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Post by brianbutler on Sept 10, 2020 0:40:09 GMT
I noticed a clunking noise in the bottom bracket of my "main" bike. There was a little too much play in the bearings so I adjusted them and all was well for a couple of days when the clunk came back. I figured dirt so I opened the bottom bracket and was dismayed to find lots of grit and the drive side spindle cone damaged beyond repair. I assume the cup is also clobbered but I dropped it into a jar of solvent before inspecting it and it is still there. This damage seemed weird because I had overhauled the BB in 2018 but I checked my maintenance records and found that I had rolled up 8300 miles on the bike since the overhaul. Miles fly when you are having fun.
So now I need a new BB. The problem is that the bike has a triple crankset and the bottom bracket is asymmetical. The drive side extends 5mm farther from the center of the spindle than the left side. The overall spindle length is 126mm. I found a spindle and matching cups on my shelf in good condition. The spindle is 126mm overall and is also asymmetrical but by only 2-3mm instead of 5mm. The granny chainring does not clear the chainstay. My plan is to insert two or three 1mm BB spacers (on order) on the right side to allow clearance and I think this solution will work but...
If I wanted to go to a sealed BB next time I'm not sure this would work. They all seem to be symmetrical so I would have to shim the right side 5mm, which might cause two problems - not enough thread on the right side to secure the BB, and the left pedal pulled too close to the BB. The meager specifications for these BB's do not mention whether left and right sides are equal but they look equal in photos.
Does anyone have other solutions or advice? I am temporarily using a double chainset with the found BB until the spacers arrive and I can put the 28T granny back on. I use this bike on mountain roads in New Hampshire and don't have other bikes for that duty. Last week I needed my lowest gear for an unpaved 18% grade.
Brian
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Post by wheelson on Sept 10, 2020 3:09:58 GMT
You're right, the BB supply is a huge problem area, especially now with the Covid situation. I've been working with a bike shop as an independent contractor since I retired from my engineering career about 10 years ago. In that time the offerings for bottom bracket replacements have really narrowed. For my own bikes, I have increasingly had to go to eBay and spend way too much time there. It sounds like you are still using a cup and cone BB rather than a sealed unit. As you say, they seem to be symmetrical regardless of manufacturer. Essentially, the sealed units come in various lengths (end to end), for 68, 70, and 73mm bb shells. And in my experience, anything other than JIS tapers are increasingly hard to find. Most of the sealed units we stock in your range are in fact JIS, for 68 and 73 bb shells, British threading, and typically 122 and 127.5mm. What crankset are you using now? I have a box full of bb spindles, both new and used, in various configurations as well as some odd sealed units. I think I also have one of those Suntour VX sealed units that is adjustable on both sides that looks like this: cdn10.bigcommerce.com/s-1rmgckn/products/6610/images/78107/nos_nib_vintage_bike_component_19061__05252.1527887376.700.950.JPG?c=2If you are using older cup and cone bb, there are also thin and thick cups which can play into offsets. That's mostly in older Campagnolo bb's but Sugino made thin cups as well. Bottom line is I have a lot of stuff (mostly British threaded) that I'd be happy to share with you (or anyone in need) if you can give me some measurements of the old spindle and the brand and model of the crankset. Best, John "wheelson" |
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Post by wheelson on Sept 10, 2020 3:33:23 GMT
Also, I don't know if Sheldon Brown's Database has been mentioned, but it's really extensive and it's here: sheldonbrown.com/bbsize.htmlAgain, I'm always happy to help if I can. Best, John "w" |
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Post by oldroadietehachapi on Sept 10, 2020 5:09:42 GMT
I have had an excellent experience with Velo Orange BBs Good luck with your hunt.
Cheers Jim
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Post by brianbutler on Sept 10, 2020 13:58:54 GMT
John, thanks for the detailed info. Jim, thanks for the Velo Orange suggestion.
I am using a Sugino GT triple crankset. The specifics of the destroyed BB are:
Cup and cone 68mm shell English threaded JIS square taper
The measurements of the spindle, using Brown's scheme, are:
A - 126mm (overall)
B - 38mm (left side)
C - 43.5mm (center section)
D - 44.5mm (right side)
Unfortunately I stupidly measured from the right side, I guess just to confuse myself and give my calculator a much needed workout.
For now, I will wait until I receive my supply of 1mm shims and see if I can make my setup work with the slightly less asymmetrical spindle from my parts bin. If that works, I'll use it while I investigate sealed BB's. As I mentioned, however, I think the sealed BB's are symmetrical so I would need one with a very long spindle and even then I would have to shim.
Brian
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Post by brianbutler on Sept 18, 2020 1:28:16 GMT
My spindle problem has been worked around but not solved. I ordered some 1mm BB spacers with the intention of using a different 126mm (but less asymmetrical) spindle and then shimming the right side 2-3mm so the granny chainring would clear the chainstay. Unfortunately this did not work because the left side of the BB is not threaded far enough to allow the left cup to be cranked in that additional 2-3mm. I reverted to the old (slighly damaged) spindle but replaced the cups. The old right cup was too messed up to use. The result is actually quite smooth and seems like it will work until the next overhaul.
I am still interested in using a sealed cartridge BB but I need a long extension on the right side. That might mean using a 73mm BB and some shims on the right side or some other unconventional approach. I have not seen specifications for the critical measurements in any of the cartridge BB descriptions so it is pretty hard to do the calculations.
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Post by wheelson on Sept 18, 2020 2:56:47 GMT
Bottom bracket cartridge units and discrete spindles are such a pain anymore. I'll look in my spares box and see what I can find. I notice at our bike shop the stock of bb units is becoming increasingly sparse. I'm starting a collection of takeoffs, as some of these units can be knocked apart and have sealed bearings that look to be easily replaced. Well, at least as easy as stock Viscount bb's. Interesting that I took apart an old Suntour VX unit, the ultimate in adjustability with perhaps the exception of the "Big Sliding". The spindle in the VX unit has snap ring grooves just like the Viscount, and it uses the same cartridge bearings as a titanium bb unit I have. Same ID as a Viscount but about half as wide. I'm temporarily using the VX spindle in an Aerospace build as the titanium spindle, while not grooved, is hollow and of unknown Ti type. Said to be Russian made, I have no idea if it is CP (commercially pure) or one of the better grades. I may use it anyway, probably better than the stress riser snap ring groove spindles. Or perhaps I'll break down, ream out the excess protruding tubing, and use a sealed unit. I've already tapped the bb out to Italian thread.
Anyway, back to your problem Brian, I'll see if I can come up with anything with your dimensions. I'm assuming you need British threaded cups?
Best,
John "w"
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Post by brianbutler on Sept 18, 2020 12:08:01 GMT
Yes, John, British threaded. But don't go to much trouble. I have a bushel (or maybe just a peck) of BB components and numerous chainsets so I can always cobble something together. I was just trying to do a straight "repair" and was surprised by the number of variables around BB's.
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Post by brianbutler on Sept 18, 2020 15:34:47 GMT
In lieu of specifications, Velo Orange offers this advice on their web site:
...a longer spindle may be require in order to ensure that the crank arms clear the chain stays. Often, the only way to be sure is to install the crank and see if the BB works. If not, measure the interference or gap and buy a second BB. Unfortunately BBs that have been installed are not returnable, but there is always E-bay.
Gee, thanks.
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