Basic question - swapping a cassette
 

This is my frist time swapping a cassette. Old one is off, new one is on. Lockring says 40 n-m. I have no idea how that should feel, so is the torque critical, or do I just hand tighten it and ride?

The torque isn't critical but 40 N-m is 29 ft-lb which is quite a lot. It's way more than hand tight so bear down rather firmly on the locknut tool.

Thanks for the help HillRider!

It is critical as far as not overtightening. if you under tighten you will probably have the lock ring come loose eventually.
Get a torque wrench.;)

"Good and tight" is just fine for a cassette lockring.

Torque wrench is totally unnecessary. Whoops, I shouldn't have said that. Just crank it down.

The lockring probably won't come loose under normal working conditions unless it's really loose to begin with. I put mine on and tighten so that I hear two or three clicks as it engages with the cassette. You can get it on too tight...trust me:(

two or three? Is that all? Now I'm worried I've been over tightening....

I think it depends on the particular cassette and lockring but I know for sure that 2 or 3 clicks would not be enough on any of my cassettes, not even close.

For my old arm "quite a bit" is the right answer. And be sure that the smallest cog is properly aligned with the splines.

Al

that makes me feel better. I have an SRAM, and 2 or 3 clicks would be extremely loose. I would estimate that when I tighten it to feel snug enough, roughly 45lb (with 8 in wrench), I hear 20-30 clicks.

+1
Mine starts clicking a good 1/2 turn before it gets snug. Maybe 3-4 clicks after "tight".

You really can't go by clicks because every cassette is different. We usually put the cassette tool in a vise and spin the wheel on that and continue until it's tight. Maybe it's just me but you get a feeling in your wrist and know when to stop.

+1 Hope this is what cyc intended

That's a whole bunch. It doesn't need to be that tight. I keep it on the loose side so that I can remove it in the field if I have to. I have Sram 9 speed too and never found I had to do much more then just snug it up. I never have had one work loose.

The problem with having the cassette loose is 1. the lockring can come off unexpectedly and 2. the cogs can shift slightly and gouge the hub body. These two thing might or might not happen its all a matter of hub body material and cassette combination. But having the lockring loose is never a good idea.

Alright, I'm going to loosen it up. Thanks alot :)

edit: I loosened fully and reinstalled. I took it 1/2 a turn after the clicking started. I think I must've been off with the "20-30" clicks - it was roughly the same spot I had it before.

Anyways, thanks again. Glad to know my stuff is right.

+1

Loose cogs can damage aluminum freehub bodies as well as rattle annoyingly.

Al

My lockring isn't loose. But it's doesn't have to be on as tight as you can get on a vise. Once it is threaded on and makes contact with the cassette, I don't find you need to tighten it past about a 1/8 to 1/4 turn. If the cassette rattles or is loose, then certainly it needs to be tightened further. But if the cassette isn't moving, I find you don't need to over do it.

I'm no saying your wrong, but you must take into account that a chain puts alot more pressure and tension, side to side, than your hand can ever exert. If the lock ring is just snug and the cassette does not move with a light tug of your hand that does not mean that the chain with not move the cogs on your hub body and tear it apart. It's better to tighten it slightly more and be sure that the cassette will not move at all.

What's so hard about getting a torque wrench and using it?
If you plan on working on your own bike at least be professional about it.
The old days you could just crank on things and not worry but todays components
are more fragile and should be torqued properly.
If you dis agree, I'm sorry. It's your bike and sometimes body that can be damaged.
Do what you like but a torque wrench IS GOOD ADVICE.

Hey all- 40 nanometers is indeed 'pretty damn tight'. I use a good torque wrench when really necessary but for this I just don't bother. I've wrenched bikes for like 14 years. Put the spline tool in and secure with a skewer, put a 15" crescent on it and tighten 'pretty damn tight', which usually is about 1/2 turn maximum after hand tight. Done. All parts greased and NEVER an issue with removal.

remember to grease the locknut.

I agree with those posters maintaining that 40Nm is much too tight. I use 5-10 Nm routinely and have never had a lockring loosen. I find that if I've had a rear wheel worked on by a mechanic, the next time I go to loosen the lockring, I need to fasten the cassette tool onto the lockring with a skewer to allow me to wield enough force to crack the lockring. 40Nm seems just so unnecessary with steel freehubs. (My comments are not necessarily applicable to alloy freehubs, as I've never used one.)

Thanks. You & others have convinced me to back off on the amt. of torque. 40 nm is definitely overkill.

Kenhill, that's Newton-Meters. N-M. Nm is a terribly small measure of distance.

Joshua-

Thanks for correction. I glossed right over that distinction. I don't believe there is any need in bike mechanics to measure in nanometers, joules, avogadro's number, any of that silly scientific stuff!

Yeah. I'm still suspicious when my caliper tells me a part is sized in non-whole millimeters.

Joules *are* useful. It's the amount of power over time! Watts/seconds! It's what biking's all about! (Not that I don't have to look that up every time it comes up...)

And Avogadro's Number describes the amount of snottiness my wife experiences when she goes in the bike shop downtown!

See? There's all sort of science things in bikes!

Sorry to be pedantic, but Nm is correct, NM is wrong.

Huh! Look at that! We're all wrong! N·m or N m. Space or dot, lower-case "m". Google also has a lot of N-m. In any event, Nm is "nanometer".

Wikipedia, if I may paraphrase, says "Newton-meter something something joule something." So now I know better!

No, "nm" is nanometer. That is why the dot or space in "Nm" is unnecessary.