ScottCommutes

No. Your method would work great for this application - the error is small.

Trakhak

I should have clarified: only one expensive torque wrench is needed. (It can be used on either the left or right crank bolt, of course.) That, and an ordinary socket wrench for the other side. The torque wrench sets both bolts to the correct spec, one after the other, in one operation.

You're right, as usual, about the conventional technique working perfectly well. I just happened to think up the two-wrench technique back in the mid-'80's, out of boredom, assembling bikes in the middle of the winter.

Back then, I don't know if any bike shops had torque wrenches. Ours certainly didn't. So I was using two socket wrenches, or maybe a Campy "peanut butter" wrench and a socket wrench, to snug up the bolts. But it did speed up the torquing process, if only by half a minute or so. Fun, too. (The "fun" threshold is pretty low in bike shops in the dead of winter.)

smd4

None of the three bike shops I worked at had torque wrenches.

ScottCommutes

The bike community is gradually getting up to speed to "torque" because modern carbon fiber parts are much, much, easier to damage via over-tightening than old school steel and aluminum parts.

Correct torque is a good practice anyway and has been used in other shops for decades.

ScottCommutes

A bolt has clamping power because it stretches as you tighten it - sort of like a rubber band. Torque in a shop is really meaningless. It doesn't matter how hard you torque a bolt. What actually matters is how much you have stretched that bolt. Fortunately, torque and bolt tension correlate pretty closely, so we can use a torque wrench to get a workable idea of bolt tension without measuring it directly (which is hard).

Too little stretch, and the bolt doesn't give its maximum holding power. Too much stretch, and the bolt can become permanently "stretched out." The optimum stretch for maximum bolt clamping power is just below that point where it permanently stretched out and ruined. However, many bolts can handle more tension than the stuff they are bolted into. Putting 100 ft-lbs. on a bolt just because the bolt can take it might flex, bend, crack, deform, or break whatever that bolt is holding. Bolt size is a decent general indicator of how much clamping pressure to apply, but not always reliable - better to look up the actual torque value or range.

choddo

If you can find a way to put 40Nm into a 2mm keyed T47 bottom bracket, I am definitely signing on to your tips newsletter. I’m confident I got close enough it’s not going to unthread but that number was not going to happen in my garage.

choddo

I think you can have one or both of expertise and torque wrenches but not neither.

Kontact 

This isn't quite true for square taper. Once the crank has pressed onto the spindle taper and you've ridden the bike, the torque on the bolt will drop. If you try to maintain that torque, you'll progressively press the arm further and further into the spindle, damaging the arm. The arm is being held on by the taper and the location of the bolt head, not the bolt's torque like the way a stem clamps.

ScottCommutes

All of us grew up with metal parts that flex politely when they are stressed, and then bend back into perfect shape when the stress is relieved.

Carbon is a whole different animal. Look at the wreck of the Titan submersible diving the Titanic wreck side. Cumulative stress on the carbon fiber hull from multiple prior dives snapped individual fibers a few at a time until the entire hull imploded catastrophically at depth.

The damage was microscopic. I don't know any way to check how much strength is left in a carbon fiber part. One thing you can do to keep carbon fiber parts in good shape is to properly torque your bolts.

choddo

Another is to not subject them to 1800bar

Trakhak

You're on your own there. I've skipped directly from square-taper bottom brackets to Hollowtech II. (With a couple of stopovers I'd rather forget, including Campy Ultra-Torque - or maybe it's Power Torque - either way, it has a click I haven't put much effort into getting rid of - and some FSA proprietary design - works fine, but I much prefer Hollowtech II.)

ScottCommutes

Also, turning tools are a particular length for a reason - the manufacturer is trying to help the less skilled achieve good torque.

IKEA furniture uses a certain size key so you don't rip right through the material.
Cars come with a tire iron that should get the job done without breaking anything (usually I wish these were longer!)
A 1/2 ratchet wrench is typically longer than a 3/8" or 1/4" ratchet wrench because it is used for higher torque.
If you look at your 11-piece metric wrench set or your hex wrenches, each one gets progressively longer to help guide your hand toward an appropriate torque.
Long pattern wrenches are fine for getting stuff apart, but not the best choice for getting stuff back together.
Even a quick release lever on a bike is designed to feel intuitive to a person of average strength.

choddo

Unfortunately this is a hollowtech ii crank but the bearings are internal threaded T47. Like trying to get hold of a jelly.

Trakhak

I was going to mention British Standard Whitworth as an example of an unnecessary wrench size and length/thread dimensions/bolt diameter/torque specification. (Working in a Raleigh dealership in the mid-'70's, I thought that Raleigh forcing their dealers to use these weird Whitworth parts and tools when there were already perfectly good metric and SAE parts and tools was ridiculous.)

Then I looked up British Standard Whitworth on Wikipedia and got schooled in a hurry. Whitworth was there first.

Trakhak

Haven't worked in a shop in decades, but the impression I get from T47 installation videos is that Shimano deliberately designed the notches on those outer cups the way they did to make it difficult or impossible to overtorque them (maybe worrying about home mechanics without torque wrenches). They could have made the outer surface of the cups octagonal, for example, to make setting the torque easier. Just guessing, though.

Kind of the way Suntour used plastic stem caps on the first AheadSet generation to keep mechanics from over-tightening the stem bolt.

But customers and mechanics jumped to the conclusion that Suntour was just cheaping out on the part and demanded metal stem caps.

Suntour said, "Fine; Have it your way" and went to metal caps.

Back to the T47 cups, though: just looked, and Shimano specifies min. 35/ max. 45 Nm. I'll check mine. They're almost certainly not tight enough by that standard.

zandoval 

Well thats a worthy question.


AmazonPic

Well I think they are just Balls Of Mystery Grease, just put there to remind you that you need to make sure your bottom bracket is greased and that a thin layer of grease is applied to the spindle and threads of the spindle cover. Also note that after the bolt is installed you can cover the head of the bolt with grease to prevent rust under the bolt cover, if you use it.

My suggestion is to remove the manufacturers grease and use Marine Grease, of any flavor, to grease your bottom bracket and spindle. If your crank is in fact worn out then you most likely need to service the bottom bracket. I dont know if you have the proper tools. Note that if you do not have the ability to remove your spindle and bottom bracket to get to the bearings you can still clean the bottom bracket. Here's a link to give you a few ideas. Youtube: Trick for Removing a Bottom Bracket on a Bicycle

ScottCommutes

I read the BSW Wikipedia article. We really take it for granted that a wrench is the size it says it is. I did not appreciate that some wrenches back in the day were instead marked with the diameter of the nut/bolt they were designed to turn.

Also, Whitworth threads to this day are used on Leica camera and enlarger lenses as well as stage lighting equipment mounts (as well as some other stuff). Goes to show you how hard it is to standardize machine tools.

SurferRosa

You place the grease balls under your pillow for the Amazon Grease Ball Fairy.

Obviously, you grease the installation of your bb shell, cups, and spindle. Always grease the pedal axle threads. Some grease the spindle taper, some don't. Some grease the crank bolts, some don't. (I use only a tiny bit on the bolts.)

base2 

It's not the fibers that snap. It's micro fractures in the matrix that holds the fibers in place.

A deflection test is the most common method to test service life. They load the part in some way initially at time of construction and measure the deflection. Then at prescribed intervals they repeat the test and compare the result against the original. When the part is deemed too flexy due to micro cracks in the matrix the part is pulled from service.

The Titan Sub was a hack job by an idiot using expired carbon fiber in initial construction in compression the way that it is weakest with no initial or subsequent testing. Per his life wishes, he is now known for all the rules he's broken. Just the way he wanted. (It's a shame about the kid tho.)

Darth Lefty 

What a winter thread this is. Two wrenches! Genius! Carbon fibers! One guy can't do 40 NM!

Kontact 

What industry does that? Navy F-18s are x-rayed.

base2 

They X-ray commercial aircraft at certain intervals, too.

I was thinking Formula 1, specifically.

choddo

Oi! It’s Nm.

I’m considering buying Praxis’ tool and sending the Park Tool on back. It seems designed for the tiny gripping space on these BB cups without scraping paint off the frame.

Heat88

When I was using a puller to pull the old arms off, one came off fine, but with the other one, the puller pulled out and stripped the threads on the arm(but the puller is OK, it screws in to the other arm). Is there anything I can do besides get a new crankshaft? I'll have to pull out the crankshaft and see whats engraved on it to help me find a new one. What specs to I need to know? Is it possible to get just the shaft without any of the other hardware? The bike is a Schwinn Sidewinder.

Edit: I don't think it'll help because my bike is too new to be in a database, but here's the serial number: SNMNG11A9137. None of you are nerdy enough to be able decode the serial number are you? I think I found Schwinn's code book, but my serial number is too new to be in it.😥
Why does the post I made after this one need to be approved by a moderator?

Heat88

I found this video on YouTube that shows how to get an arm off when the puller strips the threads on one side: watch?v=NjI5eDPjS6o In that video, it was the arm with the chain ring that he got off and he pretended the other side was stripped. In my case, Its the chain ring side that was stripped. Please tell me I can pull the crankshaft(or spindle is you cockney people call it) out the other way. Also I didn't realize I didn't know how to remove the crankshaft. I've done it a few times on a BMX bike but never a mountain bike. Is there a video I can watch? I have a Schwinn Sidewinder. Its 8-10 years old I think.

ttps://www.youtube.com
I need one more post before I can post videos. Surely you guys know that every YouTube video has the same URL except for what comes after v= so you should be able to figure out how to watch it. In case you can't, just load another YouTube video and replace that one's serial number or whatever its called with the one above.The important part is halfway through. Thanks