Loose Chain

In aviation we have standard torque tables to use when a torque is not given. Several bits on my new bike do not have the torque silkscreened or etched (as if often common practice today) so is there a bicycle specific standard torque chart? Thanks in advance.

Arthur Peabody

Spec sheets from parts manufacturers often have torques. I don't think I've ever broken a part by over-tightening (I did pull a spoke nipple through a rim once, but that's different.) and had parts rattle off only twice in 50 years, but not because they were under-tightened in the first place.

randallr

Search on "Park Tool Torque Specifications and Concepts"

Arthur Peabody

BOLTS AND TORQUE SPECS

https://www.parktool.com/assets/img/...elp/torque.pdf

WizardOfBoz

When you say "in aviation" are you Airframe and Powerplant rated ? Not asking to be confrontational, just don't want to explain something to someone who knows more than I do!

Suffice to say that in aviation you are used to dealing with AN ("Army Navy") rated fasteners. There's a certain uniformity in metallurgy (its usually high-strength steel allow, properly heat-treated) and quality (reflected in more uniform and smooth surfaces). This makes AN torque specifications more useful and uniformly applicable.

In bikes you have some very high quality steel alloy fasteners. Some are... not very high quality steel alloys, and some are not very high quality fasteners. But even if all the fasteners were high quality, there is a wide range of materials - alloy carbon steel, stainless of several different flavors, and titanium.

The point is, to use a table you need to know if its 8740 steel or 316 or 304 stainless, or titanium. Or something churned out in the bowels of China's manufacturing underbelly that has the yield strength of Manchego cheese. Furthermore, antisieze will affect the appropriate torque and it's pretty necessary on (for example) 316 or Ti bolts and nuts.

For this reason, I don't think standard tables should be used as much more than a starting guess. I always try to get the manufacturer's instructions. Shimano's stuff is excellent for giving specified torque ranges.

Loose Chain

Yes, I hold the A&P, IA and I am a self-learned engineer, my degrees were not in that subject but I have managed to accommodate. Aircraft, bicycles and motorcycles have much in common. Charles Taylor was the first A&P and he was the Wright Brothers mechanic, who themselves were bicycle mechanics. Glenn Curtis was an aviator, mechanic, inventor and motorcyclist. They all use highly stressed parts that are built to minimum weight and do not tolerate hacksaw mechanizing well. And can near about kill you if not respected.

In this case I cheated, I have a bicycle with essentially the same pieces and fastener and thread sizes and the torques are silk screened on, so I used those, lol! What the heck anyways. When I put the torque wrench on them they each moved a skosh if that. I have gotten pretty good over the years "feeling" the torque. I always try to go to the low side or at least the middle of the specification. With some exceptions. And these are not any of those exceptions (like rod cap torques that need a stretch for example).

WizardOfBoz

Very cool credentials. I'll brag a little bit, my nephew got his A&P while finishing high school. He then went to college at Moody Bible Institute in Spokane, and just finished his degree in Aviation. The idea, as I understand it, is to be able to fly, and maintain planes to fly, into remote areas. Medicine, food, people. Maybe even bikes! For now, he's working for a firm retrofitting older plans with turboprops. I think in sheet metal work. I need to chat with him: I'd like to know if he's working with English Wheels, or planishing hammers, or.. what. Anyway, he's a good kid - very polite and considerate to have around, but a hard worker and very willing to step in and help. But that's how I learned a bit about the A&P rating. BTW, my nephew just successfully soloed, so he has his private pilot's license.

And even that I are a fully (over-)trained engineer, I suspect I was right: you DO know more about fasteners that I do.

I think that, given the bikes come with matching fasteners, using the printed torque values is best. And if not printed, the dealer's manuals should have the info. I do worry a little bit when I think of some hot-shot (like I was in high school) subbing in Ti or SS bolts for a heat-treated 8740* and overtorquing the thing.

*Just kidding: I'm pretty sure that most cycles don't use AN bolts!

Jeff Wills

Others have pointed at the Park Tool reference, which is good for decent quality bike parts. Parts on department-store BSOs (Bicycle Shaped Objects) can be cheesy but most of the time the parts will hold together at the torque listed.

Things have gotten somewhat more standardized in the 40+ years I've been working on bikes. Threading is one area that's gotten better since then- don't get me started about Swiss or Argentine bottom bracket threads. And get off my lawn!

Loose Chain

Thanks guys, the Park site is a good reference I had forgotten about. The bicycle I am working on does not have a good manual, no torques are given and most of my bicycles with some exceptions are built up by me from an ecletic mix of parts. I like that many components now have torque engraved or silkscreened on them. There are so many different thread types in the cycling world it would be hard to have a torque chart(s) as in aviation where everything for the most part is plan old US threaded and metric is a rarity and there is so much standardization.