Space_doodle

I just bought a power meter and need to take off the left crank arm (Cannondale SI) I thought I could do it and researched it to death but when I started the job I can't even get the crank nut off! I really forced it and am know afraid I've hurt my precious. Threads are still intact. Any ideas how to remove a crank nut? It's speced to 30Nm and was built at LBS but I can't get this to budge. Thanks in advance.

Trevtassie

Lefty loosey, righty tighty?

Space_doodle

As in crank stays still and wrench moves counterclockwise? That's what I've been doing.

Trevtassie

Yep, wrench counterclockwise. Got a rubber mallet or deadblow hammer or a bit of heavy wood? Support the axle and crank on some padded blocks of wood with the crank to the left. With the mallet belt the allen key down. Often a sharp blow is much more effective than a steady pressure in removing recalcitrant bolts. Use the best long arm allen key (hex wrench) you can. Or a hex socket and socket arm.

Space_doodle

Thank you. I was using a rubber mallet and got some movement but still didn't come off. This is what made me paranoid about damaging the BB. I didn't support with wood blocks, just my thigh. I am using a socket wrench with 10mm hex bolt. I was using a long arm torque wrench but didn't want to start wacking that with a hammer.

If anyone here can confirm that I'm not going to destroy anything, I'll go gorilla on it tomorrow. Got too scared of screwing up my bike to continue today.

dsbrantjr

It is poor practice to use a torque wrench for loosening fasteners. That is what breaker bars are made for.

Trevtassie

The rigid support under the axle/crank is important here (with a little bit of padding to stop scratches). You want to transfer energy into the bolt axle interface, not your body.

Trevtassie

Other option would be an impact wrench, electric or air powered. A manual hammer type with a socket drive might also cut it; like this: https://www.amazon.com/TEKTON-2910-2.../dp/B000NPUJYE

sweeks

Or the BB bearings either.

SalsaShark

Place a socket wrench on the crank arm fixing bolt, positioned slighly 'ahead of time' in the clock vs the crankarm, so you can grasp both the crank arm and socket bar in the same hand. Grip both with both hands, and squeeze them together with your hands. This works great to give immense controlled breaking force, although i have a very strong grip.

andrewclaus

If this is a square tapered crank, you should either be using a 14 mm socket or 8 mm Allen.

Most of time you can get these with correct ergonomics. Some people don't have a strong enough grip or wrists, and need to use shoulders and upper body strength, arms aligned with the frame. Be sure your knuckles don't get smashed between wrench and crank--get the wrench past the crank as mentioned above.

Dan Burkhart 

You realize the SI crank requires a proprietary extraction tool? It can be hacked. At the last shop I worked at, I cut the head off a M18 crank fixing bolt and screwed it into the spindle and then a standard crank puller can be used to push against it.
The fixing bolt should come loose by rotating counter clockwise. It may take considerable force to break it loose.

Space_doodle

Hi Everyone, thanks for all your help. I did it. I used the wood block and rubber mallet approach. It still took at least a couple full turns with the 5 past the hour approach that someone here suggested. Here's the interesting part and it might explain why this 3 year old bike had such a tight nut. I think the LBS where I purchased this bike built it wrong! I found a wave washer and a spacer on the left side. In the Cannondale manual it indicates that this wave washer should be on the drive side and should be visible after installation. Well, I definitely don't have a wave washer on the drive side. It is possible that the builder then put the crank on too tight to get the proper compression in the washer (on the wrong side). I put the bike back together the way I found it because it has served me well and I know it is at least safe. When I have time some day, I might take off the right and left sides and put it back together according the manual. Anyway, thank you all for your help. This is the first post I've made here and I'm worried I might get hooked.