Bottom Bracket Spacer Ring - Disadvantages?
 

These things: http://www.bikeparts.com/search_resu...p?ID=BPC108402

So it turns out my chainline is 3mm or so off, the front chainring being closer to the centerline than the rear. I have a Shimano UN73 68x107 BB that's brand new, and I don't think Bikeparts would accept a return on an installed and slightly used BB. And I don't really want to spend $32 on a new one.. so these spacers look nice.

Anyone have any experience with them? Do they work well?

As long as your non-drive side crank clears the chainstay, they work fine.

Never used those but I have used pretty much the same thing for spacing the cog out and it seems to work just fine.

Yeah that's the only solution you have besides changing bbs, How much spacing difference does flipping the cog make?

What kind of cranks and hub are you using?

Flipping the cog sounds best to me if the chain clears the spokes that way.

Otherwise just make sure that spacer thing works w/ your BB. I don't know about that sh*t.

Flipping the cog would run my chain right into the spokes, it's a Formula cartridge.

*new*guy, this is spacing it out.. there would be more clearance (there already is enough).

My friend from AA, it's a Formula Hub with a Euro Asia Imports Cro-Mo cog, my BB is a Shimano UN73 with Bulletproof cranks (dead sexy once you take off the lettering :)) and a Dans Comp "Universal Ring", which I guess is similar to a Rocket Ring. I had trouble getting it centered on the spider, and need better chainring bolts, but it seems to be round enough.. many people who complain of rings being out of round just don't have it centered.. but I digress.

So there's little chance that this'll weaken my BB, or make it creak? I tend to think it's compatable because it meets all the criteria, and is made by Shimano..

As a side note, anyone know the quality of the LP28 by Shimano? It's half as cheap as the UN73.. so it probably wouldn't be as good?

The only downside is that they can make you pop out of your clipless pedals if you don't adjust them to compensate for the change in position...

That and if you have bad knees, the problem could be aggrivated.

You mean the symmetry of the spindle will be off? Because from the factory it's not symmetrical unless my cranks or pedals compensate for it (haven't measured). Adding the spacer would actually make it closer to perfect symmetry, albeit a little in the other direction.

And I don't know if the symmetry would affect the pedals as much.. what is your reasoning for this?

There will be more space on the drive side, but since the spindle is of a fixed length, what you pull over on one side you are taking away from the other. You will be reducing the clearance on the non-drive side.

A lot of non-symmetrical bbs have an appropriate non-symetricality to the cranks, meaning your q-factor is still evenly spaced. Even if it isn't perfectly centered, it's not that big of a deal, unless you are running a huge gear and racing on it. Then it would cause a bit of stress in your joints and tendons.

Woah Boss, just read some of your blog, definetely brings back some memories for me. Visiting my girlfriends home in Wyoming and traveling around Montana with her family. Plus a few Indiana and Michigan references hahaha.

Yeah, the blog is fun.. kinda burned out after that long chronical, but once I get my life under control I'm gonna keep updating it.

So you're saying that there is some kind of standard non-symetricality to the cranks so that similar points on each pedal are exactly the same distance from the frame centerline? Because my BB and cranks aren't made by the same company.. and then why are there symmetrical and non symmetrical BB spindles?

And yeah, Aeroplane, you're right, but the only thing that comes close to my chainstays is my chainring, which will be spaced out. So I'd be good.

I dunno.. I think I'll measure the symmetry and figure this all out (unless someone positively knows this) before buying anything.. not like I'm going to be riding soon (bloody weather).

Regarding symmetry: I really doubt you'll notice a few mm to one side or the other. And if you do, you can just reposition your cleats on your shoes.

Yeah, good point.. although lyledriver seemed to have a problem with it.

I just measured, and my non drive pedal is further from center than my drive, by a bit more than what my chainline is off by... which means I'll get closer by adding this spacer (although my drive will go out by the width of the spacer, it'll still be more symmetrical. I really think I'm not spelling this word right). Looks like I'm in the market for a circular piece of metal.

Let us know if the spacer works out for you. I just looked through my stuff, and if you find you need to go even wider, I have a 115mm un53 with a metal cup to replace the plastic one they come with. If the spacer doesn't work out just let me know and I'll send it to you.

3mm is pushing it. Most likelly it'll work but with less support on the left side I think creaking could be an issue. Also be careful with the plastic cup threading it into the frame further than intended can cause it to crack.
LP28=crap.

Thanks for the offer, fellow Arborite.. 115 might be to big, but I'll have to measure it again (this time better) to be sure.

And yeah, my UN73 doesn't have a plastic cup. So no worries there.

The non-symmetric bottom brackets are mainly for triple cranksets. You need a greater amount of space over a double for three chainrings to clear. Then, you need a bit extra on the non-drive side since the non-drive crank is thinner than the triple crank and you want the pedals equidistant from the center line. I've been running this exact bottom bracket and crankset with a 2mm spacer for two years with no issues. I'd like to swap it out for a symmetrical bottom bracket, but it works right now.