New Curved Stays and OS Bottom Bracket Shells

Fitting wide tires and/or fenders between road cranks can be a challenge. René Herse was a master of frame design, who curved his chainstays ‘just so’ to create the room he needed. On the tandem above, not a single millimeter is wasted, and the result are perfect clearances for 42 mm-wide tires, fenders and cranks with a narrow Q-factor.

The first step toward replicating Herse’s mastery in modern bikes was to make a bottom bracket shell with the correct angle for curved chainstays. We already offer this shell for standard-diameter tubes. Brand-new is the same shell for oversized down tubes. These parts eliminates the need to ‘blacksmith’ the chainstay sockets of BB shells designed for straight chainstays.

There are many ways to bend the chainstays. To obtain easily replicable results, Hahn Rossman machined dies that fit perfectly over the chainstays. They create a beautiful curve without kinks or bulges. We’ve developed the exact shape through CAD design and the experience of building numerous bikes with curved stays.

Curving stays is a labor-intensive process, to say nothing of the time and effort to make the dies, but it’s almost a necessity for modern all-road bikes.

We now offer the curved chainstays ready to go. They also are indented slightly on the inside to increase the clearance further, without creasing them as you often see on older bikes. The curved chainstays are a perfect match for the Compass bottom bracket shells. They are available separately or as part of the complete tubesets that we’ve developed  in collaboration with Kaisei, the Japanese maker of top-quality steel tubes

Also new in program are lighter-gauge chainstays, which balance the stiffness of our ‘Superlight’ tubeset.

As a final part of the puzzle, Hahn also made a gauge that visualizes the required clearances for a Rene Herse crank (177 mm length) with a 48×32 chainring combination. If the gauge fits, then your cranks will work with the recommended 110 mm bottom bracket. And since Rene Herse cranks have one of the narrowest Q-factors and a standard road chainline, other cranks will fit as well.

If the gauge fits, then smaller chainrings and shorter crankarms will fit, too. If you need more room, space out the cranks with a longer bottom bracket spindle. This gauge takes the guesswork out of the parts you need to order.

The photo above shows a fillet-brazed frame, because the new bottom bracket shell for OS tubing wasn’t available yet. With the new BB shells and curved stays, standard road cranks, even those with a narrow Q-factor, will fit, unless your rear spacing is much greater than 130 mm.

When I built my Mule (above), it was intended as a prototype for a modern all-road bike that can travel with speed and comfort over any distance, on any road and in any weather. Over the last few years, we’ve productionized most of the parts used in this build. Creating a custom all-road bike has never been easier!

Further reading:

 

About Jan Heine, Editor, Bicycle Quarterly

Spirited rides that zig-zag across mountain ranges. Bicycle Quarterly magazine and its sister company, Compass Cycles, that turns our research into the high-performance components we need for our adventures.
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27 Responses to New Curved Stays and OS Bottom Bracket Shells

  1. starground says:

    The work you are putting into enjoyable cycling is commendable… A pat on the back and tailwinds to you all!

  2. bengeldreich says:

    Jan, Thanks as always for doing the work you do and changing the way people build and ride bikes. I’ve learned a great deal from your writing. Out of curiosity have you ever written about your front pannier rack on your “Mule”? I love how simple it is and yet haven’t seen one quite like it. Would love some more info on it if you can. Thanks

  3. Gugie says:

    Great news on the BB and chainstays! I’m in the middle of designing new personal frame, since I’m not a lightweight rider, an oversize downtube and round chainstays are on my list. This solves the remaining design issues I’ve had!

  4. Dana Shifflett says:

    The Mule is a prototype? That suggests a production bike, or at least frameset, and since I not a framebuilder, I’d be interested.

  5. Thanks for continuing to reasearch, develop, and make new frame building materials available!

    Do you have any intention of offering these chainstays in a longer version for those of us that like to build with longer chainstay lengths?

    While I’m inquiring, the same goes for the the wonderful Kaisei Toei Special fork blades. A little extra length on those would be great for those bikes with bigger tires and proper fender clearance.

    • The chainstays would require new tooling to make them longer. The cost is very high, and most riders prefer shorter chainstays, so the demand isn’t there to justify the investment.

      We did get Kaisei to make the ‘TOEI Special’ fork blades 15 mm longer for us. Unfortunately, the latest shipment was taken from stocks intended for other builders, so it’s back to the original 405 mm length. The next shipment in January 2019 will include the longer 420 mm length. Those extra 15 mm should be enough to make bikes for even very wide tires.

  6. Nestor Czernysz. says:

    Out of stock? Seriously? Talk about underestimating market demand.:)

  7. thebvo says:

    I thought that the balance of the frame was due to the flexible main triangle and a stiff read triangle. In all the BQ articles I can think of you suggest that a stiff set of chain/seat stays are vital to the performance of the frame.

    • Riding the superlight J. P. Weigle from the Concours de Machines, I found that it climbs very well – yet it uses light chainstays. It appears that the balance of the frame is important, and with a very flexible main triangle, the chainstays don’t need to be super-stiff. The 0.7 mm stays aren’t noodles – and in any case, we still offer the 0.8 mm stays with all our tubesets, too.

  8. Mark Guglielmana says:

    Since many of us use CAD to design frames, we need a drawing/bend angle for the chainstays and bottom brackets. Please publish drawings for these!

  9. Dane Morrison says:

    Hi Jan – I’m building an Allroad Adventure bike. How wide of a tire will this BB/Stay combo take with Fenders? Will it take 650b x 48, 54? What about 26″ x54? How small of an inner Chain Ring with 135/142 rear? Ideally I want to run 54mm rear either 26″ or 650B and Disc.

    Thanks

  10. Ben Hudson says:

    Do you think Hahn would consider making the dies to sell to framebuilders, or are they such a labour of love that they’re only economical for curving stays on the distribution scale?

    • The latter is the case – a set of these would cost the price of a custom frame. Also, they work only for the Kaisei stays, as they are designed to form the stay to the new shape. The dies are not just bending the stays, but also flattening them on the inside – similar to the dimple that many classic bikes have for clearance, but without the sharp crease.

  11. Nazaire says:

    Hello Jan, I will surf on this post to ask a question about your René Herse bike: If you were to build it today, what would you do differently?

    I will be asking a framebuilder to make me one in the near future, so I will read your thoughts with great interest. Might be the subject of a post!

    Thanks for your great work and generosity!

    • Good question! Really, these 650B randonneur bikes now are so mature that I’d do very few things differently, even though my Herse now is 7 years old. It’s proven itself incredibly reliable and great fun to ride.

      The list of changes is short:
      – Front rack. I’d go for a more standard solution. This is a topic for a future article or post.
      – Rinko. I’d make the bike Rinko-compatible, which would preclude the internal routing of the rear brake cable.
      – Wide-Body hub. The SON Delux is fine, but I’d definitely use the Wide-Body now. Stronger wheel and better looks.
      – SL dropouts. It’s not a big deal, but I really like having the connector-less SL system on the Mule.
      – More gears. The 5-speed freewheel is fine for paved rides, but gravel roads often have steep climbs, and I’d like lower gears than the 30-22 on the bike.

      The Herse already has the curved chainstays, ‘TOEI Special’ fork blades, and Superlight tubeset, so no change needed on these counts. I’d definitely keep the low-trail geometry, the centerpull brakes, three bottle cages, the pump on the seatstay, and almost everything else. That said, I’d probably use a Gilles Berthoud saddle. My Brooks is fine, but it’s the second one; the first one turned lopsided pretty quickly. The Gilles Berthoud saddles have a much more consistent quality. (They’re also are a bit lighter.)

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