We know, there’s no such thing as a stupid question. But there are some questions you might not want to ask your local shop or riding buddies. AASQ is our weekly series where we get to the bottom of your questions – serious or otherwise. This time we ask Cycle Monkey and Rohloff about internal gear hub compatibility with single speed frames! Hit the link at the bottom of the post to submit your own question.
 
I did a double take when I saw this question from a reader sat in the list of submissions. Gears on a single speed frame? What now? Turns out, the answer is yes, you can run an internal gear hub on a single speed frame. But, as is usual with bicycle technology, there are numerous exceptions to the rule. So, the real answer is it depends… The good guys at Rohloff and Cycle Monkey are on hand to talk us through it.

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 XIV MTB internal gear hub, 14 speed thru-axle mountain bike internally geared hub
Kindernay’s XIV 543% internal gear hub is the first thru-axle internal gear hub, offering 14 speeds

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.

budnitz bicycles shimano alfine internal gear hub commuter bike

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.

Schindelhauer Heinrich Hannah Enviolo commuter e-bikes, Automatiq automatic shift Bosch city e-bikes

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.

Budnitz-0-G_Zero-G_limited-edition-titanium-ti-gravel-road-bike_studio-complete Rohloff
A 14-speed internal Rohloff Speedhub on a limited edition Budnitz Ø:G titanium gravel bike

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.

Got a question of your own? Click here to use the AASQ form to submit questions on any cycling-related topic of your choice, and we’ll get the experts to answer them for you!

3 COMMENTS

  1. I am confused. When I think of a “single speed frame” I picture 120mm rear dropout spacing (or even 126/130 for road bike conversions) and none of these options appear to fit since the spacing is 135+. Could someone help me out here?

  2. You are forgetting that belt drive hubs need a frame that can be opened for the belt to be put through, so good luck with sawing your seatstays through to get the belt in 😉

  3. When I hear single-speed I think 120mm OLD–track spacing. And there are hubs available for that, I happen to be using one on my current bike–a Sturmey Archer 8 speed. Rohloff doesn’t offer a 120, but a modification can be done with a steel frame to make the 135 fit fit. Shimano and Sturmey Archer both have 120mm hubs

    AND SunXCD makes a 7 speed cassette body hub to fit a 120mm hub–with 10spd gears and spacers

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