So today the one of brake wires snapped near the lever, so to repair it I purchased a new wire (as the housing ect. looked fine) and began the replacement.

It was all going well, until it came to change the fixing bolt unit from the old wire to the new. I cannot for the life of me get the top nut to turn. (It is for a Shimano Nexus Roller brake)

As a student I have only limited tools so what I have tried is drowning it in WD-40, then used pliers to hold the body and used a wrench to turn the nut. But to no avail.

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Could anyone provide me with some tips on how to solve this?

Thanks in advance!

3 Answers 3


Try to use someone's vice, but grab the bottom through some wood or similar.

It's useful you mentioned you're a student. Hopefully you're currently allowed to go to school in person (I'm replying during the covid pandemic and it's not obvious). If you are then your school (or other educational institution) hopefully has a maintenance person looking after replacing bulbs etc. Chances are that person has a little room where they have a vice. Failing that you might want to try a car mechanic or similar.

Or just use it as an excuse to buy a vice. A pair of locking pliers might do it too. I guess it depends which one you find easier to justify.

  • Yeah, I think I will go to the bicycle shop from where I bought the replacement wire, I saw they had a vice there, ill ask if I may use it. Thanks for the tip!
    – strox
    Feb 3, 2022 at 20:06

Looks like there are flats on the lower part, so you need a slim spanner that will fit in there. Its probably much smaller than a cone spanner, but of a similar concept.

Pliers will not work because the jaws are not parallel.

The nut on the top will work best with a ring spanner, its probably 8mm or 9mm.

If using a bench vice, be careful to not marr any surface that needs to connect cleanly with the rest of the brake.


You might try using wrenches on both, but it is likely that you will need something to stabilize the nut. You can put the nut on concrete with the two wrenches facing up in a V shape, where widening the V is loosening the nut. Then push the wrenches wider.

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