Bottom line is:

These are bicycles not Swiss watch movements!

I have a an old parts drawing from Gates LearJet that says: "MAKE TO PRINT - BEAT TO FIT - PAINT TO HIDE!" ;-)

These components were made on old machinery some of which predated WWI. After WWII most of Europe was in tatters. That included most of the manufacturing facilities on the continent.

Bikes were the first form of transportation to be manufactured after the war. By the 1950s as Europeans became a little more affluent, mopeds, scooters and eventually motorcycles became more popular. Later in the decade cars became the goal. In the meantime little or no capital was invested into the bicycle industry.

When the US Bike Boom hit in the early 70s, European bike and component manufactures were hard pressed to keep up with the demand. Bikes were being thrown together and boxed up as fast as they could push them out the door.

Last year I posted the link below in this thread.

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

Two years ago I photographed and documented a project I was working on and posted it on Flickr. I was putting together a single speed bike with Stronglight 93 cranks. Read the descriptions below the photos which explain my results.

verktyg

They left out "tighten 'til it cracks, then back off 1/2 turn."

i grease all contact points. my bikes are stealthy quiet, and everything comes apart for overhaul like it should.

John,

That was on the Assembly Print!

verktyg

I read this entire thing and don’t think I learned anything.

I work in a calibration lab and regular torque wrenches are +/- 4% so at 25 that’s 24 to 26 ft lbs possible from the accuracy of the wrench itself. How precise does this have to be to where a small amount of grease will comprise the connection?

The "no grease" theory is certainly slippery. I don't worry about it. I don't add grease and I wipe off crud including grease, but I do not degrease the surfaces. If I have a clearly pertinent torque spec, I do use it. I don't think those settings are especially tight. They are intended to be adequate to produce a joint which will not come loose. Other advice I've seen is practical - use a wrench which is the toolmaker's length for the bolt size. For crank bolts, the head is 14 mm and sometimes 15 mm. If you pull on the end until it hurts on your hand, that's practically enough. The purpose of a torque wrench is not to tighten things "tighter than &%^$##m" but to consistently tighten it well but not too tight. Bolts have to be removable by human beings, without destroying anything. When tightened, they have to stay tight until it's time to service the bike.

If I don't have a clearly pertinent spec, I look back at the Park mechanics manual or Zinn's Road Bike Repair book, and use their general guidelines.

I haven't found any of these specs to fail, though I have broken bolts by over tightening. Sometimes it poses a big problem, and sometimes not.

I thought that one was patented for the aluminum access covers on the crankcases of vintage and antique English motorcycles. It would be a violation to use that on Japanese or Italian bicycle parts and frames!

Super-interesting thread, indeed!

Hmmm. In all of this, when talking of wrenches no mention of one that was designed specifically for installation of square taper crank arms, the Campagnolo so called “peanut butter” wrench. The handle length and shape makes it virtually impossible for the average strength user to over tighten a crank bolt unless they use a cheater bar. With it, tight is right tight.
Part of the Campy Tool Set, it was one of the most common pieces sold individually by dealers.

I have heard the square taper interface likened to "a landing craft going up on a beach"

where the tapers match and the running torque goes up, that's enough

come back and re-visit after 50 miles

on Campagnolo cranks in good condition that turns out to be about 220 in/lb

the Stronglights are so soft it is hard to tell but I'd start wth 150 in/lb and again re-torque after 50 miles.

should be clean. To grease or not to grease is up to you

great pics from Chas on the details of the spindle to arm interface

/markp

I'm wondering where it became seemingly "common knowledge" that these Stronglight crankarms were "soft". I know I've heard this before, but I've straightened Stronglight crank spiders, and the slender, material seemed to resist my efforts comparably to other brand's top-tier offerings.

And I've never stripped any of their pedal eyes, nor found either arm to bottom out at the end of the spindle on any of the quite good number of Model 93's I've worked on.

I do believe though that the material is dimensionally thin, for light weight, so I always respect the stated dry assembly procedure that I learned that at the Wheelsmith shop (a comparable Shimano crank is beefier around the taper).

At the very least, it can be said that the appropriateness of the manufacturer's bolt torque spec will very much reflect (i.e. be dependent on) whether or not grease is used on the tapers as well as on the threads. When "dry" is specified, parts should be very clean of any residual grease.
I've never had a corrosion problem of note on the tapered surfaces of a Stronglight crankset.
Note also that the bolt caps are intended to prevent loosening of the bolts, though a bit of Loctite is a good substitute.

I was not aware that there was ever a "manufacturer's torque spec" published by ... Stronglight ? or Campagnolo ?

/markp

Never was aware of any required torque specs while working for Campagnolo in the 80’s. A torque wrench was not included in any Campy tool set or our personal tools. The Campy wrenches are sized to provide adequate torque for each application.
Having seen some top wrenches from various countries do their thing at World Championships, Olympics and big stage races during that time, none used a torque wrench in the heat of battle. Time was short. Fiddling with a torque wrench could be costly.
In one case, at the LA Olympics, a coach for the US team brings in a pursuit bike and says the bottom bracket bearings are shot. Sure enough, they are rough. He then says he has to get it to the start line in fifteen minutes for Harvey Nitz and that is loose ball with oil.
Three of us jumped on it immediately. Campy “peanut butter” wrench used for removal and tightening of cranks. Crank bolts were spun off and back in by holding the wrench close to the bolt and turning the cranks. Tightening was a good pull on crank arm and wrench like using bolt cutters.
Loose ball with oil meant I had to use a magnet to hold the balls in each cup until they could be placed on the spindle. A PITA no matter how much time you have.
We got it together in about ten or eleven minutes and sent the coach on his way. He got to the start in time for Harvey to win the Bronze Medal in the Individual Pursuit.
Torque wrench?! . . . . . We don’t need no bleeping torque wrench!!

I pretty much agree with you here, the torque wrench is at best a useful guideline for those who have not had the opportunity to work on 100s of bikes and develop a "feel" for what is right.

Today I use the torque wrench only on crank fixing bolts (square taper), mostly because of the unique nature of that interface, and also on modern stems with the face cap and 4 screws.

and maybe on BMW head bolts which are a discussion in themselves.

What I was trying to get to in the original post was that there's a phenomenon of "running torque" as the fastener if tightened down to approach the final torque value. On the really high quality cold forged crank arms (Shimano, TA Zephyr and Carmina) the torque value ends up being a very solid 260-280 in/lb. This is hard to describe, but it's where the increase in the running torque indicates that the fastener is sufficiently tight and the square taper joint is locked together. Exactly what you feel when you do it by hand. For classic Campy this ends up being about 220 in/lb. What I've experioenced on the Stronglight cranks (49, 57, 93) is that you never get to anywhere near that torque value. You just keep turning the wrench ! This may account for a large number of cracked crankarms.

For other types of assemblies in which failure of a fastener would be of high consequence (I'm talking aircraft and spacecraft here) the torque wrench provides a valuable "witness" that yes, in fact the bolt was tight when it left the shop. In many cases there is an actual step to accumulate evidence of this - do you know what a "Jo-Bolt" is ? Used in aerospace applications, the head breaks off when the specified torque is reached. Fifty bucks a shot.

But what do I know ?

/markp

Obviously, in a good way, more than enough to enjoy tinkering with bikes.