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Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

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Old 02-19-06, 02:50 PM   #1
dnlpnd
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I am in serious need of some bicycle mechanic expertise! I have an early 90’s Trek T200 tandem that I picked up from my LBS part-way through a bottom bracket and headset rebuild job. I became uneasy about some of the inconsistencies I was getting about the needed parts and prices from the LBS.

Now I have several bags of parts and a stripped down frame sitting in my living room. I’ve sorted and cleaned the parts and I have some technical questions.

1.) There is a plastic “accordion-looking” thing that has/had rubber o-rings at both ends. It is imprinted with “TIOGA” on it. It obviously came from somewhere in the bottom brackets. Two things about this…I am only finding one in the bag of parts and it has been mangled by my LBS. What is the purpose of this part, where does it go, and why is there only one on a tandem (meaning did my LBS throw the other one away?)

2.) There are two spindles in the bag of bottom bracket parts that I received back from my LBS. One is 132mm long and other is 126mm long. Which spindle goes is which position, captain vs stoker? Maybe even more importantly, I am no bike mechanic but it is pretty obvious the one set of bearings, cups, and spindle is severely pitted with rust. Both sets of cups are Tange K1 1.37x24T. I am finding new cups sets on-line for about $20 each, but a new spindle appears to be a little tougher to find. Since I am probably going to have to replace at least one spindle, how much more difficult or is it even possible to convert the open style bottom bracket to a cartridge style system. Is the taper on the spindles pretty much universal for all square-holed Shimano crank arms or is there a whole other can of worms to consider with how various tapers mate with various crank arms? Does the eccentric cause any complexities with an open to cartridge bearing bottom bracket conversion?

Once I get through some of these issues, I’ll probably have more questions about the headset rebuild. It’s really rough and bearings are probably shot.

Thanks In Advance for Any Assistance You Can Give,

dnlpnd

Last edited by dnlpnd; 02-19-06 at 02:56 PM.
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Old 02-19-06, 02:59 PM   #2
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Any Shimano cartridge BB of the appropriate size will work... its a lot less work and a lot cheaper than replacing cups, spindles and bearings. A basic sq. taper cartridge BB will run you about $20. I recommend that you get a Shimano BB though, most other sq. taper cartridge BB's I've use have been absolute crap. For spindles, there is really only a big difference between Shimano spindles and Campy spindles. As long as you have a Japanese crankset with a Shimano BB you're pretty safe.
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Old 02-19-06, 03:20 PM   #3
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The plastic accordian thing is a device to keep water and dirt out of an old style, non-cartridge bottom bracket. It slips into the bb shell over the spindle, between the the two cups. Notice that the ends should fit nicely into the cups. Why only one? There may have been only one to begin with, or they threw it away, or it is now hiding inside the bb shell (they sometimes do this). Whatever its fate, you can get a new one for a few dollars.

It is most likely that the longer spindle goes in the captain position. That one is probably a double, while the stoker is a single. Generally, more clearance is required with more chainrings.

Why is one spindle all rusty and pitted? Sounds like that was the one where the plastic accordian job was missing. Just a hunch.

Seely's advice on the bb sounds good, but you will want to make sure the spindle will extend far enough out on the drive side to keep chainrings from interfering with chainstays, and to keep the chainlines right - more important on a tandem. In some ways, the best thing would be to get identical spindles and cup sets - but finding them is more difficult. Harris cyclery lists lots of spindle lengths, you may have to call for availability. Look at the old spindles and note any and all markings in the middle - this is usually an indication of the type/geometry, which the shop or online source you buy from may need to help you find a compatible replacement. Measure the spindles to see whether they are symmetrical or if the drive side is longer - and note the dimensions. Check out Loose Screws. http://www.loosescrews.com/index.cgi
They carry a lot of old stuff.

I can't answer the question on the eccentric, having never dealt with one.
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Old 02-19-06, 04:05 PM   #4
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The front (Captain's) bottom bracket is probably the shorter since it only has to have a single synchronizing chainring on its left side while the rear (Stoker's) bb has to be long enough to have the other synchronizing ring on its left side and usually a triple crank on its right side.

I'd definitely check with a dealer or internet site (Sheldon Brown is a good start) familiar with Tandems for parts recommendations. You seem to be rather new at all of this and tandems are tricky even for experienced mechanics.
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Old 02-19-06, 06:05 PM   #5
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Great information guys...Thanks!

That totally makes sense that captain's BB is the sorter of the two spindles. It's only dealing with a single 38t, whereas the stoker's BB is dealing with a 38t on one side a triple set on the other side.

It would be cool if you guys could help me nail down a part number for an XT level cartridge BB with the following dimensions:

132mm spindle with 1.37x24T and 126mm spindle with 1.37x24T

Thanks Again,

dnlpnd
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Old 02-19-06, 06:20 PM   #6
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Probably only one "accordian crud catcher" came with your bike originally. It goes on the rear crank. The front crank should have an eccentric device that the bottom bracket fits into. The eccentric is necessary for tensioning the timing chain.
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Old 02-19-06, 08:42 PM   #7
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Hillrider is right on the lengths of the two spindles, I had those backwards.
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Old 02-19-06, 10:19 PM   #8
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Measure BB shell width also...Like likely 68 or 73mm.
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