Not all down-country bikes are created equal. Polygon’s Siskiu D range spans three models—D5,D6 and D7—aimed at riders from curious beginners to experienced trail shredders. In this episode we rode each bike and compared how they differ in frame design, drivetrain, suspension and overall ride feel. Although all three share the same balanced geometry and 120 mm travel platform, subtle component choices make a big difference on the trail. Here’s what we learned and which model might suit you best.

Although the geometry is identical across the range—long reach, a slack head angle and shortchainstays for a lively yet stable ride—the rear triangles differ. The D5 uses a quick-release rearaxle and is offered only with 27.5-inch wheels in sizes S, M and L. The D6 and D7 adopt aboost-spacing thru-axle and a one-piece linkage that stiffens the rear end and reduces flex onrough trails. They’re available with 27.5″ wheels in smaller sizes and 29″ wheels in M throughXL, giving taller riders a faster-rolling option. All frames include internal dropper routingshould you wish to upgrade the D5 later.

The Siskiu D5 features a Shimano Alivio 2×9 drivetrain with a wide 11–34 tooth cassette. Thisprovides plenty of gears for riders who mix pavement, fire roads and mellow singletrack. Boththe D6 and D7 move to simple 1× drivetrains for trail riding. The D6 uses a Shimano Deore 1×10setup with an 11–46 tooth cassette, while the D7 steps up to an 11-speed Deore system with an11–51 tooth cassette for easier climbing. All models are equipped with hydraulic disc brakes butthe D6 and D7 use more powerful callipers for increased control on steeper trails.

Suspension is where the biggest leaps occur. The D5 comes with an SR Suntour XCM coil forkand a matching shock featuring a lockout but no rebound adjustment. The D6 upgrades to airsuspension front and rear—an SR Suntour XCR32 fork and X-Fusion O2 Pro RL shock—givingyou adjustable air pressure and rebound for tuning. The D7 goes further with a RockShox Reconfork and a Deluxe shock offering more support and suppleness. Both D6 and D7 are deliveredwith dropper seatposts; these allow you to lower your saddle using a handlebar-mountedremote so you can get your weight back for descents and raise it again for efficient pedallingwithout stopping[2]. Sizes S and M come with 150 mm of drop, while M–XL 29ers get 170 mmtravel posts.

All three bikes roll on double-wall rims that are tubeless compatible. Running tubeless lets youdrop tyre pressure for better grip and comfort and nearly eliminates pinch flats because there’sno inner tube to pinch against the rim[1]. The D5 and D6 use 24 mm internal-width rims suitedto 2.2–2.3″ tyres, while the D7 upgrades to wider 29 mm rims for 2.3–2.5″ rubber. That extrawidth on the D7 offers a larger contact patch and more stability at low pressures.