Thru axle torque, how important is it ?

[mangid]

Stopped to help someone with a puncture this morning. The bike, a nice Cube, had a thru axle, and it had a recommended torque of 10-12Nm. When I undid it it didn't feel that tight, and I did it back up to what felt 'right', tighter than it was I'm fairly certain.

How important is the torque, 10-12 sounds like quite a lot to me ? I',m fretting a little bit that I might have left somebody with a potentially dangerous problem :-(

 

[fossyant]

I don't do my MTB's through axels that tight - rockshox Maxels, especially the QR mechanism aren't that strong.

 

[Joffey]

I just hand tighten my Cervelo QR thru axels - I'm not sure they even have a torque figure on them.

 

[raleighnut]

I'd be wary of stripping the thread at the dropout if overtightened.

 

[rugby bloke]

The thru axles on my Giant has a torque figure on them ... but as I don't have a way of measuring this I just tighten them until they feel right. Low tech but it seems to be working so far .,..

 

[fossyant]

I'd be wary of stripping the thread at the dropout if overtightened.

Which would be a problem. The rockshox ones are well known to be made of cheese. The 'alloy' washer that has a slot cut in it for the QR to be tightened is very soft, so any excess force tightening the wheel usually damages the slot.

 

[Pale Rider]

There are several designs of thru-axles.

My Suntour Q-loc has a quick release lever on one end, so I have that as tight as a standard quick release skewer.

A couple of Cube roadie bikes I've seen use an allen key bolt.

Not sure how tight that should be, other than 'nipped up'.

It taps into the fork, so overtightening may risk stripping the thread.

Carbon forks/frames might have a steel insert.

 

[mangid]

A couple of Cube roadie bikes I've seen use an allen key bolt.

Twas one of these, with the 10-12 Nm written on the front axle. Do they have a tendency to loosen if not tight enough ?

 

[keithmac]

If you work with bolts all day you get a very good "feel" for how tight things should be.

Torque values are to stop people snapping stuff or stripping threads.

I've never used a torque wrench ever on a bicycle, but if you aren't sure they are good investment.

 

[ColinJ]

Torque values are to stop people snapping stuff or stripping threads.

I overtightened the bolt in a lightweight stem once and it stripped the thread out of the stem immediately after I completed high speed descent. If the resulting 90 degree rotation of my handlebars had happened a few seconds earlier I would probably have ended up smeared all over some very large chunks of millstone grit!

 

[SpokeyDokey]

My Trek has DT Swiss 'handle' type TA's ie no over-centre cam mechanism.

Extract from the accompanying bike manual - note the tightening torque of minimum 15 Nm.

DT RWS This type of thru-axle has a handle, not a lever; it is not a quick-release. The axle works like a screw, and the handle works like a wrench to tighten the screw. To secure a wheel: Instead of flipping the lever to close, you simply rotate the handle until fully tight (Figure 4), a minimum of 15 Nm. After the wheel is secure, you can pull the handle out on the axle (Figure 5) and rotate the handle to reposition it in your preferred position.

 

[Mo1959]

My Trek has DT Swiss 'handle' type TA's ie no over-centre cam mechanism.

Extract from the accompanying bike manual - note the tightening torque of minimum 15 Nm.

DT RWS This type of thru-axle has a handle, not a lever; it is not a quick-release. The axle works like a screw, and the handle works like a wrench to tighten the screw. To secure a wheel: Instead of flipping the lever to close, you simply rotate the handle until fully tight (Figure 4), a minimum of 15 Nm. After the wheel is secure, you can pull the handle out on the axle (Figure 5) and rotate the handle to reposition it in your preferred position.

Sound like the ones on my Ruby. I just tighten them reasonably firmly. Hopefully if you then line up the handle with the fork or seat stay, you would see at a glance if it had loosened slightly?

 

[SpokeyDokey]

Sound like the ones on my Ruby. I just tighten them reasonably firmly. Hopefully if you then line up the handle with the fork or seat stay, you would see at a glance if it had loosened slightly?

That's my theory too plus I do check that they haven't moved every time I pump my tyres up - they haven't.

 

[Graeme_FK]

Most of us working professionally tend to use a torque wrench as a matter of routine, these days.
Those that don't, probably should. Liability would be one reason (obviously not a factor if you aren't working on other people's bikes).

I've been a mechanic for nearly 40 years and I'd say I have a pretty good "feel" ... but all the same, I use one for consistency.

In the context of through-axles, rotor rub can be a problem on some road and mountain bikes and the tightness of the through axle can affect that. The tightness of the through-axle can influence exactly where the caliper ends up relative to the rotor (bearing in mind you only have about 0.3mm to play with, in terms of pad-to-rotor clearance).

On road team / running neutral service, again, most of us use an electric driver with pre-set torque for the through axles, both so that we can be as quick as through axles allow us to be on a wheel change and so that we can be sure that adrenalin and rush (or, post race, tiredness) don't affect the tightness of the through-axle. This means the riders are as safe as we can make them and the rotors are less likely to rub (I'd like to say "won't rub" but that would not be true!) ...

 

[Ajax Bay]

10-12Nm sounds like quite a lot to me?

Assuming the tru-axles are being secured by a lever, and by hand, how long is that lever? What is the effective length (ie from where the force is applied by hand to the centre line) - maybe 40mm? To get 10Nm you'd need to apply a force of 250N or about 26kg wt, by hand. That's going to make a 'dent' in your palm, in much the same way as closing a QR axle lever should.