I just re-assembled by Sugino triple chain ring set and the bolts are confusing me. I think the hex heads on the big and middle ring should face outwards but for some reason they've hidden one bolt behind the crank arm. The only way I could see to get the bolt in was the opposite way around. The outer bolt (the slotted one) was shorter and fitted; the hex head was too long.

Is this right ? Should they all go this way ? Is there a way to get the hex bolt through what appears to be too small a gap ?


Thanks in advance, Davebo.

you may be able to get it through, IDK. but i'm ready with the answer to your next question if you do.

The bolt hidden behind the arm goes in backwards from the others.

Sometimes the behind the arm nut needs to be in the ring's hole before the ring is located on the spider tabs. Sometimes this nut is shorter then the 4 others. Sometimes this nut has a knurled outer edge to better grip the ring's recessed hole. Sometimes the bolt is also shorter. Sometimes the teeth of the granny ring block tool access to this bolt so tightening it before mounting the inner ring is a good idea.

I never saw that advantage of this design. (Yes, I know the claimed weight and/or stiffness changes. I just don't think they are enough to offset the hassle.) Andy.

Thanks all. I did put the nut/bolt in the other way around and it won't be seen so happy it will stay together. The hex nut was too long to go in the gap and they all looked the same length.

I guess my next question would have been 'How do I get the b***** thing out again?' ;-)

Just need to jam the slotted nuts and torque it up. I got a fair amount of tension on it but my torque wrench never clicked (40Nm).

Thanks again for all of your help.

Why are you using crank bolt torque value on a chain ring bolt?

+1 I sometimes think changes in crank designs are done like women's fashions, all appearance and no functionality improvement. The only "hidden 5th bolt" design that isn't a hassle provides a threaded boss on the inside of the crank arm and uses just a bolt, no separate nut, for the hidden one.

You get fashion trickle from what the other companies did , like The High end Record Campag hid 1 0f 5 bolts.
the Chorus and lower did not, a prestige image gained? IDK.

Of course 'Ashtabula' OPC just forged a pin in the crankarm , the chainring had a hole it fit thru ,
then the bearing race screwed onto the crankarm , holding the chainring on.

I thought it was so that the area on either side of the arm had a better transition would be less likely to crack, compared to the "classic" orientation.

How many "classic" 5-bolt cranks have you seen or heard of that cracked at the web beside the arm? It may be given as a reason but it fixes a nearly non-existent problem.

I've heard of it happening a lot with Campy NR and similar cranks -- seems like it was common BITD to use a file to round over the corners of the web to prevent cracking.

I don't have much personal experience to bring to the table either way -- I started riding road bikes in 2009, and my equipment is late-80s and newer. I may never find out if the preventative filing I've done to my cranks helps or hurts.

Because I'm a numpty ? What would a reasonable chain ring bolt torque be ?

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