How to Know What Size Wheel Bearings You Need

The fastest way to know your wheel bearing size is to read the code stamped on the old bearing or hub (for example, 6203-2RS or L68149/L68111); if that’s missing or unreadable, measure the inner diameter, outer diameter, and width with a digital caliper, or look up the OEM part number by VIN or model. Below, we explain how to identify sizes for cars, trailers, bicycles, motorcycles, and skates, how to decode bearing markings, and how to measure accurately when you must.

What “size” means for wheel bearings

Wheel bearing “size” typically means three dimensions—the inner diameter (ID, bore), outer diameter (OD, outside ring), and width (W, thickness)—plus the bearing type. Common types include deep-groove ball bearings (e.g., 6202, 6902), tapered roller bearings (cone and cup sets like L44649/L44610), and unitized hub assemblies on many modern cars. The standard numbering systems (ISO/ABMA) encode dimensions so you can match parts precisely.

Easiest ways to identify the right size

Start with the quickest, most reliable identification methods before measuring. These methods reduce errors and ensure you get an exact replacement, especially when ABS or hub configurations are involved.

• Read the bearing code stamped on the race or seal (e.g., 6203-2RS, L68149, LM67048, 608). Clean with solvent to reveal faint markings.
• Use the vehicle’s VIN or exact model/year/trim to look up the OEM part number in a service manual or trusted catalog, then cross-reference to bearing sizes.
• Check the hub or axle manufacturer’s tag (trailers often list spindle/hub series that map to bearing sets).
• Consult a reputable bearing catalog or supplier (SKF, Timken, NTN, NSK) with your code or measurements.

When codes and catalogs match, you can order confidently. If anything is inconsistent—especially on older or modified equipment—measure directly.

How to read bearing codes

Understanding common codes lets you confirm dimensions quickly and avoid size or seal-type mistakes.

• Deep-groove ball bearings (e.g., 6203-2RS): “6203” is the series; “03” indicates a 17 mm bore (rule of thumb: 00=10 mm, 01=12 mm, 02=15 mm, 03=17 mm; from 04 upward, multiply the last two digits by 5). “2RS” means rubber seals both sides; “ZZ” are metal shields.
• Thin-section series: 6802 (15×24×5 mm), 6902 (15×28×7 mm) are common in bicycle hubs and lightweight applications.
• Tapered roller bearings use separate cone and cup numbers (e.g., L44649 cone pairs with L44610 cup; L68149 pairs with L68111). You need both for a match.
• Automotive hub assemblies use brand-specific part numbers (e.g., SKF VKBA…, Timken HA590…, Moog 513…). These define bolt pattern, flange offset, ABS encoder location, and bearing geometry.

If a code is legible, decode it and verify against a catalog’s dimensions. For tapered rollers, always confirm both cone and cup numbers as a matched set.

Measuring when codes are missing

Tools you’ll need

Accurate measurements are essential. The right tools help you avoid buying a near-fit that fails prematurely.

• Digital caliper (0–150 mm/6 in) with 0.01 mm or 0.0005 in resolution
• Micrometer (optional for higher precision on bores/spindles)
• Straightedge and flashlight; solvent and rag to clean surfaces
• For trailers: spindle diagram from axle maker to reference “A/B” dimensions

Clean parts thoroughly, remove burrs, and measure multiple times to confirm consistency. Record units (mm vs in) clearly.

Cartridge (sealed) ball bearings: bikes, small motors

Cartridge bearings are measured as a single unit. Follow these steps to capture the three key dimensions.

1. Measure the inner diameter (ID) across the bore: common sizes include 12, 15, 17 mm.
2. Measure the outer diameter (OD) across the outer ring: common sizes include 24, 28, 30, 40 mm.
3. Measure the width (W) across the bearing: typical values are 5, 7, 8, 11, 12 mm.
4. Match your dimensions to a catalog series (e.g., 6001 = 12×28×8 mm; 6203 = 17×40×12 mm; 6902 = 15×28×7 mm).
5. Select seals/shields as needed: 2RS (rubber, contact) for dirt/wet, ZZ (metal, non-contact) for lower drag.

When in doubt between similar series (e.g., 6802 vs 6902), the width usually distinguishes them. Never force a near-fit.

Tapered roller bearings: trailers, older cars

Tapered rollers are identified by spindle and hub bore sizes; you’ll also need the grease seal size. Here’s how to measure correctly.

1. Measure the spindle at the inner bearing journal (larger shoulder) for the inner cone ID (e.g., ~1.378 in for L68149).
2. Measure the spindle at the outer bearing journal (smaller shoulder) for the outer cone ID (e.g., ~1.063 in for L44649).
3. Measure hub bores for the cup ODs or read the cup numbers (e.g., L68111, L44610) pressed into the hub.
4. Measure the seal journal on the spindle and the hub’s seal bore to select the correct grease seal (common 3.5K trailer seal: ~1.719 in ID, ~2.565 in OD).
5. Buy matched cone/cup pairs and a seal; replace as a set per side.

Many 3,500 lb trailer axles use inner L68149/L68111 and outer L44649/L44610; verify your spindle to be sure.

Automotive hub assemblies: modern passenger vehicles

Many late-model cars and trucks use unitized hub bearings that are not serviced by internal size; identification is via part number and configuration.

1. Look up by VIN or exact year/make/model/drive type; confirm FWD/AWD/RWD and axle (front vs rear), and left vs right if different.
2. Verify ABS encoder type and location (built-in magnetic ring on one side or tone ring external). Directional bearings must face the sensor.
3. Match flange bolt count/pattern, wheel studs, and brake package (rotor/drum dimensions).
4. Confirm torque specs and any one-time-use axle nuts or bolts required.

Subtle differences in ABS encoder orientation or flange offset can make a visually similar hub incorrect. Don’t substitute by appearance alone.

Application-specific notes

Bicycles

Bicycle wheel hubs frequently use sealed cartridge bearings. These sizes are widely standardized, but differ by hub brand/model.

• Common sizes: 6001 (12×28×8), 6002 (15×32×9), 6202 (15×35×11), 6802 (15×24×5), 6902 (15×28×7), 6903 (17×30×7)
• Choose 2RS seals for wet/muddy riding; stainless or ceramic hybrids are optional but not required for most riders.
• Press bearings by the outer race into the hub shell and by the inner race onto the axle to avoid damage.

Always verify hub manufacturer specs; some hubs use different bearings left/right or include preload collars that affect fit.

Skateboards and inline skates

Most skate wheels use the ubiquitous 608 series bearing; spacers and speed rings matter for proper load distribution.

• 608 (8×22×7 mm) is the standard size for skateboard/inline wheels.
• Spacers are typically 8 mm internal; ensure your axle and spacers match.
• “ABEC” ratings indicate manufacturing tolerance class, not size or durability.

Replace in sets to maintain smoothness and alignment across wheels.

Motorcycles

Motorcycle wheels often use sealed deep-groove bearings; sizes vary by make/model and are typically listed in service manuals.

• Common examples include 6203-2RS (17×40×12) or 6204-2RS (20×47×14), but verify for your bike.
• Replace both sides and the center spacer if damaged; confirm seal sizes and dust caps.
• Torque the axle to spec and check for free rotation and correct end play/preload.

Because wheel bearings affect stability at speed, use reputable brands and follow torque and sealing procedures precisely.

Passenger vehicles and light trucks

Newer vehicles use hub assemblies; older vehicles may use serviceable tapered rollers.

• Unitized hubs: identify by VIN; confirm ABS and flange specs. Replace the complete hub; do not attempt to size internal bearings.
• Serviceable hubs: match tapered roller cone/cup numbers; set end play per manual (typically near zero end play with free rotation).
• Consider left/right differences on some platforms due to ABS encoder orientation.

Wheel speed sensor faults after replacement often trace to incorrect encoder orientation or damaged sensor wiring.

Trailers

Trailer axles commonly use standardized tapered roller sets; spindle “A/B” dimensions map to bearing sets and seals.

• Common sets: L44643/L44610 (1.000 in ID), L44649/L44610 (1.063 in ID), L68149/L68111 (1.378 in ID), LM67048/LM67010 (1.250 in ID)
• Typical 3.5K axle combo: inner L68149/L68111, outer L44649/L44610; seal often ~1.719 in ID × ~2.565 in OD; dust cap ~1.98 in.
• EZ-Lube axles require correct seals to avoid grease migration onto brakes.

Always confirm with spindle measurements or existing part numbers—many axles look alike but use different inner/outer combinations.

Cross-checking and fitment accuracy

Before purchasing, verify all details to avoid downtime and rework.

• Match ID/OD/W exactly; typical tolerance is within 0.02 mm for cartridges and a few thousandths of an inch for tapered rollers.
• Confirm metric vs inch dimensions; don’t mix similar-but-not-same sizes.
• Inspect spindle/hub for wear, scoring, bluing, or out-of-round that can ruin new bearings.
• Replace seals whenever you replace bearings; contamination is the top cause of early failure.
• Replace in pairs (left/right) on vehicles to maintain symmetry and reliability.
• Choose quality brands (SKF, Timken, NTN, NSK, Koyo) and avoid unverified generics for critical applications.

A quick cross-check against a major bearing catalog or supplier database is often the difference between a perfect fit and a repeat job.

When to replace vs. repack/service

Knowing the condition of your current bearings helps you decide what to buy and when to act.

• Replace if you feel roughness, notchiness, or see pitting, spalling, or heat discoloration.
• Replace if there’s excessive play (clunk) or a growling/humming noise that changes with speed or turns.
• Serviceable tapered rollers can be cleaned, inspected, and repacked if smooth and within spec; otherwise replace cone, cup, and seal.

If one side has failed due to contamination or age, the opposite side is often close behind—plan accordingly.

Quick reference examples

These commonly encountered bearings illustrate how codes map to dimensions.

• 608: 8×22×7 mm (skate wheels, some small devices)
• 6001-2RS: 12×28×8 mm (bicycle hubs, small motors)
• 6203-2RS: 17×40×12 mm (bikes, motorcycles, machinery)
• 6902-2RS: 15×28×7 mm (bicycle hubs)
• L44649/L44610: 1.063 in ID cone with matching cup (common trailer outer)
• L68149/L68111: 1.378 in ID cone with matching cup (common trailer inner)

Use these only as patterns; always verify your exact application by measurement or part number.

Safety and installation notes

Correct installation matters as much as correct sizing for longevity and safety.

• Press only on the race being fitted: outer race when installing into a hub; inner race when fitting onto a shaft/axle.
• For tapered rollers, seat the bearings by tightening while rotating the hub, then back off and set end play to spec (often 0.001–0.005 in) or finger-tight plus cotter pin per manual.
• Torque axle/hub nuts to manufacturer specifications; use new one-time-use nuts/bolts where required.
• Mind ABS encoder orientation on hub units; the magnetic ring must face the sensor.
• After installation, spin-test for smoothness, check for heat after a short drive or tow, and re-check torque/end play.

A correctly sized bearing installed with proper technique will run cooler, quieter, and last much longer.

Where to verify sizes and buy

Reliable sources help you confirm specs and avoid counterfeit parts.

• OEM service manuals and electronic parts catalogs (by VIN)
• Major bearing manufacturers’ catalogs and online tools: SKF, Timken, NTN, NSK, Koyo
• Trusted parts databases and retailers with fitment verification
• Local bearing supply houses—bring your old bearing(s) or precise measurements

Cross-reference across at least two reputable sources when possible, especially for hub assemblies with ABS.

Summary

To know what size wheel bearings you need, first read the code on the existing bearing or hub and confirm it in a trusted catalog. If markings are missing, measure the inner diameter, outer diameter, and width with a caliper—or, for tapered rollers, measure spindle journals and hub bores and match cone/cup sets and seals. For modern vehicles with unitized hubs, identify by VIN and configuration (including ABS). Verify details before purchase, replace seals and related parts, and install to spec for safe, long-lasting performance.

How do I know what size wheel bearings I need?

There are two ways to do this: 1) Look for the bearing number on the bearing itself. 2) Use a caliper to measure the diameter of the spindle where the bearings ride.

How do I know what size main bearings I need?

1 main journal in the block and subtract the diameter of No. 1 main journal from the crankshaft then subtract the oil clearance that you require, divide the result by 2, this will be the thickness of the bearings that you require.

How do you determine bearing size?

How Bearings Are Sized. Bearings are measured by their inner diameter, outer diameter, and width; the size of a bearing is normally listed as such: ID x OD x W. These measurements are normally taken in millimeters, but can be converted to inches.

What size is a 9 * 20 * 5 bearing?

This 9 x 20 x 5 mm (699W5) bearing is a metric deep groove ball bearing. The 699W5 inner diameter is 9 mm, the 699W5 outer diameter is 20 mm, the 699W5 width is 5 mm. This bearing is Open, it does not have seal on neither side.