Mercedes-Benz Mercedes A-Class 2018-present Brake System Bolt Torque Specifications & Fastener Values
Mercedes-Benz Mercedes A-Class 2018-present

Mercedes-Benz Mercedes A-Class 2018-present Brake System Bolt Torque Specifications

Detailed torque specifications for brake components on the 2018-Present Mercedes A-Class, including caliper bolts, carrier bolts, and rotor screws.

Updated

Important Information

Safety guidelines and reference information for proper torque application

Quick Reference Guide
ft-lbs → Nm
× 1.356
ft-lbs → kg-m
× 0.138
Nm → ft-lbs
× 0.738
in-lbs → ft-lbs
× 0.083

Common Torque Patterns

Star Pattern

Used for wheels and other circular bolt patterns

Star Pattern torque pattern diagram showing proper bolt tightening sequence
Cross Pattern

Used for gaskets and cover plates

Cross Pattern torque pattern diagram showing proper bolt tightening sequence
Sequential Pattern

Used for head bolts and other critical components

Sequential Pattern torque pattern diagram showing proper bolt tightening sequence

Common Mistakes to Avoid

Over-tightening

Exceeding the specified torque value can stretch or break fasteners, damage threads, or crack components.

Prevention:

Always use a calibrated torque wrench and follow specifications exactly.

Incorrect Torque Sequence

Tightening bolts in the wrong order can cause uneven pressure distribution and potential leaks or damage.

Prevention:

Follow the manufacturer's specified torque sequence pattern.

Dirty Threads

Dirt, rust, or old thread locker can affect torque readings and proper fastener tension.

Prevention:

Clean and inspect all threads before assembly. Use new thread locker if specified.

Reusing TTY Bolts

Torque-to-yield bolts are designed to stretch and must not be reused.

Prevention:

Always replace TTY bolts with new ones. They are single-use only.

Dry vs. Lubricated

Not accounting for whether torque specs are for dry or lubricated fasteners can lead to incorrect tension.

Prevention:

Check if specs are for dry or lubricated threads. Use specified lubricant when required.

Recommended Tools

Torque Wrench (1/4" Drive)

Range: 2-25 ft-lbs
Small fasteners, delicate components

Torque Wrench (3/8" Drive)

Range: 10-100 ft-lbs
Most common automotive fasteners

Torque Wrench (1/2" Drive)

Range: 30-250 ft-lbs
Large fasteners, wheels

Angle Gauge

Torque-to-yield (TTY) bolts

Torque Wrench Care

  • Calibrate annually or after 5,000 clicks
  • Store at lowest setting
  • Keep clean and lubricated

Search Specifications

Search by component name, bolt size, or description

Torque Calculator

Convert between different torque units

Brake caliper assembly

Components securing the brake caliper to the rotor or drum.

1

Brake Caliper Bolts

M12 x 1.5
Torque Value
79 ft-lbs (107 N·m)
2

Brake Caliper Mounting Bracket Bolts

M14 x 1.5
Torque Value
116 ft-lbs (157 N·m)

Brake rotor and drum assembly

Components securing the brake rotor or drum to the hub or wheel bearing.

1

Brake Disc/Drum Retaining Bolts

M10 x 1.25
Torque Value
61 ft-lbs (83 N·m)
2

Brake Rotor/Hat Retaining Screws

M6 x 1.0
Important Notes
Estimated torque value based on industry standards. Consult vehicle manufacturer's recommendations or a reliable repair manual for accurate torque values.

Brake pads and master cylinder

Components securing the brake pads and master cylinder.

1

Brake Pad Retaining Clips

M5 x 0.8
Important Notes
Estimated torque value based on industry standards. Consult vehicle manufacturer's recommendations or a reliable repair manual for accurate torque values.
2

Master Cylinder Mounting Bolts

M10 x 1.25
Important Notes
Estimated torque value based on industry standards. Consult vehicle manufacturer's recommendations or a reliable repair manual for accurate torque values.

Wheel and brake line fittings

Components securing the wheel and brake lines.

1

Wheel Lug Nuts

M14 x 1.5
Torque Value
96 ft-lbs (130 N·m)
2

Brake Line Fittings

M10 x 1.0
Important Notes
Estimated torque value based on industry standards. Consult vehicle manufacturer's recommendations or a reliable repair manual for accurate torque values.

Troubleshooting Guide

Common issues, diagnostic steps, and prevention guidelines

Common Issues

Bolt stretching, stripped threads, uneven torque patterns

Loose Components

Symptoms:
  • Rattling or vibration noises
  • Visible movement in components
  • Uneven panel gaps
Solutions:
  • Clean threads and mounting surfaces
  • Replace damaged fasteners
  • Apply proper torque in sequence
  • Use thread locker if specified

Stripped Fasteners

Symptoms:
  • Unable to achieve proper torque
  • Fastener spins freely
  • Visible thread damage
Solutions:
  • Use thread repair kit if appropriate
  • Install thread insert (HeliCoil)
  • Replace component if threaded hole is damaged
  • Upgrade to higher grade fastener if recommended

Overtightened Components

Symptoms:
  • Cracked or deformed parts
  • Broken fasteners
  • Compressed gaskets or seals
Solutions:
  • Replace damaged components
  • Use new fasteners
  • Follow proper torque sequence
  • Verify correct torque specifications

Diagnostic Steps

Visual inspection, torque verification, thread assessment

1

Visual Inspection

Inspect the affected area for any visible signs of damage or wear

  • Check for cracks or deformation
  • Look for signs of excessive wear
  • Verify proper fastener installation
2

Torque Verification

Verify the torque applied to the fasteners

  • Check the torque wrench calibration
  • Verify the torque specification
  • Compare the applied torque to the specification
3

Thread Assessment

Assess the condition of the threads

  • Check for signs of thread damage
  • Verify the thread type and size
  • Check for proper thread engagement

Prevention Guidelines

Best practices, maintenance tips, tool care

Best Practices

  • Always follow the recommended torque specification
  • Use the correct type and size of fasteners
  • Verify the torque wrench calibration regularly

Maintenance Tips

  • Regularly inspect the affected area for signs of wear or damage
  • Replace damaged or worn-out components promptly
  • Keep the work area clean and organized

Tool Care

  • Regularly clean and maintain the torque wrench
  • Store the torque wrench in a dry and secure location
  • Verify the torque wrench calibration before each use

Frequently Asked Questions

Find answers to common questions about torque specifications

Q1

What is the recommended torque specification for brake caliper bolts on a 2018-Present Mercedes A-Class?

The recommended torque specification for brake caliper bolts on a 2018-Present Mercedes A-Class is typically 85 Nm (63 lb-ft). However, always refer to the vehicle's service manual or manufacturer guidelines for the exact specification, as it may vary depending on the model and brake system configuration.

Q2

How often should brake bolts be checked for proper torque?

Brake bolts should be checked for proper torque during routine brake maintenance, such as when replacing brake pads or rotors. Additionally, if you notice any unusual noises, vibrations, or braking performance issues, it is advisable to inspect and retorque the bolts as needed.

Q3

Can I reuse brake caliper bolts, or should they be replaced?

Mercedes-Benz generally recommends replacing brake caliper bolts during brake service, as they are often designed as single-use torque-to-yield bolts. Reusing them can compromise their integrity and lead to brake failure. Always follow the manufacturer's guidelines for your specific model.

Environmental Considerations

Temperature, humidity, and seasonal effects on torque specifications

Temperature Effects

Includes: High Heat, Cold Weather, Thermal Cycling

Temperature can significantly impact torque values and fastener behavior

Cold Weather

Effects:
  • Increased material brittleness
  • Higher torque required due to thread contraction
  • Reduced thread lubricant effectiveness
Recommendations:
  • Allow components to warm to room temperature when possible
  • Consider using winter-grade thread lubricants
  • Check torque values more frequently during winter months

Hot Weather

Effects:
  • Thermal expansion of components
  • Decreased friction in threads
  • Accelerated lubricant breakdown
Recommendations:
  • Check torque when components are at normal operating temperature
  • Use temperature-resistant thread lockers
  • Consider re-torquing after heat cycles

Humidity and Corrosion

Covers: Rust Prevention, Salt Exposure, Moisture Control

Moisture and corrosion can affect fastener integrity and torque values

High Humidity

Effects:
  • Accelerated corrosion formation
  • Reduced friction coefficient
  • Potential thread seizing
Prevention:
  • Use corrosion-resistant fasteners
  • Apply appropriate anti-seize compounds
  • Maintain proper protective coatings

Salt Exposure

Effects:
  • Rapid corrosion development
  • Thread damage
  • Seized fasteners
Prevention:
  • Regular underbody washing
  • Use of sacrificial anodes where appropriate
  • Application of protective coatings

Seasonal Maintenance

Spring, Summer, Fall, and Winter maintenance schedules

Spring

  • Inspect for winter damage
  • Clean and protect exposed fasteners
  • Check torque on critical components

Summer

  • Monitor heat-affected components
  • Check expansion-related loosening
  • Inspect cooling system mounts

Fall

  • Prepare for winter conditions
  • Apply corrosion protection
  • Verify all fasteners are properly torqued

Winter

  • More frequent inspection of critical fasteners
  • Check for salt damage
  • Monitor suspension component torque

Related Resources

Tools, service procedures, and technical bulletins

Recommended Tools

Digital Torque Wrench

A precision tool for applying the correct torque to brake system bolts.

  • Adjustable torque settings
  • Digital display for accurate readings
Learn more

Breaker Bar

A long-handled tool used to loosen tight bolts before applying torque.

  • Durable construction
  • Extended leverage for ease of use
Learn more

Torque Angle Gauge

Used to measure the angle of rotation when torque-to-yield bolts are used.

  • Easy-to-read scale
  • Magnetic base for secure attachment
Learn more
Service Procedures

Front Brake Caliper Bolt Torque Specification

Procedure for applying the correct torque to front brake caliper bolts on a 2018-Present Mercedes A-Class.

  • Loosen the front brake caliper bolts using a breaker bar.
  • Clean the bolt threads and apply a small amount of thread locker if specified.
  • Tighten the bolts to the specified torque using a digital torque wrench.
  • Use a torque angle gauge to apply the final angle if required.
View full procedure

Rear Brake Caliper Bolt Torque Specification

Procedure for applying the correct torque to rear brake caliper bolts on a 2018-Present Mercedes A-Class.

  • Loosen the rear brake caliper bolts using a breaker bar.
  • Clean the bolt threads and apply a small amount of thread locker if specified.
  • Tighten the bolts to the specified torque using a digital torque wrench.
  • Use a torque angle gauge to apply the final angle if required.
View full procedure
Technical Service Bulletins

Brake Caliper Bolt Torque Specification Update

2021-05-15

Updated torque specifications for brake caliper bolts on 2018-Present Mercedes A-Class models.

2018-Present A-Class

Resolution: Refer to the latest service manual for updated torque specifications and ensure proper tools are used during installation.

Brake System Noise and Vibration

2020-08-10

Reports of noise and vibration from the brake system due to improper torque application.

2018-Present A-Class

Resolution: Verify that all brake system bolts are torqued to the correct specifications and inspect for any signs of wear or damage.

About the Author

Expert automotive knowledge and experience

Alan Montanye - Automotive Technical Specialist
ASE

Alan Montanye

Automotive Technical Specialist

ASE Master Certified Technician with over a decade of hands-on experience in automotive repair and diagnostics.

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