Reading with interest your adentures with the Modal project bike, and curious about what you’d think about an adaptation I’ve been wanting to try with a slider dropout bike (should I ever get one.) My most recent frame was built with 132.5 mm dropouts at the builder’s recommendation (Moots) to run 130 or 135mm hubs. In normal derailleur “mode” I run 130s (or Bullseyes with extra spacers to be 132.5 exactly), but I also run a 135mm Rohloff hub without having to force the dropouts apart. Nice. But would this work and be better: build a slider frame with 135mm spacing and run stronger 135mm wheels for touring and general riding. But when road racing or in any other situation where borrowing a spare or panic-bought wheel might happen replace the stock sliders (the sliding aluminum parts) with another pair that have dropouts spaced 130mm (and the derailleur hanger positioned to match). That is, offset sliders. Whaddaya think? Thanks, –Eric
Dear Eric Your Modal bike concept sounds interesting and in concept seems workable. However, there a few more things you should consider.
When I design according to the Modal Concept, I first fully define each mode that I will try to incorporate into the bike. And by mode, I mean the complete bike. If I was to design the bike for you, I would want to know more than just the axle over-locknut distance (OLD) and the type of shifting system (or lack thereof) for each mode. Brakes, tire clearance, geometry, and braze-ons all need to be accounted for.
From your inquiry, it isn’t clear that you are definitely intending to make use a Rohloff internally geared hub on this hypothetical modal bike. Of course, use of the Paragon “slider” dropouts makes a Rohloff system very easy, since Paragon offers a leftside replaceable dropout specifically for mounting a Rohloff in the most convenient configuration. So let’s assume that the “touring” mode is two-fold, one derailleured and one Rohloff.
What kind of brakes are we using? If disc brakes are being used, the slider dropouts easily accommodate that as the left dropout (both standard and Rohloff-specific) come with IS disc caliper mount. But are you really intending on using this bike for road racing? Because I don’t consider the current generation of cable-actuated disc brakes to be responsive enough, though they are powerful. But if you go with a rim brake, the frame builder will need to be careful with brake placement on the seatstay, otherwise the slider dropout position may be limited by the the rim brake’s pad adjustment range. However, you could conceivably plan on using a disc brake for the Rohloff touring mode and a rim brake for sporty road mode (with derailleurs). This would make sense as the sport mode would likely use skinnier tires, allowing you to run the slider dropouts forward without the tire fouling the stays of seatstay bridge while bringing the rim closer to a dual pivot caliper (rim) brake.
What kind of front brake would you be using? If you go with a disc brake up front, that decision will definitely reduce your available choices for forks. You could choose 2 different forks, one touring with a disc mount and one for a rim caliper brake. However, if the heights of the forks are different (and typically such forks do differ greatly in height) , then the bike handling will be compromised.
Yet if we are talking about disc brakes, we are probably drifting away from the idea of easily replaceable wheels. More important than the 130mm v 135mm OLD issue, 700C wheels with disc hubs are just not that available in the typical bike shop. And there are no neutral support wheels as 700C disc brake. Maybe this will change in the future, but at the moment disc brakes are definitely a liability in terms of instant demand replacements.
I guess I would just need to know more about the modes you would like to incorporate into your design. The Modal Concept is about identifying the points that several modes all share and then seeing how far you can stretch the design to include the desired modes, and maybe some modes yet to be envisioned. Sometimes though there are modes that somewhat exclude each other.
A true fully loaded touring bike and a road racing bike are not likely to mesh in the same frame. A touring bike needs long chainstays for stability, tire clearance, and to get the rack away from your feet. Slider dropouts allow adjustability for the first two, but since the rack braze-ons would be on the seatstays rather than the sliders, the rack/bags end up being closer to your feet. And with all that weight, a touring bike needs to be stout for frame longevity and bike handling. A race bike needs tighter geometry and lightness. Though I have done touring on my own Modal Concept bike, it was more of a credit card tour with only about 42 lbs of bags and supplies. Though I had a seatpost mounted trunk bag and handlebar bar, rather than using rear panniers, I had a second fork made with low rider mounts for loading up the front. Both forks had the same height, so the geometry wasn’t thrown off. But my bike cannot run 28mm tires and fenders, nor can it carry enough load for a fully self-sufficient tour. As such, I saw little need to pursue the moderate increase in strength that comes from the wider spoke bracing of a 135mm OLD vs 130mm.
I think I would advise against trying to have dual 130/135mm modular dropouts. You would either have to acquire custom-machined thick dropouts for the 130mm hubs (a good machine shop could do it, but that’s likely to be costly) or shave down some dropouts for 135mm hubs (weakening them, bad idea). If you had the dropouts made wide, in a pinch you could cinch down the dropouts over a 130mm hub with the skewer. Or you could split the difference like Moots did with your current frame.
Maybe I am overestimating the extremes of modes you chose, but to clarify, I think that the Modal Concept works best if you pick a group of modes that have a similar wheelbase. Both Byron’s Modal bike and mine are primarily short wheelbase bikes, and so they are biased more on the sporty end of design. His bike has road race/sport-tour/singlespeed/Nexus modes, while mine currently has road race/fixie TT/road fixie/pursuit/mass-start track/light touring. Another group of modes that might work based on a long wheelbase would be a touring/cyclocross/rigid 29er/single speed. I could see that as 3 handlebars, two sets of derailleurs, two forks, 2-3 sets of wheels, and 2-3 sets of brakes (cable disc, hydro disc, and maybe canti). Another concept that popped into my head is a tandem/longtail cargo bike with a Rohloff. The rear half of the bike would have a really low top tube, and you could slide the seat all the way down and then double the cargo space without the stoker.…