BMW 340i 2012-2018 Suspension Bolt Torque Specifications
Detailed torque specifications for all suspension bolts on the 2012-2018 BMW 340i, covering F30, F31, F32, F33, and F36 chassis variants. Includes front and rear suspension components.
Important Information
Safety guidelines and reference information for proper torque application
Safety First
- Always verify torque specifications with your vehicle's factory service manual
- Use properly calibrated torque wrenches
- Replace all torque-to-yield (TTY) bolts - they are single-use only
- When in doubt, consult a professional mechanic
Quick Reference Guide
Quick Reference Guide
Common Torque Patterns
Star Pattern
Used for wheels and other circular bolt patterns
Cross Pattern
Used for gaskets and cover plates
Sequential Pattern
Used for head bolts and other critical components
Common Mistakes to Avoid
Common Mistakes to Avoid
Over-tightening
Exceeding the specified torque value can stretch or break fasteners, damage threads, or crack components.
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.
Follow the manufacturer's specified torque sequence pattern.
Dirty Threads
Dirt, rust, or old thread locker can affect torque readings and proper fastener tension.
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.
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.
Check if specs are for dry or lubricated threads. Use specified lubricant when required.
Recommended Tools
Recommended Tools
Torque Wrench (1/4" Drive)
Torque Wrench (3/8" Drive)
Torque Wrench (1/2" Drive)
Angle Gauge
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
Front Strut Assembly
Specifications for fasteners related to the front strut assembly, including mounting to the chassis and steering knuckle.
1 Strut Mounting Bolts to Chassis
M12 x 1.5
Strut Mounting Bolts to Chassis
M12 x 1.5Torque Value
Important Notes
2 Strut Pinch Bolt to Steering Knuckle
M14 x 1.5
Strut Pinch Bolt to Steering Knuckle
M14 x 1.5Torque Value
Important Notes
Front Control Arms
Specifications for fasteners related to the front control arms, including mounting to the subframe and steering knuckle.
1 Control Arm Bolts to Subframe/Chassis
M14 x 1.5
Control Arm Bolts to Subframe/Chassis
M14 x 1.5Torque Value
Important Notes
2 Ball Joint Nut to Control Arm
M12 x 1.5
Ball Joint Nut to Control Arm
M12 x 1.5Torque Value
Important Notes
Steering Linkage
Specifications for fasteners related to the steering linkage, including tie rod ends.
1 Tie Rod End Nut to Steering Knuckle
M12 x 1.25
Tie Rod End Nut to Steering Knuckle
M12 x 1.25Torque Value
Important Notes
Sway Bar
Specifications for fasteners related to the sway bar, including links and mounting brackets.
1 Sway Bar Link Nut
M10 x 1.25
Sway Bar Link Nut
M10 x 1.25Torque Value
Important Notes
2 Sway Bar Mounting Bracket Bolts to Subframe/Body
M8 x 1.25
Sway Bar Mounting Bracket Bolts to Subframe/Body
M8 x 1.25Torque Value
Important Notes
Rear Subframe
Specifications for fasteners related to the rear subframe.
1 Rear Subframe Mounting Bolts to Chassis
M14 x 1.5
Rear Subframe Mounting Bolts to Chassis
M14 x 1.5Important Notes
Rear Control Arms
Specifications for fasteners related to the rear control arms, including mounting to the hub carrier.
1 Rear Lower Control Arm to Hub Carrier (Knuckle) Bolts
M14 x 1.5
Rear Lower Control Arm to Hub Carrier (Knuckle) Bolts
M14 x 1.5Torque Value
Important Notes
2 Rear Upper Control Arm to Hub Carrier (Knuckle) Bolts
M14 x 1.5
Rear Upper Control Arm to Hub Carrier (Knuckle) Bolts
M14 x 1.5Torque Value
Important Notes
Troubleshooting Guide
Common issues, diagnostic steps, and prevention guidelines
Common Issues
Bolt stretching, stripped threads, uneven torque patterns
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
Diagnostic Steps
Visual inspection, torque verification, thread assessment
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
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
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
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 Why is using the correct torque specification so important?
Why is using the correct torque specification so important?
Using the correct torque specification ensures that bolts are neither too loose, which can lead to component failure or loosening over time, nor too tight, which can stretch or break the bolt or damage the surrounding components. For example, an under-torqued control arm bolt could allow excessive movement, leading to instability and premature wear. An over-torqued bolt might break or strip its threads upon installation or during driving.
Q2 Do I need to use new bolts when replacing suspension components?
Do I need to use new bolts when replacing suspension components?
While not always mandatory, BMW often recommends using new bolts, especially for critical suspension parts. This is because many bolts are designed to stretch slightly when tightened to their specified torque, a process known as 'torque-to-yield.' Reusing these bolts can result in an incorrect clamping force and potential failure. For example, using old bolts on the strut assembly could lead to compromised structural integrity.
Q3 What type of lubricant should I use on suspension bolts?
What type of lubricant should I use on suspension bolts?
Generally, it is not recommended to apply lubricant to the threads of suspension bolts unless specifically indicated by BMW. The torque specifications are usually calibrated for dry threads. Applying lubricant can alter the friction and lead to over-torquing, even with the correct torque wrench setting. Some bolts may have a thread locker applied from the factory, which is typically replaced if the bolt is replaced.
Q4 How often should I check my suspension bolt torque?
How often should I check my suspension bolt torque?
It's a good practice to check your suspension bolt torque after performing any work on the suspension system, usually after driving a short distance (e.g., 50-100 miles) as the bolts can settle or stretch. After that, you should inspect your suspension at every service and re-torque as needed. If you regularly drive on rough roads, more frequent checks might be beneficial. For example, after replacing front struts, rechecking the torque of the strut mount bolts after a week would be advisable.
Q5 What is the difference between Nm and ft-lb for torque specifications?
What is the difference between Nm and ft-lb for torque specifications?
Nm (Newton-meters) and ft-lb (foot-pounds) are different units of torque. BMW usually provides torque specifications in Nm. 1 ft-lb is approximately equal to 1.356 Nm. You must use a torque wrench capable of measuring in the correct units and convert correctly if needed. For example, if a spec is 100 Nm, and your wrench is in ft-lb, you must convert to ~73.7 ft-lbs.
Environmental Considerations
Temperature, humidity, and seasonal effects on torque specifications
Temperature Effects
Includes: High Heat, Cold Weather, Thermal Cycling
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
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
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
Torque Wrench
A calibrated torque wrench is essential for tightening fasteners to the correct specification. This will ensure safe and reliable suspension operation.
- Wide torque range (typically 20-150 ft-lbs for suspension components)
- Click-type or digital display for accurate readings
- Ability to set torque in ft-lbs or Nm
Socket Set
A comprehensive socket set with various sizes, including metric, is needed for all bolt and nut sizes encountered in the suspension system.
- Variety of sizes from 8mm to 24mm (or larger for wheel bolts)
- 6-point sockets preferred for better grip and less rounding of bolt heads
- Deep sockets for accessing recessed fasteners
Allen Key/Hex Bit Set
Allen keys or hex bits on sockets are needed for certain suspension components, especially strut top bolts and sway bar links.
- Metric sizes from 5mm to 10mm common
- Hardened steel construction for durability
- Ball-end hex keys can be useful for angled access
Open End/Combination Wrenches
Open end and combination wrenches will be needed as backups or for access in areas where sockets will not fit.
- Metric sizes to match socket set
- Combination styles are generally preferred
- Thin style wrenches for access in tight areas
Service Procedures
Front Strut Removal and Installation
Detailed procedure for removing and installing the front strut assembly, including proper torque specs for all associated fasteners.
- Loosen wheel bolts, raise and secure the vehicle on jack stands, and remove the wheels.
- Disconnect the sway bar end link from the strut assembly.
- Disconnect brake line and ABS sensor wiring from strut assembly.
- Loosen the two strut mount bolts under the hood.
- Remove the lower strut mounting bolt.
- Carefully remove the strut assembly from the wheel well.
- Install in reverse order, torquing all fasteners to spec.
- Reconnect all connections and wiring and remount wheel and lower the vehicle
Rear Shock Absorber Removal and Installation
Detailed procedure for removing and installing the rear shock absorber, including proper torque specs for all associated fasteners.
- Loosen wheel bolts, raise and secure the vehicle on jack stands, and remove the wheels.
- Remove any trim or coverings as needed to access the shock absorber.
- Loosen the top shock absorber mount nut.
- Loosen the lower mounting bolt.
- Remove the shock absorber.
- Install in reverse order, torquing all fasteners to spec.
- Remount wheel and lower the vehicle
Sway Bar End Link Replacement
Step-by-step instructions for replacing the sway bar end links, noting the correct torque for mounting bolts and nuts.
- Loosen wheel bolts, raise and secure the vehicle on jack stands, and remove the wheels.
- Support the sway bar and remove upper and lower mounting nuts/bolts on end link
- Remove the old end link
- Install new end link, tightening top and bottom mounting fasteners to spec.
- Remount wheel and lower the vehicle
Technical Service Bulletins
Updated Torque Specifications for Front Control Arm Bolts
2015-06-15BMW issued a bulletin regarding updated torque specifications for front control arm bolts to address premature bushing wear and potential suspension issues. All models within the F30 range, including the 340i, may be affected.
Resolution: Verify and apply updated torque values on all front control arm bolts during maintenance. See detailed bulletin for torque values.
Rear Subframe Mounting Bolt Torque Check
2017-11-20Technical bulletin regarding the importance of verifying the torque of the rear subframe mounting bolts due to potential loosening from repeated thermal cycling.
Resolution: Check and re-torque the rear subframe mounting bolts to the updated specifications during routine servicing. See bulletin for torque values.
Front Strut Top Nut Torque Recommendation
2013-03-01A bulletin was released to provide best practices for properly torquing the top strut mount nut, as over-tightening may cause damage and under-tightening could lead to suspension issues
Resolution: Tighten the front strut mount nuts to the specified torque value using a calibrated torque wrench. Do not over or under tighten. See bulletin for torque values.
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Technical Information
- All specifications, including torque values, fluid capacities, and maintenance procedures, should be verified against your vehicle's factory service manual.
- Vehicle specifications and procedures may vary by model year, trim level, and region.
- Always follow the manufacturer's recommended procedures and safety precautions.
- Working on vehicles can be dangerous. Always take proper safety precautions and use appropriate safety equipment.
- If you're unsure about any procedure, consult a qualified professional mechanic.