
Shimano Ultegra CS-R8101 12-Speed Cassette Silver, 11-30T, 12-Speed
12-Speed
Velopedia Bicycle Archive
Original specifications: 6.78kg (14 lb, 15.2 oz) published weight · geometry for 6 published sizes.
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At a glance
| Frame Construction | Aethos FACT 10r Carbon, Rider First Engineered™, Threaded BB, 12x142mm thru-axle, flat-mount disc |
|---|---|
| Frame Material | Carbon Fiber |
| Fork | FACT Carbon, 12x100mm thru-axle, flat-mount disc |
| Fork Material | Carbon Fiber |
| Shifters | Shimano Ultegra Di2 R8170, hydraulic disc |
|---|---|
| Front Derailleur | Shimano Ultegra Di2 R8150, braze-on |
| Rear Derailleur | Shimano Ultegra Di2 R8150, 12-speed |
| Crankset | Shimano Ultegra R8100 with 4iiiis Precision 3+ Power Meter |
| Bottom Bracket | Shimano Threaded BSA BB |
| Cassette | Shimano Ultegra, 12-speed, 11-30t |
| Chain | Shimano M8100, 12-speed w/ quick link |
| Brakes | (F) Shimano Ultegra R8170, hydraulic disc, 160mm rotor / (R) Shimano Ultegra R8170, hydraulic disc, 140mm rotor |
|---|
| Handlebar | S-Works Short & Shallow, 125mm Drop, 75mm Reach w/Di2 Hole |
|---|---|
| Stem | Specialized Pro SL, alloy, 4-bolt |
| Saddle | Body Geometry Power Pro with Mirror, hollow titanium rails |
| Seatpost | Roval Alpinist Carbon Seatpost |
| Wheels | (F) Roval Alpinist CL II, 21mm internal width carbon rim, 33mm depth, Win Tunnel Engineered, DT for Roval 350 hub, DT Swiss Aerolite spokes, Tubeless Ready / (R) Roval Alpinist CL II, 21mm internal width carbon rim, 33mm depth, Win Tunnel Engineered, DT for Roval 350 hub, DT Swiss Aerolite spokes, Tubeless Ready |
|---|---|
| Front Tire | S-works Turbo 2BR, 700x28mm |
| Rear Tire | S-works Turbo 2BR, 700x28mm |
Frame measurements by size.
Published frame view
Select an available measurement to locate it on the frame.
| Measurement | 49 | 52 | 54 | 56 | 58 | 61 |
|---|---|---|---|---|---|---|
| Seat tube | 431 mm | 462 mm | 481 mm | 504 mm | 532 mm | 567 mm |
| Effective top tube | 508 mm | 531 mm | 540 mm | 562 mm | 577 mm | 595 mm |
| Head tube | 109 mm | 120 mm | 137 mm | 157 mm | 184 mm | 204 mm |
| Head-tube angle | 71.75° | 72.5° | 73° | 73.5° | 73.5° | 74° |
| Seat-tube angle | 75.5° | 74° | 74° | 73.5° | 73.5° | 73° |
| Chainstay / rear center | 410 mm | 410 mm | 410 mm | 410 mm | 410 mm | 410 mm |
| Wheelbase | 973 mm | 975 mm | 978 mm | 991 mm | 1005 mm | 1012 mm |
| Bottom-bracket drop | 74 mm | 74 mm | 72 mm | 72 mm | 72 mm | 72 mm |
| Bottom-bracket height | 266 mm | 266 mm | 268 mm | 268 mm | 268 mm | 268 mm |
| Reach | 375 mm | 380 mm | 384 mm | 395 mm | 402 mm | 408 mm |
| Stack | 514 mm | 527 mm | 544 mm | 565 mm | 591 mm | 612 mm |
| Standover height | 705 mm | 728 mm | 748 mm | 769 mm | 796 mm | 824 mm |
| Fork offset / rake | 47 mm | 47 mm | 44 mm | 44 mm | 44 mm | 44 mm |
| Front center | 574 mm | 577 mm | 579 mm | 591 mm | 606 mm | 613 mm |
| Trail | 63 mm | 58 mm | 58 mm | 55 mm | 55 mm | 52 mm |
| Fork length / axle-to-crown | 369 mm | 369 mm | 369 mm | 369 mm | 369 mm | 369 mm |
| Crank length | 165 mm | 170 mm | 172.5 mm | 172.5 mm | 175 mm | 175 mm |
| Stem length | 80 mm | 90 mm | 100 mm | 100 mm | 110 mm | 110 mm |
| Handlebar width | 380 mm | 400 mm | 420 mm | 420 mm | 440 mm | 440 mm |
Measurements may vary by configuration, wheel size, or frame setting where noted in the published chart.
Parts & serviceability

12-Speed


170mm, 50-34T
Based on the original build. Confirm the model, size and fit before ordering; installed parts may differ. As an Amazon Associate I earn from qualifying purchases. Velopedia may also earn from qualifying eBay purchases. Velopedia may also earn from qualifying retailer purchases.
This checklist uses the archived equipment for this bike. It cannot confirm the condition, service history or later component changes of the example in front of you.
Archived: 2025 Specialized Aethos Pro · Road · Published sizes: 49, 52, 54, 56, 58, 61
Archived: Frame: Aethos FACT 10r Carbon, Rider First Engineered™, Threaded BB, 12x142mm thru-axle, flat-mount disc · Fork: FACT Carbon, 12x100mm thru-axle, flat-mount disc · Carbon Fiber
Archived: Shifters: Shimano Ultegra Di2 R8170, hydraulic disc · Front derailleur: Shimano Ultegra Di2 R8150, braze-on · Rear derailleur: Shimano Ultegra Di2 R8150, 12-speed · Crankset: Shimano Ultegra R8100 with 4iiiis Precision 3+ Power Meter · Bottom bracket: Shimano Threaded BSA BB · Cassette: Shimano Ultegra, 12-speed, 11-30t · Chain: Shimano M8100, 12-speed w/ quick link
Archived: Brakes: (F) Shimano Ultegra R8170, hydraulic disc, 160mm rotor / (R) Shimano Ultegra R8170, hydraulic disc, 140mm rotor
Archived: Front tire: S-works Turbo 2BR, 700x28mm · Rear tire: S-works Turbo 2BR, 700x28mm
Archived: Handlebar: S-Works Short & Shallow, 125mm Drop, 75mm Reach w/Di2 Hole · Stem: Specialized Pro SL, alloy, 4-bolt · Seatpost: Roval Alpinist Carbon Seatpost · Saddle: Body Geometry Power Pro with Mirror, hollow titanium rails
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Specifications are presented as a reference. Components may vary by market, size, production run, or later manufacturer revisions.