Had a 26″ Inbred Slot Dropout for nearly 5 years and it’s been a great bike. It just suits me and my riding, basic coil fork up front and 32/17 gearing.
Over the last few months of riding it’s been increasingly more difficult not to drop the chain off the rear sprocket (WI screw on 17t).
Chainline dimensions measured at the rear dropout and also at the crank end are perfect….., BB bearings new, Freehub bearings new, all drive chain etc all good but still it kept happening and with an increasing regularity. Checked all the usual, chain bends, bent sprocket teeth, bent chain rings etc etc.
What I hadn’t checked was frame alignment.
Stripped the bike down yesterday and by using a 1000 spirit level fixed along each side of the top tube and a 450 spirit level secured to the inside of the each dropout I could measure the dropout geometry in relation to the seat tube. From this I could see a 6-7mm bend in the rear triangle. This would in effect give me a misaligned chainline even if the measurements taken from centre of seat tube to centre of chain ring/centre of dropouts to centre of sprockets we’re the same.
Now, it’s easy enough to pull it back but I am just wondering if I am going to get the problem again or if anyone else has had a similar problem with rear triangles bending like this.
Obviously it’s a problem that only manifests itself with a Singlespeed bike.
