Bicycle Mechanics - question about crank arms on '05 Bianchi Pista track bike

The 05 bianchi pista has Sugino rd crank arms and from my best guess has a cheapy shimano UN-73 bb with the tapered square axle. To get correct chain alignment the chainring is mounted behind the crank arm instead of in front. This is driving me crazy at the moment. Does anyone know if the Sugino 75 crank arms will fit properly on this bb?

The 05 bianchi pista has Sugino rd crank arms and from my best guess has a cheapy shimano UN-73 bb with the tapered square axle. To get correct chain alignment the chainring is mounted behind the crank arm instead of in front. This is driving me crazy at the moment. Does anyone know if the Sugino 75 crank arms will fit properly on this bb?The un-73 is ultegra quality. QBP says the s75 needs a 109 square taper BB,and it may require iso rather than jis taper.

I am going to have to take one crank arm off to see if their is any markings on the bb to make certain of the brand and model. Thank you for the head's up.

I am going to have to take one crank arm off to see if their is any markings on the bb to make certain of the brand and model. Thank you for the head's up.My old QBP catalogue says the sugino 109 sq taper for that sugino track crank is iso taper.

Just saw a bike in the ss/fixed gear room, has the 73 bb and the sugino 75's.

Just saw a bike in the ss/fixed gear room, has the 73 bb and the sugino 75's.You can stick a iso crank on a jis taper.Don't make it right tho.

I'd hardly call the UN-73 cheapie considering they typically cost $35-$40 at an LBS. Actually the '05 Pista likely has a real cheapie OEM square-taper BB, I know my '04 Axis did. You might save yourself some money and move the chainring to the outside and get a lighter, better quality, shorter spindled BB like a UN-73. Just make sure you have enought clearance on the chainstay.

The reason why I say I think its the un73 is that I had a bmx bike with one and it looks like it has the same cups with the weird splined internal lip and they are sealed bearing'd. I did figure it was cheap ($29.99, danscomp.com) comparing to all the bb's that the fixie guys are getting, IE phil wood, campy, sugino, Hatta.

Another thing that bothers me about the RD cranks is the fact that its not a true 165 crank, its a 175 with a hole drilled and tapped in the 165mm position. I know I am just knit picking, but Im starting to get the itch for upgrades. I can't help myself.

In the future I will be getting a quality (expensive) bb but will be running the sugino 75's. If I were to get the un-73 bb and switch the chainring now I would just be throwing away 30 bucks I guess. Just thinking aloud.

Another thing that bothers me about the RD cranks is the fact that its not a true 165 crank, its a 175 with a hole drilled and tapped in the 165mm position. I know I am just knit picking, but Im starting to get the itch for upgrades. I can't help myself.

Eeew. That is kinda cheesy. Makes sense for manufacturing ease. I'd hold off and get the 75s and a proper BB.

Are you sure your cranks are 165mm? That's weird, as my '05 Bianchi Pista has 170mm Sugino RD cranks. Also, the bottom bracket is some cheap no-name POS (I pulled it out of curiosity).

In response to Blastradius:

I agree that the chainring looks cheesy on the inside of the spider arm, although I don't think that installing a bb with a longer spindle will solve the problem, because it doesn't appear (at least on my bike) that there's enough clearance to move the crank arm closer to the bottom bracket cup (5-6mm??). The base of that RD crank arm is so fat, that it will rub up against the bottom bracket cup.

I meant the 175 length crank drilled and tapped in the 165 position was cheesy.

BTW, are the RD cranks "double" cranks with just one chainring on it?

Are you sure your cranks are 165mm? That's weird, as my '05 Bianchi Pista has 170mm Sugino RD cranks. Also, the bottom bracket is some cheap no-name POS (I pulled it out of curiosity).

In response to Blastradius:

I agree that the chainring looks cheesy on the inside of the spider arm, although I don't think that installing a bb with a longer spindle will solve the problem, because it doesn't appear (at least on my bike) that there's enough clearance to move the crank arm closer to the bottom bracket cup (5-6mm??). The base of that RD crank arm is so fat, that it will rub up against the bottom bracket cup.


I eye balled the measurement, but either way they do use a longer crank arm and drill for their intended length.

I have scene these crank arms with a double chainring.

On my set of double cranks there was a "ledge" that the inner ring would sit upon but I hack sawed them off and got back about 3mm of space that I could now move closer to the chainstay.