Originally Posted by
Bjenkins
Hello All,
I'm slowly moving through cleaning, servicing, lubing, etc. on my '77 Motobecane Grand Jubile. It came to me in almost perfect shape and I don't want to screw anything up. I'm a novice and I'm buying tools as I need them, and watching videos. So far, I've done the front and rear axles and the freewheel (clean, replace bearings, re-lube). Now I'm on the bottom bracket. I've pulled the cranks (with the correct classic SR Sakai puller that I bought used from a bike repair guy who was closing his shop), and ordered a couple of Park Tools, the HCW-4 and HCW-5, in order to remove the fixed and adjustable cups, so no problems so far.
Here's my conundrum: I've seen a couple of videos of this operation and in one the mechanic says that that the square tapered spindle and the female crank opening should be cleaned of all lubricant when re-fitted or the crank may be drawn up too far on the spindle and crack at the corners. I have a problem with this theory. I've lived on boats for many years and I know that dis-similar metals tend to destroy one another in the absence of any lubricant/sealant, so I instinctively want to lightly grease the spindle contact surface. Also, I would think that there is a standard torque setting for the bolts that would correct this issue (although I haven't seen it yet).
Here's my question for the experts: Should I leave an aluminum/steel interface clean of all protection in the interest of friction or not?
Here's my second question: Does anyone know the torque setting for drawing up the crank arms to the spindle?
I know these might seem like small matters in today's world, but I'm taking the Hippocratic approach to this beautiful machine – First, do no harm.
Thanks,
Brian
While I applaud your concern I will tell you that IME, I have never really seen any serious galvanic corrosion between crank arms and axles.
The boat analogy is apples and oranges, they suffer from electrolysis, hence the anodes and sacrificial plates used for that.
Most/all vintage cranks and axles now have been in service long enough and are sound enough that they rarely crack at the square taper hole, I've never seen one do so but I have seen a few that have stretched so the bolt bottoms out on the axle before it is tight enough.
The torque specs are easy enough to find but I suspect many here do it by feel with experience over many years of servicing.
The grease question is an age old conundrum and while I see many that seem to not have had any grease, it may not hurt.
On the other hand however I have often thought it possible that the grease may facilitate the stretching by helping the arm seat on further than it should.
The stiction of the interface may be the balance of tight enough without overtightening and stretching, maybe.
The really fun part is yet to come, removing the fixed cup if it is very tight can be one of the greatest cycling adventures you will encounter, many here will advocate for leaving it alone, cleaning as best you can from the other side.
I remove every single one for proper service and inspection, period.