Re: Stripped crank arms = replace Tiagra cranks with 105 or Ultegra, new BB needed?


M-gineering wrote:
> Brad Ford wrote:
> > Tonight I experienced the joy of riding 15 miles home on one leg. The
> > ride started out fine, though my left cleat felt like it had a little
> > more play than usual. Within minutes this feel intensified -- stepping
> > on the pedal with any force felt like my foot was hanging off of it at
> > a 45 degree angle below horizontal. I thought maybe a rock had taken a
> > big chip out of the front of the SPD-SL cleat. I stopped and clicked
> > out, and the pedal came along for the ride....not good. The threads on
> > the inside of the left crank were stripped bare, and the pedal was
> > literally dangling there.
> >
> > This is my commuting bike, Trek 1200 with Tiagra triple + 9 spd
> > cassette. I've put about 7000 miles on it.
> >
> > This unfortunate incident brings up several questions:
> >
> > 1) How did this happen? I use Ultegra spd-sl pedals, and frequently
> > service them (i.e. once every month to 6 weeks) - cleaning them, then
> > applying a thin film of grease across the threads before tightening
> > them back in the ends of the crankarms. Did I overtighten?
> >
>
> not tight enough is more likely
>
> > 2) So now that my left crank is totally useless, I surfed around for a
> > while and could not find anyone selling replacement Tiagra triple
> > crankarms or even cranksets. Does anyone know where I can find some?
>
>
> LH cranks are available from Shimano as a spare. Try a bikeshop instead
> of a mailorderhouse. Instead of a new crank they might even be able to
> repair the destroyed thread with an insert
>
>
>
> > 3) If #2 is not possible, I might consider upgrading to a 105 or
> > ultegra triple crankset, though I really don't want to pour too much
> > money into this commuting bike. Is my existing Tiagra BB compatible
> > with a 105 or Ultegra triple replacement,
>
> early Tiagra has a square axle, later ones are the MTB style octalink,
> not compatible with roadcranks

Small point-'MTB' style octalink, for all MTB except XTR were a unique
spline dimension not compatible with anything else. XTR and road
Octalink were the same spline dimensions altho the spindle lengths
varied for road and MTB XTR.

.

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