Stronglight crankset install question
 

The other day, I attempted to install my Stronglight BB and crankset and ran into an issue I was hoping to get some help with (this is my first time doing this type of work, bear with me.)

The BB install went smoothly, but when installing the driveside crank, I ended up snapping the bolt. I couldn't find my torque wrench (I have found it since, though) and went with some internet guidance of "tight as #$%@", which ended up being too tight.

The thing that kept me tightening was the amount of taper showing behind the crank arm, which looked to be too much in my uninformed opinion.

http://i.imgur.com/yOzY2l.jpg

Compared to the non-driveside

http://i.imgur.com/YmPFDl.jpg

But looking at the gap between the recessed area of the crank and the end of the taper, it looks correct (again, to my uninformed eye)

http://i.imgur.com/dxlAql.jpg

This is a standard Stronglight 118 spindle, by the way. One thing I'm not sure of is whether I installed the spindle in the correct orientation, as the guide I was following didn't make mention of the fact that it's asymmetrical. I did get the snapped bolt out though, so all is not lost (as long as I didn't damage the taper or crank in the process :innocent:).

When I install any crank on a BB, I never base the "correctness" of the install on how far down the taper it goes, but more on how tight I am torquing the bolt. I also never expect the spindle end to be flush to the bottom of the bolt well on the crank arm. All my installs always have a gap between the end of the spindle and the top of the tapered square hole, sometimes a bit more than what you show. You should have stopped tightening the bolt when you were feeling a lot of resistance already as it could only result in a snapped or stripped bolt. If the bolt was already so tight, you should trust that the crank will not go anywhere/move on the spindle anymore.
I'd remove what's left of the bolt and put on a new one but not try to tighten it too much again to try and get the spindle deeper into the crank. I just hope you did not overtighten it so much with the first bolt that cracks might start to develop at the tapered hole.
BTW, I also never use torque wrenches and do all my bolt tightening by feel which had worked for me for many years.

Chombi

Thanks for your reply! As I said, I thought the gap between the crank surface and the end of the spindle taper looked correct, and I'm definitely aware that it should not be flush. I mostly just want to make sure that everything looks okay otherwise and that I can do as you say - put a new bolt on and monitor for cracks. This is a pretty common configuration as it's the stock 70s PX-10 setup, but I can't seem to find any pictures showing this detail.

do you grease the tapers?

I used a very light coating of grease.

For reference, this is the non-driveside-

http://i.imgur.com/qDs1El.jpg

I too had this concern the last time I removed my model 93 crank and reinstalled it. The drive side looked way too far outboard, and I thought it might be effecting my chain line and perhaps affecting my rear derailleur performance. Try as I might though, I couldn't get it to go up onto the spindle flats any further. I even tried a large C clamp and blocks of wood, after removing the non drive side crank, trying to nudge the crank further up on the spindle. No go. So, I left it where it was. It seems a little too far outboard to me but seems to work OK.

BTW, I never, ever lubricate the spindle flats on my BB spindles. I've always heard that is bad practice as it can allow the soft aluminum square taper to slide too far up the flats and thus, eventually, ruin the crank tapers. I wipe both spindle flats and crank holes down with alcohol before I install them. YMMV.

For the last 35 years or so, I have used a light coating of grease on my bottom bracket spindles. My concern is making sure I can remove parts when I need to so I grease everything, bolts, spindles, everything. I use feel to tighten any bolts as Chombi suggests. As far as allowing the crank to slide on too far, I figure that if that happened, the front derailleur would need adjustment as that occurred. I haven't seen this happen yet and I have a few BB/crank combinations that have been taken apart and reinstalled many times and used for many years.

Certainly, we all must use whatever works for us. I've been using the dry mount method for the last 35 years but, far be it from me to be dogmatic on techniques. Perhaps I'll just quote, if I may, from Sutherland's, 6th edition, chapter 2, page 4:
"The spindle end and the hole in the crank must be clean and dry. Do not use oil or grease or anti-sieze compound. The tapered square system depends on the crank coming up firmly on the spindle. Any lubrication will cause the arm to go on too far in tightening or to float on the spindle. Either way the arm will be ruined."

With respect, front derailleur alignment is the least of the worries with regard to crank tapers sliding on too far.

Thanks to all for the advice, definitely a good learning opportunity for me.

Yeah, 40 years ago I was taught no grease, so have always done it that way. And I've always tightened to bolt by hand, pretty firm but not super human bigfoot kind of tight.

Personally, I think the "dangers" of grease on a spindle taper is pure BS in practice. There is no way a greased taper will allow the crank arm to sit further on the spindle than a non-greased taper. It all comes down to how tight you torque the bolts and the hardness of the flats on the crank arm and spindle. If a crank arm is sitting too far on the spindle it's because the flats on the crank deformed because the fixing bolt was over-torqued, not because there was grease on the spindle. A square peg doesn't fit into a round hole just because there's grease on it.

With all due respect to Sutherland's book, that's pure conjecture on their part.

Still, for the last year or so I've used Teflon tape and no grease on the tapers.

Stronglight cranks are soft. Don't over tighten the fixing bolts. How do I know how tight is tight enough? The same way I know when my steak is done. I just do.

You may be right Colonel. I think the concern is, or could be, that a lubricant would allow the soft metal of the crank to move too easily up the hard steel spindle flats and, perhaps, allow the operator to "over-tighten" the bolt and thus deform the aluminum of the crank arm, thus, hastening the demise of the crank arm flats by enlarging them more than what otherwise might occur. Just conjecture on my part, of course.

Same here; I've done no scientific testing. But I don't buy that not applying grease is going to keep the heavy-handed mechanic from over torquing the fixing bolt. Once again I'm arguing semantics that don't really matter. Whether to grease spindle tapers or not is akin to which shoe you choose to put on first. Still, I'm staying in the "grease don't hurt nothing" camp for the time being.

Since Sutherland was quoted, why not throw a little Jobst Brandt in:

The need for a front derailleur adjustment is only an indication that the chainrings have moved in relation to the front derailleur. If the drive side crank is removed and replaced and soon after, the front derailleur needs adjustment, the crank is moving further in each time you tighten it. That's what would happen if the soft crankarm flats are enlarged. If this doesn't happen when the drive side crank is removed and replaced many times, it is an indication that the perceived problem is nothing but a myth. No conjecture there, just proof.

Sure. The no grease theory might be all wet. I thought it made a certain amount of sense way back when, so I stuck with it. My holes haven't gotten any bigger either, but I'd be loathe to offer that as anything close to being "proof". Whatever works.

Oh, I don't buy that either. But I do buy the prospect that if applying the same torque to a greased and a non-greased crank taper, the possibility of driving the greased crank arm further up on the spindle flats is real. And I'm not sure that's a good thing. I aint no engineer of course, but I'm not aware that press fits in general require lubrication. Sort of counter intuitive in my book, but, my book is often a strange read.

I never put any grease on my spindles in all the years I've been installing and removing cranksets from BB's, and I never had a problem doing so. I would say though that there might still be a little bit of grease residue on the tapers left over from maybe servicing the BB, but that would be it. What is important is you have the correct crank removal tool and you install it correctly before you try to remove the cranks. I followed that rule religiously and have been successful with all my crank extractions even on bikes where the crank had been on the bike good and tight, exposed to all sorts of weather for many years. Haven't had one yet that I could not remove with my Park crank removal tools.

Chombi

Here's some pictures that I posted last year showing differences in spindle fit. Notice how far the old style 118mm Stronglight spindle fits into the crank arm vs. a later model 118mm Stronglight spindle.

http://www.flickr.com/photos/2826722...7627678462359/

Chas. verktyg

Hmm.. yours fit a lot deeper onto the spindle taper, but as others have said, that could be due to manufacturing tolerances. It's also a different model crank, so maybe that has something to do with it as well. Can you comment on the asymmetry of the spindle? Is one taper longer than the other, and if so, which side is DS and which is NDS? I've found conflicting info on this subject.

This is an interesting point too Chombi. I'm supposing the ostensible reason for greasing the spindle is the same as for other parts like seat posts, fasteners, etc. To keep corrosion from setting up between the mating parts. I guess. And one would think that that could be a real problem since a BB spindle and crank arm are of dissimilar metals. Now, I haven't taken apart tons of bikes but I have never seen one where there was corrosion between the flats on the arm and on the spindle. Doesn't mean it doesn't happen of course.

I will add that I only looked up the info on whether or not to lubricate spindles in Sutherland's just yesterday. In 1972, I din't even know what a Sutherland's was. I'm pretty sure it didn't even exist back then. I think I went with what the guy at the shop who sold me my bike told me. He was selling all those fancy imported ten speeds so I just went with what he told me, later to learn the same from Sloane's bike book I believe, which is what I used in the 70's. And that book has several mistakes in it, I've subsequently learned.

Whichever method is "correct" may be unimportant, I guess. One could, including myself, tend to become a tad defensive about stuff one thought was gospel for so many years, but I learn new stuff on this forum all the time. I haven't got nearly as much experience as many of the members here who wrench on many more bikes than I ever have. I strive to remain open to learning new tricks and techniques.

As for the asymmetrical spindle Dphi, better let the more experten confirm but, the length of the flats on the spindle should be the same length on both ends, I believe. It is the length between the outboard bearing land and the end of the spindle that will be longer on one side than the other, and as far as I know, and the longer side always goes toward the drive side. Subject to verification of course.

I personally don't think that grease or no grease is of a major significance.

I DO think that maybe folks are forgetting the re-installation (CLOCKING) of the square taper (spindle to crank arm) to be of greater importance.

Manufacturing tolerances and the previous (as removed) taper set / relationship should be observed (witness marked) and re-installed in the same relationship IMO. One has a potential choice of four different reassembly positions. Reassembly to the original relationship would offer the optimum (factory) alignment with regard to taper-on-shaft advancement, chain ring radial and axial trueness and chain / DR alignment. No? ;)

I don't profess to be a bike mechanic Guru, but my many years of Naval Engineering, Automotive expertise and Machinist training, guide my thoughts here. I also happen to have recently rebuilt the crank on my ST with the same components as the OP.

I don't where that came from but I think it's bogus as hell!

I'm surprised that nobody has really addressed this point.

Somewhere(probably Sutherlands) I found a spec in inch/pounds for crank bolts that equates to about 22 foot/pounds.

I've always gone to 25 lbs./ft as it's easier to see on my torque wrench, but still not enough to damage anything.

Please don't ruin your classic vintage cranks for future owners/users.