Bottom Bracket Question
 

Last bit of help needed, I'm changing out my original crankset on my old '93 Giant Sedona with the shimano FC-M361. On Shimano's website, they say to use the UN26 bottom bracket.

http://techdocs.shimano.com/media/te...9830667768.PDF

But so many reviews of that bb say that the plastic part is flimsy and will break and the UN55 is all metal and more durable. Can I use the UN55? Don't know why Shimano would't list it since it costs more and you'd think they'd want folks to buy the more expensive one.

Thanks

That is puzzling, but the 113mm UN55 ought to work. Perhaps the crankset is specified for lower-priced bikes, and Shimano knew owners would be upset if the bike shop accidentally used a pricier replacement BB? That's just a wild guess.

I believe ThermionicScott is correct that a more expensive bottom bracket would not sell well along with an inexpensive crank.

However, the UN26's plastic non-drive side cup works well and is only broken by improper installation and removal. To install it properly, install the cartridge unit firmly first, then install the plastic cup loosely, torque the cartridge to spec and finally tighten the plastic cup snugly but no to anywhere near the full torque a metal cup specifies. To remove the bb, remove the cartridge side first, then the plastic side will come out by hand. Done right these plastic cups are creak free and last as long as the bb.

Thanks for the help guys. [MENTION=38165]HillRider[/MENTION], even though I'm sure you are correct about the UN26 still being a decent product, I'm not too concerned about weight on this bike and I'd rather pay a little more for a solid metal piece. Looks like you guys think the UN55 should fit fine so I think I'm gonna go with it. Thanks for the help

Actually the UN55 will weigh slightly less than the UN26 so you have the best of both worlds.

Bonus!

Ok, I've started the project and removed the existing crankset and BB. It took superhuman strength to get the BB off, 20 years of grit and tightness. I measured my existing BB spindle length and it's 117mm. The crankset I was considering is 113mm compatible and I'd have to buy a 73x113mm BB (the Shimano UN55).

So my new question - will 4mm difference in spindle length affect my chainline too much? I know it's only 2m on each side, but I'm reading on some sites that it would probably affect shifting. And if it does, how would I fix that?

BB lengths are specified for the crankset so that it can achieve the right chainline. The BB length for the prior crankset is more or less irrelevant if you're not going to use it anymore. :thumb:

A-ha! Man I feel stupid, but I'm learning a lot from you guys. Makes sense now. [MENTION=251447]ThermionicScott[/MENTION], thanks so much! I'm waiting for the new crankset and BB to come in, but the bike is all primed and ready for them