Freewheel Remover, 2-pin Suntour

SunTour's freewheel pattern is its own thing. Two and four-prong variants existed across the SunTour catalog from the 1970s through the early 1990s, and they don't interchange with the Shimano spline that came to dominate the post-cassette era. The 1670.3/4 is sized to the SunTour 4-prong pattern, the more common of the two on touring bikes, mid-tier road bikes, and the cross-country mountain bikes that defined the early 1990s.

The 4-prong layout is the difference. Where Shimano-pattern freewheels engage with internal splines and SunTour's older 2-prong tools (see 1670.2/4) catch the freewheel through two flats, the 4-prong design distributes engagement around four points at the freewheel's center. The result is a more positive grip than the 2-prong on a stuck freewheel, which is exactly the scenario the 1670.3/4 gets used in. SunTour freewheels are old now; most have been sitting on bikes for decades.

The dimensions are sized for the SunTour 4-prong specifically: prong-to-prong inside spacing 19.9 mm, outside spacing 23.9 mm, prong height 5.4 mm, prong width 6.8 mm. A 24 mm wrench flat on the opposite face takes a 1/2" ratchet or breaker bar.

How to use it

Same anchoring trick as every freewheel tool: seat the four prongs into the freewheel's matching pockets, then re-thread the wheel's QR skewer through the tool and snug the skewer nut against the tool's back face. The QR stops the prongs from popping out under load. Turn the 24 mm wrench flat counter-clockwise; loosen the skewer a quarter turn each time the freewheel breaks free further.

If the prongs don't seat: this isn't the right tool. Either the freewheel is a SunTour 2-prong (use 1670.2/4), a Shimano-pattern unit (use 1670.1/4), or a BMX 4-prong with wider spacing (use 1670.6/4).

Compatibility

• SunTour 4-prong freewheels (1970s through early 1990s catalog)
• Some Sachs / Sachs-Maillard freewheels using the SunTour 4-prong pattern
• Prong-to-prong inside spacing 19.9 mm, outside spacing 23.9 mm
• Not for SunTour 2-prong (use 1670.2/4)
• Not for Shimano-pattern or BMX freewheels (use 1670.1/4 or 1670.6/4)

Specs

• 4-prong SunTour engagement pattern
• Inside spacing 19.9 mm, outside 23.9 mm
• Prong height 5.4 mm, width 6.8 mm
• Overall height 23 mm
• 24 mm hex wrench flat for ratchet or breaker bar
• Trivalent chrome plated to ISO 1456:2009
• Article number: 1670.3/4

Built in Zreče, Slovenia

Unior has been forging hand tools in Zreče since 1919, and is the official technical partner of multiple World Tour and downhill teams. The catalog still carries the SunTour patterns because the bikes still come into shops; Schwinn Voyageurs, Bridgestone XO-1s, early Specialized Stumpjumpers, and the rest of the era's bikes have a thirty-year service life when the owners care for them. Workshops doing classic-bike restoration need the SunTour-specific tools; the 1670.3/4 is the right one for the more common 4-prong pattern.

Pro tip from our mechanics

Identify the prong pattern before you reach for the tool. SunTour 2-prong freewheels have two opposing flat-faced engagement notches at the freewheel center; the 4-prong has four pockets in a square pattern. Visually, the 2-prong looks symmetric across one axis and the 4-prong looks symmetric across two. If the freewheel is too corroded to identify, the Universal Single-Speed Freewheel Remover 1722/2BI-US clamps the outside of the freewheel body and bypasses the engagement-pattern question entirely. The cassette-replacement workflow has more on legacy freewheel identification: When and how to replace your cassette →