Bottom Bracket BB 1988 SM 600

[Kenright73]

As the title states, I own an SM600 in near immaculate condition. She is near 100% stock and I plan to keep her that way as she spends her time on asphalt as my cruise around town bike. I noticed yesterday after a drivetrain cleaning and lube that the crankarms wobble slightly. I figure it's probably a good idea to lube and or replace the bearings since I have no idea when it was done last. They might be original considering her condition. If a replacement is deemed necessary, what is the axle length? It is a Sugino Sealed BB, but that is all the info I can find. I have OEM replacements on eBay, as well as bearings, caps, axles, etc. But I'd like to know length before I proceed, if anyone here can provide that information.
Thanks, Ken

 

[Kenright73]

Well I did find axle length on the main page here under Technical. It's a standard 68mm. I'll update my progress tomorrow or the next day as I'm really wanting to get her back on the road. Hopefully it's a simple fix, aka a tightening of the cups.

 

[Jon K.]

Well I did find axle length on the main page here under Technical. It's a standard 68mm. I'll update my progress tomorrow or the next day as I'm really wanting to get her back on the road. Hopefully it's a simple fix, aka a tightening of the cups.

You'll have to measure the axle itself. 68mm is the width of the bottom bracket shell. The axle itself will probably be 100mm or more - I've seen them up to 113mm. It all depends on the bottom bracket, double/triple chainrings, chainline, etc.

 

[black lightning 1987]

It could be mainly adjustment needed. I would pull it apart and check the condition of the spindle and cups. If they don't have any obvious damage, just replace the balls and add fresh grease. I'm not sure I have a bottom bracket loose to check ball size but will try to look. My guess is 1/4".

 

[MojoZ]

Shimano BB-UN300 comes in various lengths and is; BSA or English whatever you prefer to call it, JIS square taper, sealed, inexpensive, available and what I put in my F1000. Not likely to be the same length as the spindle that’s currently in bike, however should you need to replace Shimano tech support I spoke to in replacing the F1000 BB suggests using the next higher width closest to what was originally installed. BTW I have a 1989 SM600 that is a U-brake away from a finished restomod, I applied a 1x 11 speed drivetrain, Praxis Mountain crank and external BB

 

[Kenright73]

You'll have to measure the axle itself. 68mm is the width of the bottom bracket shell. The axle itself will probably be 100mm or more - I've seen them up to 113mm. It all depends on the bottom bracket, double/triple chainrings, chainline, etc.

I'm sorry, I feel like such a noob regarding axle length. I assure you, I am very comfortable around tools, bikes, cars, engine and trans rebuilds, etc.

I prefer to do as much as I can regarding maintenance and repair, before I call my one guy for bikes, or another guy for my cars.

Life got in the way, so I'll be pulling her apart this weekend. I really hope it's just a simple adjustment and relube as she's pulling on my eyes to take her out for a long ride. I need the escape, if only for an hour around town. Nursing at the hospital and being a caretaker at home is starting to break my sanity.

Updates to follow all! Thanks again!!

 

[Jon K.]

Life got in the way, so I'll be pulling her apart this weekend. I really hope it's just a simple adjustment and relube as she's pulling on my eyes to take her out for a long ride. I need the escape, if only for an hour around town. Nursing at the hospital and being a caretaker at home is starting to break my sanity.

Updates to follow all! Thanks again!!

Do remember to take care of yourself, as well as your patients and your loved one at home.

Mojo's advice above is sound. If the Sugino BB is too far gone, the BB-UN300 is pretty common and relatively inexpensive. It also can use several different axle widths, so you can find a length that's close. A little bit too long is better than a little bit too short.