Bicycle Mechanics - chainline with chainguide
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10-16-03, 11:55 PM
I have a problem "dialing" in my chainline. I have a UN-72 BB with a non-ISCG chainguide. I believe a truvativ. I still run a square taper crankset as this is what came with the bike. Well, when I shift the rear der. into the largest ring in the back, it really drags on the chainguide, thus requiring more work by me. anyway, is there a way to bring the line of the crankset inward a little more in order to line up the chain correctly in order to reduce drag.
You are using the stock BB. That's your problem.
What you need is a BB designed for use with an E-Type Bottom Bracket (Specialized FSR designs used to use that). That'll space it out enough for you.
10-17-03, 09:44 PM
where might I get one of these E-type BB's and is there a model number for it, such as the UN-72. Well, I have a P3 and the BB is actually a replacememnt for the original. The one replacing the original is a UN-52.
The E-Type can be gotten at your LBS. I think it's just the UN72-E or something stupid like that.
Don't the P3's have ISCG mounts? Why didn't you get a ISCG chainguide? You have to cut off the ISCG mounts if you want to use a non-ISCG guide. That's what I would have had to do on my Banshee if I was going to run a standard BB mounted guide. I know it's something like that...
10-18-03, 05:31 PM
yeah the new P3's have the ISCG tabs, however this is a 2000 or 2001 whichever was the first year for them to make the P3, therefore no tabs, no horizontal rear dropouts either. I talked to a guy at my LBS and he suggested a Raceface BB, but it doesn't look like the cg will accept that type of BB, is there a spacer or something that I can put inside the BB cup to move the whole spindle over like 2 mm?
I could be wrong you should be able to buy a BB that is let's say 4mm shorter then it would move both crank arms in about 2mm. Worst case you can get a Phil Wood BB and they are completely adjustable to fine tune the chainline.
10-18-03, 11:02 PM
I would be able to do that, except for one problem. The Chainguide is a non-ISCG compatible guide. The drive side shell holdts the CG to the bike by a lip that is the same inner dizm. as the BB shell. This moves the whole BB over by 2mm, which just happens to be enough to screw everything up. If I were to use a smaller spindle length (I have a 113 right now) then I would have NO clearance on the non drive side(I only have about 2mm as it is. I have almost an inch of clearance on the drive side. I feel like I need some sort of spacer to put inside the drive side BB cup in order to move the whole thing over. But I know that drive side cups aren't supposed to come off the BB. It is quite a quandry.
Get a BB designed for an E-Type derailuer
OR get a Truvative Gigapipe BB.
I have the Team DH (top of the line), and there is a spacer that you keep in if you aren't using a BB mounted guide, or you take it out if you are using a BB mounted guide.
hmm, my buddy has a first gen P3 and his had vertical dropouts and ISCG tabs... weird.
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