Replacing Cassette-Do I need a torque wrench
 

My daughter is building a bike from scratch.
I think she is getting a bit anal.
First she sprayed the inside of her frame with fogging oil to help prevent rust/corrosion.
She was than tightening the cassette onto the hub.. I told her to just use the lock ring tool and tighten by hand.
She insists on using a torque wrench.

Is this really necessary? and if so what should it be calibrated at.
I have never used a torque wrench to change cassettes

If the mechanic (and I use that term loosely) has a good feel for tightness then, NO. But if the mechanic is ham fisted or too OCD to know what's good enough then YES. Andy.

Lock rings are 40Nm. It says so on the lock ring.

Everyone that has never been an aviation mechanic will tell you that you don't need one.

I think they're a good idea and I use one torque to lock rings.

Depends on what you mean by "lockring tool" and "tighten by hand".

If you mean just turning one of these with your bare hand, then no, that's not gonna be good enough unless she has incredible gripping and arm strength.

http://www.parktool.com/assets/img/p...l/FR-5_001.jpg

If you mean something like this, then yeah, tighten by hand should be fine, don't be afraid of the clicks.

http://d2plslj6xljffa.cloudfront.net...WLT_P1.jpg?v=t

Same with the mother of all cassette lockring tools:
http://cdn.shopify.com/s/files/1/018...g?v=1422641429
First style tool with a 12" crescent or a socket wrench with a standard ratchet handle will fork fine, too.

No, you don't need one for a cassette. Turn it with a 12 inch wrench till it stops turning with reasonable pressure. (Don't put your weight on it.) It clicks when you tighten it. Generally it'll tighten with a bunch of clicks, then get caught on one. I'll usually go one or two more clicks then call it good.

I use a torque wrench on mine; 40N-m (~30lbf-ft) is a surprisingly large amount. My lockring tool has a 1/2 inch drive fitting.

:thumb: x2

Hi kenshireen,

I recommend using a torque wrench. As dsbrantjr wrote, "40 Nm is a surprisingly large amount" and it's true. I use SRAM cassettes on all my family's bikes and they use 40 Nm. I would never have tightened the aluminum SRAM lockring as tight as I should if I was doing it "by hand" and I think I have a fairly good "feel" for this kind of work.

When purchasing a torque wrench, I recommend going "old school" and buying the old "beam" type because they don't go out of calibration as easily as the "click" type. Park Tool's TW-1 and TW-2 are good examples. Plus, they are usually less expensive. If you purchase a click type, be wary of the cheap ones because they may not be calibrated correctly. And be extra wary of inexpensive automotive click-type torque wrenches because some only work in one direction. Bicycles have a number of prominent parts that use reverse threads (drive-side bottom bracket end caps and pedals) so your daughter should have a torque wrench that works in both directions.

Torque is much more important with modern bikes than old bikes. I care for two carbon-frame bikes in my family and you MUST be very mindful of torque or you can damage the frames, carbon handlebars and aerobars. I think your daughter is probably showing wisdom by recognizing the benefit and, in some cases, need for a torque wrench.

The range of torque used in bikes is quite wide. Some components may require only 2-5 Nm of torque like the bottle cage bolts attached to a carbon frame. They must be tight enough so the parts don't rattle apart on a bumpy road---but if they are tightened too much, they may pull the metal sleeves out of the carbon. Other components may require over 500 Nm of torque (like a bottom bracket end cap). It is impossible for one torque wrench to handle such a wide range accurately. So most bike mechanics have two---a small low-range torque wrench for small torques and a larger high-range torque wrench for big torques.

Finally, there is one more thing your daughter may need to know. One way to achieve a good grip at a lower torque is to use friction compound at the joint. It is available at most any bike shop (I use Park Tool SAC-2). It is used for most joints that include carbon. But it is just as good with metal joints and is becoming popular with softer metals like aluminum. It allows you to get a good joint that won't move or squeak at a lower torque, thereby not over-tightening and breaking bike parts.

Kind regards, RoadLight

Yes Shimano data sheets on cassette do state a torque value, they have to, to protect themselves, but dealing with mechnics, nuts bolts, torque wrenches all my life one has a good feel on something being suitably tight for its application, I never use a torque wrench on a bike unless its CF: but if someone has no experience then best they follow the manufacturer's set value.

+2! Andy

If a Touring build , consider how you will get the cassette off , when a drive side spoke breaks in the field .

Maybe the Fiber Fix emergency one will get to to a shop. but if not going to Max Torque , but Adequate Instead,

Its possible to do a field repair with a real spare spoke.

She sounds sensible, not anal.
40Nm is a lot of torque, so it's easy to under-torque a cassette when tightening by hand. This matters if you're using an aluminum freehub, as under-tightening the cassette lockring will lead to worse scoring of the cassette. Otherwise, I would say it's not super critical.

The high torque value is designed to firmly clamp the cogs together and distribute the load across all the cogs. With low torque, each cog acts essentially independently. Theoretically, the high torque value is better for preventing gouged free-hubs. And yes, 40 N-m (30 ft*lbs) is far tighter than I would have ever imagined. You really need a 16in wrench.

I tighten my car lug nuts to ~80 foot pounds, so I put a bit less than half of that pressure (adjusted for wrench length) on my cassettes.

I've got Shimano hubs on all my bikes, and they have steel freehubs. The 40 Nm spec is far enough above what feels "really tight" that I just tighten it "really tight" and call it done. I'm pretty sure I'm under the spec most of the time. I haven't had a serious problem with it. Just the other day I noticed while cleaning the drivetrain on one bike that the cogs had a little play in them, so I pulled the wheel and tightened it some more. Chances are that I've had sloppy shifting caused by an under-torqued cassette at some point, but I've never diagnosed it as such.

Aluminum freehubs are a curse sent to punish cyclists for being weight weenies. Every time I'm shopping for wheels and I see something with a really low listed weight I remind myself that my rims are as light as is practical for me (~420g) and that any weight savings would come from too few spokes and/or a super light freehub, which even if titanium ($$$) wouldn't actually provide the supposed "rotating mass" bonus, and go back to being happy with my dependable but kind of heavy wheels. </rant>

Blame the same cyclists; Shimano was forced by the market to change the deep-spline Dura-Ace from economical aluminum, back to titanium/shallow-splines, under the weight of complaints they received. Campagnolo figured it out early, but it turns out people won't accept that from Shimano (see: mountain bike '11' speed cassettes). Wouldn't we really all be in a better place now, had people not complained about it?

I'd be pleasantly surprised if my daughter recognized a torque wrench if she tripped over it... I can't think of a reason to dissuade a young mechanic from using one. After they've learned for a while, perhaps they'll get confident enough to skip it.

I have had a cassette lockring come unscrewed on me, fortunately just a couple of miles from a SAG stop with a mechanic (it was a supported ride). I haven't pulled the torque wrench out for that lockring yet, I just go for really tight. But I do measure the torque on my bottom brackets.

What are the consequences of using insufficient torque? The design looks smart enough that it wouldn't be anything horrible.

I use a torque wrench on cassette lockrings ever since I learned the hard way that what I thought was "tight enough", wasn't.

Clunking.
A big clunk every time you start pedaling, and random clunks.
In my case, it was loose enough that I could grab the cassette and make it visibly wobble.
Quite a few miles elapsed between installation, and the lockring getting loose enough to start clunking.

A bit off topic, but I'd just like to say that I have one of these, and it is easily my favorite tool. I limped by for years with the FR-5 and an adjustable wrench, but since I bought the Crombie I find myself looking for reasons to use it. It's a wonderfully designed tool. Future generations will point to it as evidence that we were visited by benevolent aliens with superior technology.

thread locking compound
 

Since I seldom use the mating serrated lockring inner cog (custom ratios), I don't know if the stated torque is correct. So I always use a reusable thread locking compound like Vibratite.

You need to be careful with a torque value: While the steel lockrings I have are indeed marked 40kg-m, the aluminum ones are marked 400kg-cm.

I have a couple of non-serrated setups too but have never used Loctite on 'em. I'd imagine the non-serrated setup would give more accurate torque values,

No, you don't need a torque wrench on cassette lock rings provided you are not ham fisted. I'll share a story. I once ruined a Shimano Dura-Ace hub by stripping the lock ring while replacing the cassette. Luckily, Shimano warrantied it, to my surprise. So, now, I use a torque wrench. I'll be the first to admit that I am a bit ham fisted though.