# torque wrench for crank arm?



## sponger (May 14, 2006)

I'm planning to replace the chain rings on a 2x10 shimano XT crankset. But, I don't have a torque wrench, which is required for the crank arm bolts. I don't plan on upgrades, and I don't think I'll be needing to remove the crank again anytime soon. So, I'd like to get around needing to buy a torque wrench just for this one job. 

Any success stories about accomplishing this task without a torque wrench? Not a carbon bike, btw.

Thanks.


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## Lone Rager (Dec 13, 2013)

Crank arm security is very important. If it starts getting loose it can damage the crank arm. Let it go far enough and if the crank arm gives out it can damage the rider. The pinch bolts need to be successively tightened as tightening one loosens the other. 12-14 Nm is a fairly high torque for the screw size. Ensure the wrench fits well and is fully seated so as not to damage the screw head. Put it together, take it to a shop and have them check the torque. Better yet, of course, is to buy a torque wrench.


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## EABiker (Jun 24, 2004)

While the advise given was right on, I will say that I've removed and replaced crank arms dozens of times without a torque wrench, and never had any issues. I have, however, been wrenching on cars and bikes for close to 40 years and have developed a "feel" for how tight is right. Or maybe I am just lucky!


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## mack_turtle (Jan 6, 2009)

There are some small adjustable torque wrenches kits on Amazon for about 45 bucks that includes every driver you'll ever need on bike. Worthwhile investment. I am a big proponent of torque wrenches. Unless you have been working on bikes professionally for many, many years, you can't approximate proper torque by feel. I use a torque wrench on almost every bolt on my bike for this reason.

After working in bike shops for six years, i know better than to trust "feel." I have seen people crush aluminum bars, strip out 24mm cranks, lose ST cranks arms and strip out every part imaginable. 99% of the people who tighten M5 bolts by feel are kidding themselves, or getting lucky. [Edit: wrote that before reading EABiker's post, ha!]

If you don't want to spend the cash now, tighten them up and borrow a torque wrench from a bike shop. Bring cookies.


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## Slash5 (Nov 27, 2011)

At least a Shimano crank is likely the easiest crank to do without a torque wrench. If you Google around, you can even calculate how much pressure you need to put on your hex wrench at get the correct torque.
I just installed a Race Face crank and now I understand all the posts about that style of cranks coming loose or destroying the spline. Without a torque wrench there was no way I would have used that much torque on the drive side bolt. Anyone doing that without a torque wrench would probably have half the required torque, or less.


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## IRBent (May 11, 2015)

mack_turtle said:


> There are some small adjustable torque wrenches kits on Amazon for about 45 bucks that includes every driver you'll ever need on bike.


I've had decent success with this little kit and as Mack said, it has just about every driver size you'd need.
https://smile.amazon.com/VENZO-Bicy...1491576295&sr=8-2&keywords=bike+torque+wrench


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## DethWshBkr (Nov 25, 2010)

I have NEVER torqued any of my Shimano cranks, but like someone else said too, I have done a ton of work on a lot of things.

The only thing I like to really torque properly are carbon parts, cylinder heads, and wheel lugs.

If you use a 5mm T handle allen key, you should never need to use the high leverage side, and you don't need to be a superman/he-man/hulk to do it either.

I bet it's only a "seat" the bolt, then 1/2 turn, then repeat on the other side. Repeat again, but I bet it's only 1/3 of a turn then or so.

See, now I need to go torque my bolts and check to see if I'm right on the amount of turns. It's hard to "say" how far to do it, as opposed to "feeling" it. I may make a video just for fun to show if I was way off, or pretty close.


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## Harold (Dec 23, 2003)

Slash5 said:


> At least a Shimano crank is likely the easiest crank to do without a torque wrench. If you Google around, you can even calculate how much pressure you need to put on your hex wrench at get the correct torque.
> I just installed a Race Face crank and now I understand all the posts about that style of cranks coming loose or destroying the spline. Without a torque wrench there was no way I would have used that much torque on the drive side bolt. Anyone doing that without a torque wrench would probably have half the required torque, or less.


Shimano Cranks are the only ones that I don't use a torque wrench on. If you're not comfortable with that, I recommend one of these for higher torque stuff. Especially my RaceFace CINCH cranks with 50Nm torque spec for the fixing bolt. Park used to sell one, but it appears they discontinued it last year.

Craftsman Beam Torque Wrench (00932999) - Socket Sets - Ace Hardware


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## One Pivot (Nov 20, 2009)

In the last 20 years I've been working on bikes, I've literally never torqued anything. Ever. Not once. 

Ive also had zero torque related failures. I also do own carbon parts.


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## mack_turtle (Jan 6, 2009)

One Pivot said:


> In the last 20 years I've been working on bikes, I've literally never torqued anything. Ever. Not once.
> 
> Ive also had zero torque related failures. I also do own carbon parts.


So what is your advice to someone who has zero years of experience? Working in shops, i have seen dozens of torque related failures, mostly by customers and a few of my own. The failures never occur when someone use a proper torque wrench.

i am not saying you should be using one if you're comforatable without it. I just don't think it's helpful to tell a hesitant newbie to just wing it without a net, to use the parlance of our times.


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## IRBent (May 11, 2015)

mack_turtle said:


> So what is your advice to someone who has zero years of experience? Working in shops, i have seen dozens of torque related failures, mostly by customers and a few of my own. The failures never occur when someone use a proper torque wrench.


Where's the like button? :thumbsup:


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## Mr Pig (Jun 25, 2008)

Slash5 said:


> I just installed a Race Face crank and now I understand all the posts about that style of cranks coming loose or destroying the spline. Without a torque wrench there was no way I would have used that much torque on the drive side bolt. Anyone doing that without a torque wrench would probably have half the required torque, or less.


Very timely post. I never use a torque wrench on crank bolts, I just do them up...tight.

I put a Race Face crank-set on my son's new bike last week and your post got me wondering. Pulled out the big torque wrench and was stunned by how much more I had to tighten it to get it up to spec. I honestly thought it must be some mistake and I was about to strip the bolt.

Then I checked the RF cranks on my full-sus, which were on the bike from new. They were not as tight as they should have been either, although they possibly loosened off with use.

Thanks for the post, lesson learned.


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## milliesand (Jun 29, 2015)

If you don't want to buy a torque wrench, you can barter a few beers with your neighbors. Likely they'll have a wrench that reads in foot pounds, so you should already have googled how many foot pounds equals the Shimano spec.


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## sponger (May 14, 2006)

All the insightful info is really appreciated. I was at the LBS tonight and the mech said bring her in tomorrow for a quick adjustment on the house. I wouldn't have thought of it had it not been mentioned, so this thread was certainly handy.


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## Lone Rager (Dec 13, 2013)

Personally, I think that single axial bolt type cranks are less problematic. Just make them really freakin' tight. The bolts (screws, technically) on the shimano cranks need to be disproportionately tight compared to their size and it is fairly easy to strip out the head if the wrench doesn't fill well, isn't fully inserted due dirt in the bolt head, or if there is excessive non axial torque applied to the wrench. It's more common to tighten bolts this size to 5-9 Nm. IMO. 

Of course the basic problem with this is that one person's really freakin' tight can be quite different than another's really freakin' tight, and that's where torque wrenches come in. They remove the subjectivity.


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## Mr Pig (Jun 25, 2008)

I just wish they would pick one BB type and stick to it! I have a brand new BB30 crankset here that's on eBay because I can't use it on anything.


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## White7 (Feb 9, 2015)

One Pivot said:


> In the last 20 years I've been working on bikes, I've literally never torqued anything. Ever. Not once.
> 
> Ive also had zero torque related failures. I also do own carbon parts.


Yup,,,,But now i feel like i should go out and buy one of those torque wrench thingys


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## cjsb (Mar 4, 2009)

If you are only comfortable with correct torque spec. Then shop around for an affordable t wrench. But for Shimano cranks, which I have done many times, I have never used one. At one point I had to do it for the first time. I first read the instructions and then followed them in turns of doing the pre-load only hand tight and just snug. Then when tightening the bolts I gripped the wrench at the elbow end to reduce leverage and tightened both bolts like turn at a time so they went in evenly. Kept doing that until they would not move. Then I tightened down from the long-end of the hex wrench. Not full force, just enough to see if the bolts moved some, which they did--and that was the end.

You really don't need a torque wrench for this task, but there is nothing wrong with getting one either. There are plenty videos out there that will walk you through the process, too.

I appreciate what others have posted above on the force needed to tighten Race Face cranks, for example. I have installed those, too and the instructions might as well say, "no torque wrench needed, just go ape-****." And the sad thing is that Race Face cranks are still likely to come loose.


Sent from my iPad using Tapatalk


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## One Pivot (Nov 20, 2009)

mack_turtle said:


> So what is your advice to someone who has zero years of experience? Working in shops, i have seen dozens of torque related failures, mostly by customers and a few of my own. The failures never occur when someone use a proper torque wrench.
> 
> i am not saying you should be using one if you're comforatable without it. I just don't think it's helpful to tell a hesitant newbie to just wing it without a net, to use the parlance of our times.


I started when I was about ~10, with a cheap allen set and a crescent wrench. My advice would be to buy one of those 3 sided hex key tools, in 4-5-6mm, and to figure it out. Myself, like many riders, had to figure it out.

What do you guys do when something breaks trailside? Or someone needs a quick tuneup before a ride? Or if you find a fellow stranded rider on the side of a trail? You bust out your multi tool and get the job done.

I think its a critical tool all riders should possess. You *really* need to be able to tighten up a bicycle by feel. It will save you one day on the side of the trail. Or it'll save a riding buddy. I cant count how many times on group rides someone has critically needed something fixed, or the ride was over for them. We always got them going within a couple minutes with a pocket tool.

But again, get that 3 sided hex tool. Its very small and has low leverage, it makes feeling the fastener easy. Its something I feel everyone needs to learn.


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## bob13bob (Jun 22, 2009)

do it by hand. take the wrench with you for your first few rides. check it occasionally to make sure it's not loosening up. After a few where it your'e sure it never budges you're good to go. remember to grease your bolts.


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## mack_turtle (Jan 6, 2009)

When you torque something correctly the first time at home, it's extremely rare that you will need to fix it on the trail. If you undertorque or strip something out by hamfisting it with an L-wrench, that is when trailside repairs become more necessary. I RARELY have to touch anything on my bike during a ride because I do it right the first time. When I do need to adjust something tailside, i know that I torqued it correctly in the first place, so I can losen a bolt, move whatever need adjustment, and turn the bolt back to the same position to acheive the same level of security.

I am a belt-and-suspenders kind of guy. I have seen too many people learn the hard way by crushing handlebars, stripping out brake posts on suspension forks, losing chainring bolts in the middle of a ride, snapping fork leg bolts in half, killing hubs by stripping or breaking rotor tabs, etc. If you feel confident without a precision tool, it's your money to spend if you F up your bike, and it's you skin on the line if something fails while you are riding. It certainly can't hurt to do up you nuts and bolts right the first time and have the peace of mind to know that your stuff is buttoned up exactly the way that engineers designed them to work.


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