(Crossposted to alt.mountain-bike)
On Tue, 02 Dec 2003 19:58:57 GMT, Al Frost <
[email protected]> wrote:
>Chris B. <bikerider@-NOSPAM_THANKS-rogers.com> wrote in
>
news:[email protected]:
>
><snip>
>>
>> Well, what does that tell you? I have heard quite a few reports of bolts which have gotten loose,
>> gone missing or even sheared off at the head - not to mention stripping of the threads in the
>> hub. The fact that the rotor bolts that are supplied with disc brakes have thread locking goo on
>> them (and that Shimano *also* includes locking tabs to use with their non-splined rotors) would
>> serve to discomfort me if I still used a disc brake. I mean, leaving aside whatever Shimano's
>> motives are, does it not make more sense for the torque to be transferred directly from the rotor
>> to the hub? Engineer types, what sayest thou?
>
>The idea of a splined rotor makes sense for transfering the braking loads directly from the rotor
>to the hub, however, XTR rotors are a two piece design and therefore the "weak" link of the
>attaching bolts is now moved to the disk/splined rotor spider interface rivets. Granted the rivets
>are exposed to lower loads, in either design failure ultimiately depends on the strength of the
>bolt/rivet and the number of bolts/rivets versus the load.
I see no reason why the rotor could not be one piece. The comment of mine that you initially quoted
was a sidebar questioning why the 6-bolt IS standard became the standard in the first place if a
splined design can be superior. It's not like I'm a Shimano fanboy, the only XTR component I own of
theirs is a 12 year old rear hub which I bought used.
> My guess is most (if not all) failures of the 6 bolt configuration are due to improper assembly
> and/or poor attention to maintenance not design.
This is the standard response right out of the cyclist textbook. I have no evidence to show
otherwise but I wonder on what basis you reach your conclusion?
I'd be interested to hear if any disc brake users reading this have had or witnessed problems with
disc brake rotor bolts loosening, shearing or stripping the hub shell.
>I guess we should dump all of our 3,4 or 5 bolt cranks in favor of Shimano's yet to be released
>splined chainrings/cranks. Those pesky chainring bolts always come lose or break.
You can be snide all you like but I see no reason why a splined design again wouldn't be superior
here and if Shimano is going to go from 4-bolt cranks to 6 or 3 anyway, then they may as well
engineer a good splined design. Now that you mention it, I do think that chainring bolts can be
quite a pain in the ass, especially if there is corrosion and if you don't have a tool handy to keep
the sleeve from spinning as you tighten the bolt.. However, as you point out, there is such a huge
number of cranks out there working OK that switching from the half a dozen bolt circle and bolt
number 'standards' we have now to something else would be...uh, nevermind.
Your red herring still doesn't explain why disc brakes which have only in the last few years need to
use an inferior design - it's not like the designers didn't already have freehubs around to take a
lesson from.
