.
Check for pad imprints on the discs
WHY? Holding the brake pedal depressed when the brakes are overheated may imprint or weld pad material on to the discs. The DTV will often be visible as the outline of a brake pad on the disc surface.
THE SOLUTION: It should normally be sufficient to remove the pad imprint using a brush or sanding paper.
Useful links
https://ebcbrakes.com/race-motorsport-articles/bedding-in/
https://www.bremboparts.com/europe/en/support/fitting-and-maintenance/indications-and-bedding-in-903
https://www.febi.com/en/car/braking/
Epic brakes inside!
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