Tim McTeague writes:
> I have a hard time believing people can really "feel" the flex in modern cranks. With all the
> flexing going on in your tires, bars and stem it seems unlikely the crank bends enough to be felt
> my human nervous systems. My other hobby is audio and it is truly amazing what people are
> convinced they hear. Bricks on amps, frozen cables, green ink on CD's
, the list goes on.
I think you are correct with that assessment but it isn't why ISIS spline standard was introduced.
There are a sizable number of failures, in cranks, spindles failures, and bearing pitting from the
overload causes by such a small diameter shaft. Just because people who own bicycles for occasional
outings have no failures does not mean there are none. Proof of this is the controversial
instruction of mounting cranks with no lubricant on the square shaft. This is a mistaken notion
brought on by crank failures due to the high loads at this interface and of course ill advised
tightening of the retaining bolt.
> I think the major reason for the shift to splined cranks, other than just having something new to
> hype (and tying you into buying the manufacturers BB), is that they are cheaper to make. Square
> holes are more difficult to make with the tighter tolerances needed. But, I guess that's all we
> are going to have when Campy finally makes the switch.
The main impetus behind this is the same as Shimano's splined hollow crank spindles. There is a
reliability problem regardless of conjecture about motivations for change. The crank spindle is a
great leap better today than with steel cranks and cotters of old, but it is not reliable to the
degree that there are no liability claims for failures.
>> I've switched from "square" XT to splined LX. For me LX is way stiffer (I simply "feel" it, and
>> during hard pedaling with chain on largest chainring there's no rub against the front
>> derailleur). I think that XTR won't be significantly stiffer than LX (both are hollowtech and
>> splined).
The larger diameter of Shimano splined crank spindles greatly reduces stress and especially bending
from the outboard load from the pedal. I doubt that a rider can feel this but, as you say,
chainwheel lateral deflection is a good measure of spindle flex and spindle bearing clearance, both
of which are magnified at the rim of the chainwheel.
>> Melon - grandmaster of sweat, pain and suffering himself.
What does this have to do with square or splined crank attachment, or are you one of those who rides
bike to get self awarded merit badges for suffering. I think of these folks when I see them walking
around with "I survived the Death Ride" shirts. Look at me, I'm tough. I grimace a lot on bicycle
rides to look like Lance Armstrong in his publicity photos.
Jobst Brandt
[email protected] Palo Alto CA
) how noticable the difference is. I'm not saying that it improves performance
