Linear Guide Load Ratings Explained

Sep 17

Linear guide load ratings tell you how a profile rail carriage is expected to perform under static and repeated loading, but the numbers in a catalog do not all mean the same thing. The basic static load rating describes resistance to permanent deformation under a high stationary or peak load, while the basic dynamic load rating is used to calculate rolling-fatigue life during motion.

Other values—including directional load ratings, permissible moments, equivalent load, and static safety factor—help determine whether a guide can safely support the actual forces acting on an industrial machine.

The most important distinction is:

Static load rating tells you about maximum-load safety. Dynamic load rating helps predict fatigue life.

Neither number should be treated as a simple “maximum weight capacity.”

Key Takeaways

C generally represents the basic dynamic load rating.
C₀ generally represents the basic static load rating.
Dynamic load rating is used to calculate expected rolling-fatigue life.
Static load rating is used to evaluate maximum applied load and permanent deformation.
The static safety factor compares static capacity with maximum applied load.
Profile rail guides may carry radial, reverse-radial, and lateral loads.
Some guide families have equal ratings in all major directions; others do not.
Combined loads may need to be converted into an equivalent load.
Pitch, yaw, and roll moments must also be evaluated.
Catalog load ratings normally apply to an individual carriage unless the manufacturer states otherwise.
Four carriages do not automatically provide four times the usable system rating.
Load distribution depends on rail spacing, carriage spacing, center of gravity, alignment, and machine structure.
Dynamic load ratings from different catalogs should only be compared when their rating definitions are compatible.
A guide can have adequate load ratings but still lack sufficient rigidity for the application.

What Is a Linear Guide Load Rating?

A linear guide load rating is a standardized engineering value used to evaluate the load-carrying performance of a linear rolling bearing.

For profile rail guides, ratings commonly describe:

basic dynamic load capacity,
basic static load capacity,
load capacity in different directions,
permissible static moments.

These values are established from bearing geometry, rolling-element contact, material, raceway design, and standardized rating procedures.

They allow engineers to compare a candidate guide's capability with the forces acting on a machine.

But a catalog rating is not the same thing as saying:

“This carriage can safely carry exactly this many pounds.”

The real machine introduces:

load direction,
multiple carriages,
moments,
acceleration,
shock,
preload,
mounting errors,
contamination,
duty cycle.

Those factors must be incorporated into the selection.

The Two Load Ratings You Will See Most Often

The two primary values are:

Basic Dynamic Load Rating — C

The basic dynamic load rating is used when calculating the expected rolling-fatigue life of the guide.

It applies to repeated operation.

Basic Static Load Rating — C₀

The basic static load rating is used when evaluating whether a high stationary or peak load could produce excessive permanent deformation in the rolling contacts.

It is associated with maximum-load safety.

These ratings answer fundamentally different engineering questions.

Static vs. Dynamic Load Ratings at a Glance

RatingTypical SymbolPrimary PurposeBasic dynamic load ratingCCalculate rolling-fatigue lifeBasic static load ratingC₀Evaluate maximum-load safetyStatic permissible momentM₀ or manufacturer-specific notationEvaluate moment loadingEquivalent loadP or PERepresent combined loading for calculationMaximum applied loadPmaxUsed in static safety calculationStatic safety factorfSMargin between static capacity and maximum load

Manufacturer symbols can vary, so always confirm terminology in the applicable catalog.

What Is the Basic Static Load Rating?

The basic static load rating represents the static load associated with a defined amount of permanent deformation at the most heavily stressed rolling contact.

THK defines its basic static load rating as the constant-direction load at which the combined permanent deformation of the rolling element and raceway at the highest-stress contact equals 0.0001 times the rolling-element diameter.

This definition provides a standardized reference for evaluating whether a carriage is sufficiently protected from excessive permanent deformation.

The static load rating is usually expressed in:

newtons,
kilonewtons,
or occasionally converted to pounds-force.

It is commonly identified by:

C₀

Why Permanent Deformation Matters

A profile rail carriage depends on extremely precise rolling contact.

If an excessive peak load permanently dents or deforms:

a ball,
roller,
rail raceway,
carriage raceway,

the guide may no longer roll smoothly.

Possible symptoms include:

vibration,
noise,
increased running resistance,
rough motion,
degraded precision,
reduced life.

The guide does not have to visibly bend or break for an overload to cause damage.

Microscopic raceway deformation can be enough to affect performance.

Does C₀ Mean the Maximum Safe Load?

No.

This is one of the most important misunderstandings surrounding linear guide ratings.

C₀ is a reference static load rating—not a recommended operating load.

The machine should normally maintain a safety margin between:

the basic static load rating,
and the maximum applied load.

That margin is expressed through the static safety factor.

What Is Static Safety Factor?

Static safety factor represents the relationship between static load capacity and the maximum applied load.

A commonly used form is:

fS = C₀ ÷ Pmax

where:

fS = static safety factor,
C₀ = basic static load rating,
Pmax = maximum applied load.

If a carriage has:

C₀ = 20,000 N,
maximum applied load = 5,000 N,

then:

fS = 20,000 ÷ 5,000 = 4

That does not by itself prove the guide is correctly selected.

The result must be compared with the selected manufacturer's recommended minimum static safety factor for the application.

How Much Static Safety Factor Do You Need?

There is no single universal safety factor for every guide and every machine.

For many of its LM Guide products, THK currently provides general lower-limit guidance of approximately:

fS = 2 without vibration or impact,
fS = 5 with vibration or impact.

Specific guide families can have different recommendations.

The appropriate factor can also depend on:

shock,
vibration,
acceleration,
emergency stops,
mounting accuracy,
structural rigidity,
lubrication,
application severity.

Always use the manufacturer's requirements for the selected guide family rather than treating a generic number as universal.

Why Shock Loads Matter

A machine may operate under a moderate normal load but experience much higher transient loads.

Examples include:

sudden starts,
abrupt stops,
emergency stops,
crashes,
cutting impact,
stamping,
product collision,
machine vibration,
heavy overhung tooling.

These short-duration events may control the required static capacity.

That is why static safety should be based on the maximum realistic load condition, not merely normal running load.

What Is the Basic Dynamic Load Rating?

The basic dynamic load rating, commonly identified as C, is primarily used in calculating expected rolling-fatigue life.

It does not mean:

“This is the maximum force the bearing can carry while moving.”

Instead, C is a standardized reference value tied to bearing fatigue performance.

ISO 14728-1 establishes methods for calculating basic dynamic load ratings and basic rating life for linear-motion rolling bearings.

The standard allows engineers and bearing manufacturers to connect:

applied load,
bearing dynamic rating,
probability of survival,
travel life.

Why Is It Called a Dynamic Rating?

The rating addresses fatigue produced by repeated rolling contact as the bearing moves.

During operation, rolling elements repeatedly enter and leave loaded raceway zones.

Over a sufficiently large number of load cycles, microscopic material fatigue can develop.

Eventually, this may produce:

flaking,
spalling,
surface fatigue damage.

The basic dynamic load rating is therefore closely connected to expected fatigue life.

What Is Basic Rating Life?

The basic rating life, often written as L10, represents a standardized fatigue-life concept.

In bearing terminology, L10 corresponds to the life associated with a 90% survival probability for a sufficiently large population of nominally identical bearings operating under defined conditions.

It is a statistical engineering value.

It does not mean every guide will fail exactly at that distance.

Some may operate longer.

Some may experience other failure mechanisms earlier.

Basic rating life deals specifically with rolling-contact fatigue under defined conditions.

Why Dynamic Load Rating Is Not a Maximum Load Limit

Suppose a carriage has:

C = 30 kN

It would be incorrect to conclude:

“This carriage can safely carry 30 kN continuously.”

The usable application load may be substantially lower because the engineer may require:

long service life,
high static safety,
low deflection,
reduced moment loading,
protection from impact.

Dynamic load rating is inserted into the manufacturer's life equation along with actual load.

The ratio between C and applied load determines the calculated fatigue life.

Why Load Has Such a Large Effect on Life

Linear rolling-bearing life changes rapidly as applied load changes.

For many ball-type linear guides, nominal-life equations use a load relationship with an exponent of approximately:

For applicable roller guides, the exponent may be:

10/3

This means small changes in applied load can create large changes in calculated life.

For example, reducing carriage load does not merely improve life proportionally.

Because of the exponent, it can improve calculated fatigue life significantly.

This is why:

wider rail spacing,
longer carriage spacing,
lower moving mass,
reduced acceleration

can have a surprisingly large effect on bearing life.

Basic Static vs. Dynamic Rating

Consider a hypothetical carriage:

C = 25 kN,
C₀ = 40 kN.

These values do not mean:

moving load limit = 25 kN,
stationary load limit = 40 kN.

Instead:

C = 25 kN is used in the manufacturer's life calculation.

C₀ = 40 kN is used to evaluate static safety against maximum applied loading.

Actual acceptable machine load may therefore be much lower than either rating.

Why Is C₀ Often Larger Than C?

For many profile guide carriages, the catalog static rating is greater than the dynamic rating.

This does not mean something unusual is occurring.

The two numbers come from different criteria.

Static rating concerns a defined permanent-deformation threshold.

Dynamic rating concerns repeated rolling-contact fatigue over a standardized travel life.

The values therefore should not be directly interpreted as two versions of the same “capacity.”

What Are Directional Load Ratings?

A profile rail guide can encounter forces in several directions.

Common terminology includes:

radial,
reverse radial,
lateral.

Some guides are designed so that their rated capacity is essentially equivalent in the major directions.

These are often described as four-way equal-load guides.

Other guide architectures are optimized primarily for radial loading.

For those guides, the:

lateral,
reverse-radial

ratings can differ from the radial rating.

THK's current selection documentation specifically distinguishes between four-way equal-load guide types and radial-type guides.

Why Load Direction Matters

Suppose a catalog lists:

C = 20 kN

That may refer specifically to the primary radial direction.

If the application loads the carriage laterally, the usable rating could differ.

Therefore, never assume that the headline rating applies identically in every orientation.

Verify:

radial rating,
reverse-radial rating,
lateral rating

for the exact carriage.

What Is a Four-Way Equal-Load Guide?

A four-way equal-load profile guide is designed so that its rolling-element and raceway geometry provides approximately equal load capacity in:

downward radial,
upward reverse-radial,
left lateral,
right lateral

directions.

This gives designers considerable flexibility.

THK's HSR guide, for example, uses ball rows arranged at a 45-degree contact angle and is described as a four-way equal-load guide.

Four-way capability is particularly useful in machines where loading changes direction.

Does Four-Way Equal Load Mean Equal Machine Loading?

No.

The guide may have equal catalog ratings in four directions, but that does not mean the machine distributes forces equally.

Actual carriage loading still depends on:

center of gravity,
guide geometry,
rail spacing,
carriage spacing,
acceleration,
external forces,
moments.

A four-way equal-load guide simply provides similar rated capability in those load directions.

What Is Equivalent Load?

A carriage may experience several directional loads simultaneously.

For example:

downward radial load,
plus lateral process force.

Rather than calculate life separately for each force, the manufacturer may convert the combined loading into an equivalent load.

Equivalent load represents a single calculated force that produces the relevant bearing effect of the combined forces.

A manufacturer may use a relationship such as:

PE = X × PR + Y × PT

where:

PE = equivalent load,
PR = radial or reverse-radial load,
PT = lateral load,
X and Y = manufacturer-defined factors.

The actual equation and coefficients vary by guide type.

Never assume one universal equation applies to all profile rails.

Why Equivalent Load Matters

Imagine a carriage carrying:

2,000 N downward,
1,000 N sideways.

It would usually be wrong to ignore the lateral load and calculate life using only 2,000 N.

It may also be wrong simply to add them arithmetically.

The manufacturer's equivalent-load procedure reflects the guide's actual raceway geometry.

Therefore, use the technical catalog for the exact series.

What Are Permissible Moments?

Linear guide catalogs often include permissible moment values.

A moment attempts to rotate the carriage rather than simply translate it.

The three major types are:

pitch,
yaw,
roll.

Manufacturers may represent them using symbols such as:

or another notation.

Moment capacity is usually expressed in:

N·m,
kN·m,
or equivalent imperial units.

Why Moment Ratings Matter

Consider a 100 lb tooling load.

If it sits directly over the carriage, the load may be relatively simple.

Move that tool 24 inches away from the carriage center and the system now experiences a significant moment.

The relationship is:

Moment = force × perpendicular distance

A light cantilevered load can therefore create a more severe bearing condition than a much heavier centered load.

Static Permissible Moment vs. System Moment Capacity

A catalog's static permissible moment may describe what an individual carriage can tolerate.

But many industrial machines use:

two rails,
two or more carriages on each rail.

In that arrangement, the moment can be resisted through the geometry of the entire system.

The individual carriage moment rating therefore does not tell the whole story.

System moment resistance is heavily influenced by:

rail spacing,
carriage spacing.

Why Rail Spacing Changes Carriage Load

Suppose a machine experiences a roll moment.

Two rails spaced far apart provide more mechanical leverage than two rails positioned close together.

Increasing rail spacing can reduce the reaction forces required at the individual carriages.

This can improve:

static safety,
calculated life,
rigidity.

Sometimes changing machine geometry can solve a loading problem without moving to a much larger rail.

Why Carriage Spacing Changes Load

The same principle applies to longitudinal carriage spacing.

Two carriages located far apart have more leverage against pitch and yaw moments than two carriages positioned close together.

Therefore:

Load rating should never be evaluated independently from guide geometry.

Does Adding More Carriages Increase Load Capacity?

Potentially—but not as simply as multiplying the rating.

Suppose one carriage has a dynamic rating of:

20 kN.

Four carriages do not automatically create a usable system dynamic rating of:

80 kN.

Why?

Because actual loading may not divide perfectly equally among them.

Load distribution depends on:

center of gravity,
moments,
structural stiffness,
rail alignment,
carriage alignment,
preload,
mounting-surface accuracy.

Manufacturers may apply contact or load-sharing factors when multiple carriages operate together.

Why Four Carriages Rarely Carry Exactly 25% Each

Perfect 25/25/25/25 load distribution requires an idealized machine.

Real systems contain:

tolerances,
rail-height differences,
table deflection,
preload variations,
mounting errors,
offset loads.

One carriage may therefore carry substantially more load than another.

The correct design process calculates individual carriage reactions.

What Is Maximum Applied Load?

Maximum applied load is the largest force experienced by a carriage during any relevant operating condition.

That may occur during:

stationary loading,
rapid acceleration,
deceleration,
emergency stop,
machining,
collision,
impact,
maximum payload.

This value is typically used in the static safety calculation.

It is not necessarily the same load used for fatigue-life calculations.

What Is Average Load?

Industrial machines often experience changing loads during one operating cycle.

A carriage might see:

high load during acceleration,
lower load during constant-speed travel,
high load during machining,
low load during return travel.

Manufacturers provide methods for converting fluctuating loading into an appropriate average load for fatigue-life analysis.

This is not necessarily a simple arithmetic average.

Rolling-bearing fatigue is nonlinear with load.

Why Arithmetic Average Can Be Wrong

Suppose a guide operates half its travel at:

1,000 N

and half at:

5,000 N.

A simple arithmetic average would be:

3,000 N.

But because fatigue damage changes nonlinearly with load, the manufacturer's equivalent-average load for life calculation may differ.

Use the prescribed calculation method.

Static Rating vs. Static Safety Factor

These terms are sometimes confused.

Static Load Rating

A physical rating assigned to the bearing:

C₀

Static Safety Factor

A calculated margin:

fS = C₀ ÷ applied maximum load

The rating belongs to the carriage.

The safety factor belongs to the application.

Dynamic Rating vs. Calculated Life

These are also different.

Dynamic Load Rating

A catalog property:

Calculated Life

A result derived from:

C,
applied load,
guide type,
rating convention,
correction factors.

The same carriage can therefore have very different calculated lives in different machines.

Why Two Machines Using the Same Rail Can Have Different Life

Imagine two machines using the exact same carriage.

Machine A:

centered load,
low acceleration,
wide rail spacing,
clean environment.

Machine B:

offset load,
high acceleration,
narrow rail spacing,
impact loading.

Even with the same carriage:

maximum applied load differs,
static safety differs,
fatigue load differs,
calculated life differs.

Bearing performance belongs to the application, not merely the component.

What Is Modified Life?

Some manufacturers provide life calculations that adjust basic nominal life for operating conditions.

Potential factors can include:

material hardness,
operating temperature,
contact conditions,
lubrication,
contamination.

Use the manufacturer's current life-calculation method.

Do not apply correction factors borrowed from another manufacturer unless the methodology explicitly supports it.

Why Rating Distance Matters

Dynamic load ratings must be interpreted in the context of their rating definition.

Some historical catalogs and standards have used different reference travel distances.

Schaeffler, for example, notes that certain guide ratings may be based on:

100 km,
versus 50 km

reference displacement distances and provides conversion relationships for comparison.

This matters because two catalog numbers can appear different even when they represent comparable bearing capability under different rating conventions.

Can You Directly Compare C Ratings Between Brands?

Only after confirming the definitions.

Before saying:

Brand A has a higher dynamic rating than Brand B,

verify:

applicable standard,
reference travel distance,
guide type,
rating direction,
carriage configuration.

Otherwise, the comparison may be misleading.

What Does ISO 14728-1 Cover?

ISO 14728-1 establishes standardized methods for:

calculating basic dynamic load ratings,
determining basic rating life

for linear-motion rolling bearings of conventional design.

This provides a common engineering framework for fatigue-related rating calculations.

What Does ISO 14728-2 Cover?

ISO 14728-2 addresses static load ratings for linear-motion rolling bearings.

Together, the two standards distinguish the two major rating concepts:

dynamic fatigue life,
static deformation capacity.

Load Rating vs. Rigidity

Load capacity and rigidity are not the same thing.

A carriage may have enough load capacity to:

survive the maximum load,
provide adequate calculated life,

while still deflecting more than the machine can tolerate.

Rigidity describes resistance to elastic deformation.

It is critical for:

machine tools,
inspection equipment,
robotics,
semiconductor equipment,
dispensing,
grinding,
precision automation.

Schaeffler's technical research shows that linear guide rigidity can be influenced by:

rolling-element type,
raceway geometry,
number of rows,
preload,
internal construction.

Therefore:

Do not use C or C₀ as substitutes for stiffness data.

Load Rating vs. Preload

Preload intentionally loads the rolling elements inside the guide.

It can improve:

rigidity,
response to reversing forces,
positional stability.

But preload also creates internal load before any external machine force is applied.

Higher preload can influence:

rolling resistance,
internal stress,
heat,
calculated life.

If the manufacturer's life procedure requires preload to be included, it should not be ignored.

Load Rating vs. Accuracy

Load rating also does not describe accuracy.

A carriage can have high:

C,
C₀

without being the appropriate accuracy class for a precision machine.

Accuracy characteristics may include:

running parallelism,
carriage height variation,
dimensional tolerances.

Choose load capacity and accuracy independently according to the machine requirements.

Load Rating vs. Speed

Dynamic load rating does not directly mean maximum speed.

Speed limits can be influenced by:

ball recirculation,
seals,
lubrication,
acceleration,
carriage design,
heat.

Use the manufacturer's speed data for the specific guide series.

Load Rating vs. Shock Capacity

A guide with a high dynamic rating can still be vulnerable to severe shock if static safety is inadequate.

Shock loading should be evaluated against:

static capacity,
static safety factor,
moment loading,
structural geometry.

This is why C alone should never drive guide selection.

A Practical Example

Consider a hypothetical carriage with:

C = 30 kN,
C₀ = 45 kN.

Assume the maximum calculated carriage load is:

9 kN.

Static Check

Using:

fS = C₀ ÷ Pmax

we get:

45 ÷ 9 = 5

The calculated static safety factor is 5.

Whether that is acceptable depends on:

guide series,
vibration,
shock,
manufacturer recommendation.

Dynamic Check

Now assume the equivalent operating load is substantially lower than the 9 kN peak.

That value would be used with the manufacturer's dynamic-life equation and C = 30 kN.

The result might indicate a long calculated fatigue life.

The key point is that:

9 kN maximum load drives the static check,
equivalent operating load drives the fatigue-life check.

The two calculations use different loads because they answer different questions.

Example: Why a Large C Rating Can Be Misleading

Suppose an engineer sees:

C = 50 kN

and assumes the machine has plenty of capacity because the payload produces only 10 kN of weight.

But the center of gravity sits far outside the guide footprint.

That offset generates a large moment.

One carriage may actually experience:

25 kN

during acceleration.

The 10 kN payload number therefore tells very little about the most severely loaded bearing.

Individual carriage reaction matters.

Example: Why C₀ Can Control Selection

Consider a machine that normally operates under light load but experiences an abrupt emergency stop.

Its average fatigue load is low.

A small guide might therefore have excellent calculated dynamic life.

However, the emergency-stop force produces a high peak carriage reaction.

If static safety is inadequate, the guide may still be undersized.

In this machine:

static capacity—not fatigue life—controls the selection.

Example: Why Rigidity Can Control Selection

Now consider a precision inspection machine.

Loads are modest.

Static safety is excellent.

Calculated fatigue life is extremely long.

But the carriage deflects enough under the measurement load to produce unacceptable positional error.

The guide must be changed despite passing both load-rating calculations.

Here:

rigidity controls the selection.

How to Read a Linear Guide Catalog Table

When viewing a carriage specification table, look for:

basic dynamic load rating C,
basic static load rating C₀,
permissible moments,
guide size,
carriage style,
preload,
accuracy class,
dimensions.

Then ask:

Which direction does C apply to?
Is the guide four-way equal-load?
Are lateral ratings different?
Is C rated on a 50 km or 100 km basis?
What static safety factor does the manufacturer require?
Are permissible moments for one carriage?
Is the rating for the exact carriage length/style being considered?
What preload is assumed?
What life equation applies?

This prevents catalog numbers from being interpreted out of context.

Common Mistakes With Linear Guide Load Ratings

Mistake 1: Treating C as Maximum Moving Load

Dynamic rating is primarily used in life calculations.

Mistake 2: Treating C₀ as Recommended Maximum Load

Static rating requires an appropriate safety factor.

Mistake 3: Ignoring Load Direction

Not every guide has equal capacity in all directions.

Mistake 4: Adding Carriage Ratings Together

Multiple carriages may not share load equally.

Mistake 5: Ignoring Moments

Offset loads can dramatically increase individual carriage reactions.

Mistake 6: Ignoring Acceleration

Dynamic machine forces can exceed simple gravity loading.

Mistake 7: Using Average Load for Static Safety

Static safety should consider the relevant maximum applied load.

Mistake 8: Using Peak Load as the Only Life Load

Fatigue-life calculation generally requires the appropriate equivalent or average operating load.

Mistake 9: Comparing C Ratings Without Checking the Standard

Reference-distance conventions can affect rating values.

Mistake 10: Assuming High Capacity Means High Rigidity

Load capacity and stiffness are separate characteristics.

How Linear Guide Load Ratings Fit Into the Sizing Process

A useful selection sequence is:

Machine geometry

↓

Forces and moments

↓

Individual carriage loads

↓

Equivalent directional load

↓

Maximum applied load

↓

Static safety factor

↓

Average operating load

↓

Dynamic life

↓

Rigidity

↓

Preload

↓

Accuracy

↓

Environment

↓

Final guide selection

This is much more reliable than:

machine weight → rail size

Linear Automation USA's Perspective

From Linear Automation USA's perspective, linear guide load ratings are most useful when they are treated as engineering calculation inputs rather than purchasing specifications.

We frequently see questions framed as:

“How much weight will a size 25 rail hold?”

The correct answer depends on far more than the nominal rail size.

We need to know:

exact carriage series,
dynamic load rating,
static load rating,
load direction,
number of carriages,
rail spacing,
carriage spacing,
center of gravity,
acceleration,
external forces,
moments,
required life,
required rigidity.

Two size 25 carriages can have significantly different ratings because of differences in:

carriage length,
flange or rectangular geometry,
rolling-element arrangement,
preload,
guide series.

Even within a single manufacturer's product family, a long carriage can have different C and C₀ values from a short carriage in the same nominal rail size.

This is visible in real profile rail product families where several:

standard,
long,
flange,
rectangular

carriages may all fit the same nominal rail series but carry different ratings.

Linear Automation USA currently provides profile rail products from SBC Linear and WON Linear, along with Schaeffler linear-guide solutions.

Our recommendation is to use the complete model number whenever possible.

For replacement applications, never assume:

same rail width = same load capability.

A dimensional interchange still requires verification of:

C,
C₀,
permissible moments,
preload,
accuracy,
carriage dimensions,
rail dimensions,
mounting pattern.

For new designs, we recommend calculating the individual carriage loading first and using catalog ratings afterward.

Our guiding principle is:

C tells you about fatigue life. C₀ helps protect against peak-load damage. Neither tells the complete application story by itself.

Frequently Asked Questions

What Does C Mean on a Linear Guide?

C normally represents the basic dynamic load rating used in fatigue-life calculations.

What Does C₀ Mean on a Linear Guide?

C₀ normally represents the basic static load rating used to evaluate maximum-load safety and permanent deformation.

Is Dynamic Load Rating the Maximum Load?

No. It is a standardized fatigue-life rating, not simply the maximum moving load.

Is Static Load Rating the Maximum Safe Load?

No. The application should normally maintain an appropriate static safety factor between C₀ and the maximum applied load.

Why Is Static Load Rating Often Higher Than Dynamic Load Rating?

They are defined using different engineering criteria. Static rating concerns permanent deformation, while dynamic rating concerns fatigue life.

What Is a Good Static Safety Factor?

Use the manufacturer's recommendation for the specific guide and application. Some manufacturers recommend significantly higher factors where vibration or impact is present.

Can a Linear Guide Carry Side Load?

Many profile rail guides can carry lateral forces, but the rating may differ from the radial rating depending on the guide design.

What Is a Four-Way Equal-Load Linear Guide?

It is a guide designed to provide comparable rated capacity in radial, reverse-radial, and both lateral directions.

What Is Equivalent Load?

Equivalent load is a calculated single load representing the bearing effect of multiple simultaneous directional loads.

What Is Static Permissible Moment?

It is a manufacturer's rating related to the carriage's ability to withstand a specified static pitch, yaw, or roll moment.

Can I Add the Ratings of Four Carriages Together?

Not automatically. Actual load sharing depends on machine geometry, alignment, rigidity, moments, and center of gravity.

Does Rail Spacing Affect Load Rating?

It does not change the carriage's catalog rating, but it can change the actual reaction load experienced by the carriage.

Does Carriage Spacing Matter?

Yes. Greater spacing can reduce carriage forces created by moments.

Does Preload Reduce Load Capacity?

Preload introduces internal loading and can influence life and running resistance. Use the manufacturer's preload-specific engineering guidance.

Does a Higher Dynamic Rating Mean a Stiffer Guide?

Not necessarily. Load capacity and rigidity are related to different performance characteristics.

Can I Compare Dynamic Load Ratings Between Different Brands?

Only after confirming that the rating definitions, load directions, and reference-distance conventions are compatible.

Need Help Interpreting Linear Guide Load Ratings?

For a new industrial application, gather:

moving mass,
mounting orientation,
center of gravity,
external forces,
acceleration,
deceleration,
stroke,
cycle rate,
rail spacing,
carriage spacing,
number of rails,
number of carriages,
required life,
rigidity requirements.

For an existing guide, provide:

manufacturer,
complete carriage part number,
rail part number,
clear photographs,
rail size,
carriage dimensions,
preload if known,
machine application.

Contact Linear Automation USA for assistance identifying, sizing, sourcing, or replacing profile rail guides.