You just got a fresh set of new tires, but now your car vibrates or shakes when braking. This frustrating combination can have several causes that require investigation.
Shakes and pulsations during braking after new tires often stem from factors beyond just the tires. Issues with wheels, rotors, suspension and wheel alignment can all contribute to brake pedal vibration.
Understanding the various causes makes it easier to pinpoint the real reason your car shakes under braking after new rubber. Addressing the root problem results in a smooth and confident braking feel.
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Even brand new wheels right out of the box can be unbalanced. High-speed wheel balancing is crucial after new tires are mounted to ensure smooth rotation.
Ask if your tire shop performed a precision computer balance on the new wheel and tire assembly. If not, have them properly balanced to specification.
Tire Defects or Non-Uniformity
Some new tires come from the factory with density variations or other defects that make them vibrate. They will shake the car when braking despite rebalancing attempts.
Carefully inspect new tires for any signs of tread belt separation or sidewall buckling that indicates defects. Return problem tires for warranty replacement to resolve the wobble.
Brake Rotor Thickness Variation
Excessive tolerance in new rotor thickness or runout makes the braking surface uneven. This pulsates the brake pads and calipers, sending vibration into the chassis, wheel and steering.
Measure rotor thickness variation and lateral runout with a dial indicator. Compare to manufacturer maximums. Replace any rotors outside spec that cause pedal pulsation.
Rotors Out of Parallel
Rotors must be precisely parallel to prevent thickness and runout issues from developing as they wear. Even minor deviations here can lead to brake pedal vibration.
Inspect machined rotor mating surfaces for evidence of uneven discoloration indicating runout problems. Remachine or replace rotors that are out of parallel.
Glazed Brake Rotors
Overheated and glazed rotors cause harsh brake pedal vibration and pulsation. They lose stopping power and normal friction levels due to hardened deposits on the braking surface.
Inspect rotors for shiny, darkened areas indicating excessive heat damage. Correct pad issues causing overheating. Lightly sand or lathe glazed rotors to renew the friction surface.
Surfaces Not Cleaned
Brake dust, oil and grease deposits left on rotors, pads and calipers prevent full contact. This inconsistent contact causes pulsation each wheel revolution.
Ensure all braking surfaces are sanded and thoroughly cleaned before new pads are installed. Carefully follow bed-in procedures to transfer pad material for uniform friction.
Contaminated Brake Pads
Oil or grease on just the edge of the brake pads causes vibration by preventing full rotor contact and uniform friction level. This occurs more with new pads.
Inspect pads for any edge interference or contaminants marring the friction surface. Sand any problem spots and properly clean the rotors, calipers, pads and brackets.
Wheel Bearing Wear
Loose, worn wheel bearings allow the wheel torque and movement under braking. This transfers vibrations through the steering and chassis rather than being isolated at the wheel.
Check for any bearing play by rocking the tires. Replace any loose, grinding or damaged bearings to restore proper suspension control when braking.
Sticking, frozen or unevenly retracting caliper pistons distort rotors and cause pedal pulsation. Caliper slides wear over time and prevent uniform pad contact as well.
Lubricate and ensure free caliper piston movement. Check rubber slides for deterioration. Rebuild or replace any damaged calipers.
Pad and Rotor Mismatch
Using the wrong pads or rotors leads to braking noise, uneven wear and pedal vibration. Always match OEM friction levels and specifications to avoid these issues.
Use manufacturer recommended replacement parts for your specific vehicle. Mixing components risks diminished braking performance.
While new tires necessitate rebalancing and realignment, vibration when braking also requires looking at the brakes themselves for potential causes.
Methodically inspecting pads, rotors, calipers and wheel bearings helps isolate the root source of vibration. Correcting underlying issues provides optimal contact, friction and braking control.