Dura-Ace 7700-->7703 crank mod?

[InertiaMan]

Hello RBT,

I'm trying to piece together a decent triple road crank in 180mm, which
is not an easy task. Objectives are: 180mm crank arms, 45mm
chainline, 30/39/53 or 30/42/53 rings, and ideally a splined BB
interface.

To achieve this, I'm considering buying a used 180mm Dura-Ace 7700
double crank, milling off the inner chainring "shelves", taking the
triple chainrings from a 175mm Dura-Ace 7703 triple, and then
installing those rings on the modified 180mm double.

As far as I know, this is exactly how Shimano "created" the 7703
cranksets -- just a mod to the doubles (milling the shelves), and then
the 30T ring is bolted directly to the 39T middle ring. But so far as
I know, they never offered the triple in 180mm, hence my kludge.

Can anyone confirm that this is (or is-not) viable?

 

[Wasatch5k]

InertiaMan wrote:
> Hello RBT,
>
> I'm trying to piece together a decent triple road crank in 180mm, which
> is not an easy task. Objectives are: 180mm crank arms, 45mm
> chainline, 30/39/53 or 30/42/53 rings, and ideally a splined BB
> interface.
>
> To achieve this, I'm considering buying a used 180mm Dura-Ace 7700
> double crank, milling off the inner chainring "shelves", taking the
> triple chainrings from a 175mm Dura-Ace 7703 triple, and then
> installing those rings on the modified 180mm double.
>
> As far as I know, this is exactly how Shimano "created" the 7703
> cranksets -- just a mod to the doubles (milling the shelves), and then
> the 30T ring is bolted directly to the 39T middle ring. But so far as
> I know, they never offered the triple in 180mm, hence my kludge.
>
> Can anyone confirm that this is (or is-not) viable?
>

You could try something like this-

http://www.vintage-trek.com/tripleizer.htm

--

Let the bridges I burn light my way...

 

[Sheldon Brown]

Somebody wrote:

> I'm trying to piece together a decent triple road crank in 180mm, which
> is not an easy task. Objectives are: 180mm crank arms, 45mm
> chainline, 30/39/53 or 30/42/53 rings, and ideally a splined BB
> interface.
>
> To achieve this, I'm considering buying a used 180mm Dura-Ace 7700
> double crank, milling off the inner chainring "shelves", taking the
> triple chainrings from a 175mm Dura-Ace 7703 triple, and then
> installing those rings on the modified 180mm double.
>
> As far as I know, this is exactly how Shimano "created" the 7703
> cranksets -- just a mod to the doubles (milling the shelves), and then
> the 30T ring is bolted directly to the 39T middle ring. But so far as
> I know, they never offered the triple in 180mm, hence my kludge.
>
> Can anyone confirm that this is (or is-not) viable?

It's viable but would require buying in to Shimano's proprietary 92 mm
BCD and you'd be stuck with a 30 tooth inner ring, since that's the only
size available.

You'd be much better off with a TA or Willow Triplizer, and wouldn't
need to modify the crank. See: http://harriscyclery.com/130

Better yet, just buy a 175 Ultegra triple. There's no benefit to the
180 mm cranks worth the trouble, expense and the unpleasant side effects.

See: http://sheldonbrown.com/cranks

If you're dead set on 180, we have Sugino AT 180 arms, 110/74, one of
the finest cranks ever made. (Sorry 180 is the only length we can get.)
Sheldon "Insert Nickname Here" Brown
+-------------------------------------------------------+
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