I wrote yesterday that I’ve been having trouble with the front derailleur on my mountain bike. Well yesterday afternoon, out on the single track, the mess wreaked havoc on my ride. When you’re trying to ride a bike up hills that you can’t run up, you kind of have to have the third chain ring, and it’s usually all of a sudden. I ended up horsing it into the small chain ring and riding the last two-thirds of the ride in that – at least I wouldn’t have to worry about getting up the tougher hills in the second loop – they’re huge. So I left my bike in the truck last night and decided to get to the office early and see if I couldn’t get it working properly again.
Now, I’ve messed with index adjustments before, even got lucky one time and did it quickly, but this one had me nervous… I’ve spectacularly screwed up my derailleur settings before taking well over an hour to get them back to square before I got lucky and fixed it. So it was with that memory still vividly etched in my memory that I tackled the front derailleur. To make things even more interesting, just a couple of months ago I had a new chain, bottom bracket and crank installed on the bike – which brought with it the specter of having to adjust the H and L set screws into the equation (generally a no-no) and after messing with it yesterday just to get it into the little ring in the first place (using the L screw), I had my hands full today – or so I thought.
I finally get it. I had the whole thing trail ready in ten minutes. All I had to do was consult my Bike Repair App a couple of times to make sure I was turning the set screws and the barrel adjusters the right way.
So here’s what I was doing wrong: I was making adjustments in whatever gear I happened to be in at the time. A proper adjustment can only be made when the chain is in the smallest possible ring or cog for the derailleur I’m working on. In other words, if I’m working on the front derailleur, I want the small chain ring and the biggest cassette gear. If I’m working on the rear derailleur I’m in the smallest cassette gear and the big dog up front. Once I got this straight, it was easy as pie.
A few minor tips… The barrel adjusters tend to end up twisted all the way “loose” (clockwise) – some mechanics (one of mine) even do this on purpose. This is unwise and unnecessary. Best to twist it all the way clockwise, then a couple of full turns counter-clockwise. This allows for minor adjustments incase you didn’t quite get it right when you try the bike on the ground (rather than in the stand). DON’T MESS WITH THE SET SCREWS. Once you get your bike properly indexed you’ll just end up going back and putting them back where they were in the first place – the chance that you need to mess with those is somewhere between slim and none (one of these days I’ll learn). The steps in the Bike Repair app are pretty much right on, just follow that and you’ll be good. Finally, if your bike isn’t shifting perfectly, tinker with the index adjustment. You cannot get it so wrong that a real mechanic can’t fix it. Had I not tinkered with my bikes so much I’d have been lost on the trail yesterday and I’d be stuck taking it into the shop this afternoon – and paying someone to fix something that only took ten minutes, with a 5mm Allen wrench.