I'm contemplating replacing the bottom bracket (Swiss) and crank (Nervar w/ 128 mm BCD) on my Moto GJ as very early preventative maintenance. Everything is in great condition, but I've been thinking, maybe it makes sense to do it now, keep the stuff in great condition, and not have to worry about failure later on. Plus, who knows what the availability of replacement Swiss-threaded BBs in the future. Right now I can get a Phil Wood or MUCH cheaper IRD. Is this a crazy idea or good idea? Am I thinking too much?

My wife calls it "painting legs on a snake". I do it all the time. That said, I would opt for the new Swiss BB. Stick it in there and save the old one for posterity and a spare.

IMHO, that's a good reason to buy replacement parts now, but not necessarily to go ahead and start using them...

I read something in the Zinn Road Bike maintenance book and I'm curious what others think -- he seemed to recommend replacing things like stems/handlebars every few years. Perhaps that is only for racers/people who are very hard on components. Should I be worried about my old Cinelli stem/handlebar set on my bike?

A cartridge bb is a good idea ( especially if you rack up the miles on this bike and are remiss in servicing the bearings!)

PS - I can't speak for "Phil" cartidge bb's, but based in my limited experience with Shimano cartridge bb's, I'd plan on replacing it often.

You all must have a lot of spare time on your hands. My wife is forever finding work for me to do!

Age: My commuter bike is 38 yrs old, stock. My go fast bike is 29 years old, other than an upgrade in cranks and RD it's stock. I have no reason to believe either of these bikes is likely to suffer a component or wheelset problem anytime soon. Replacing handlebars and stems, that seems like utter nonsense to me..but I'm no pro rider.

Parts: I might acquire key replacement parts, I'd love to have a NOS Mark-II GT RD in the tool box for a rainy day. But I would not start replacing stuff until there is a reason. Most of my bike's components will out live me, I'm certain.

I'm having trouble reconciling the two sentences. Why would it be considered a "good idea" if one should "plan on replacing it often"?

I wouldn't consider actually replacing a properly functioning BB, but it might be reasonable to get spare parts if you anticipate availability issues in the future. OTOH, I picked up a spare headset for my tandem after it started to develop slight 'indexing' in the late '70s. But replacing the ball cage in the existing headset cured the indexing issue and the spare headset is still sitting somewhere in my garage waiting for the original part to fail.

Zinn's recommendation to replace bars and stems is a different situation since those parts sometimes fail suddenly and result in serious injury - especially for riders who put a lot of stress on the bars.

Sounds like he is recommending a sealed BB, but not necessarily a Shimano. Maybe ....

1- It is good to preserve the original parts on your bike - to keep it original.
2- The downside is that cartridges ARE disposable, and don't seem to last very long, compared to a conventional bb.

I think we're all thinking in a too limited viewpoint. I would suggest buying upgrades/replacements of everything. That way you have a 2nd bike to ride.

N+1 is always a good policy!

Solution: Break things so you will have no choice but to fix them.

If it were me, it seems you have time to accumulate some replacements (maybe even OEM ones). Ride the thing, fix it when it is broken. Assuming regular maintenance, the stock BB should last for thousands of miles.

+1 having a spare part, especially a difficult to source one, isn't a bad idea. I picked up a French Stronglight HS a couple years ago when VO had them, but I believe and hope it will be many years until I need to install it.

The Formulative Theory of n+1:

Keep all your spare parts on a spare bike.

Of course, you'll need spares for that in case you need to use a spare part from it.

Old saying:
"If it ain't broke, fix it till it is"

The idea of changing the crank doesn't sound right. Cranks don't wear out chain rings do. BB's do wear out and French or Swedish sizes are vary hard to find, so buy the replacement BB. Keep the original parts in a box and ride the replacement parts so that one day when your bike is the last one left you can say you have all the original parts. Then sell it on fleebay to some rich guy in Japan.

And Nervar-compatible chainrings are all but impossible to find. My thoughts are that I'd rather have a rideable AND maintainable bike. Right now my bike is maintainable but if I mess up a chainring, I can't just run to the local shop and buy a new one, or order one on-line, or likely find one on fleabay.

Two words when you have a desirable bike in the keeper fleet with obscure part sizing: "Donor bike".

+1 Based on my unscientific poll, out of around 300 vintage neglected bikes with cup and spindle bb, less than 10% were worn out. Out of 25 vintage neglected bikes with cartridge bb, close to 90% were worn out. So if you are stocking swiss cartridge bbs to save your stock swiss parts, better buy several.

Maybe veering slightly off topic, but with regards to your new swiss bottom bracket decisions, has anyone tried one of these Velo Orange threadless bottom brackets?

https://store.velo-orange.com/index.p...-brackets.html

May be a nice bb to use in place of the swiss bb and have in the arsenal in case you get a frame with buggered up bb threads etc.

I'm curious how well they work, if anybody has any good or bad experiences with them, please share.