DJI Agras T100 OEM Bearing (OD=21 mm) (YC.ST.CT000163)

DJI Agras T100 OEM Bearing (OD=21 mm) (YC.ST.CT000163) — This is the bearing (od=21 mm) in the spinner disk assembly of the DJI Agras T100. Structural and mounting parts like this one hold alignment for everything that bolts to them — and on an aircraft that works for a living, cracked mounts and worn structure never stay a cosmetic problem for long. DJI material number YC.ST.CT000163. Bearing (OD=21 mm) | Structural Component | DJI Agras T100 Spreading System | Field-Ready OEM Replacement Component.

DJI Material Number (SKU): YC.ST.CT000163 — this is the official DJI part number for this exact component. Match it to your parts diagram or your old part's label to confirm fitment before ordering.

🇺🇸 U.S.A. FIRST

Ares Acres LLC is a U.S.-based authorized DJI Agras reseller supporting American agricultural drone operators with genuine DJI Agras OEM replacement parts, accessories, and field-ready inventory.

FREE & FAST Shipping is included for all U.S. customers.

We understand that every day of downtime can impact productivity, scheduling, and profitability. That's why we focus on providing fast fulfillment, responsive customer support, and reliable access to the parts operators need most.

✅ DJI Agras T100 Compatibility Guarantee

• 🇺🇸 USA Compatibility Guarantee
• 👍🏻 Satisfaction Guarantee
• 💵 Money Back Guarantee
• 📦 Same Day Shipping & Tracking
• DJI material number YC.ST.CT000163 — listed verbatim on the official DJI Agras T100 parts breakdown
• Supplier-listed fitment: DJI Agras T100
• Brand new condition — never installed, never flown

📦 Package Includes

• 1 × OEM Bearing (OD=21 mm) (YC.ST.CT000163)
• OEM protective packaging

🔧 Component Overview

The DJI Agras T100 OEM Bearing (OD=21 mm) is the OEM bearing (od=21 mm) in the spinner disk assembly of the DJI Agras T100, part of the structure metering and throwing granular material in a controlled swath.

Metering and throwing granular material in a controlled swath is the job description for the spinner disk assembly, and this component is part of how it gets done. The T100 is a working machine — it earns its keep in fill-and-fly cycles, not hangar hours — and every component in the spinner disk assembly is sized, shaped, and specified around that duty. On the official parts diagram it sits alongside Thumb Nut, R-Type Pin, Spinner Disk.

Ignore a failing bearing (od=21 mm) and the bill compounds: downtime in the middle of an application window, collateral wear on the parts around it, and jobs that slip to a competitor while the aircraft sits. Replacing it costs a part; not replacing it costs acres. That trade only runs one direction.

For professional farmers, aerial applicators, and commercial drone operators, this component is how the spinner disk assembly stays field-ready instead of becoming the reason the aircraft sits.

This is a working part on a working aircraft.

The T100 works brutally hard for its living, including:

• Metering and throwing granular material in a controlled swath
• Dawn-to-dusk spray campaigns during narrow application windows
• Repeated fill-fly-return cycles with minutes on the ground between loads
• Full-payload takeoffs from field edges, dozens of times per day
• Chemical exposure from fungicides, herbicides, insecticides, and foliar fertilizers
• Pressure-washer rinse-downs at the end of every spray day
• Vibration from eight propulsion motors running at working power
• Transport bouncing on trailers and truck beds between fields
• Temperature swings from cold morning starts to full-sun afternoons

What attacks this component in the field:

• Vibration from the propulsion system every flight hour
• Chemical exposure from spray drift and washdown
• UV degradation across a season outdoors
• Shock loads from field-edge landings
• Grit and dust working into interfaces
• Thermal cycling from dawn starts to afternoon heat
• Stress concentration at mounting points
• Wear from repeated maintenance access

That duty cycle is exactly what retires this component. None of these stresses is dramatic on its own — the accumulation is what does it. This is why structural and mounting parts are inspection items every time the spinner disk assembly is opened up, and why operators who run hard keep spares on the shelf.

A healthy bearing (od=21 mm) delivers:

• Factory-correct fit in the spinner disk assembly — no modification, no adaptation
• Exact OEM behavior the surrounding components were engineered around
• Restored function you can verify on the first post-repair check
• Sealing and protection maintained to the factory standard
• One less known-weak point flying through your application window
• Confidence that the repair is done, not patched
• A maintenance log entry with a real DJI part number behind it
• Full compatibility with the parts around it — because it is the part the diagram calls for

Stock the bearing (od=21 mm) before the season does its work, and the spinner disk assembly never becomes the reason the aircraft sits.

Judge the bearing by hand before you judge it by symptom. With the aircraft powered down and the spreader empty, turn the spinner disk slowly by hand a full revolution and feel what comes back through your fingers. A bearing that is still good turns smoothly, quietly, and with the same resistance the whole way around, and the disk coasts a little when you flick it. A bearing that is finished feels gritty, catches at one or two points in the revolution, rumbles, or stops dead the moment you let go. Do it slowly, because a fast spin masks exactly the roughness you are trying to find.

Check for play at the rim, where it is easiest to see. Hold the spinner disk at opposite edges and try to rock it against the assembly, then try to lift and push it along its axis. The distance from the bearing out to the rim multiplies any wear inside the bearing, so a small amount of looseness at the bearing shows up as movement you can plainly see at the edge of the disk. A bearing in good order gives you almost nothing. If the rim visibly moves, the disk is not running true at speed either.

Use the other spinner as your reference. The spreading system gives you two of nearly everything, and the second spinner assembly is a free known-good comparison sitting right beside the one you are worried about. Turn both by hand back to back and listen to both. Differences in feel and sound between the two are far more reliable than trying to remember what a good one felt like last season, and if both feel the same you have learned something useful as well.

Separate a bad bearing from a bent or worn spinner disk by swapping the disks between the two positions. A disk that has been struck, dropped, or has lost material off one vane will wobble and spread unevenly with a perfect bearing behind it. Move each disk to the other side and run the system. If the wobble and the uneven pattern follow the disk, the disk is the fault and a new bearing changes nothing. If the trouble stays at the same position no matter which disk is on it, the bearing, the shaft, or the motor at that position is where to look.

⚙️ Functional Purpose

The bearing (od=21 mm) is designed to do one job in the spinner disk assembly and do it to specification: metering and throwing granular material in a controlled swath.

The component:

• Serves the spinner disk assembly of the DJI Agras T100 exactly as the factory intends
• Supports metering and throwing granular material in a controlled swath
• Maintains the tolerances and interfaces the surrounding parts depend on
• Withstands the chemical, vibration, and washdown environment of agricultural work
• Preserves the sealing and protection strategy of the platform
• Keeps failure modes visible and diagnosable instead of mysterious
• Restores factory behavior immediately upon correct installation
• Protects the more expensive components it works alongside
• Carries the exact DJI specification for its position
• Supports safe, predictable operation under full payload
• Eliminates the guesswork of near-fit substitutes
• Keeps the aircraft inside its designed maintenance program
• Holds up across a full season of professional duty

Function on the T100 is a chain: spreading system performance depends on the spinner disk assembly, and the spinner disk assembly depends on every part in it holding specification. This component is one link in that chain — and chains fail at the worn link, not the average one.

That is why the platform's maintenance philosophy is inspection and renewal, not run-to-failure. The operators with the best uptime records are not the ones with the newest aircraft — they are the ones who replace parts like this when inspection says so, on their own schedule instead of the failure's.

A failing bearing (od=21 mm) costs you:

• Downtime in the middle of an application window — the most expensive hours in agriculture
• Acres not covered while the aircraft waits on a part
• Collateral wear on the components around the failing one
• Diagnostic hours chasing symptoms instead of causes
• Rework when a temporary fix lets go mid-job
• Customer trust when scheduled work slips
• Higher repair bills the longer the fault runs
• Risk exposure every flight the fault remains aboard
• Resale value on an airframe with deferred maintenance

Fix it on your schedule, not the failure's.

Take the spinner assembly apart in the order the design intends. The disk is retained by a thumb nut and an R-type pin so it comes off without tools for cleaning, and that is how it should come off for this job as well. Do not hammer a stuck disk and do not lever against the face of it with a screwdriver. The disk is a balanced rotating part with thin sections, and a disk that has been pried on will wobble afterward, which produces the same complaint you are trying to fix.

Clean the whole area down before you open anything. Granular fertilizer packs into every corner of a spinner assembly and it is both abrasive and corrosive, so anything that falls loose while you are working ends up in the bearing seat. Brush and rinse the disk, the hub, and the surrounding housing, then dry it. Working dry and clean also lets you see the corrosion, the wear track on the shaft, and the staining that tells you how long the bearing has been unhappy.

Press a bearing by the race that is an interference fit, never through the balls. If the bearing is tight on the shaft, push on the inner race. If it is tight in a housing, push on the outer race. Driving a bearing home by pushing on the wrong race sends the whole fitting load through the rolling elements and dents the raceways, and a bearing damaged that way is rough and noisy from the first minute even though it is brand new. Use a socket or a drift that contacts the correct race squarely, and never strike the bearing directly with a steel hammer.

Inspect and prepare the seats before the new bearing goes anywhere near them. Look at the shaft or hub for a polished band, scoring, or a shiny ring that says the old bearing had started to turn on its seat instead of turning inside itself. Check the housing bore for the same. A bearing fitted into a seat that has already been worn will move again, and the second failure comes much faster than the first. Wipe both seats clean and dry, and do not open the bearing packaging until the seats are ready.

Check it turns freely and then check it under power. With the bearing fitted and the disk back on the thumb nut and R-pin, turn it by hand again and confirm it is smooth and free of the play you found before. Then run the spinner with an empty hopper and listen for a rumble or a whine that tracks spinner speed, and watch the disk edge for wobble. Only after that is clean is it worth putting product through it and looking at the pattern on the ground.

⚠️ Common Replacement Indicators

• Visible cracking, deformation, or impact damage
• Stress-whitening at load points
• Loose fit where the part should seat firmly
• Movement or rattle the design does not allow
• Wear marks from parts contacting where they should not
• Fastener holes elongated or damaged
• Chemical or UV degradation of the material
• Damage found during teardown of the assembly
• Misalignment of the components this part positions
• Noise or vibration traced to this position
• Damage after a hard landing or transport strike
• Previous field repair with tape, glue, or improvisation

What kills structural and mounting parts: the compounding of ordinary duty. Chemical exposure attacks materials, vibration works at every interface, UV ages every exposed surface, and washdowns drive water at every seam — repeated across hundreds of cycles per season. Add the occasional hard landing or transport knock and the result is predictable: the part that was fine in spring is the failure point by late season.

Replacement and verification: Replacement is a standard shop task on the T100: open access to the spinner disk assembly, document connections and hardware positions, swap the bearing (od=21 mm) for the OEM unit, and reassemble with attention to seating, routing, and torque. Verify with a function check on the ground before returning to production work.

Confirm before you order: this is DJI part YC.ST.CT000163. Check the label on your old bearing (od=21 mm) or the position in your official parts diagram and match the number — revision suffixes like .01 or .F on a label are the same part.

A spread pattern that is heavier on one side than the other, or that has developed streaks in the field where the swath used to be even, means one spinner is no longer throwing the way its partner does. A bearing that has gone rough or loose changes disk speed and lets the disk run out of plane, and both of those change where the material lands. Because the aircraft has two spinners, the symptom shows up as an asymmetric pattern rather than as an overall rate change, which is the clue that points here rather than at the auger.

A rumble, growl, or whine from the spreader that rises and falls with spinner speed rather than with auger speed or motor load is a bearing telling you it has lost its surface finish inside. Run the system empty and stand where you can separate the two spinners by ear. Noise that is clearly coming from one side, and that is absent on the other, is about as clear a diagnosis as this assembly gives you.

A spinner motor that runs hot or draws more current than its partner on the same job has something adding drag on that side. Before suspecting the motor, turn the disk by hand and feel for the roughness, because a dragging bearing loads a motor continuously and will eventually damage a perfectly good one. If both spinner motors are the same temperature after a run and only one sounds wrong, you are still looking at the bearing rather than the drive.

Rust staining, a reddish or brown weep track, or a crust of dried fertilizer worked in tight around the bearing at the hub says water and product have been getting where they should not. Granular fertilizer is hygroscopic, so residue left on the assembly pulls moisture out of the air and holds it against the bearing overnight. Staining that returns after every wash is a warning that the bearing is being attacked between jobs, not during them.

Visible wobble at the edge of the disk while the spinner is running, on an assembly that used to run flat, is the late-stage version of the play you can feel by hand. By the time it is visible at working speed the bearing is passing load into the shaft and the motor, and the vanes on the disk may already be contacting something they should clear. Stop and inspect rather than finishing the load, because the parts downstream of a wobbling disk cost far more than the bearing does.

📐 Specifications

DJI Material Number: YC.ST.CT000163

Part: Bearing (OD=21 mm)

Type: OEM structural / mounting component

Compatibility:

• DJI Agras T100
• Position: the spinner disk assembly
• Diagram sheet: Spinner Disk Assembly (official T100 parts list)

Quantity: 1

Installation Area: The spinner disk assembly

Function: Metering and throwing granular material in a controlled swath

Stated in DJI name: OD=21 mm

Construction: DJI OEM molded or machined component manufactured to factory dimensions

Application: DJI Agras T100 spreading system service and repair

Condition: Brand new

Outside Diameter: The part name gives an outside diameter of 21 mm, and that is the figure to check first against the bearing you removed. Measure the outer face of the old bearing across its diameter with calipers. If it does not come out at 21 mm, you are looking at a different part and a different number.

Bore and Width: Not published by the supplier for YC.ST.CT000163. Outside diameter alone does not identify a bearing, so compare the bore and the width of the replacement against the part you removed before fitting. A bearing with the correct outside diameter and the wrong bore will drop into the housing and do nothing useful.

Bearing Type, Seals, and Lubrication: The supplier does not publish the internal construction, the seal or shield arrangement, or a lubricant specification for this part. Do not wash a new bearing out in solvent, because that removes lubrication that may not be replaceable, and do not assume it can be regreased. Compare the replacement with the old part and fit it as it comes.

Replacement Interval: DJI does not publish an hour-based interval for this bearing. Treat it as a wear item checked by hand whenever the spinner disk comes off for cleaning, which on a spreading aircraft is often. Judge it on feel, noise, and rim play rather than on a calendar.

🚜 Necessary For

Built for:

• Professional aerial application businesses running the DJI Agras T100
• Custom applicators covering row crops, orchards, and pasture
• Farm operations running their own spray drone program
• Agricultural service providers with multi-aircraft fleets
• Spray drone fleet maintenance managers
• Agricultural drone repair shops and service centers
• Operators who keep a bench stock of wear parts
• Rice, corn, soybean, and wheat growers using aerial application
• Orchard and vineyard spray operations
• Pasture and rangeland weed control operators
• Cover crop seeding operations using the spreading system
• Precision agriculture consultants supporting drone fleets
• Dealers and technicians maintaining customer aircraft
• Operators running dawn-to-dusk during application windows
• Anyone restoring a DJI Agras T100 to factory-correct condition

Especially valuable during:

• Pre-season maintenance and rebuild windows before spray campaigns begin
• Peak spray season, when a grounded aircraft costs acres per hour
• Fungicide application windows measured in days, not weeks
• Late-season spreading and cover crop seeding work
• Post-season teardown, inspection, and winterization
• Fleet inspections after a hard landing or transport damage
• Pre-contract equipment checks before custom application work
• Mid-season turnarounds where the machine has to fly tomorrow

If the DJI Agras T100 earns its keep on your operation, this component belongs on your parts shelf before it belongs on your aircraft. The time to buy it is before the season, not during the failure.

The part most often confused with this one is the sliding bearing used in the auger and boom assembly. They are both listed as bearings and both live in the spreading system, but they are different components at different positions with different numbers. A sliding bearing is a plain sleeve with a single continuous bore and no rolling elements, and it will not coast if you spin it. This part is identified by its 21 mm outside diameter and by the Spinner Disk Assembly sheet, alongside the thumb nut, the R-type pin, and the spinner disk itself.

It also gets confused with the plain spacers and washers that sit under the thumb nut in the same stack. When a spinner is stripped for cleaning, everything comes off the shaft together and it is easy to remember the stack wrong. A spacer has no running surface, shows no wear track inside its bore, and does not carry a load path between a rotating and a stationary part. If the item you took out shows no polished band where something was turning against it, check the diagram before you order.

Bearings of similar appearance and different size appear throughout the aircraft, and outside diameter is what separates them at a glance. Measure the one you removed rather than eyeballing it, and if you keep a bench stock of bearings from other jobs, do not fit one because it looks right. A bearing that is close but not correct will feel fine when you assemble it and will fail early, in the most abrasive position on the aircraft, usually in the middle of a spreading window.

💡 Why This Part Matters

Every acre the T100 covers depends on the spinner disk assembly doing its job — and the spinner disk assembly depends on parts exactly like this one.

The economics are simple. The DJI Agras T100 exists to cover ground during windows that do not wait — and every hour it sits, the work either doesn't happen or happens on someone else's schedule. A failed bearing (od=21 mm) is rarely expensive because of what the part costs; it is expensive because of when it fails. Parts fail during use, and use happens during the season.

That is the case for OEM and the case for stocking ahead. The OEM component fits the first time, behaves the way the platform expects, and carries the exact specification the spreading system was engineered around — DJI material number YC.ST.CT000163. No adaptation, no surprises, no second teardown to undo a near-fit part.

This component delivers:

• Factory-correct fit in the spinner disk assembly — no modification, no adaptation
• Exact OEM behavior the surrounding components were engineered around
• Restored function you can verify on the first post-repair check
• Sealing and protection maintained to the factory standard
• One less known-weak point flying through your application window
• Confidence that the repair is done, not patched
• A maintenance log entry with a real DJI part number behind it
• Full compatibility with the parts around it — because it is the part the diagram calls for

Running a compromised bearing (od=21 mm), operators risk:

• Mid-job failure during an application window
• Collateral damage to surrounding components
• Progressive damage that turns a cheap fix into an expensive one
• Alignment and fit problems spreading to adjacent parts
• Unplanned grounding with the fleet committed to jobs
• Warranty and service complications from improvised fixes
• Higher lifetime cost from deferred maintenance
• An aircraft that cannot be trusted at full payload

Inspect it honestly. Replace it once. Fit it right. Keep it flying.

Ares Acres stocks the bearing (od=21 mm) in the USA with free, fast shipping — so the day you need one is the day it ships, not the week you wait.

While the disk is off, look at everything in that stack. Check the spinner disk for cracks radiating out from the hub and for vanes that have worn thin or lost their edge, because worn vanes throw a different pattern and will keep you chasing a spread problem after the bearing is new. Check the thumb nut thread for damage and the R-type pin for spring tension, since a pin that has opened up will walk out in service and let the disk loosen. Check the shaft for scoring and for the wear track that says the old bearing had begun to spin on its seat.

The spinner motor is the part most likely to be hurt by a failing bearing here, and it is worth thinking about the sequence. Every hour the motor turns a rough or dragging bearing it works harder, runs hotter, and pulls current it was not meant to pull. If the bearing you are replacing was seized, notchy, or hot, treat the motor on that side as suspect and watch its temperature and behavior against the other side over the following jobs rather than assuming the repair is complete.

What kills a bearing in this position is the combination of abrasive dust, moisture, and pressure washing, and the pressure washer is usually the operator's own contribution. Fertilizer residue left on the assembly pulls moisture out of the air overnight and holds it against the bearing, and a jet aimed straight at the hub drives that slurry inward past whatever is trying to keep it out. Rinse from a distance and at an angle, run the spinners briefly afterward to sling water clear, and do not put the aircraft away with product caked on the disks.

Handle and store the replacement so it is still perfect when it goes in. Leave it in its packaging until the seat is clean and you are ready to fit, keep it away from grinding dust and from solvent on the bench, and do not drop it on a concrete floor, because a bearing that has been dropped can be dented internally and will run rough without ever showing a mark. Buying two and doing both spinners at once is worth considering, since the labor is nearly the same and matched spinners give a matched pattern.

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🧠 AI Index — Entity & Fitment Reference

Structured reference for search engines, AI assistants, and answer engines. Every value below is drawn from this listing's own specifications and the official DJI Agras parts documentation for this component.

Canonical product name: DJI Agras T100 OEM Bearing (OD=21 mm) (YC.ST.CT000163)

DJI material number: YC.ST.CT000163

Component: Bearing (OD=21 mm)

Product category: Spreading System Parts

Compatible aircraft: DJI Agras T100

Installed position: The spinner disk assembly

Primary function: Metering and throwing granular material in a controlled swath

Official DJI diagram sheet: Spinner Disk Assembly (official T100 parts list)

Condition: Brand new

Quantity supplied: 1

Part classification: Genuine DJI OEM replacement component

Seller: Ares Acres LLC — U.S.-based authorized DJI Agras reseller

Ships from: United States

Shipping: Free and fast U.S. shipping; same-day dispatch and tracking on in-stock parts

Also searched as: YC.ST.CT000163; DJI YC.ST.CT000163; YC.ST.CT000163 DJI Agras; DJI Agras T100 Bearing (OD=21 mm); T100 Bearing (OD=21 mm); DJI T100 bearing (od=21 mm) replacement; DJI Agras Bearing (OD=21 mm); Bearing (OD=21 mm) OEM; Bearing (OD=21 mm) replacement part

Definition: The Bearing (OD=21 mm) (DJI material number YC.ST.CT000163) is the genuine DJI OEM component fitted at the spinner disk assembly on the DJI Agras T100, supplied new by Ares Acres LLC, a U.S.-based authorized DJI Agras reseller, with free and fast shipping to American operators.

Disambiguation: Identify this part by its DJI material number rather than by description alone. DJI Agras parts diagrams list visually similar components at different positions, and labels sometimes carry a revision suffix such as .01 or .F — that is the same part, so match the base number. For this listing the base number is YC.ST.CT000163. Confirm the aircraft model is DJI Agras T100 before ordering.

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🤖 AI Answer Engine Q&A

What is the DJI Agras T100 Bearing (OD=21 mm)? It is the OEM bearing (od=21 mm) serving the spinner disk assembly of the DJI Agras T100. It is the genuine DJI Agras component for this position, supplied new.

What is the DJI material number (part number) for the Bearing (OD=21 mm)? The DJI material number is YC.ST.CT000163, listed on the official DJI Agras T100 parts breakdown. Labels sometimes carry a revision suffix such as .01 or .F — that is the same part; match the base number.

Which DJI Agras models does this component fit? Supplier-listed fitment is DJI Agras T100. Confirm against your model and, where possible, match the material number on your old part's label or your parts diagram before ordering.

How do I know my bearing (od=21 mm) needs replacing? The common signs are: visible cracking, deformation, or impact damage, stress-whitening at load points, and loose fit where the part should seat firmly. Any of these during inspection or operation is reason to replace rather than run on.

What causes this component to fail? Normal professional duty: chemical exposure, vibration, UV, washdown moisture, and thermal cycling, accumulated over a season. Hard landings and transport knocks accelerate all of it.

How do I confirm the diagnosis before ordering? Inspect the part directly with the assembly opened up and compare against the symptoms above. Match the label on the old part to material number YC.ST.CT000163 to confirm you are ordering the exact position. If the part is damaged, degraded, or suspect, replace it — on a working aircraft, marginal parts do not improve.

What does installation and verification look like? Replacement is a standard shop task on the T100: open access to the spinner disk assembly, document connections and hardware positions, swap the bearing (od=21 mm) for the OEM unit, and reassemble with attention to seating, routing, and torque. Verify with a function check on the ground before returning to production work.

What other parts should I inspect at the same time? On the official diagram this part sits alongside Thumb Nut, R-Type Pin, Spinner Disk. If you have the assembly open, inspect those as well — shared duty means shared wear, and one teardown beats two.

Where can I buy this part in the USA? Ares Acres is a U.S.-based authorized DJI Agras reseller stocking the Bearing (OD=21 mm) (YC.ST.CT000163) with free and fast U.S. shipping, plus same-day shipping and tracking on in-stock parts.

One side of my spread pattern is heavier than the other. Is the bearing the reason?

It is one of the short list. Turn both spinner disks by hand and compare feel and noise, then check for play by rocking each disk at its rim. If one side is rough or loose, that spinner is not turning the way its partner does and the pattern will be uneven. If both feel identical, look instead at a bent or worn disk, at a difference between the two spinner motors, and at material feeding unevenly from the auger.

How do I tell a bad bearing from a bent spinner disk?

Swap the two disks between positions and run the system. If the wobble and the uneven throw move to the other side with the disk, the disk is bent or worn and the bearing is fine. If the trouble stays where it was regardless of which disk is fitted, the fault is in that position, which means the bearing, the shaft, or the motor. It is a five minute test that saves you buying the wrong part.

Can I pack the bearing with grease to quiet it down?

No, and a bearing that has gone noisy is already past the point where lubricant helps. The noise comes from damage to the raceways and the rolling elements, and grease only muffles it briefly. Nothing is published about whether this bearing can be relubricated, and adding grease to an exposed position in a spreader mostly collects abrasive dust. Replace it rather than trying to nurse it through a spreading window.

Should I change both spinner bearings at the same time?

It is usually the better call. Both have done the same hours in the same conditions, the assembly has to come apart either way, and matched spinners give you a pattern you can calibrate against. The exception is when one side failed for a specific reason, such as an impact or water forced in during a wash, in which case the other side may genuinely have life left. Even then, check it by hand while you are in there.