How important is it to torque the rear axle nuts on an e-bike?

Wallyboy

New Member
I need to change out the rear wheel on my new Radrover 5. Here's the question: is it safe to hand-tighten the rear axle nut to re-assemble the rear wheel after changing a flat, etc?

More detailed Q: How do I torque the rear axle nut to the correct nm? There is a cable coming out of the middle of that nut!! In the Rad Bike youtube video, it shows the owner hand tightening with an open-ended wrench, no Torque wrench.


The written instructions say to torque to 35 or 40 Nm, implying a Torque wrench with a socket on it should be used - how to do this on the motor cable side? This can only be reached with a (fancy IMO) clawfoot attachment to a Torque wrench.


Summary - is it safe to hand-tighten the rear axle nut to re-assemble the rear wheel after changing a flat, etc? Or is there sig. danger of under-tightening or stripping the bolt?

Thanks in Advance
 

jim6b

Active Member
you don't need a torque wrench but you do need a wrench. nice and snug will do it.
It's not difficult. Remember "quick release" hubs? If you do they were not over tightenable.
You can always fall back on, "tighten as hard as you loosened." With the same wrench its quite accurate and if you want to test, do a comparison open ended vs. torque wrench.
 
Last edited:

AHicks

Well-Known Member
Region
USA
City
Snow Bird - Summer S.E. Michigan, Winter Gulf Coast North Central Fl.
I think if you're an average size guy, you could put one hand on the end of the wrench, with your arm stretched out straight in front of you, and tighten away. In other words, don't use your body weight to tighten those nuts.

Just as a safety precaution, you can make yourself a note to check it again when you get a few miles on it.
 

harryS

Well-Known Member
Use a crows foot if you want to be accurate. And here's how to align it if you're really anal.


I use an 8" wrench.
 
Last edited:

Sierratim

Well-Known Member
I need to change out the rear wheel on my new Radrover 5. Here's the question: is it safe to hand-tighten the rear axle nut to re-assemble the rear wheel after changing a flat, etc?

More detailed Q: How do I torque the rear axle nut to the correct nm? There is a cable coming out of the middle of that nut!! In the Rad Bike youtube video, it shows the owner hand tightening with an open-ended wrench, no Torque wrench.


The written instructions say to torque to 35 or 40 Nm, implying a Torque wrench with a socket on it should be used - how to do this on the motor cable side? This can only be reached with a (fancy IMO) clawfoot attachment to a Torque wrench.


Summary - is it safe to hand-tighten the rear axle nut to re-assemble the rear wheel after changing a flat, etc? Or is there sig. danger of under-tightening or stripping the bolt?

Thanks in Advance
A torque wrench that will accept open end wrench adapters is the best way to gl.

Lacking that, you can estimate the correct torque. 40Nm is just about 30 ft-lbs. If your wrench is 1 foot long you need to apply 30 lbs of force to the end of the wrench to get the right torque. That's about the same as the weight of 4 gallons of water. Considering that most wrenches in this size range are less than a foot long, you need to scale up this force to get the 30 ft-lb torque.

This spec works with clean threads. Clean them up if they are dirty or corroded.
 

Wallyboy

New Member
Thank you AHIcks and harryS - those are great answers - exactly what I was looking for. I'll probably order an 18 mm Crow's foot open end, and I also got a torque wrench off Amazon, because.... well, just because its kind of fun to own a torque wrench.