Every day I wake up and think my Bike Thoughts. I think about handlebar wrap colors. I think about about reach and bike fit. I think about riding the Pyrenees and Shimano’s eight-speed XTR cassettes made partially out of titanium. I normally text these thoughts to my bike friends and let them drift out of my mind. But I have a new bike thought so tedious that I can’t even bring myself to voice it aloud. I have no choice but to share it with you, all you total strangers.
Why I spend my mornings deep in Bike Thoughts I do not know. I am not meant to understand the mysteries of the human condition. I am meant to live them. And this morning, living them means diving into old Shimano catalogs to get the specs of my rear derailleur, because I wanted to know how much more I could max out this 31-year-old mechanical component.
The rear derailleur remains the most unknowable of my bike’s components. I vaguely understand what I must do to make it do its job, but I cannot say that I really understand how it works. When my shifter cable is at its most slack, the rear derailleur hovers in line with the smallest cog on my cassette. As I click through each indexed gear, I add a small amount of tension to the shifter cable and pull the derailleur up the cassette. Each amount of added tension moves the derailleur one cog’s worth of distance over, and a perfect shift is made.
There are endless compatibility questions in relation to this process. Different shifters pull different amounts of cable, different derailleurs translate that pull into different movements meant for different spacing between cogs, different numbers of gears, different sizes of chains. These compatibility questions often come up when people mix and match cassettes from one company with a derailleur from another with shifters from a third. Mine is a different one. More pointless.
When I was first building this bike, Big Green, I put new wheels on it. Those new wheels needed a new cassette. I wanted to keep the number of speeds (seven) the same, so I went and got a new seven-speed cassette from the nice bike shop near me, happy that I could even find a new cassette with so few years. More joy: the smallest cog on the new cassette was smaller than the one originally on the bike, and the biggest bog was bigger than the one originally on there, too. In my fastest gear I could go faster than before, and in my slowest gear I could go slower. I could fly faster on downhills, pedal easier up steeper grades. It worked great!
Well, it worked great except for in one case: if I was in the smallest chainring at the front and shifted to the smallest cog on the cassette at the back, the bike stopped working. The rear derailleur would lock up! This is called cross-chaining. My case of the derailleur locking up is an extreme one, and a problem that I rarely encounter on the road. Not often you’re in your lowest chainring (your granny gear) trying to go as fast as possible on your smallest (fastest) cog.
This can sound a little confusing, so I’ll give a little demo. Here is the bike in its happy place. It’s in its largest chainring and its smallest cog, 50 teeth at the front, 12 at the back:
Here it is in an unlikely scenario that looks as uncomfortable as I’m sure the bike feels. Look at how stretched out the rear derailleur is. It’s largest chainring to largest cog, 50 chainring to 32 cog:
Here is a more normal one: smallest chainring to largest cog. This is the ultimate granny gear setting, for ripping up the opposite side of a creekbed or slugging up a hill with a few dozen pounds of gear on the bike. It’s 28 front to 32 rear.
And here’s the critical cross-chaining, 28-32. The bike does not actually pedal like this; the derailleur is locked up.
What I’d found was the limit of what my drivetrain could handle in terms of cross-chaining. What I did not yet know was if my setup could take yet bigger big cogs or yet smaller small cogs. Luckily for me, Shimano still keeps all of its old service documents online, so it took only a google search to find the specs of my derailleur. They’re laid out here, including everything from installation procedure to bolt-by-bolt torque specs. To my surprise, I am actually over capacity on this derailleur.
What derailleur is it exactly? Well I am assisted in that both my bike and the derailleur itself have at least some total nerd following. This bike is a Schwinn Voyageur, and one owner went out of their way to publish a year-by-year specifications comparison chart. I can see that I have a 1989 model with a Shimano 544 GS derailleur. The GS denotes that it has a “long cage” for handling extra big cogs, as opposed to the short-cage SS version or the super-long-cage SGS. I know that because yet more nerds (this time hailing from Cannondale fandom) have published Shimano’s 1989 catalog, which has each model of this derailleur laid out.
Yet more nerds are involved, as this particular derailleur has some technical novelty in the way that it shifts. As such, a derailleur-specific fan site has a full profile of its predecessor in the “light action” line. In the interest of brevity, I will not get into any more depth on that subject, but I do encourage you to read about it.
To cut to the chase, this derailleur is only spec’d out to handle a 30t cog at the largest, a 13t cog at the smallest. I am already out of the range of what this derailleur is meant to do, asking more of it than it was designed to give.
Certainly, I could take this knowledge and press it more. I could hunt down another cassette with an 11-tooth cog at the smallest, pushing for another mile an hour or two on a downhill. I could hunt for a 34 tooth cog at the largest and scramble up yet steeper grades, maybe carry more gear.
But there’s a nice part about the bike as it sits. It carries enough weight. It goes fast enough. Short of ripping out the whole drivetrain as it is, there’s nothing I really need to do to it. I don’t need to push it. Why would I bother?
Over these past few weeks I have been warming up to the idea of my years-long Green Bike project completed. I have a bike that is light and strong and comfortable and I’ve already fixed once just about everything on it that can break. I am in the riding stage of the bike. I am not in the building stage of the bike.
As much of all these details that I sweat, the more I get that none of them have any major bearing on the experience of riding itself. I spend hours going back and forth over these absolutely minute differences in components, knowing full well that none of them could meaningfully improve any ride that I do, and their absence would not keep me off of any roads or trails. What I have works; I have no need to change any of it. I often while away great amounts of time thinking about bikes and bike parts I know I’ll never ride. I spent a non-zero number of minutes reading about the production of Schwinn Homegrown mountain bikes, produced for Schwinn by Yeti in Durango. Why do I know these things? Why do I even endeavor to know these things?
It still feels valuable, somehow, to pore over these old Shimano catalog pages, looking at the old tow rigs they used back in the late ‘80s, and wonder about these parts in question. They’re all sturdy and well-made. They’ve lasted this long. I wonder if they’ll break, and if I’ll have to wonder about replacing them myself with parts more modern. If I’ll run their development at an accelerated schedule, I myself a tiny bike industry switching from seven speeds to eight, nine, or 10. But I also wonder if they’ll outlast my ownership altogether, and someone else will plug numbers into gear calculators after me.