Rear tire: 27.5×2.25.
Velopedia Bicycle Archive
2021 Polygon Syncline C3
Original specifications: geometry for 5 published sizes.
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At a glance
Archive #900001791- Model year
- 2021
- Category
- Mountain
- Original MSRP
- $1,249.00
- Sizes
- 27.5” SM, 27.5” MD, 29” MD, 29” LG, 29” XL
- Colors
- Brown Charcoal
- Geometry
- 5 manufacturer sizes
- In this record
- 21 specifications · archived image · original MSRP · geometry
Original buildCarbon Fiber
Frameset
| Frame Construction | ACX XC Performance |
|---|---|
| Frame Material | Carbon Fiber |
| Fork | RockShox Recon Silver RL, 120mm |
Drivetrain
| Shifters | Shimano Deore SL-M6100-R 12-speed Trigger |
|---|---|
| Rear Derailleur | Shimano Deore RD-M6100-SGS Direct Attach |
| Crankset | Shimano FC-MT510-1 32T 2-Piece-Crank |
| Bottom Bracket | Shimano BB-MT500-PA |
| Cassette | 12 Speed 11-51T |
| Chain | KMC New X-12 |
| Pedals | Alloy Cage Pedal W/ Reflector |
Brakes
| Brakes | Shimano BR-MT201; Levers: Shimano BL-MT201; Rotors: Shimano SM-RT10 F:180mm R:160mm Centerl Lock |
|---|
Cockpit & Contact Points
| Headset | Integrated W/ Sealed Bearing for Taper Head Tube, IS 42/28.6 | IS 52/40 |
|---|---|
| Handlebar | ENTITY XPERT, W: 740mm, BB: 31.8mm, R/D: 12mm, B: 9degree |
| Stem | Integrated W/ Sealed Bearing for Taper Head Tube, IS 42/28.6 | IS 52/40 |
| Saddle | Entity Void Saddle |
| Seatpost | Entity Xpert, 27.2X350mm |
Wheels & Tires
| Hubs | F: Shimano HB-MT400-B 15x110mm 32H Center Lock / R: Shimano FH-MT510-B 12x142mm 32H Center Lock |
|---|---|
| Wheels | Alloy Double Wall |
| Rims | 584-30 / 622-30 32H for Tyre 584 / 622-54/76 Tubeless Ready |
| Front Tire | WTB Trail Boss Tire, 27.5X2.25 / 29x2.25 |
| Rear Tire | WTB Trail Boss Tire, 27.5X2.25 / 29x2.25 |
No specifications match. Try a component name or clear your search.
Geometry
Frame measurements by size.
Frame diagram
Select an available measurement to locate it on the frame.
All geometry measurements5 sizes · 13 measurements
| Measurement | S (27.5”) | M (27.5”) | M (29”) | L (29”) | XL (29”) |
|---|---|---|---|---|---|
| Seat tube | 380 mm | 420 mm | 420 mm | 460 mm | 500 mm |
| Effective top tube | 569 mm | 594.6 mm | 597.7 mm | 621 mm | 649.15 mm |
| Head tube | 100 mm | 120 mm | 100 mm | 120 mm | 140 mm |
| Head-tube angle | 67° | 67° | 67° | 67° | 67° |
| Seat-tube angle | 75.3° | 75.3° | 75.3° | 75.3° | 75.3° |
| Actual seat-tube angle | 73° | 73° | 73° | 73° | 73° |
| Chainstay / rear center | 425 mm | 425 mm | 435 mm | 435 mm | 435 mm |
| Wheelbase | 1106.94 mm | 1134.8 mm | 1149.5 mm | 1176.9 mm | 1204.76 mm |
| Bottom-bracket drop | 45 mm | 45 mm | 64 mm | 65 mm | 65 mm |
| Bottom-bracket height | 308.5 mm | 308.5 mm | 307.5 mm | 307.5 mm | 307.5 mm |
| Reach | 410 mm | 430 mm | 430 mm | 450 mm | 470 mm |
| Stack | 596.6 mm | 615 mm | 633.2 mm | 651.6 mm | 670 mm |
| Standover height | 690.9 mm | 729.2 mm | 730.8 mm | 763.7 mm | 779.2 mm |
Dimensions as recorded.
Gearing
Lower gears help on climbs. Higher gears suit higher speeds.
RPM = pedal turns per minute.
Rear tire: 29×2.25.
How it works
Ratio = front teeth ÷ rear teeth. Hub gears also include the hub’s internal ratio. A 400% range means the highest ratio is four times the lowest.
Speeds are estimates from tire size and pedal cadence. Actual speeds vary.
Try your current gearingChanged tires or gears? Calculate your setup.
Your changes apply to this calculation. The archived build stays unchanged.
Gearing results
| Measure | Original | Your setup |
|---|---|---|
| Lowest ratio | — | — |
| Highest ratio | — | — |
| Total range | — | — |
| Lowest-gear speed | — | — |
| Highest-gear speed | — | — |
Speeds are estimates. These calculations do not establish component compatibility or available tire clearance.
Parts & serviceability
Find replacement parts
27.2x350mm

Race Face Ride XC Seatpost Black, 27.2x375mm
Replacement option
27.5x2.25 / 29x2.25
More parts (5)Fewer parts
Levers: SHIMANO BL-MT201; Rotors: SHIMANO SM-RT10 F:180mm R:160MM CENTERL LOCK
Based on the original build. Check fit and installed parts before ordering. Affiliate links may earn Velopedia a commission. As an Amazon Associate I earn from qualifying purchases.
Parts and service referenceQuick reference before buying parts
Archived specifications for reference. Check the fitted parts before ordering.
- Front tire
- WTB TRAIL BOSS TIRE, 27.5x2.25 / 29x2.25
- Rear tire
- WTB TRAIL BOSS TIRE, 27.5x2.25 / 29x2.25
- Drivetrain
- 12-speed
- Seatpost diameter
- 27.2 mm
- Bottom bracket / shell
- SHIMANO BB-MT500-PA
Equipment inspection checks 14 checks based on 6 archived component groups Open equipment checksClose equipment checks
Checks selected from the archived equipment. Confirm what is fitted today. This is not a complete safety inspection; use the full inspection guide before test riding.
Full used-bike inspection guide →
Frame and fork
Inspect the frame and fork →Archived: Frame: ACX XC PERFORMANCE · Fork: ROCKSHOX RECON SILVER RL, 120mm
Suspension
Evaluate the suspension →Archived: Fork: ROCKSHOX RECON SILVER RL, 120mm · Rear shock: -
Drivetrain
Check drivetrain wear →Archived: Shifters: SHIMANO DEORE SL-M6100-R 12-SPEED TRIGGER · Rear derailleur: SHIMANO DEORE RD-M6100-SGS DIRECT ATTACH · Crankset: SHIMANO FC-MT510-1 32T 2-PIECE-CRANK · Bottom bracket: SHIMANO BB-MT500-PA · Cassette: 12 SPEED 11-51T · Chain: KMC NEW X-12
Brakes
Inspect the brakes →Archived: Brakes: SHIMANO BR-MT201; Levers: SHIMANO BL-MT201; Rotors: SHIMANO SM-RT10 F:180mm R:160MM CENTERL LOCK
Wheels and tires
Check wheels and tires →Archived: Wheels: ALLOY DOUBLE WALL · Rims: 584-30 / 622-30 32H FOR TYRE 584 / 622-54/76 TUBELESS READY · Hubs: F: SHIMANO HB-MT400-B 15x110mm 32H CENTER LOCK / R: SHIMANO FH-MT510-B 12x142mm 32H CENTER LOCK · Front tire: WTB TRAIL BOSS TIRE, 27.5x2.25 / 29x2.25 · Rear tire: WTB TRAIL BOSS TIRE, 27.5x2.25 / 29x2.25
Controls and contact points
Archived: Headset: INTEGRATED W/ SEALED BEARING FOR TAPER HEAD TUBE, IS 42/28.6 | IS 52/40 · Handlebar: ENTITY XPERT, W: 740mm, BB: 31.8mm, R/D: 12mm, B: 9degree · Stem: INTEGRATED W/ SEALED BEARING FOR TAPER HEAD TUBE, IS 42/28.6 | IS 52/40 · Seatpost: ENTITY XPERT, 27.2x350mm · Saddle: ENTITY VOID SADDLE · Pedals: ALLOY CAGE PEDAL W/ REFLECTOR
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Specifications are presented as a reference. Components may vary by market, size, production run, or later manufacturer revisions.




