Quoted message said:It's entirely possoble to destroy the splines inside the crank (I've seen that done, even by good
mechanics);
sure, but it's not something you see very often. you can replace brake pads on a car and mistakenly
put metal to metal - there's only so much allowance a manufacturer can make for fitting error.
[truth is, in the auto world, maintenence mistake-proofing is one of the biggest design challenges
faced, not engineering or materials.]
Quoted message said:there is a significant possibility of developing backlash in the left crank-axle interface;
see above. only if fitted incorrectly.
Quoted message said:and it wasn't an interference fit in the past, the crank coming to a stop against the bottom of
the splines and held in place by the bolt tension.
are you sure it's bottoming? i see no evidence of that on mine. it's close, but the taper is doing
it's job and stopping the arm /just/ short of bottoming.
Quoted message said:I have a number of buddies with the Shimano spline cranks and about 10% of them have had to
replace a crank thus far because of spline damage.
the spline damage /i've/ seen is because the retainer bolts have been fitted without the washer that
protects the soft aluminum as the bolts approach torque - everything got all mashed up. i don't see
that as a design problem specific to shimano other than the isis bolts i've seen have captive
washers and shimano don't.
<snip>
Quoted message said:My ISIS crank, OTOH, has a tight interference fit against which it bottoms out, just like a square
taper fit
contrary to what i thought earlier, isis is in fact tapered - or at least, the one i've just
measured is - so yes, you do have exactly the same thing going on for isis as you do for
square taper.
<snip>
Quoted message said:The shape of the splines seems much less likely to result in backlash.
yes, it's an improvement on square taper in that the shape of the splines are less likely to cause
debilitating damage if it's used without being properly torqued. but i still believe that shimano is
the best system - any machinist will tell you how well a [round] morse taper works.
<snip>
Quoted message said:Of course, I've never had a problem in 30 years with a square taper crank
that's great, but your experience is not the case for a lot of people as you will have seen here.
people consistently argue about bolt torques, use of threadlock, greased/non-greased tapers, etc.
square taper is fine if fitted properly, but it's very easy to get wrong.
Quoted message said:- these splined things are a solution to a nonexistent problem, IMHO.
i think octalink /is/ an excellent move towards a system that is /way/ more mistake-proof than
square taper. add to that the fact that it has the benefits of a morse-type taper [/and/ at the same
time, shimano really raised the bar on bearing quality] - seems like a good thing to me.
