What length BB spindle?
 

I'm replacing the cup and cone BB on my 1984 Trek 520.

Here are the details:

SR square taper crankset, triple 110/74 BCD 24x34x45, J.I.S.
Old BB: 68mm width, english treaded, 126mm spindle length, J.I.S. Came with the bike.
I'm running a tiagra 130mm OLD hub in the back with 8 speeds

Shimano makes a UN55 cartridge BB in 122.5mm and 127.5mm spindle lengths. Which one should I go for? I'm not sure how to measure the "ideal" spindle length.

http://www.amazon.com/Shimano-Square.../dp/B0068FVOEM

Thanks for the help!

Tyler

Look for a "code" on the spindle such as 3-N or 3-P etc.

http://sheldonbrown.com/bbsize.html

Stamped:

3 T (123mm total length, 3mm shorter than my own caliper measurement)
D-1
B

Also, my current BB spindle is threaded on the end, so it uses a nut to tighten the square taper. Will a new hollow spindle BB come with crank bolts, or will I have to find something suitable at the hardware store?

Wow, 3T is long. There are multiple "right" answers, depending on whether a low Q-factor is important to you, or whether you want the bigger rings to line up with the outside (fast end) of the cassette. I personally like to use as short a BB as I can get away with to bring the pedals together and bring the big ring closer to the center of the cassette. If you reassemble your BB/crankset and measure how much extra clearance you have from the cranks and rings to the frame, then you can figure out what range of available BBs will work for you. :thumb:

Your measured length can vary a bit. I'm pretty sure the "reference measurement" is taken at some point on the taper where it is X width.
If you scroll down a bit on the link I gave you, you can see the dimensions of the "T".
LONG!
One other thing to check is that the LONG end is the DS. IF SO, the longest cartridge is a 127.5.
That's going to be a bit short, so it pretty much depends on how much clearance you have from the chain stay to the rings.

Another option is to just replace the bearings in what you have.

IF your spindle is bad, I found this source. I don't know what quality they are though. I bought some for the parts bin, but haven't used any yet,.
http://www.huskybicycles.com/Merchan..._Code=CrkParts

Thanks for the info! I've got pitting on the spindle, cups, and bearings. I'm looking forward to not regreasing my BB every year. =)

I'll measure my chainring clearance and see what's the best option for me.

I believe 127.5 should be fine, may need a spacer for the chainline you want.

They also have cup sets w/ retainer bearings for about $5 ea.
Buy 5-6 sets & spindles & replace when bad every x years??:rolleyes:

Just an FYI for future mechanics with my setup:

I bought a UN54 shimano cartridge (with the plastic endcap) BB in 122.5mm size at my LBS; it works beautifully!

Very cool, Scheherezade! :thumb:

Bill, I bought a handful of those new Chinese(?) spindles, branded as "Pyramid". They've installed and adjusted well, but a couple were off-center enough to impart some axial runout to the crankset. I guess you get what you pay for...

I bought about 7-8 of the (mostly extreme) various lengths for the CL bikes I flip. I have several usable cups, so I figured the price would be good, even with shipping. I also found some low price axle/cone sets (for less than one Wheels Mfg. cone) for some of the older (HB RM-40, FH-M570 etc.) Shimano hubs I have laying around that were missing those parts. I even save old spokes if they aren't TOO bad. Hopefully I can "reconstruct" a few wheels for these CL bikes, when needed. I'm retired, so time isn't a problem.