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Saturday, November 19, 2016

An Overhaul (part 4) - Drivetrain

Other than multiple flats, catastrophic failure of the drivetrain is probably the most common mechanical deal breaker in a gravel race.  Rear derailleurs and chains are particularly vulnerable to jams and breaks from the small, odd-shaped chunks of gravel that can travel with muddy soil.  And the rest of the drivetrain is far from immune.

I focus on prevention by prioritizing durable components, frequent maintenance and careful operation in adverse conditions.  That is, I choose heavier (not race light and not carbon) components, clean off any accumulation of anything, and stop pedaling when something doesn't sound or feel right.  Sure, I've broken stuff, but this approach has carried me through many messy miles, including the infamous 2014 Odin's Revenge 180 mile gravel race, where only six racers finished ahead of a long, muddy trail of broken bikes, parts and dreams.  (Yes, I passed a fellow racer holding up a broken carbon frame.)  Now that this drivetrain is disassembled and really clean, let's see how it's held up after all those miles.

Damage assessment after the first Minimum Maintenance Road at the 2014 Odin's Revenge.
That was it for some racers, over 150 miles of rough roads short of the finish.  (photo by Scott Redd)
Rear Derailleur (Shimano Deore LX).   Even cleaned up and polished a bit, this rear derailleur looks like it's been through some medieval battles.  Scuffs and scratches abound.  But, more importantly, the main spring, joints and pulleys look solid, feel good and move right.  I don't have to do much of anything with this derailleur.  Remarkable.  It's going right back on.

Front Derailleur (Shimano XT Top Pull).  Practically new when pulled off my old Torelli cyclocross bike in a single speed conversion, this front derailleur is elegantly simple and functional.  The top pull design allows the shift cable to run along the top tube and down the seat tube directly into the derailleur.  No need to run the cable below the derailleur, around a pulley and back up, as required by a bottom pull derailleur.  That's one less spot to collect mud and debris that can cause failure.  Cleaned up and polished a bit, this derailleur looks and works great.  Back on it goes.

Go ahead, call me a curmudgeon.  I am not removing the front derailleur for a 1X drivetrain, which inflicts considerably greater lateral forces on the often gunked up chain as it moves across the breadth of the now necessary wide range cassette.  I know experienced cyclists who love their 1X drivetrain for this application and that's great.  It's certainly the trend and may be the wave.  But I like closer spacing in mid-range gears.  I also know from years of single speeding how little a chain wears when the drive line between the chain ring and cog is always perfectly straight, and how much greater a chain wears even when properly operating a 3X drivetrain, let alone a 2X.  Cranking through gunk with a chain torqued from a single chain ring to a 36, 42 or even larger cassette cog does not fit my design criteria for this bike.

Functional, durable, serviceable.  Choose all three.
 Cassette/Chain (Shimano Ultegra 12-27/SRAM 971).  Yes, I still run 9 speed, mostly on the relatively close gear range of a 12-27 cassette and occasionally on a 11-34.  That's plenty of gears, especially for this curmudgeon whose other bikes are all single speed or fixed.  So, I don't need to even address the relative merits of 10 or 11 speed systems.  Although this Ultregra cassette would not make Guitar Ted's page of #bikeshophorrors, it's worn enough to warrant replacement.  This time, I'm moving to an even more road-like, closer range 13-25 cassette, to close down a couple of mid-range gaps.  I can always switch to that 11-34 for a long ride with particularly steep, technical climbs or for a bike packing trip.  With a new cassette, I'll put on a new chain, since I replace the chain about once a year anyhow.

Crankset/Chainrings (FSA 50/34).  The crankset and chainrings take some serious work just to get clean, even with a chemical assist.  Whoa.  Those rings are beat.  I'm surprised I haven't experienced chain skips or drops.  And that basic crankset, never pretty to begin with, simply will not clean up or polish up.  I could install some new chain rings on that dowdy crankset.  Instead, I'm replacing the whole enchilada with a Velo-Orange Grand Cru crankset with 48/34 chain rings.  Much better.

The right crankset for this bike.
Pedals (Time ATAC Alium).  I like Time ATAC pedals.  I have ridden, raced, commuted, toured and goofed with various versions of ATACs on every type of bike since my first pair in 2001.  They are functional, durable and mudophilic.  Once the cleats are worn in a little, they engage effortlessly without a thought and disengage only when truly needed.  Not so great in the snow, but clipless pedals just aren't.  This three year old pair no longer looks new.  In fact, they look pretty rough.  But I don't see anything wrong functionally to warrant replacement.  Their track record carries them back on this bike.

Bottom Bracket (Shimano UN55).  Nothing says "retrogrouch" quite like a threaded, square taper bottom bracket.  However, nothing says durable, dependable, serviceable and replaceable quite like one, either.  Once committed to square taper, the alternatives to Shimano's best are limited to high end offerings costing several times as much from the likes of Phil Wood and White Industries.  I tried the White Industries bottom bracket on my single speed mountain bike a few years ago.  It exploded within a year of moderate use and left me walking out on an important ride.  Not doing that again.  This one is barely broken in.  Back on it goes.

In sum, I'm replacing the cassette, chain, crankset and chain rings, but not the rear derailleur, front derailleur, pedals or bottom bracket.  I think that's doing pretty well for all those rough miles.

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