Bicycle Mechanics - Urgent! Shimano RX100 won't fit on UN54!

On my friend's Bertoni road bike, I replaced a Stronglight bottom bracket with a Shimano UN54 (70x113), thinking that the Shimano RX100 crankset that I bought would fit.

It doesn't seem to fit properly. Unlike the other bike I put together, the right crank does not go all the way in the BB shaft and the left crank doesn't seem to go in as much either.

None of the bike shops around carry Italian bottom brackets, so I would have to order it. My friend is leaving on Friday, so I would have to order the right one ASAP. :twitchy:

Edit: I double checked and tried to make it work. It seems to work, but ---> see bolded sentence above.

The problem was that the crank did not go in far enough for room to shift to the big chainring.

According to Sheldon Brown's Bottom Bracket Size Database (http://www.sheldonbrown.com/bbsize.html#rx100), the RX100 crankset's "Length" is "113".

Am I overreacting about the cranks not going in as far?

113 is the axle length. You need to determine the axle length required for the RX100 cranks. I didn't double-check, but if Sheldon's site says 113, then 113 it is.
As far as shifting the front chainring, it is possible that you have to adjust the front derailer limit screw that controls the outboard movement of the DR.
Apparently it was set for the bb spindle that was on there originally.

Just adjust the derailleur. I can't imagine that your chainline is off - if any - a significant amount.

the cranks shouldn't bottom out on the axle, if that's what you're talking about.

Which version or RX100 do you have?

RX100 A550 Double 113 Square 43.5 130 7-speed 1990-93

RX100 A551 Double 107 Square 43.5 130 8-speed 1994-2000

113 is the axle length. You need to determine the axle length required for the RX100 cranks. I didn't double-check, but if Sheldon's site says 113, then 113 it is.
As far as shifting the front chainring, it is possible that you have to adjust the front derailer limit screw that controls the outboard movement of the DR.
Apparently it was set for the bb spindle that was on there originally.

That makes sense. Thank you.


Just adjust the derailleur. I can't imagine that your chainline is off - if any - a significant amount.

Sounds good. Thank you.


the cranks shouldn't bottom out on the axle, if that's what you're talking about.

I see. A different bike that I was working on had old JIS cranks with the right side "bottomed out" on the UN54 bottom bracket, so I thought these would fit the same way.
Thank you.

Which version or RX100 do you have?

RX100 A550 Double 113 Square 43.5 130 7-speed 1990-93

RX100 A551 Double 107 Square 43.5 130 8-speed 1994-2000

I have the 7-speed set.

Are you greasing the flats and using a torque wrench? I usually go for about 25ftlbs on my cranks.