Exploring Elevator Guide Rail Roller Shoes: Grades, Properties, and Practical Industrial Uses

Types of Elevator Guide Rail Roller Shoes

Elevator guide rail roller shoes are essential components in vertical transportation systems, ensuring the safe, stable, and smooth movement of elevator cars. By guiding the car along the rails, these shoes reduce vibration, distribute weight evenly, and minimize wear on the system. Selecting the right type of guide shoe is crucial for optimizing performance, comfort, and longevity based on building height, load capacity, speed, and environmental conditions.

Conventional Guide Shoes

Featuring a robust metal frame with resilient rubber rollers, conventional guide shoes offer reliable performance for standard elevator applications.

Advantages

• Durable and long-lasting
• Low maintenance requirements
• Effective vibration damping
• Cost-effective solution

Limitations

• Not ideal for high-speed elevators
• Rollers may degrade over time under heavy use
• Limited adjustability

Best for: Low to mid-rise buildings, residential and light commercial elevators

Roller Guide Shoes

Equipped with multiple small rollers arranged in a triangular configuration, these shoes provide even load distribution and minimal friction.

Advantages

• Smooth, quiet operation
• Reduced rolling resistance
• Excellent for high-speed travel
• Handles heavy loads efficiently

Limitations

• Higher initial cost
• More complex maintenance
• Sensitive to misalignment

Best for: High-rise buildings, commercial towers, high-speed passenger elevators

Sliding Guide Shoes

Utilizing a sliding contact mechanism between the shoe and rail, this design emphasizes simplicity and quiet movement.

Advantages

• Simple, robust design
• Very quiet operation
• Lower manufacturing cost
• Fewer moving parts

Limitations

• Higher friction compared to rollers
• Increased wear on rails over time
• Not suitable for high-speed applications

Best for: Residential buildings, low-speed elevators, small commercial installations

Maglev Guide Shoes

Using magnetic levitation technology, these advanced guide shoes suspend the elevator car without physical contact with the rails.

Advantages

• Near-zero friction and wear
• Extremely smooth and silent ride
• High-speed capability
• Precision control and minimal vibration

Limitations

• Very high installation and maintenance costs
• Requires specialized infrastructure
• Complex engineering and calibration

Best for: Ultra-high-rise buildings, cutting-edge smart buildings, research facilities

Heavy-Duty Guide Shoes

Built for extreme conditions with reinforced steel frames and durable rollers, these shoes withstand heavy loads and harsh environments.

Advantages

• Exceptional strength and durability
• Resistant to contaminants and temperature extremes
• Ideal for industrial applications
• Long service life under stress

Limitations

• Bulkier design
• Higher weight adds to system load
• More expensive than standard models

Best for: Freight elevators, industrial plants, warehouses, mining operations

Adjustable Guide Shoes

Featuring modular and tunable components, these shoes allow for real-time alignment adjustments to compensate for building settlement or rail deformation.

Advantages

• On-site alignment correction
• Adaptable to structural shifts
• Extends system lifespan
• Improves ride quality over time

Limitations

• Requires skilled technicians for adjustment
• Slightly more complex design
• Potential for improper setup if not calibrated correctly

Best for: Older buildings, structures prone to settling, retrofit installations

Type	Speed Suitability	Noise Level	Durability	Best Application
Conventional	Low-Medium	Low	High	Mid-rise residential, light commercial
Roller Guide	High	Very Low	Very High	High-rise offices, skyscrapers
Sliding Guide	Low	Very Low	Medium	Residential, small buildings
Maglev	Very High	Negligible	High (with maintenance)	Smart buildings, futuristic installations
Heavy-Duty	Low-Medium	Medium	Exceptional	Industrial, freight, extreme environments
Adjustable	Low-High	Low	High	Older buildings, variable conditions

Expert Tip: Regular inspection and lubrication of roller guide shoes—especially in high-rise elevators—can significantly extend their lifespan and maintain ride smoothness. For adjustable models, periodic alignment checks are recommended to ensure optimal performance as buildings settle over time.

Function and Features of Elevator Guide Rail Roller Shoes

Elevator guide rail roller shoes are essential components in modern vertical transportation systems, playing a pivotal role in ensuring the safe, smooth, and efficient movement of elevator cars within hoistways. These precision-engineered parts interface directly with the guide rails to maintain alignment, minimize vibration, and support dynamic loads throughout the elevator’s operation. Their performance directly affects ride quality, system longevity, and passenger safety.

Core Functions of Elevator Guide Rail Roller Shoes

Stability

Roller shoes stabilize the elevator car by constraining lateral and torsional motion during travel. This prevents swaying, tilting, or oscillation—especially at higher speeds or during sudden stops—ensuring a平稳 and secure ride. Advanced roller shoe designs incorporate spring-loaded or elastomeric damping mechanisms to further enhance stability under variable load conditions.

Load Support

These components bear the entire weight of the elevator car, counterweight, and passengers, transferring these loads evenly to the guide rails. By distributing forces across multiple contact points, roller shoes reduce localized stress on both the car frame and the rails, helping prevent deformation and premature fatigue in the structural system.

Friction Reduction

Equipped with precision ball or roller bearings, elevator roller shoes significantly reduce sliding friction between the moving car and stationary guide rails. This allows for smoother acceleration and deceleration, reduces motor load, improves energy efficiency, and extends the service life of both the rollers and rails by minimizing abrasive wear.

Alignment Maintenance

Roller shoes ensure continuous alignment of the elevator car with the vertical guide rails. Even minor misalignments can lead to binding, increased noise, or accelerated wear. Properly functioning roller shoes maintain precise tracking along the rail path, which is critical for safe door operation, accurate leveling at floors, and overall system reliability.

Vibration and Shock Damping

Modern roller shoes often integrate elastomeric bushings, rubber inserts, or hydraulic dampers to absorb shocks from rail joints, guide rail imperfections, or abrupt stops. This damping capability enhances passenger comfort by reducing noise and jolts, while also protecting sensitive elevator components such as control systems and door mechanisms from vibration-induced damage.

Key Features of High-Performance Elevator Roller Shoes

Durability: Constructed from high-strength steel, hardened alloys, or reinforced composite materials, roller shoes are built to endure millions of cycles under heavy loads and varying environmental conditions. Many models feature heat-treated or case-hardened surfaces to resist wear, pitting, and corrosion—especially in humid or industrial environments.

Precision Engineering: Manufactured to tight tolerances using CNC machining and advanced quality control, roller shoes ensure consistent performance. Integrated ball or needle bearings provide near-frictionless rotation, enabling silent operation and minimal resistance. Precision fit also reduces play and backlash in the guide system.

Adjustability: Many roller shoe models include threaded adjusters or eccentric cams that allow technicians to fine-tune the position and pressure of the rollers against the guide rails. This adjustability compensates for rail misalignment, wear over time, or manufacturing variances, ensuring optimal contact and performance throughout the system's lifecycle.

Compatibility: Designed to work with standard guide rail profiles—including T-rails, flat rails, and V-shaped rails—roller shoes offer versatility across different elevator makes and models. Universal mounting configurations and modular designs simplify retrofitting and reduce inventory needs for maintenance teams.

Low-Maintenance Design: Sealed bearings prevent the ingress of dust, moisture, and debris, eliminating the need for frequent lubrication. Some models use self-lubricating polymers or wear-resistant coatings that extend service intervals. This reduces downtime, lowers maintenance costs, and supports clean-room or hygienic environments like hospitals and laboratories.

Feature	Benefit	Common Applications
Sealed Bearings	Prevents contamination; extends service life	High-rise buildings, humid climates
Adjustable Mounts	Enables precise alignment; compensates for wear	Retrofits, older installations
Hardened Steel Rollers	Resists wear and deformation under heavy loads	Freight elevators, industrial lifts
Elastomeric Dampers	Reduces noise and vibration for smooth ride	Residential buildings, luxury hotels
Composite Housing	Lightweight, corrosion-resistant, low-noise	Hospitals, cleanrooms, coastal areas

Important: Regular inspection and maintenance of roller shoes are crucial for elevator safety. Worn, misaligned, or damaged roller shoes can lead to excessive noise, poor ride quality, rail damage, or even derailment in extreme cases. Always follow manufacturer guidelines and local safety codes when inspecting or replacing roller shoes. Prompt replacement of degraded components ensures continued safe operation and compliance with elevator regulations.

Scenarios of Elevator Guide Rail Roller Shoes

Elevator guide rail roller shoes are critical components that ensure smooth, stable, and quiet vertical transportation in various types of elevating systems. These roller shoes reduce friction between the elevator car and guide rails, minimizing wear and enhancing ride comfort. Below are detailed applications across different elevator types and operational environments.

Passenger Elevators

Widely used in office buildings, hotels, and residential complexes, passenger elevators rely on precision-engineered guide rail roller shoes to deliver a quiet and comfortable ride. These roller shoes dampen vibrations and maintain alignment, even during frequent starts and stops. Brands like Otis incorporate advanced roller shoe designs that meet strict noise and performance standards, making them ideal for high-traffic environments where passenger comfort is paramount.

Key Benefit: Enhanced ride quality with minimal noise and reduced maintenance frequency.

Construction Lifts

Also known as construction hoists or material lifts, these temporary elevating systems operate in rugged conditions on building sites. Guide rail roller shoes in construction lifts are built for durability, handling heavy loads of materials and workers while enduring dust, moisture, and temperature fluctuations. Their robust design ensures consistent tracking along guide rails, preventing misalignment and enhancing safety during vertical transport.

Durability Note: Often constructed with sealed bearings and corrosion-resistant materials to withstand harsh job site conditions.

Escalators and Moving Walks

While not traditional elevators, escalators and moving walks use roller shoe technology on inclined or horizontal guide tracks to maintain smooth, continuous movement. These roller shoes support the steps or pallets and ensure precise alignment throughout the system’s loop. In high-traffic areas like airports and shopping malls, they contribute to reliable operation under constant use and varying passenger loads.

Design Feature: Low-friction polymers and self-lubricating components reduce energy consumption and maintenance needs.

Service Elevators

Commonly referred to as freight or dumbwaiter elevators, service elevators are designed to transport heavy cargo, food trays, or medical supplies between floors. The guide rail roller shoes in these systems are reinforced to handle significantly higher loads than standard passenger elevators. They provide stability during loading/unloading cycles and maintain alignment despite uneven weight distribution.

Load Capacity: Engineered for extended service life under repetitive heavy-duty operation in hospitals, hotels, and industrial facilities.

High-Speed Elevators

Installed in skyscrapers and high-rise buildings, high-speed elevators require aerodynamically optimized guide rail roller shoes to minimize wind resistance and vibration at speeds exceeding 3 meters per second. These roller shoes are precision-tuned to maintain stability and reduce noise, even during rapid acceleration and deceleration. Advanced damping systems are often integrated to enhance passenger comfort.

Innovation Focus: Use of lightweight composite materials and streamlined profiles to improve efficiency and reduce energy usage.

Traction and Hydraulic Elevators

Both traction (cable-driven) and hydraulic (piston-driven) elevators utilize guide rail roller shoes, though their operational demands differ. Traction elevators benefit from low-friction roller shoes that support smooth travel over long distances, while hydraulic elevators—typically used in low- to mid-rise buildings—require roller shoes that handle slower, steady movement with consistent alignment. The roller shoes are tailored to match the dynamics of each lifting mechanism.

Compatibility Tip: Ensure roller shoes are matched to the specific elevator drive system for optimal performance and safety.

Outdoor Elevators

Found in scenic overlooks, beachfront properties, or cliffside resorts, outdoor elevators are exposed to rain, UV radiation, salt air, and temperature extremes. Their guide rail roller shoes are made from weather-resistant materials with protective seals to prevent water ingress and corrosion. These features ensure uninterrupted operation and long service life despite challenging environmental conditions.

Environmental Protection: Stainless steel components and UV-stable polymers enhance longevity in exposed installations.

Specialized Elevators

In specialized environments such as hospitals, laboratories, libraries, and cleanrooms, elevators have unique operational requirements. Hospital elevators must accommodate stretchers and sensitive medical equipment, requiring ultra-smooth starts and stops. Library elevators handle heavy book carts, demanding high load tolerance. Roller shoes in these applications are customized for specific load profiles, noise levels, and cleanliness standards (e.g., non-marking, low-dust materials).

Customization Advantage: Tailored solutions ensure compliance with industry-specific safety and operational regulations.

Professional Insight: When selecting guide rail roller shoes, consider the operating environment, load requirements, speed, and expected maintenance intervals. High-quality roller shoes not only improve ride quality but also extend the lifespan of guide rails and reduce overall system wear. For critical applications, opt for OEM-recommended or certified aftermarket components to ensure reliability and compliance with safety standards.

Elevator Type	Primary Function	Roller Shoe Features	Operating Environment
Passenger Elevators	Transport people comfortably	Low-noise, vibration-dampening	Indoor, high-traffic
Construction Lifts	Moving materials and workers	Durable, sealed bearings	Outdoor, dusty, rugged
Escalators & Moving Walks	Continuous foot traffic transport	Self-lubricating, low-friction	Indoor/outdoor, high-use
Service Elevators	Frequent heavy cargo transport	Reinforced, high-load capacity	Commercial, industrial
High-Speed Elevators	Fast vertical transit in tall buildings	Aerodynamic, precision-balanced	Indoor, high-rise
Traction/Hydraulic Elevators	General vertical transport	System-specific design	Varies by type
Outdoor Elevators	Scenic or access lifts	Weather-resistant, corrosion-proof	Exposed to elements
Specialized Elevators	Industry-specific transport	Customized for load/noise	Controlled or unique settings

Additional Considerations for Roller Shoe Selection

• Maintenance Intervals: Sealed roller shoes require less frequent servicing, ideal for hard-to-access installations.
• Noise Reduction: Rubber-damped or polyurethane rollers minimize operational sound in noise-sensitive areas.
• Energy Efficiency: Low-friction designs reduce motor load and energy consumption over time.
• Material Compatibility: Match roller shoe materials to guide rail type (steel, aluminum) to prevent premature wear.
• Safety Compliance: Ensure roller shoes meet local and international safety codes (e.g., EN 81, ASME A17.1).

How to Choose Elevator Guide Rail Roller Shoes: A Comprehensive Guide

Selecting the right elevator guide rail roller shoes is a critical decision that directly impacts the safety, efficiency, and longevity of an elevator system. These components play a vital role in guiding the elevator car and counterweight along the rails, minimizing vibration, reducing noise, and ensuring smooth vertical movement. Making an informed choice involves evaluating several interrelated technical and operational factors. This guide provides a detailed breakdown of the key considerations to help engineers, maintenance professionals, and facility managers make optimal selections for their specific elevator applications.

Safety Note: Always consult the elevator manufacturer’s specifications and local safety codes (such as ASME A17.1 or EN 81) before replacing or upgrading roller shoes. Incorrect installation or incompatible components can lead to derailment, excessive wear, or catastrophic system failure.

Key Factors in Selecting Elevator Guide Rail Roller Shoes

• Load Capacity

  One of the most critical specifications, load capacity refers to the maximum weight the roller shoes can safely support under dynamic operating conditions. This includes not only the static weight of the elevator car and its rated passenger load but also dynamic forces generated during acceleration, deceleration, and emergency stops. Roller shoes are engineered with specific load ratings based on the strength of their frame, axle, bearings, and roller material.

  Choosing roller shoes with insufficient load capacity can lead to premature fatigue, deformation, or structural failure, posing serious safety risks. Conversely, selecting shoes with excessively high load ratings may result in unnecessary costs and potentially stiffer ride characteristics due to over-engineered components. Always match the roller shoe’s rated load to the elevator’s total operating weight as specified in the system design documentation.

• Rail Compatibility

  Roller shoes must be precisely matched to the profile and dimensions of the existing guide rails—common types include T-rails (e.g., 55 mm, 75 mm, 100 mm) and modular rails. The roller configuration (single, double, or triple rollers), spacing, and alignment must correspond exactly to the rail’s geometry to ensure proper contact and guidance.

  Incompatible roller shoes can cause misalignment, uneven pressure distribution, increased friction, accelerated rail wear, and excessive noise. In severe cases, improper fit may lead to binding or derailment. Always verify the rail type, width, and mounting dimensions before selecting replacement or upgrade components. Manufacturer cross-reference charts and technical drawings are essential tools for ensuring compatibility.

• Quality and Durability

  The longevity and performance of roller shoes depend heavily on the quality of materials and manufacturing processes. High-performance roller shoes typically feature hardened steel rollers, precision ball or roller bearings, and robust housing made from cast iron, ductile iron, or high-strength steel.

  Premium materials resist wear, corrosion, and deformation under continuous stress. Look for components with heat-treated rollers and sealed bearings to extend service life. While higher-quality shoes may have a greater upfront cost, they often provide better long-term value through reduced maintenance, fewer replacements, and improved ride quality. Certifications such as ISO 9001 or compliance with elevator safety standards can serve as indicators of manufacturing quality.

• Maintenance Requirements

  Different roller shoe designs have varying maintenance needs. Traditional models with open bearings may require regular lubrication and inspection, while modern sealed-bearing or self-lubricating polymer roller shoes are designed for minimal maintenance.

  Consider the accessibility of the elevator shaft and the availability of maintenance personnel when selecting components. In high-traffic or hard-to-access buildings, low-maintenance roller shoes can significantly reduce downtime and labor costs. Additionally, some advanced roller shoes come with wear indicators or monitoring systems that alert technicians when replacement is needed, enabling predictive maintenance strategies.

• Environmental Considerations

  The operating environment plays a significant role in roller shoe performance and lifespan. Factors such as temperature extremes, humidity, dust, moisture, and exposure to corrosive chemicals (e.g., in industrial or marine environments) can degrade materials and lubricants.

  For harsh conditions, select roller shoes with corrosion-resistant coatings (e.g., zinc plating or powder coating), sealed bearings, and weather-resistant materials. In cold climates, ensure lubricants remain effective at low temperatures. In dusty environments, sealed housings prevent contamination of internal components. For outdoor or high-humidity installations, stainless steel or composite materials may be preferable to prevent rust and degradation.

Selection Factor	Key Evaluation Criteria	Risks of Poor Selection	Recommended Verification Methods
Load Capacity	Match to total elevator operating weight including dynamic loads	Structural failure, excessive wear, safety hazards	Review manufacturer load charts, consult elevator specs
Rail Compatibility	Rail type, profile dimensions, roller alignment	Binding, misalignment, noise, derailment risk	Use technical drawings, measure rails, check OEM specs
Quality & Durability	Material grade, bearing type, manufacturing standards	Shortened lifespan, frequent replacements	Inspect material certifications, look for ISO compliance
Maintenance Needs	Lubrication frequency, wear monitoring features	Increased downtime, higher labor costs	Review maintenance manuals, assess site accessibility
Environmental Resistance	Corrosion protection, temperature tolerance, sealing	Component degradation, lubricant failure	Evaluate installation environment, choose appropriate coatings

Expert Tip: When upgrading or replacing roller shoes, consider conducting a full system audit of the guide rails, brackets, and alignment. Worn or misaligned rails can compromise even the highest-quality roller shoes. Regular inspections (recommended every 6–12 months) help maintain optimal performance and extend the life of both the shoes and the rails.

Additional Selection Best Practices

• Always source roller shoes from reputable manufacturers or certified suppliers to ensure authenticity and performance consistency.
• Keep detailed records of roller shoe specifications, installation dates, and maintenance history for each elevator.
• Train maintenance staff on proper inspection techniques, including checking for roller wear, bearing play, and frame cracks.
• Consider retrofitting older systems with modern low-noise, low-vibration roller shoe designs to improve passenger comfort.
• When in doubt, consult with the elevator OEM or a qualified elevator engineer before making changes to critical guidance components.

Choosing the right elevator guide rail roller shoes is not just about matching parts—it's about ensuring the safety, reliability, and comfort of the entire elevator system. By carefully evaluating load requirements, rail compatibility, material quality, maintenance needs, and environmental conditions, you can make a well-informed decision that enhances performance and reduces long-term operational costs. Remember, the guidance system is a foundational element of elevator safety; never compromise on quality or proper installation procedures.

Elevator Guide Rail Roller Shoes: Frequently Asked Questions

Q1: What are the common types of elevator guide rail roller shoes?

Elevator guide rail roller shoes play a crucial role in ensuring smooth and stable elevator operation by minimizing friction and guiding the car along the rails. There are several common types, each designed for specific performance needs and operating conditions:

• Rubber Shoes: Known for excellent vibration absorption and noise reduction, rubber shoes are ideal for low-to-mid-speed elevators where ride comfort is a priority. They provide good grip but may wear faster under heavy loads or high temperatures.
• Nylon Shoes: Offering superior durability and resistance to wear and heat, nylon shoes are commonly used in medium-speed applications. They maintain dimensional stability and require less frequent replacement than rubber variants.
• Roller Shoes (Roller Guides): These use rotating rollers instead of sliding surfaces, significantly reducing friction. Roller shoes are typically found in high-speed elevators, enabling smoother travel and reduced energy consumption. They require regular lubrication and maintenance to ensure optimal performance.
• Steel Shoes: Rarely used in modern passenger elevators due to high noise and wear, steel shoes are sometimes found in industrial or freight elevators where extreme durability is required and ride comfort is secondary.

The choice of shoe type depends on factors such as elevator speed, load capacity, building height, and desired noise levels. Regular inspection and timely replacement are essential to maintain safety and performance.

Q2: What are the three main components of an elevator guide rail roller shoe?

An elevator guide rail roller shoe is a precision-engineered assembly composed of three key components that work together to ensure proper alignment, stability, and motion control of the elevator car:

• Frame (or Bracket): This is the structural base that attaches the roller shoe to the elevator car's guide rail mounting structure. It must be rigid and precisely aligned to maintain consistent contact with the guide rail. The frame is typically made from cast iron, steel, or reinforced aluminum for strength and durability.
• Wheel/Roller: Mounted within the frame, the wheel or roller rotates as the elevator moves, reducing friction between the shoe and the guide rail. In roller guide systems, ball or roller bearings allow smooth, low-resistance movement. The wheels are often made from hardened steel, polyurethane, or composite materials depending on application requirements.
Rubber or Nylon Shoe (Guide Pad): Positioned between the frame and the rail (or integrated with the roller assembly), this component absorbs vibrations, dampens noise, and provides lateral stability. Rubber offers better shock absorption, while nylon provides longer wear life and resistance to environmental factors like moisture and temperature changes.

Proper assembly and alignment of these components are critical to prevent excessive wear, noise, and potential derailment risks. Technicians must follow manufacturer specifications during installation and maintenance.

Q3: What are the primary functions of an elevator guide rail roller shoe?

Elevator guide rail roller shoes are essential safety and performance components that serve three core functions in elevator systems:

• 1. Smooth Ride Quality: By minimizing friction and absorbing vibrations between the elevator car and the guide rails, roller shoes significantly enhance passenger comfort. This is especially important in high-rise buildings where long travel distances can amplify noise and shaking if not properly damped.
• 2. Lateral Stability and Alignment: The shoes keep the elevator car securely aligned with the guide rails, preventing swaying, tilting, or lateral movement during ascent and descent. This ensures safe operation and prevents binding or jamming within the hoistway.
• 3. Structural Support and Load Distribution: Roller shoes help distribute the weight of the elevator car and its passengers evenly across the guide rails. This reduces stress on individual components and extends the lifespan of both the guide system and the car structure.

Together, these functions contribute to safe, quiet, and efficient elevator operation. Regular maintenance, including lubrication, alignment checks, and wear inspections, is necessary to preserve these critical functions over time.

Q4: What are the two main types of elevators, and how do they relate to guide rail systems?

The two primary types of elevators are hydraulic and traction elevators, each with distinct operating mechanisms and implications for guide rail and roller shoe design:

Feature	Hydraulic Elevators	Traction Elevators
Operating Principle	Uses a hydraulic piston and fluid system to lift and lower the car. Typically limited to low-rise buildings (up to 6 floors).	Uses steel ropes or belts connected to a motor-driven sheave (pulley) system. Can operate in mid- to high-rise buildings.
Speed Range	Low speed (typically up to 150 ft/min).	Medium to high speed (150–2,000+ ft/min).
Guide Rail Requirements	Lower dynamic forces; often use simpler guide systems with rubber or nylon shoes.	Higher speeds and loads require precision guide rails and advanced roller guides with bearings for smooth, stable travel.
Roller Shoe Type	Commonly use sliding guide shoes (rubber/nylon) due to lower speeds and smoother operation.	Frequently use roller guide shoes with ball or roller bearings to reduce friction and handle rapid movement.
Maintenance Needs	Less frequent guide system maintenance; focus is on hydraulic components.	Requires regular inspection of guide rails, rollers, and alignment due to higher operational stresses.

While both types rely on guide rail roller shoes for stability and safety, traction elevators demand higher precision and more robust components due to their speed and height capabilities. Proper selection and maintenance of guide shoes are essential for reliable performance in either system.