Pace RC21 STX Adapter

[LEG33]

Hi All,

Made an error and ordered a new granny ring for my STX FC-MC34 but didn't realise the middle ring carries the granny. Doh! So was just wondering if anyone has an adapter going?

Cheers,
Lewis

 

[LEG33]

Re:

Bump

 

[cherrybomb]

Re:

The granny ring is a standard size and is fitted in the normal way, so you should be fine. The middle ring forms the spider for the big ring on the earlier STX cranks and its a unique BCD.

I do actually have one of the Pace adapters, but it would probably be cheaper just to buy a new crank.

 

[LEG33]

Re:

Haha, no problem! I wouldn't have a clue how much those things are anyway!

 

[cherrybomb]

Re:

It's finding the Pace adaptors in the first place that's the real issue, hence my reluctance to part with it.

If you find you can't get the new granny ring to fit, let me know - I think I may have a couple of original rings knocking about.
It should work fine though, the only issue I can think is that you may need some spacers.

 

[Anonymous]

Are you looking for a STX middle ring?

 

[one-eyed_jim]

The RC21 adapter is for the earlier STX cranks that used a 58mm primary bolt circle and mounted the outer ring on the 58mm middle. Your MC34 crank uses a 94mm bolt circle, and the granny is mounted to the middle ring. The outer and middle rings mount to the spider as normal. You can't attach an RC21 adapter to an MC34 crank.

 

[one-eyed_jim]

MC34 - 94mm bcd:

http://bernd.sluka.de/Fahrrad/Shimano/T ... 4_1996.gif

MC33 - 58mm bcd:

http://bernd.sluka.de/Fahrrad/Shimano/T ... 3_1995.gif

RC21:

https://fstatic1.mtb-news.de/img/photos ... Spider.jpg

 

[cherrybomb]

The RC21 adapter is for the earlier STX cranks that used a 58mm primary bolt circle and mounted the outer ring on the 58mm middle. Your MC34 crank uses a 94mm bolt circle, and the granny is mounted to the middle ring. The outer and middle rings mount to the spider as normal. You can't attach an RC21 adapter to an MC34 crank.

You never stop learning... I always believed that the later cranks went to a 'normal' design & it was just the earlier versions that had the unique mounting system. Didn't realised they'd just flipped it round.

I've always thought it was odd that Shimano decided to do this on the STX cranks, they never used this design on any of the other groupsets did they?

I think I've got a pair of earlier cranks complete with chain rings if that's of any use?