Big Wheel Evolution?

Recently some paradigm shifting technologies have been seen on some new road and mountain bikes that are raising some eyebrows in the cycling world. Probably the most obvious is the extended seat mast on road and mountain bike models, but some other even more important changes have been put forth that I think will have an effect on what sort of 29″ers we will be riding in the near future.

First I would like to point out the head tube/steering tube changes seen on some road bikes and at least one mountain bike I am aware of. The change involves using a different, larger sized lower bearing with a corresponding larger sized steer tube. This is done to stiffen and strengthen the head tube/steer tube to allow for a more precise steering front end. In the case of mountain bikes, it also strengthens the head tube against frontal impacts and helps fork manufacturers make a stronger fork at the crown.

With a 29″ers head tube being short to keep the handlebar height at bay, I can see this technology being adapted to help strengthen the front ends of 29″ers, making them torsionally stiffer and steer more precisely. In fact, the headtubes on some 29″ers are so short, the size differential from upper bearing to lower bearing might create a steer “cone”, rather than a steer tube!

The other change I see making an impact is the integration of outboard bearing cups to an inboard posistion. This has been done on road bikes and now I have seen a mountain bike company doing this too. This results in an over 90mm bottom bracket shell width without changing the distance between the crank arms. That means the chainstays can be a bit bigger in this crucial area and allow designers to make room for fatter tires with shorter chainstays while still making the whole she-bang as solid as the Rock of Gibraltar.

Of course, this begs the question about “Q” factors and why we went the road of outboard bearings in the first place. Well, that’s an argument for another post. The thing is, outboard bearings and two piece crank sets are here to stay. At least this gets the bearing cups in a place where dirt and spooge can’t so easily intrude. It might even eliminate the outer cup altogether, placing the bearing race right on the bottom bracket shell itself, ala an integrated headset.

Whatever happens, it’ll be a fun time to be riding a bike, as it seems that a lot of old ways are being challenged and a whole new set of “retro-grouches” are being created!


No Responses to “Big Wheel Evolution?”

  1. Cloxxki Says:

    I know for a fact that one key manufacturer is looking into that head tube thing, and has been for at least over a year. Patience, but it WILL happen that way in the future.

  2. BearSquirrel Says:

    What is an example of inboard bearing bottom bracket shells?

  3. martini Says:

    Take a look see at what Wolfhound cycles has done for one example. Browsing through Eurobike photos I also saw this application on road bikes. Smart move in my mind. Should prove to be a much stiffer interface.

  4. MMcG Says:

    I think the new Pivot Cycles (Chris Cocalis and Dave Weagle) mountain bikes witll have this type of “inboard” bearing bottom bracket set up.

  5. Vandal Says:

    Examples of the steerer tube changes and integrated bb bearings can be seen on the Trek Madone.
    The lower headtube cup is 1.5″ while the top is the standard 1.125″. This addresses the stress riser created at the junction of the fork crown/steerer tube.
    The Madone also captures what would be the external bb cups in the carbon bb shell. The carbon is now molded to act as the seat for the cartrige bearings rather than having a metal cup for that purpose. The crank bolt pulls everything snug and play-free.

    In the case of the head tube, plenty of mtb manufacturers have started a trend towards integrated headsets. Does this spell the end for Chris King?

  6. Guitar Ted Says:

    BearSquirrel: My example is the new Yeti carbon AS-R bike that uses a standard Shimano outboard bearing, but it’s inside the BB shell. My bet is that soon we will see a “Madone” approach, (which is closely related to what Cannondale does with their SI bottom brackets) and the cup will altogether be eliminated. Another example is Crank Brothers new headsets which are nothing more than bearing races and bearings with no “cup” in the traditional sense.

    Of course, all this “new” stuff is really old. The direct placement of bearings on the frame is a trick used by old racing bikes from the 30’s and 40’s, which usually did this with head set bearings.

    Vandal: I’d be surprised if Chris King went the way of the dodo bird, because not everyone is going to buy into the “new” ways. Of course there will always be lots of custom builders and old frames about that will be needing traditional headsets too. Think about how many OE King headsets there are. Not many! King does most of their business aftermarket, and I suspect that will always be the case.

  7. Cloxxki Says:

    King will just do what they always do : launch a standard of their own, suiting their convenience. They did it with the Perdido intergrated headset, and will do it againn now with 1 1/4″ headsets, which they did offer for some time after Fisher had been pushing that.

  8. George Krpan Says:

    Retro-grouches make me grouchy.

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