Shimano UN72 BB question

[NHAero]

Last night I pulled an old Shimano XT crankset (FC-M737, 94/58 BCD, 44-34-22 if this helps) off my Klein MTB, and mounted a 110mm UN72 BB on my Litespeed Unicoi to check clearances and chainline. When I pulled it off, I noticed a rusty steel ring on the drive side of the BB. I don't think it was there before, so I surmise it was part of the crankarm and ended up on the BB spindle. Looking at the photo with the crank arm (the NDS but the DS is the same) there is a small circular recess on the inner face of the crank arm around the square hole, and I wonder if the steel ring was originally located there.

???

Thank you

[oldpotatoe]

Last night I pulled an old Shimano XT crankset (FC-M737, 94/58 BCD, 44-34-22 if this helps) off my Klein MTB, and mounted a 110mm UN72 BB on my Litespeed Unicoi to check clearances and chainline. When I pulled it off, I noticed a rusty steel ring on the drive side of the BB. I don't think it was there before, so I surmise it was part of the crankarm and ended up on the BB spindle. Looking at the photo with the crank arm (the NDS but the DS is the same) there is a small circular recess on the inner face of the crank arm around the square hole, and I wonder if the steel ring was originally located there.

???

Thank you

That's a ring put on UN series shimano BBs to prevent the crank from being pushed on too far..It's normal and came with the BB. This is a lower end BB but same gig..you may not have seen it with the RH cup on..GREASE inside those cups!! To prevent creaking.

[NHAero]

Grazie!

[-dustin]

That's a crazy looking BB. When did they make those?













:banana:

[oldpotatoe]

That's a crazy looking BB. When did they make those?


:banana:

UN26..lotsa of OE use for lower end bikes...About $10-$12 retail and ayup, shimano is still making money at that price point...:eek:

[mt2u77]

UN26..lotsa of OE use for lower end bikes...About $10-$12 retail and ayup, shimano is still making money at that price point...:eek:

OT, but it boggles my mind what Shimano can produce and sell for a profit. A BB for $10 is impressive, but take for example a $30 fishing reel-- insane. The parts diagram for those things look like a veritable explosion. How they make, assemble, package, distribute, and market those things and turn a profit is a marvel.

[zzy]

Honestly the quality of Shimano's low end stuff, like Altus, is pleasantly surprising too.

[-dustin]

UN26..lotsa of OE use for lower end bikes...About $10-$12 retail and ayup, shimano is still making money at that price point...:eek:
I was joking. Implying that tapered BBs were relics.

[dddd]

I was joking. Implying that tapered BBs were relics.

We thought you were one of the young ones who wouldn't recognize downtube shifters, and who probably couldn't use a telephone with a dial on it.

[Ronsonic]

I've considered busting apart one of Shimano's modern bottom brackets to take the bearings for Ultra-Torque cranks for a fraction of the price.

Hasn't happened because the Campy bearings keep running and even I'm not that cheap.

[oldpotatoe]

I've considered busting apart one of Shimano's modern bottom brackets to take the bearings for Ultra-Torque cranks for a fraction of the price.

Hasn't happened because the Campy bearings keep running and even I'm not that cheap.

PLus shimano bearings are 7mm width and UT needs 6mm..PowerTorque are indeed 7mm. But I get ya..:)

[GonaSovereign]

Honestly the quality of Shimano's low end stuff, like Altus, is pleasantly surprising too.

Agreed. Those low-end sealed Shimano BBs would be great at double the price.