http://www.cyclingnews.com/tech.php?id=tech/2003/news/apr24
As used by L.A.
-Robert
In one of the photos it looks like the 10 speed cogset is splined onto a standard 9 speed body. That would be great, we all wouldn’t have to buy new wheels.
Yeah, but what about the two piece integrated bottom bracket and crank? :),
-Robert
I’ll bet the first people to take issue with the new crank will be PC and SRM users. No doubt it will be light and stiff, but it will preclude those aftermarket “training” cranks.
The new crank design will have little or no effect on these products. Shimano may have changed the spacing on the chainrings (c to c,) but then again, maybe they haven’t. I haven’t measured a set yet. If they have, all SRM (and the other aftermarket companies) need to do is modify their products to meet this dimension, and they will be compatible. Note also, that there really is no obvious mechanical rationale for Shimano to have changed this dimension. The existing 9 speed spec would work just fine with 10 speed; indeed, the 9spd Shimano crankset already has narrower chainring spacing than Campy 10 speed - contrary to popular belief.
The Outside-the-BB mounting of the bearing set is designed to do 2 things: increase the stiffness of the crankset/BB and, MUCH more importantly, increase the longevity of the bearing set in the BB.
Dura-Ace Octalink BB’s have a notoriously low life expectancy in difficult conditions - here in the Northwest, they are essentially an untenable product - and Shimano knows this. The Octalink spindle, quite simply, pushes the edge of the design envelope allowed by the standard BB shell dimensions (The ISIS spindle is infinitesimally larger than Octalink, and durability issues have been a nightmare for ISIS designers/producers.) By placing the bearings exterior to the Shell, Shimano can use a larger bearing set, with a potentially exponential increase in life expectancy for the BB - and you won’t have to overhaul your BB after every rainy race (which you should do with the Octalink unit.)
MH
The new crank design will have little or no effect on these products.
How do you figure that? The drive side, with spider, and the axle are one unit as in not separable. That being the case, the only way you can swap between PCs or SRM cranks is to swap both BB and cranks. That’s a mess and not practical for anyone. The pros are lucky enough to have a bike they can dedicate to the SRM or PCs. I’m not. And I’m not swapping the entire BB, just to use SRMs. If I want to use SRMs well, I’ll be using some other crank, probably FSA with an ISIS BB.
I don’t know anyone who uses an SRM who takes it off for every race - maybe once or twice a year for the “A” event, but that’s it. PC’s are another story, but according to Frank, you should never take them off anyways.
If the DA crankset is like the new XTR (and it looks like it is) it is very easy to take the whole thing off the bike (the crankarm/bb spindle, as you pointed out, come off in one piece.) A pretty quick operation, actually. It wouldn’t take me much more time to swap the cranks/BB back and forth than it would take me to re-adjust the derrailleurs. Not a big deal - then again, I’m a pretty good mechanic (and I got used to overhauling my Dura-Ace bb once a week, back when I was pig-headed enough to use one.)
Personally speaking, though, I would go the FSA/Isis route, too (which is what I do, although I run the Campy version on most of my bikes.)
Don’t get too comfortable with that setup, though. The entire bike industry is looking at a change in BB standard in the next couple of years (to a bigger BBshell ID.) I think this Dura-Ace/XTR setup will be seen as “transitional” ten years down the road.
Shimano and Campy are both working on a new BB spec, and FSA and the ISIS folks already have competing specs at or near market. A Campy designer told me directly that they WILL go to an “oversize” BB (and probably some kind of a splined interface at the same time), but the final design will be determined by their larger Italian customers. You can translate this as Campy is waiting for the dust to clear from the FSA/ISIS design group battle. Bear in mind that FSA is starting to have a profound impact on the Italian bike market, which is the driving force behind “road” components. Their probably wouldn’t be a Record carbon crank if FSA hadn’t killed Campy’s crank presence on the marquee bikes at the Milan show.
The telling quote (as regards these changes) came from Shimano about about a year ago: in the early pre-release publicity for the '04 Dura Ace kit, they said (I paraphrase,) “The next version of Dura-Ace will take the bicycle groupset as far as it can go, given the constraints of the design parameters. The following version will see a change in some of the basic bicycle design elements.”
Word is, these will be:
BB I.D.
Brake mount standard - discs on the road.
Hub spacing - 135mm to allow discs and more gears/less dish
MH