Tandem Ultegra front crank arm replacement?

[PatC]

I boutght an ebay tandem with an Ultegra crank. The right side crank arm
pedal hole was apparently stripped, then tapped for a 5/8 instead of the
stock 9/16. The left side is still 9/16 and is OK.

Is there a coil kit I can put in it to replace the threads, or should I
replace the crank arm? Or, do I have to replace the whole crankset?
Whichever option, where do I source the parts?

Thanks in advance, from the home bike mechanic...

PS - and I thought I would be able to ride it this weekend. )-:

 

[JeffWills]

PatC wrote:
> I boutght an ebay tandem with an Ultegra crank. The right side crank arm
> pedal hole was apparently stripped, then tapped for a 5/8 instead of the
> stock 9/16. The left side is still 9/16 and is OK.
>

It sounds like the insert came out with the pedal after the crank was
repaired. Did the previous owner keep the pedals? If so, the insert is
probably still attached to the pedal, I wouldn't bet on it still being
intact, though.

> Is there a coil kit I can put in it to replace the threads, or should I
> replace the crank arm? Or, do I have to replace the whole crankset?
> Whichever option, where do I source the parts?
>

It sounds like this has already been done, unsuccessfully. Pedal thread
inserts were commonly available, but I can't find them in any current
online listing.

Depending on the crank, though, you could replace it with anything
off-the-shelf. Since there's no chainrings, any right front crankarm
would fit. (You don't state what version of Ultegra you have, so it's
tough to make any definitive statement.) However, separate Shimano
crankarms are available from any knowledgeable dealer. Harris Cyclery
(cue Sheldon) should be able to get one for you, also.

Jeff

 

[PatC]

Thanks Jeff. Turns out after emailing the seller, the story is the
original buyer wanted a 172.5 Ultegra crank arm. The original shop used
a standard crank, flipped, drilled and tapped, I guess to 5/8. Funny
thing is, the left arm properly accepts the 9/16 pedal. Thinking about
this story, I don't know exactly what happened.

The seller said to use a 5/8 pedal. Not only do I not have one, that
sucks. It's amazing how well kept this bike has been. The tires are
worn down, but it's clean and there's hardly a scratch on the thing. My
bikes are mechanically correct, but they're always filthy and scratched!

We have a couple of good mechanics here in Nashville that I hope can
straighten it out for me with a coil. Otherwise, I'll be hunting a 172.5
front right crank arm (which may not be standard for tandems.)



"JeffWills" <[email protected]> wrote in
news:[email protected]:

>
> PatC wrote:
>> I boutght an ebay tandem with an Ultegra crank. The right side crank
>> arm pedal hole was apparently stripped, then tapped for a 5/8 instead
>> of the stock 9/16. The left side is still 9/16 and is OK.
>>
>
> It sounds like the insert came out with the pedal after the crank was
> repaired. Did the previous owner keep the pedals? If so, the insert is
> probably still attached to the pedal, I wouldn't bet on it still being
> intact, though.
>

>> Is there a coil kit I can put in it to replace the threads, or should
>> I replace the crank arm? Or, do I have to replace the whole
>> crankset? Whichever option, where do I source the parts?
>>
>
> It sounds like this has already been done, unsuccessfully. Pedal
> thread inserts were commonly available, but I can't find them in any
> current online listing.
>
> Depending on the crank, though, you could replace it with anything
> off-the-shelf. Since there's no chainrings, any right front crankarm
> would fit. (You don't state what version of Ultegra you have, so it's
> tough to make any definitive statement.) However, separate Shimano
> crankarms are available from any knowledgeable dealer. Harris Cyclery
> (cue Sheldon) should be able to get one for you, also.
>
> Jeff
>

 

[Jasper Janssen]

On Sat, 19 Nov 2005 13:55:47 GMT, PatC <[email protected]> wrote:

>We have a couple of good mechanics here in Nashville that I hope can
>straighten it out for me with a coil. Otherwise, I'll be hunting a 172.5
>front right crank arm (which may not be standard for tandems.)

If you use a regular right and take off the rings, you'll jsut be left
with some pieces of spider that aren't particularly in the way. Might be
easier than finding a left crank with right thread which you'd need
otherwise.

Jasper

 

[JeffWills]

PatC wrote:
> Thanks Jeff. Turns out after emailing the seller, the story is the
> original buyer wanted a 172.5 Ultegra crank arm. The original shop used
> a standard crank, flipped, drilled and tapped, I guess to 5/8. Funny
> thing is, the left arm properly accepts the 9/16 pedal. Thinking about
> this story, I don't know exactly what happened.
>
> The seller said to use a 5/8 pedal. Not only do I not have one, that
> sucks. It's amazing how well kept this bike has been. The tires are
> worn down, but it's clean and there's hardly a scratch on the thing. My
> bikes are mechanically correct, but they're always filthy and scratched!
>

Ohhh-kay... AFAIK, there's only 4 different threads that have been used
for pedals:
1/2" (used on steel one-piece cranks)
9/16" (used on nearly every other modern crank)
14mm (the possibly-extinct "French" thread:
http://www.sheldonbrown.com/velos.html#pedal )
1" (the truly-extinct Shimano "Dyna-Drive" pedal)

In 30 years of hanging around and pestering bicycle shops (15 of those
working in the business), I have never heard of a 5/8" thread pedal.
It's possible that it exists- but it's also possible that I'll win the
lottery tomorrow- without buying a ticket.

As I said- the seller probably extracted the threaded insert when
removing the pedal. It's *really* odd that the left crank is 9/16"
thread- are you certain it's 172.5mm length? The references I can find
show only two lengths for the Ultegra tandem crank: 170mm and 175mm:
http://www.tandemseast.com/parts/cranks.html (scroll down a bit).

> We have a couple of good mechanics here in Nashville that I hope can
> straighten it out for me with a coil. Otherwise, I'll be hunting a 172.5
> front right crank arm (which may not be standard for tandems.)
>

Note that Tandems East lists FSA tandem cranksets in 172.5mm. Pricey,
though. You could also see if Peter White Cycles has a TA tandem setup
in 172.5mm: http://www.peterwhitecycles.com/zephyr.asp

It's up to you to decide if the 172.5mm length is important to you. If
it were my bike, I'd just put 175mm arms on it like all my other bikes.
But then, I'm 6-foot-4, and 175mm cranks feel "short" to me.

Jeff

 

[PatC]

Thanks everyone for the replies. I found a LBS Here's what I think
happened:

The original cranks were Ultegra cranks that were flipped. Since that
sets the threads "backwards", they were drilled, tapped and helicoiled to
the correct threading. I guess the original owner wanted 172.5 length
(which is what I'd want!)

At some time, I think the helicoil came out, and stuck to the pedal. The
coil is probably still on the pedal, since the original owner thought I
needed a 5/8. Apparently that size is for some BMX stuff?

Long story short, I found a bike shop that could re-coil the threads, and
I'm in business now!





"JeffWills" <[email protected]> wrote in
news:[email protected]:

>
> PatC wrote:
>> Thanks Jeff. Turns out after emailing the seller, the story is the
>> original buyer wanted a 172.5 Ultegra crank arm. The original shop
>> used a standard crank, flipped, drilled and tapped, I guess to 5/8.
>> Funny thing is, the left arm properly accepts the 9/16 pedal.
>> Thinking about this story, I don't know exactly what happened.
>>
>> The seller said to use a 5/8 pedal. Not only do I not have one, that
>> sucks. It's amazing how well kept this bike has been. The tires are
>> worn down, but it's clean and there's hardly a scratch on the thing.
>> My bikes are mechanically correct, but they're always filthy and
>> scratched!
>>
>
> Ohhh-kay... AFAIK, there's only 4 different threads that have been
> used for pedals:
> 1/2" (used on steel one-piece cranks)
> 9/16" (used on nearly every other modern crank)
> 14mm (the possibly-extinct "French" thread:
> http://www.sheldonbrown.com/velos.html#pedal )
> 1" (the truly-extinct Shimano "Dyna-Drive" pedal)
>


> In 30 years of hanging around and pestering bicycle shops (15 of those
> working in the business), I have never heard of a 5/8" thread pedal.
> It's possible that it exists- but it's also possible that I'll win the
> lottery tomorrow- without buying a ticket.
>
> As I said- the seller probably extracted the threaded insert when
> removing the pedal. It's *really* odd that the left crank is 9/16"
> thread- are you certain it's 172.5mm length? The references I can find
> show only two lengths for the Ultegra tandem crank: 170mm and 175mm:
> http://www.tandemseast.com/parts/cranks.html (scroll down a bit).
>
>> We have a couple of good mechanics here in Nashville that I hope can
>> straighten it out for me with a coil. Otherwise, I'll be hunting a
>> 172.5 front right crank arm (which may not be standard for tandems.)
>>
>
> Note that Tandems East lists FSA tandem cranksets in 172.5mm. Pricey,
> though. You could also see if Peter White Cycles has a TA tandem setup
> in 172.5mm: http://www.peterwhitecycles.com/zephyr.asp
>
> It's up to you to decide if the 172.5mm length is important to you. If
> it were my bike, I'd just put 175mm arms on it like all my other
> bikes. But then, I'm 6-foot-4, and 175mm cranks feel "short" to me.
>
> Jeff
>
>