Square taper crank longevity
 

I was wondering about the crank longevity with repeated removal and reinstallation. I have read here of others going tens of thousands of miles which would indicate greater maintenance with repeated removal for service. Even every year or every other year over a 30 year timespan would be quite a few maintenance cycles. Do these regular reinstallations eventually cause the crank square tapers to expand and deform? I don’t ride enough for this to affect me, and most bikes I have or work on have greatly deferred maintenance. Just wondering. A quick google search didn’t really show much.

Yes, they can eventually deform. How much and how soon is dictated more by the quality of the crankset than anything else.
With proper torque, it’s not unusual to see these old cranks go through many removal/replacement cycles but 30 is a lot.
Service periods are better scheduled based on actual use and conditions. In my case, I don’t have to service the BB for years but someone who rides in more adverse conditions might have to do it annually. But under those conditions, everything needs more frequent attention.

That was my feeling too, and mine will greatly outlast me. I’ve not really seen any posts of high mileage riders lamenting their nice crank finally being used enough to wear out the internal taper. Perhaps the sealed bottom brackets have been the answer for them.

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after re-installing arms it can be a good procedure to withdraw the fixing bolts so as to check on where the spindle end is sitting

you want to have at least one mm of freeboard in there; if the spindle is bottoming out in the arm it is possible it may loosen with use


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I'm still using a Campy 9s Chorus crankset that has over 100,000 miles on it. I've probably removed it 15 - 20 times. It's getting close to bottoming out. I'd say I have about 1.5mm to go before it does.

now I see a grease or not to grease the tapers argument coming.

Use a torque wrench. That will reduce the chance of pushing the arms on too far. You can also reduce the need to remove the crank arms by going to a cartridge bearing bottom bracket. The maintenance interval is greatly reduced.

This is one of the main reasons I have largely switched over to cartridge BBs. My oldest crankset currently (c. 1971 Stronglight 93s) are now mounted on a Phil Wood bottom bracket, and hopefully that setup will last the rest of my life undisturbed. My bikes that are still cup and cone don't go out to play when the weather is bad or the roads are really gritty and dusty.

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have wondered for decades why no one has ever produced an investment cast shim which could be fitted so as to extend crank arm useful life...

...or perhaps one has and i have been unaware of it...

minor side tip on this subject -

it has been reported that the OFMEGA taper is smaller than others

if this is correct it would not be a "Class A" fit to combine OFMEGA with other parts in a square taper assembly

[ have little experience with OFMEGA meself ]


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I suppose racers of the 70s and 80s had a pretty good idea how many on off cycles the crank could withstand. Consumables for them. Maybe cottered cranks held on for a bit, as I would assume they were much more durable with just cotter replacements.

On the other end of things, earlier this year I did a tune-up on a bike that had less than 100 miles on it, and it needed it's crankset replaced because the ham-fisted mechanic who built it over-tightened the crank bolts so much that the crank was already bottomed out on the spindle. This is why crank bolts should be installed with a torque wrench.

I get out the torque wrench, and even at 20 ft/lbs I feel like it is more than I would try if I didn’t have the wrench. Someone must’ve really cranked on yours.

I've hinted at this in the past (albeit not in its own thread) but I do believe there is a life cycle for cranks. Material, construction, etc do have an impact. As does the care in installation and removal.

Lots of riders in this sub have had cranks they moved across half a dozen or more different bikes. Some people find a crank they love and take it with them across their discovery of other frames.

one of the best arguments for cartridge / sealed bearing BBs is that you don't have to take the crankarms off very often for bearing service

I use 240-280 inch pounds for crank bolts. Classic Campagnolo Record cranks are at the low end of that range. TA and Stronglight are below that range

it's good to be sensitive to how the bolt feels as the fiinal torque is approached. The Shimano DA and XTR cranks for example, pull up very solid. **ClicK !**

remember that these "classic" cranks are now approaching 50 years old and who knows what indignities they've been subjected to before you acquired them.

I personally would not ride Campagnolo Record 144 cranks for anything other than a "parade" ride.

/markp

That, or the other mistake is to grease the square taper spindle. It's designed to go together dry. If you grease it you'll end up pushing the crank arm in too far.

says you.

I've never ridden hard enough to break anything on a bike.

Never broke anything but chains at the dragstrip, seen plenty of others have failures and chocked it mostly up to lack of understanding on their part.

Fail to plan, plan to fail.

I have always had a very good sense of what can, will go wrong and evaluated things with a practical, critical eye and process.

All of my cranks will likely outlast me by a long shot. :twitchy:

I would like to ride enough to have this problem one day. Doesn’t look like happening though. Why would I take off a crank that isn’t giving any trouble? Just wipe the axle with an oily rag. The cartridge BBs I’ve had have lasted 10 years each on Old Bike. If you take off one crank at a time, you always get them back in exactly the same orientation on the taper. Ought to be snug as a bug once it’s settled in.

All my BBs are cartridge type. Even if they are still smooth, I remove them every 2-3 years just to grease the threads. This way I never have a problem with seized cups. Same goes for seat posts and stems.

m a i n t e n a n c e

r e s p e c t, could Aretha do maintenance?

Probably ;)

That isn’t an argument, it’s a schism.

Sheldon says grease, though. A little bit.

I will add my own discovery in the field and that is that the super slippy Teflon grease that comes in a little syringe is not good.

After washing the tapers with acetone and using a smidgen of copper paste instead (which has a kind of a greasy base, but not super slippy greasy) they seem happy.