I took a pause in the Deore drivetrain swap for Hornsby when I had some alignment and clearance issues with the new derailleur. In addition to sleeping on the issue for a couple of nights, I consulted the shop manual several times to make sure I had done everything by the book.

While I was still figuring things out yesterday, I took a photo showing how the derailleur’s cable stop was too close to both the chain and the cassette teeth. While I was at it, I put Hornsby back on the scale, knowing that any further work I did wasn’t going to affect the final weight appreciably. And I was in for a surprise! Based on individual component weights, I’d calculated an increase of 121g with the upgrade. Instead, Hornsby gained a whopping 440g. I have yet to figure out where the additional 320g came from. It certainly wasn’t from the chain (one component I hadn’t weighed) or the untrimmed end of the shifter cable.

Not me turning the wrong way

What I realized in my two days of reflection was I’d been turning the B-limit screw the wrong way. This screw affects the spacing between the upper jockey wheel of the derailleur and the bottom of the cassette. It also changes the angle at which the derailleur hangs from the frame, and hence the clearance of the bits noted above.

I had the day off today, so this afternoon I put Hornsby back in the stand and started turning the B-limit screw in the opposite direction. And in fact I took it to the opposite extreme, and could have gone even farther if things had allowed. (The derailleur can handle cogs up to 51T, and the largest on this cassette is 42T.) And this had an immediate and positive effect on the clearance.

Once the clearance was good, I cut a new chain to the correct length and had that installed in a jiffy. (I’ve put the previous, unused chain into the spares pile.) After that, adjusting the derailleur was going pretty smoothly except for the largest cog. I kept adjusting the tension, checking the limit screws, etc. And then I finally noticed the cable was stretched tight between the chainstay and derailleur stop. I’d cut it to size on Saturday with the derailleur in the wrong position, and it wasn’t long enough now that I’d sorted that out.

It was a minute’s work to find the remainder from the initial installation and cut off an appropriate length. (I still haven’t needed the extra meter I ordered in anticipation of this project.) It’s good I hadn’t yet trimmed the cable!

And with the longer housing and the cable stop re-tightened, it all came together. It was just another couple of minutes of fine-tuning the cable tension and limit screws, and all was good.

Happy with that

Of course, the proof is in the riding, and that won’t happen for a couple of days yet at least. On the stand, it takes an extra nudge of the shifter to get into the largest cog, but it stays there securely once the shift is complete.

The new groupset brings some lower gearing. It’s gone from 40T on the front to 32T, which is a 20% reduction. Meanwhile the largest cog on the rear has increased from 40T to 42T. Taken together, that means the lowest gear has dropped from 26 gear inches to 21. I should be able to climb up walls — if I can balance at that speed. At 60rpm, that’s about 2km/h, if I’ve calculated correctly. Meanwhile, the top end has dropped from 96 gear inches to 77. I don’t mind the loss on the top end, but Fearless Leader Joe — who rode Dionysus on the old drivetrain and used the top two gears exclusively — may have a hard time keeping up with the pack.

One other, less fortuitous change is the loss of the purple crankset bolts. The Deore crankset takes a different size and shape.