cookja0113

Hi! This is my first post, I hope it's in the right spot.
I bought an old Schwinn Sprint for a project I am doing just for fun and was wondering if the tightness of the torque wrench really matters on old bikes (specifically on the crankset). I need to know because I am planning to take drivetrain apart and clean up/re-lube all the threads and bolts because there's a bit of clicking in the bottom bracket when I stand and pedal. Do you have any recommendations as well for how I should go about cleaning this area up and re-lubing it? Sorry if I'm asking too many questions in one post. Thanks.

fietsbob

There may be Books to buy to offer the data you wish to have,
Ones on Bike Mechanics worth owning.. (or use your public library?)







....

cny-bikeman

No need to purchase or check out a book for that: https://www.parktool.com/assets/img/r...elp/torque.pdf. As far as greasing goes, I recommend against overtly greasing crank fixing bolts or spindle tapers. The grease film on your fingers after a BB overhaul is sufficient.

LesterOfPuppets

Crank bolts? Get 'em REALLY tight, then ride it a bit, then tighten them a little more. I'm not sure what torque values.

cookja0113

You're completely right, I really should be reading before I go any further. If you have any book recommendations that would be great as well. Thanks

fietsbob

Lennard Zinn is contemporary has 1 for road & 1 for MTB, but the basic ones in the circulating collection of your library are also a good background..

You can find torque specs relative to bolt size,
but dry and greased are different numbers..


but bike cranks being aluminum stretch irreversibly if over tightened ,
or are damaged if left too loose.. and almost falling off,
but continuing to be ridden..
then there is cold forged vs cast..

after decades of working on bicycles it's a felt thing , I cannot offer a rote number ..

If I were overhauling my car engine, I got out the repair manual..





....

AnkleWork

Maybe focus more the concept of torque as applied to threaded fasteners. The torque wrench is just an artifice to get the desired results, not an end in itself.

fietsbob

Main advantage is shop manual technical writers are able to use a specific number to indicate 'how tight' , in print.

Computer people became anti book and so they think their computer is where all knowledge is.. public library became too socialist egalitarian, , I guess..






....

Andrew R Stewart 

Bob- Interesting concept and one I've thought about a lot but never got the words as right as yours are.

IIRC the Sprint has a common tapered square cotterless 3 piece crank. If so then the arm retaining bolt will ne 25-32 ft/lbs of torque when tightening. I very much agree with cny-bikeman's suggestion of keeping the tapered surfaces dry of real lube but I do lube the bolts' threads and heads. I also agree with LesterOfPuppets regarding revisiting the retaining bolt tightness after a few rides for a few cycles. I do suggest lubing every fitting otherwise. Chain ring bolts can make all kinds of creaks and clicks if dry and not really tight.

As for which book to get- most are technically correct for the stuff they cover but I find the difference is often the style of layout, the writing style and if the book's pages can have grime wiped off easily. I think the book as just one more tool so how it fit's in my hand, metaphorically, is how well it will be used. Andy

nfmisso

NO !!! What you describe is the fastest way to ruin a set of crank arms.

Tighten crank bolts for three piece cranks with tapered steel axles and aluminum crank arms with M8 threads to between 30 and 40 ft-lbs.

JohnDThompson 

Well, it's arguably not the fastest way to ruin a crank arm, but it can still be pretty effective at ruining them, especially if you service the bottom bracket frequently.

That's a better suggestion. If you don't have a torque wrench, tighten them as tight as you can comfortably get them with a 6" lever arm, like the infamous "peanut butter" wrench.

LesterOfPuppets

Your torque spec sounds close enough to me. Shimano spec for square taper is 35 - 50 N·m (about 26-37 ft-lbs) and they clearly state to test ride after torquing, then recheck torque.

I've never used a torque wrench on a square taper, but you really have to lean on this tool to get it suitably torqued, IME.

cny-bikeman

I would recommend not taking too much time with that reading if you are already experiencing clicking. I doubt you will be causing much harm by tightening pedals, crank arms and chainring bolts a bit.

Andrew R Stewart 

Just about every warning to not retighten retaining bolts has no reference to how tight to not retighten to. Just a NO. Instead I have always said you check and retighten to the proper torque, not more. Otherwise how do you know that the arm is still at the right bolt torque? Do you assume that a initially tightened fixture will always remain at that torque regardless of use? Andy

Rogerogeroge

Well, it makes more sense than cutting down a tree, printing and shipping a book when you can distribute virtually unlimited number of books electronically.

And to add to the thread subject matter, the one thing that needs the most torque on an old school bike is the drive side fixed cup of the BB.

TimothyH

Keep in mind that the specs provided by Park are generalizations. They can be wildly inaccurate depending on the component and manufacturer.

Always go with the manufacturer's spec when available.


-Tim-

Ronsonic 

Torque wrenches simply weren't used back in the day. The mechanic was expected to have a feel for this.

Square taper cranks: Do NOT grease the taper. I degrease them and recommend that. Do use a bit of grease on the bolt or nut after setting the arm in place. Tighten to good and snug. You'll see the arm move onto the spindle as you tighten. Do not over-tighten.

TimothyH

The fact that torque wrenches were not used in the past does not negate their use in the present.

JohnDThompson 

More to the point, torque wrenches were not often used in the past because steel frames and over-engineered components were not as sensitive to damage from excessive torque.

Modern materials and computer-assisted design have led to significant decreases in weight for bicycles and components, but do require attention to specific torque values when installing and maintaining a modern bike.

davidad

Never re-tighten crank bolts. Installing Cranks by Jobst Brandt

LesterOfPuppets

Shimano instructs mechanics to recheck torque on square taper crank bolts/nuts after first ride.

I'm gonna stick to Shimano's suggested technique.

Looks like Jobst is saying not to repeatedly tighten crank bolts, presumably increasing torque each time. Yeah, I could see how that would be bad.

Kontact 

Brandt is not saying to fail to check your crank bolts after the first post-installation ride. You should. You just shouldn't do it more than once.

davidad

He is not saying that.
I have 126,166 miles on a TA Alleze crank that has been off numerous times. I grease the tapers and torque them to 25 lb.ft. I have had no problems.