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Do I need a torque wrench to install rotors?

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View Poll Results: Do I need a torque wrench to install brake rotors
Yes
13
41.94%
No, a good guestimate of 3 to 6 Nm is good enough
18
58.06%
Voters: 31. You may not vote on this poll

Do I need a torque wrench to install rotors?

Old 06-01-19, 12:37 PM
  #1  
tyrion
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Do I need a torque wrench to install rotors?

Yes.

No - a guestimate between 3 and 6 Nm is good enough, as long as it's consistent between the 6 bolts and sequenced in the proper star sequence.
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Old 06-01-19, 02:02 PM
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Originally Posted by tyrion View Post
Yes.

No - a guestimate between 3 and 6 Nm is good enough, as long as it's consistent between the 6 bolts and sequenced in the proper star sequence.
I have always felt this "cross tightening" method, which is what I was taught to do on car wheel studs/bolts, is nonsense for a bike rotor. The rotor will just bend and take to whatever surface flatness (or not) that the hub is faced off at. I don't think there's anyway a rotor could induce a warping to the hub, and since we gladly true a rotor any run out of it is easily dealt with (whether or not run out is hub induced or in the rotor before installing).

Now I have no problem maintaining a false belief if it makes us pay more attention and take due care to insure a correct outcome. But in my eyes that is what is cross tightening is for bicycle disk brake rotor bolts. Andy
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Old 06-01-19, 02:38 PM
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Go by the rotors instructions, yes, when I worked in a LBS, we did it with a digital torque wrench, for personal use, no, have been using discs for pushing 20 years and not had any bolts come loose, I do with centerlocks, simply as they are the same setup torque wrench wise as a cassette install.
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Old 06-01-19, 03:35 PM
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Yes.
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Old 06-01-19, 07:04 PM
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Haven't had to change out rotors yet but when the time comes I'll use a torque wrench. I've gotten to the point where I torque just about everything on the bike. I figure I've since spent the money on the torque wrenches I might as well use them.
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Old 06-01-19, 07:08 PM
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It is easy to damage a soft aluminum thread in a hub if you over-tighten or mis-thread a bolt. The problems of too loose bolts should be obvious.

You could probably get away with having only three of the six bolts in, if they are symmetrically disposed. The point is to have some redundancy, and having each bolt torqued the same amount contributes to that.
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Old 06-02-19, 08:30 AM
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I've experienced the effect of loose bolts, in the form of the disc rotating on the hub when rocking the bike back and forth. It seemed to be more than just the pads shifting in the caliper, and indeed discovered that the disc itself was shifting. Combining this with the unsavory possibility of stripping a hole in the hub, I've used a torque wrench to install discs ever since.
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Old 06-02-19, 10:23 AM
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I have access to a preset click torque wrench with a Torx bit in it.. for disc brakes .. in the LBS..

You can buy a preset torque key if you do a lot of them.. know what torque is specified?

but ... after decades of dealing with 5 mm bolts, on bikes in the shop,

You may need a torque wrench I do Not.















...

Last edited by fietsbob; 08-09-20 at 03:12 PM.
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Old 06-02-19, 11:00 AM
  #9  
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Install it with a cordless drill, with the torque setting at some reasonable point and use a dab of loctite. At least then you know they are all torqued the same and wont fall out. I just made that up in my head. Never tried it ;-)
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Old 06-02-19, 11:04 AM
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Well, I install mine with one of these,


A 12V Bosch Impactor, fitted with one of the countless 2" T25 bits I have from buying equally countless boxes of decking screws. I give each bolt a brrt-brrt-brrt from the impact driver, and tighten in criss-cross. Like on a car.

Never had a bolt loosen at all. Miles: lots.
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Old 06-02-19, 01:43 PM
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Been using discs since 2001. Never used a torque wrench for the rotor bolts, even though I have one that I use for other things. Never had one come loose or strip any threads.

Not making a recommendation for what others should do, as I donít know how ham-fisted others are.
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Old 06-02-19, 02:10 PM
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I was thinking just get a tool like this and crank it down almost as hard as I can with only 4 inches of leverage:

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Old 06-02-19, 07:50 PM
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Originally Posted by tyrion View Post
I was thinking just get a tool like this and crank it down almost as hard as I can with only 4 inches of leverage:

Pretty sure I could do some damage with that if I tightened as hard as I could.
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Old 06-02-19, 07:53 PM
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Originally Posted by DrIsotope View Post
Well, I install mine with one of these,


A 12V Bosch Impactor, fitted with one of the countless 2" T25 bits I have from buying equally countless boxes of decking screws. I give each bolt a brrt-brrt-brrt from the impact driver, and tighten in criss-cross. Like on a car.

Never had a bolt loosen at all. Miles: lots.
I have one of those, too, but it never occurred to me to get it anywhere near my bikes.
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Old 06-02-19, 07:53 PM
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Originally Posted by tyrion View Post
I was thinking just get a tool like this and crank it down almost as hard as I can with only 4 inches of leverage:
Yea....doing that you'll sheer the fastener head right off.
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Old 06-02-19, 07:54 PM
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Originally Posted by Kapusta View Post
Pretty sure I could do some damage with that if I tightened as hard as I could.
Thanks for the tip.
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Old 06-02-19, 08:12 PM
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It is my very humble opinion that anyone who works on a bike should absolutely be using a torque wrench
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Old 06-02-19, 08:42 PM
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Yes. These are your brakes, not a seatpost bolt. The tightness of each bolt must be the same or the rotor can warp (bad) or work loose ("more badder"). Others will argue that you don't need to torque, but why? If you have a torque wrench or can borrow one, why wouldn't you torque them down?


..

Last edited by drlogik; 06-02-19 at 09:04 PM.
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Old 06-03-19, 07:27 AM
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No, you don't need one.
But buy one and use it anyway. You'll also use it on other stuff that has a specific torque requirement, like carbon parts.
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Old 06-03-19, 08:33 AM
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Originally Posted by drlogik View Post
Yes. These are your brakes, not a seatpost bolt.
..
Actually, I am more likely to use a torque wrench for a seat post clamp than for rotor bolts.
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Old 06-03-19, 12:38 PM
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Rotor bolts are really not that hard to get right. Tight enough to not come loose, but not so tight that you strip the threads or break off the bolt heads. For people who wrench regularly, that is pretty simple. There is no risk of crushing the rotor or having it slip.

Things like seatpost clamps and stem face-plates are a different story. you need to get the torque high enough to keep the seatpost/bar from slipping, but not too high to crush/damage it, and it is really hard to know what that feels like when tightening.

But like someone else said, even if you don't use a torque wrench for rotor bolts, you should still get one for all the parts that you DO want one.
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Old 08-08-20, 10:13 PM
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How about for centerlock rotors? Recommendation is 40 Nm.

I have a torque wrench, but not one that goes to 40 Nm and I don't have a ratchet large enough to fit over the Lockring tool. Also, I don't see much other need for having a torque wrench that goes to such high torques. Certainly I've never felt the need for one in order to install a cassette. Is this different?

These seem less finicky than the rotors with multiple bolts. Seems I should be able to wrench it down tight without being in danger of making it too loose or damaging the threads?

No?
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Old 08-08-20, 10:40 PM
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Originally Posted by Andrew R Stewart View Post
I have always felt this "cross tightening" method, which is what I was taught to do on car wheel studs/bolts, is nonsense for a bike rotor. The rotor will just bend and take to whatever surface flatness (or not) that the hub is faced off at. I don't think there's anyway a rotor could induce a warping to the hub, and since we gladly true a rotor any run out of it is easily dealt with (whether or not run out is hub induced or in the rotor before installing).

Now I have no problem maintaining a false belief if it makes us pay more attention and take due care to insure a correct outcome. But in my eyes that is what is cross tightening is for bicycle disk brake rotor bolts. Andy
I totally agree about the "cross tightening" method. This made total sense for car wheels in the days when all cars had drum brakes. Not so much now that most cars have 4 wheel disc brakes, However, it does make sense that all bolts of a disc brake rotor be tightened to the same torque value. If the installer wants to go around a second time, so be it
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Old 08-09-20, 06:59 AM
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Originally Posted by MinnMan View Post
How about for centerlock rotors? Recommendation is 40 Nm.

I have a torque wrench, but not one that goes to 40 Nm and I don't have a ratchet large enough to fit over the Lockring tool. Also, I don't see much other need for having a torque wrench that goes to such high torques. Certainly I've never felt the need for one in order to install a cassette. Is this different?

These seem less finicky than the rotors with multiple bolts. Seems I should be able to wrench it down tight without being in danger of making it too loose or damaging the threads?

No?
Cassette lockrings and bottom brackets have torque specs in this realm.
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Old 08-09-20, 03:04 PM
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This is not rocket science. Just tighten until the bolt head breaks free and back off 1/8 turn.
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