Middleburn RS7 splines too tall to secure chainring

Nick Payne

I have a couple of pairs of Middleburn RS7 square taper cranks with Duo chainrings that I use on touring bikes. On one pair, I was getting a persistent clicking noise each pedal rev, particularly when climbing out of the saddle. After investigating pedals, bottom bracket etc for the cause, without success, I eventually noticed that although the lockring that holds the chainrings to the crank was tight, I could still move the chainrings very slightly relative to the crank. I undid the lockring and found that the splines on the crank were very slightly taller than the thickness of the chainring, so that when the lockring was tightened, it was bearing on the splines on the crank and not on the chainring.

I checked with a couple of the spare Duo chainrings I have, and found that they were all the same thickness at the splines and all had the same problem with this crank, so I used a small file to remove a bit of the height off each spline on the crank. After that I was able to tighten the chainrings down securely (and the clicking noise disappeared).

Anyone else come across this problem?

keezx

No, but your solution seems spot on.....

Nick Payne

This photo shows the problem quite clearly. As manufactured, the splines on the crank stand above the surface of the chainring and prevent the lockring from holding the chainring securely. The splines had to be filed down for the lockring to engage the chainring (full res image available here: https://photos.app.goo.gl/vAv1VMqd87isIlQk2).