Audi Audi S4 1991-1994 Suspension Bolt Torque Specifications
Comprehensive guide to suspension bolt torque specifications for the 1991-1994 Audi S4 (C4 chassis). Includes torque values for various suspension components, ensuring proper installation and safety.
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
Torque specifications for components related to the front strut assembly, including the upper mount, strut-to-spindle bolts, and piston rod nut.
1 Upper Strut Mount to Body Bolts
M8 x 1.25
Upper Strut Mount to Body Bolts
M8 x 1.25Torque Value
Important Notes
2 Strut to Spindle/Steering Knuckle Bolts
M12 x 1.5
Strut to Spindle/Steering Knuckle Bolts
M12 x 1.5Torque Value
Important Notes
3 Strut Piston Rod Nut
M14 x 1.5
Strut Piston Rod Nut
M14 x 1.5Torque Value
Important Notes
Front Control Arms
Torque specifications for upper and lower control arm bolts, including inner pivot and spindle/knuckle connections.
1 Upper Control Arm Inner Pivot Bolt (to Frame)
M12 x 1.5
Upper Control Arm Inner Pivot Bolt (to Frame)
M12 x 1.5Important Notes
2 Upper Control Arm to Spindle/Steering Knuckle Bolt (Pinch Bolt)
M10 x 1.5
Upper Control Arm to Spindle/Steering Knuckle Bolt (Pinch Bolt)
M10 x 1.5Important Notes
3 Lower Control Arm Inner Pivot Bolt (to Frame/Subframe)
M12 x 1.5
Lower Control Arm Inner Pivot Bolt (to Frame/Subframe)
M12 x 1.5Important Notes
4 Lower Control Arm Ball Joint Nut (to Spindle)
M12 x 1.5
Lower Control Arm Ball Joint Nut (to Spindle)
M12 x 1.5Torque Value
Important Notes
Front Sway Bar
Torque specifications for front sway bar links and mounting brackets.
1 Sway Bar Link to Strut Bolt/Nut
M10 x 1.5
Sway Bar Link to Strut Bolt/Nut
M10 x 1.5Torque Value
Important Notes
2 Sway Bar Bracket to Body/Subframe Bolts
M8 x 1.25
Sway Bar Bracket to Body/Subframe Bolts
M8 x 1.25Torque Value
Important Notes
Rear Strut Assembly
Torque specifications for rear strut/shock components including upper mounts, lower control arm connections, and piston rod nuts.
1 Upper Shock Mount Bolts (to Body)
M8 x 1.25
Upper Shock Mount Bolts (to Body)
M8 x 1.25Torque Value
Important Notes
2 Lower Shock/Strut to Lower Control Arm Bolt
M12 x 1.5
Lower Shock/Strut to Lower Control Arm Bolt
M12 x 1.5Important Notes
3 Strut Piston Rod Nut
M14 x 1.5
Strut Piston Rod Nut
M14 x 1.5Torque Value
Important Notes
Rear Control Arms
Torque specifications for rear upper and lower control arm bolts, including inner and outer pivot points.
1 Upper Control Arm Inner Bolt (to body)
M12 x 1.5
Upper Control Arm Inner Bolt (to body)
M12 x 1.5Important Notes
2 Upper Control Arm Outer Bolt (to spindle)
M10 x 1.5
Upper Control Arm Outer Bolt (to spindle)
M10 x 1.5Important Notes
3 Lower Control Arm Inner Bolt (to body)
M12 x 1.5
Lower Control Arm Inner Bolt (to body)
M12 x 1.5Important Notes
4 Lower Control Arm Outer Bolt (to Spindle)
M12 x 1.5
Lower Control Arm Outer Bolt (to Spindle)
M12 x 1.5Important Notes
Rear Sway Bar
Torque specifications for rear sway bar links and mounting brackets.
1 Sway Bar Link to Control Arm Bolt/Nut
M10 x 1.5
Sway Bar Link to Control Arm Bolt/Nut
M10 x 1.5Torque Value
Important Notes
2 Sway Bar Bracket to Body/Subframe Bolts
M8 x 1.25
Sway Bar Bracket to Body/Subframe Bolts
M8 x 1.25Torque 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 are correct torque specifications so important for suspension bolts?
Why are correct torque specifications so important for suspension bolts?
Proper torque ensures the bolts are tightened to the manufacturer's specified tension. Under-torquing can lead to bolts loosening, resulting in suspension component failure, poor handling, and potential accidents. Over-torquing can stretch or damage bolts, leading to fatigue, failure, and difficulty with future removal. Correct torque creates the correct clamping force for secure component attachment.
Q2 Do I need to replace suspension bolts after removing them?
Do I need to replace suspension bolts after removing them?
It's highly recommended to replace one-time use torque-to-yield bolts. For standard bolts, inspect them for damage, such as stretching or thread issues. If damage is present, replace them. It’s good practice to replace any bolt that’s been removed, especially in high-stress areas of the suspension, to guarantee proper clamping force and prevent potential failures in the future.
Q3 Should I use thread locker on suspension bolts?
Should I use thread locker on suspension bolts?
Generally, thread locker is not required on the majority of suspension bolts if they are torqued correctly. However, certain bolts, such as those securing the subframe or control arm, may benefit from a medium-strength thread locker to prevent loosening under vibration, especially if the car is used in demanding driving conditions like track days or rally events. Always refer to the repair manual. If thread locker is used, torque specifications may need to be adjusted.
Q4 Can I reuse suspension nuts, or should those be replaced too?
Can I reuse suspension nuts, or should those be replaced too?
Self-locking nuts (nylock nuts) should always be replaced when removed. The locking insert is designed for single use, and reusing them can lead to loss of clamping force. Other types of nuts should also be inspected for damage before reuse, and if any damage is found, they should also be replaced.
Q5 What tools will I need to accurately torque suspension bolts?
What tools will I need to accurately torque suspension bolts?
You will need a calibrated torque wrench, sockets of the correct size, and potentially extensions or universal joints to access certain bolts. Using an accurate torque wrench that has been periodically calibrated ensures proper torque is applied. It’s also good practice to use a torque angle gauge for bolts that require a torque-to-yield spec.
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 (1/2" Drive)
A calibrated torque wrench is essential for tightening suspension bolts to the correct specifications.
- Accurate torque measurement
- Ratchet mechanism for ease of use
Torque Wrench (3/8" Drive)
A smaller torque wrench for lower torque fasteners on the suspension.
- Accurate torque measurement
- Smaller profile for tighter areas
Socket Set (Metric)
A comprehensive set of metric sockets to fit the various bolt and nut sizes on the suspension.
- Various sizes including 10mm, 13mm, 16mm, 17mm, 18mm, 19mm, 21mm, 22mm
- Deep sockets for recessed bolts
Socket Extensions
Extensions to access hard-to-reach bolts.
- Various lengths
- Allows access in recessed areas
Breaker Bar
Used to initially loosen stubborn, high torque suspension fasteners.
- Long handle for leverage
- Robust construction
Jack Stands
Essential for safely supporting the vehicle during suspension work.
- Heavy duty load capacity
- Adjustable height
Vehicle Jack
Used to lift the vehicle to install the jack stands.
- Appropriate lift rating for the Audi S4
- Easy to operate
Service Procedures
Front Suspension Lower Control Arm Bolt Torque Procedure
Proper procedure for tightening the lower control arm bolts to spec after suspension work.
- Raise and support the vehicle safely on jack stands.
- Loosely install the control arm bolts, and then install all other suspension components on that corner of the car.
- With the suspension at ride height (or with a simulated load), torque the front lower control arm bolts to 90 Nm + 1/4 turn.
- Double-check the torque on all fasteners.
- Lower the vehicle and remove the jack stands.
Rear Suspension Upper Control Arm Bolt Torque Procedure
Proper procedure for tightening the rear upper control arm bolts to spec after suspension work.
- Raise and support the vehicle safely on jack stands.
- Loosely install the upper control arm bolts, and then install all other rear suspension components on that corner of the car.
- With the suspension at ride height (or with a simulated load), torque the rear upper control arm bolts to 70 Nm + 1/4 turn.
- Double-check the torque on all fasteners.
- Lower the vehicle and remove the jack stands.
Front Strut Top Mount Nut Torque Procedure
Proper procedure for tightening the front strut top mount nuts to spec after suspension work.
- Raise and support the vehicle safely on jack stands.
- Loosely install the strut mount nuts.
- Torque the strut mount nuts to 25 Nm.
- Double-check the torque on all fasteners.
- Lower the vehicle and remove the jack stands.
Technical Service Bulletins
Suspension Bolt Loosening
1993-04-15Reports of suspension bolts loosening after improper tightening or reuse. This bulletin recommends replacing all torque-to-yield bolts after removal. Always follow torque specifications and procedure.
Resolution: Replace all suspension bolts with new ones, apply proper torque specs, and follow recommended procedures.
Control Arm Bolt Alignment
1992-08-22Some technicians have reported difficulty with control arm alignment during reinstallation. This bulletin emphasizes that control arm bushings must be in neutral position at ride height to avoid binding.
Resolution: Install suspension components with the car at ride height, or on simulated load, and torque the fasteners when the bushings are in their neutral position
Strut Top Mount Failure
1994-10-01Reports of the strut top mount failing prematurely. Improper torque and installation are leading factors. Ensure the strut top nuts and mounting bolts are torqued to the proper specs, and replace if necessary.
Resolution: Inspect strut top mounts for wear, replace if necessary, and follow proper torque specifications during installation.
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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.
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- If you're unsure about any procedure, consult a qualified professional mechanic.