Bicycle Mechanics - I can overhaul my hub! \o/ ...but...
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02-11-09, 07:20 PM
So a friend helped me a lot today by teaching me how to remove my cranks and bottom bracket. It was cool. :thumb:
The problem is, we found pitting on the ball bearings and on my spindle. So, we reassembled the front end of my drivetrain, and I rode home weighing my options-- this is where I solicit your sage advice.
I'm on a 1992 Schwinn Criss Cross (it is great for my needs!) and am a grad student. Replacing the bottom bracket cuts into my food budget this month, but I rely heavily on the bike to get around. Paying LBS labor is out of the question, so how do I figure out what size BB to order online for home installation?
Finding 1992 criss cross info on the web is... difficult. One of the bearing cups ( think that's what it is, this is an older, non-cartridge BB) indicated that it is English threaded and the threads per inch, so that helps. But what size?
And how much a risk am I running that I will hurt my frame riding on pitted bearings and spindle? I'm not fat and I commute maybe only 20-30 miles a week depending on groceries runs. A BB is tough to afford right now so a frame is unthinkable...
Thanks for helping me to pull this off cost-effectively!
02-11-09, 07:59 PM
Continuing to use a pitted bottom bracket spindle and balls won't hurt your frame at all. I'd certainly replace the balls but the spindle should last a bit longer.
If you do want to replace it, take the old spindle to a bike shop and see of they can match it and buy new balls. The entire cost should be very low. Otherwise measure your spindle end to end (if it has threaded stubs at the ends, don't include them) and get a cartridge bb that is the came length. These can also be quite cheap and the installation tool is also.
And, yes, your frame is English threaded.
02-11-09, 08:03 PM
Honestly, given your situation (and I've been there) I'd keep riding it. Assuming you greased the threads on assembly you're not going to hurt your frame by continuing to use it. It will slow you down a bit as it gets worse, but it sounds like that last little bit of speed isn't of the utmost importance to you. I would consider putting new bearings in (cheap) but the worst you can do is make the cones and spindle more pitted. Delaying that repair will not increase your future repair cost in any way. Given the choice between food and this, I'd keep eating.
As others have said, You wont do any damage to the frame; Most likely problem you will encounder is that the surfaces will continue to wear and the pedaling will become increasingly and annoyingly harsh. New bearings will delay that.
If you do go the replacement route, you can figure out the spindle length you need by taking some basic measurements. The most important one is simply the end to end measurement but knowing the respective lengths of the right and left side of the spinde (from bearing surface to end of spindle) -- see diagram in attached -- http://www.sheldonbrown.com/bbsize.html will also be helpful as knowing whether the spindle is symetrical or asymetrical will ensure you get a replacement that works with your crankset.
The other thing you need to determine is the taper of the spindle (I am assuming it a square taper BB). Most Japanese spindle use JIS taper (JIS means Japanese Industrial Standrad), while Campy and other Euro makers use use ISO (International Org for Standardization). Basically ISO tapers to a smaller end that JIS. Old Suntour spindles use third taper somewhere in between JIS and ISO (I have Suntour cranks on a campy spindle and the work fine). Based on make of the bike, I would guess you have a japanese BB with JIS taper. Who is manufacturer of the BB and the crankset? Prices for cup and cone BBs vary widely depending on make and quality (like everything else). Replacing it with a more modern cartridge BB may also be an option -- and perhaps cheaper -- as long as the spindle lengths and tapers are the same.
02-11-09, 08:14 PM
I'd suggest a cartridge, as a fellow student, my time is better spent than fiddling with a cup and cone bottom bracket. If you don't feel like the 20 dollar investment, you can ride your old one all you like, and only harm the bottom bracket.
02-11-09, 08:47 PM
Hey guys, thanks for the speedy advice and encouragement. It has been a medium bad day, and it's nice to know that there are helpful folks out there.
I would consider putting new bearings in (cheap) but the worst you can do is make the cones and spindle more pitted.
So the cups are the parts that the bearing cage (the ring holding the bearings) fits inside, and the part that screws to the bottom bracket holder? The lock ring screws onto the non-driveside one. Gotcha.
Assuming you greased the threads on assembly you're not going to hurt your frame by continuing to use it.I greased the crap out of that thing. It was like fingerpainting. Much fun! Actually, it was fun to crack open the BB for the first time and to see how it all works. I admit I was a little disappointed to not find any hamsters or gnomes powering the works. I wasn't raised in a mechanically-inclined family, so all this is a grand adventure, except to the extent I'm harming my ride. :)
Here's what I know about the BB:
English threaded, the measurements we collected by hand were 68x127 mm. The assembly consists of the lockring, the cones (the lockring screws onto the non-drive side one), the spindle, and the bearing/cages.
The chainring is labeled Dia Compe XCM, the brakes and things are Suntour.
As far as I can tell, all the parts are original from 1992. I bought the bike this past fall for a song and if I had known to check that the BB grease had not dried out (it was-- to the consistency of little rusty boogers), I certainly would have. I wonder if I should check the headset...
I hope that armed with this info I can march into my bike shop (or, even better, the local co-op) and find the replacement parts...
02-11-09, 09:30 PM
Sorry, I wrote that wrong. I meant to say cups and spindle. In a hub it would be cups and cones, which is what I had started to type. The outer race is in the cup (the part that threads into your frame) and the inner race is on the spindle (or cone threaded to axle in a hub). Also, in case your friend didn't tell you, you ALWAYS thread in the cups BY HAND most of the way, then use a tool. If you don't have them at least 5 turns in smoothly by hand it's very likely that you will cross thread and destroy the threads in the frame, I've seen that a lot. Sometimes if it's stiff working it back and forth by hand, or cleaning the threads with a wire brush will help.
You should probably check the headset, and the hubs when you get time. I'd do the hubs first. Also, err on the side of slightly too tight rather than slightly too loose on these things. In the case of a new hub, if it's slightly too tight you will prematurely destroy the inner race (cone on a hub). Cones are fairly cheap. If you leave it too loose you will destroy the outer race (the hub which is built into the wheel). Replacing a cone is way cheaper than replacing a hub, and building it into a wheel. You also need a bit of preload anyways. Also, it's a cardinal sin to use cone wrenches on anything other than cones, even if your life is at stake.
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