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Bottom bracket dilemma

Old 07-02-20, 09:32 PM
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dedhed
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Bottom bracket dilemma

I'm going over a by all indications 1987 Bianchi Premio for someone.
Asian made Bianchi so English threaded, no problem, pull it apart.

5P spindle is pitted. Alright I'll pick up a UN55 and throw it in. Measure twice and buy once - What! shell with is 70mm (measured 3x) and English threaded.
Adding to it everything shows a 5P to be 35mm on DS and 32mm on NDS. I maked the spindle end before removing and this was opposite. I'll assume whomever may have serviced it in the past (looked like green Phil grease) put the spindle in the other way, but it worked. Crank is a Sugino VP double.
Question is do I get a 73x122 or a 68x122? Or clean up the old one with some emery cloth and new bearings?

The person who will be riding this isn't a biker, won't be putting lots of miles on, and probably won't notice a bit of crunchy crank. She got the bike free with a stipulation to donate to the guy's college. I'm basically making it safe and ready to ride. Lube all the bearings, new brake pads, lube everything else, new bar tape, true up wheels etc.
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Old 07-02-20, 09:35 PM
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I've heard of people using toothpaste to grind cups/cones smooth. Good luck whatever the solution!
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Old 07-02-20, 09:48 PM
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-----

possible shell may be 71 rather than 70

Japan built a great many cycles with 71mm BSC shells

they were copying a British size

-----
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Old 07-03-20, 06:09 AM
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Originally Posted by dedhed View Post
5P spindle is pitted. Alright I'll pick up a UN55 and throw it in. Measure twice and buy once - What! shell with is 70mm (measured 3x) and English threaded.
70mm English thread shells are not uncommon on Japanese production bikes. Takeaway: don't assume shell width is a reliable indicator of thread spec!

Question is do I get a 73x122 or a 68x122? Or clean up the old one with some emery cloth and new bearings? The person who will be riding this isn't a biker, won't be putting lots of miles on, and probably won't notice a bit of crunchy crank. She got the bike free with a stipulation to donate to the guy's college. I'm basically making it safe and ready to ride. Lube all the bearings, new brake pads, lube everything else, new bar tape, true up wheels etc.
You'll have to do a bit of finagling to get a Shimano cartridge to work, but it can be done. Personally, I'd check the LBS/co-op for a 5P spindle in better condition and failing that, just use the old spindle.
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Old 07-03-20, 06:23 AM
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I just went through this with my Nishiki mixte. I did a bunch of reading up, and apparently the commodity Shimano cartridge BBs can work, with the non-lipped side (is that the drive side? edit: nope, it's the non-drive side...) recessed into the shell by 2mm. It doesn’t affect functionality, just looks a tiny bit weird.

The other option, and the one I chose, is to source a 70mm spindle of the right length and re-use your existing cups (or use better ones). The spindle I found was a NOS Shimano 600.
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Old 07-03-20, 06:34 AM
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Is it possible(do you have the tools and ability) to "face" the bb shell?
Milling off a mm or two isn't out of the question. This would make fitting a conventional or cartridge bb easier.

If the cups are ok, a Sugino spindle is available in the bicycle universe(i have a couple) .
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Old 07-03-20, 06:50 AM
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I have cleaned up old Campy spindles with excellent results. It takes a professional grinder with the right equipment, which is my situation. It probably is not worth doing for the average bike mechanic. I just did it a few times to save some mildly worn (over tightened) bottom brackets that I got cheap. They work beautifully if done right. If the cartridge type is available for the bike it may be the way to go. I like the idea for those that don’t enjoy the maintenance of the old style, even though if done correctly, only needs doing every few years.
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Old 07-03-20, 07:44 AM
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dedhed , how bad are the old parts, really? It is possible to just clean it up and use it, or replace only the part of the BB that is actually worn.

​​​​Kabuki12 , I don't have the grinding skill to try this but have discussed it with some mechanical engineer/machining experts. They wonder "don't you have to case-harden the old surface? How can you do that evenly and to the correct depth?" Their conclusion was better to replace the originals with original, re-use the originals, or find something else that might work.
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Old 07-03-20, 07:57 AM
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Grinding back the bearing surface is not impossible but not easy. Hand working can visually clean up the track but it is not round.

i am pretty sure the hardening done on cheap spindles is the last step, on expensive parts the grinding is- just not beyond the hardened depth.
think about how these parts appear.

a common un55 cartridge will probably work everything else being equal- might just push the chain line out a bit- front derailleur requiring adjustment.

in the last two weeks I have found two bottom bracket spindles on bikes I bought with pitting
always a bummer.
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Old 07-03-20, 12:13 PM
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Check out eBay seller “iweld”. He has lots of unusual bottom brackets and spindles, you may find what you need.
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Old 07-03-20, 12:39 PM
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Originally Posted by repechage View Post
Grinding back the bearing surface is not impossible but not easy. Hand working can visually clean up the track but it is not round.

i am pretty sure the hardening done on cheap spindles is the last step, on expensive parts the grinding is- just not beyond the hardened depth.
think about how these parts appear.

a common un55 cartridge will probably work everything else being equal- might just push the chain line out a bit- front derailleur requiring adjustment.

in the last two weeks I have found two bottom bracket spindles on bikes I bought with pitting
always a bummer.
Yes, my guys gave me that comment, as well! The end result needs to be round, the right shape of bearing track, hardened, and durable. So if the original system is worn, there's a lot to be said for a cartridge replacement if you can get one to fit and work.

The drive side face of a 71 mm shell is only 1.5 mm outboard of the expected alignment for the UN55. It will move your chainline 1.5 mm away from center line, and move the NDS crank arm 1.5 mm closer to the left chainstay. This impact to the as-new alignment of the bicycle seems rather small. I would say buy the UN55 and see if it works. Br prepared to measure up the results so you can order the next size up or down if it does not work out.

If it turns out you can't make a Shimano series BB work, then do a good assessment on your old BB cups and see if you can buy an NOS 7P spindle, and BB cups if you need them. Here it would be very useful to have access to a copy of Sutherland's 5th edition. It not only tabulates all the characteristics of the replacement spindle set of parts, it explains all the issues involved in choosing the best replacement parts when you can't find an exact replacement easily. Barnett's Handbook also has a very good chapter about this, with an amazing flowchart that will walk you through the replacement process. Older bike shops often have a box of spindles either new old stock and never used, or used ones they decided to keep because somebody might need it someday. It that case, pay them whatever price they ask to reward them for their foresight and strong community values!

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Old 07-03-20, 01:45 PM
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...if you remember that far back, a lot of the early sealed unit cartridges Shimano made and sold were marked 68-71 mm. At least that's how I remember it. I think the reason was they figured out that the non drive side locking cup you put in there is lipless, so you can pretty much put it in however far you need to hold the cartridge unit in place. That drive side spindle end extension is really the money ball on something like this. You don't want chain ring interference with the stays.

If it comes down to it, and you put it together and discover there's not enough spindle sticking out on the non drive side when the thing is in position, you go with the next longer spindle.

Of course, if you were truly OCD, I guess you could face down the shell a mm or so on each side. But that's a lot of work just for being OCD. OCD people already suffer enough. I am OCD enough that I would probably put in a new cartridge.
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Old 07-03-20, 02:43 PM
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Here's the outcome.
Cups were fine. Took some fine emery cloth and knocked down any high spots on the pit edges. Reinstalled the spindle with new balls and grease same way it came out. Spins much much better than when it came in. A lot of that was proper adjustment and new balls. Should be good for a long time seeing as the owner is all about horses and owns 2. I'd be surprised if it sees 100 miles at over 10 MPH in the next year. Not having any Suntour index experience I was surprised at how well the 6s accushift works. And "Prostar" brakes, a brand I've never encountered previously.

If she has any issues in the future I'll go the UN route.
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Old 07-03-20, 03:04 PM
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Originally Posted by dedhed View Post
Here's the outcome.
Cups were fine. Took some fine emery cloth and knocked down any high spots on the pit edges. Reinstalled the spindle with new balls and grease same way it came out. Spins much much better than when it came in. A lot of that was proper adjustment and new balls. Should be good for a long time seeing as the owner is all about horses and owns 2. I'd be surprised if it sees 100 miles at over 10 MPH in the next year. Not having any Suntour index experience I was surprised at how well the 6s accushift works. And "Prostar" brakes, a brand I've never encountered previously.

If she has any issues in the future I'll go the UN route.

ProStar was formerly ChangStar, so have been around for ages. Made good enough copies of DiaCompe sidepulls at the lower end of the market.
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