Can I run an internal gear hub on a single speed frame?
Neil Flock, Cycle Monkey: The answer is almost always going to be yes. The Rohloff hubs are designed to be compatible with almost any frame ever produced through various frame interface components. Quick release, threaded, and bolt-on axles are offered to accommodate vertical, horizontal, and through axle dropouts and 135, 142, 148, 170, 177, 190, and 197mm spacing options.
We have seen occasionally in the past that some carbon frames have a small flat surface area on the inside of the left dropout before widening towards the middle of the bike or joining a seatstay or chainstay which sits inboard of the dropout surface. This causes interference with the axle plate on the left side of the hub. In those isolated cases, some riders have ground the interfering material away while others have looked to other frames. Otherwise, it is rare to find a frame where a Rohloff will not fit, especially a SS frame.
Kindernay hubs will fit into most SS frames as well. Their hubs are all set up with thru axles with compatibility for 12×142, 12×148, 12×197 or 10×135 or 10x170mm frame spacing. For quick release frames, a through bolt is used, which could also be used in a horizontal dropout in combination with an axle tensioner like the Surly Tuggnut.
There may be some situations where a frame has a low-mount/chainstay-mounted brake where the brake-mounted torque adapter interferes with the seatstay but if the brake is mounted above the seatstay (high mount) then there will not be any interference issues.
Shimano Alfine should fit into any SS frame without a thru axle. These hubs have threaded axles only and are compatible with vertical or horizontal dropouts.
Enviolo/Nuvinci CVT hubs should fit into just about any non-fat bike frame. They are mostly seen with threaded axles for vertical or horizontal dropouts, but they also offer 12×142 and 12×148 adapter kits for thru axle compatibility.
Rohloff: There are many different gear hubs and many different styles of “single speed” frame available. The sheer number of variables make it impossible to provide one answer to cover all possibilities.
Lets start with the hub. All gear hubs need to anchor the internally created torque (hugging moment) to the frame. If they don’t, the axle will rotate (usually backward) as the sprocket is driven forward. Forward drive will only be created once the axle is hindered from rotating.
Some gear hubs anchor this hugging moment by incorporating a flat-sided axle with external toothed washers. The tooth of these washers grips inside the dropout slot to prevent the unwanted rotation.
Some gear hubs use a little arm which clamps to the chainstay preventing the unwanted axle rotation. Some gear hubs use a larger internal washer which connects with special features integrated into the dropout design itself. Some gear hubs offer a choice of several options for maximum frame compatibility.
Onto the frame. What constitutes a single speed specific frame?
- Forward open, elongated, almost horizontal dropout slots (think classic dutch bicycle)*
- Horizontal, rear open fork ends (BMX style)*
- Adjustable dropouts (sliding or rocker style)
- Eccentric bottom bracket
* how long is the slot? Adjustment room must be 25mm or above to facilitate correct chain tension with the desired primary transmission ratio and to accommodate component wear.
Lastly, onto the axle. Quick-release axles are designed to work in unison with a vertical horizontal slot. This dropout form will enable the wheel to be held securely in place by gravity. The skewer need only prevent the wheel from falling out when lifted off the ground.
Use of a quick-release hub, in a frame with horizontal dropout slots, will lead to the wheel moving under load. The classic fix is to tighten the Q/R skewer. This can have adverse effects upon the inner-workings of a gear-hub so it is vital that the correct axle style is selected for the dropouts it is to be mounted in.
The dropout itself will eliminate some gear hub options as not every hub is available with a choice of axle styles. The dropout will also dictate whether the torque anchoring method offered by the remaining gear-hubs is compatible. Some hubs will therefore fit in some frames. Others will not.
Thank you as always to this week’s contributors to the Ask A Stupid Question series. Your expert from Cycle Monkey was Neil Flock, a rider with 7 years of regular Rohloff use, 4 1/2 years on Pinion, 3 years on Effigear, and a few months on Kindernay. Your expert from Rohloff was Stewart Stabik, their Sales Manager and OEM Technical Support.