This Space for Rent

Trouble comes in twos

Well, my grand plan yesterday was that today would be a good day for an R200, but that plan died the true death when it took me until 1am to finish tweaking the MLCM’s handlebars. So I decided that this would be a good day to just do an R100 in the afternoon, so I zipped out and up the Springwater Trail at a pretty good speed (despite many slow sections where I had to creep around small children doing field experiments with brownian motion) and got up to the edge of Boring in about 65 minutes, where my plans to continue up to Sandy and then return via Ten Eyck and Bull Run Road were abruptly aborted when a drive-side spoke went snap as I went stomping up the steepish hill at the east end of Telford.

So, after wrapping the fractional spoke around a couple of still-intact ones, I turned around and rolled back into town so I could replace the offending thing (and if I was very lucky, maybe go out again before daylight vanished.) But when I reached 82nd, I tried to rotate the pedals backwards while I waited for traffic to clear, only to have the chain hang up in the derailer.

Huh. That was funny. But it became a little bit less funny when it happened again at 17th & Tacoma, and a lot less funny when I looked at the rear derailer (in my case, the only derailer, but it happens to be the one by the rear wheel, so “rear derailer” counts) and saw that it was canted quite a bit off towards the wheel.

Needless to say, I did not make it out again. When I got home, I checked out the derailer by shifting it from 42×32 down to 42×11, and got the chain jammed between the (woefully bent out of line) derailer hanger and the cassette at ×11. So after replacing the broken spoke (my LBS provided a few spare spokes when I had the rear wheel built, but my woeful lack of organization has resulted in them becoming hidden somewhere in the basement. So I took a straight-gauge spoke off the old el-cheapo 700c wheel I bought to test whether skinny 700c t[iy]res were faster than the 650b wheels that were originally under the MLCM (answer: yes, they were considerably faster, even with el-cheapo wheels and tires) and used it instead) and cleaning the chain, cassette, and derailer pullies (it’s amazing just how much crud gets onto them even with fenders. I may have to buy or build a partial chaincase to cover the chainwheel and the chain at least as far back as the rear wheel rim to try and reduce the amount of crud that gets splattered up onto the chain,) I had to take my precision derailer hanger adjustment tool and adjust the hanger so (a) the derailer stands vertically and (b) the hanger doesn’t capture the chain when shifted into ×11.

I’m not particularly happy with the durability of the SRAM x-5 derailer, either. There’s a lot of play in that thing these days (the shift pulley arm is loose enough that I can easily move it ±10° out of line, and when I unbolted the derailer part of the mounting bolt assembly spontaneously disassembled and fell to the floor.) I did buy it used, of course, but it didn’t feel nearly as loose when I first put it onto the MLCM, and I’ve only ridden the bicycle 6-7000 miles since then :-(

On the bright side the handlebar tweak seems to have made a positive difference. I’ve messed up my right wrist somehow so it’s still uncomfortable to ride in the drops on that side, but the left hand is much happier with the somewhat squooshier and larger diameter handlebars now. And rotating the brake hoods down means that my hands don’t try to jam themselves into the valley formed by the hood & the bars.

And in the grand scheme of things, I’d much rather have a spoke snap when I’m 17.5 miles out from home instead of being 45 miles out and on the other side of a steep drop down into the Sandy River ravine.


The rear derailleur hanger is a generally frangible part, isn’t it?

This is outside of my expertise, but even the Paragon Machine Works custom Ti expedition weight rear dropouts – 7mm thick Ti plate is not fragile stuff – come with a separate, bolt on, replaceable rear derailleur hanger in various aluminum alloys, so I have to suspect that if it was possible to make one tough enough not to break, there would be at least an option. And there doesn’t seem to be any such option, so I suspect this is one of those “fatigue will kill it, make it replaceable” cases.

Also, SRAM doesn’t warrant wear parts on the X-5 rear derailleurs at all, which leads me to suspect you’ve simply run it past its MTBF rating. 6000 miles is a lot; 6000 miles significantly in hundred-mile chunks is a lot, too, when it comes to wear on bicycle parts.

Graydon Sun Jan 30 12:14:45 2011

The derailer hanger on the mlcm is part of the rear dropout assembly, so it’s not particularly frangible unless you’re someone who routinely cuts apart and rebuilds bicycle frames :-)

But it is a steel casting, and a visual inspection of the hanger didn’t show any obvious signs of stress, so as long as I can avoid getting it bent again it should be okay (the worst case is that it would snap off, which would be inconvenient, but not fatal; I believe it’s possible to get separate derailer hangers for breezer-style dropouts, and if that didn’t work I could always either (a) make it into an xtracycle or (b) use an internally geared rear hub.)

I suppose I’ll put “rear derailer” onto my list of things to possibly upgrade on the bike, so I can at least have a plan when the thing disintegrates 150 miles out from home and I have to limp home in 42×16 (the straightest chainline on that bike.) The plan won’t be “replace it”, but will instead be “curse lots as I wind up hills at a snails pace, then think about replacing it when I finally get back.”

David Parsons Sun Jan 30 15:33:37 2011

Well, the rear derailler hanger on the town bike is part of the welded-in Al dropout, too, but I must admit that I think of it as a “break this, it’s a new frame” part. (Which isn’t so bad in that case; it’s a cheap-ish frame.)

My brain is having issues with the idea of being able to bend a cast steel part in the first place, but have to suppose if it bent and then bent back it obviously can bend without snapping.

Any idea how it got bent in the first place?

Graydon Sun Jan 30 23:14:09 2011

Well, I did crash a couple of times a few months ago, and one of them was in the drive-side direction, so it’s possible that it got adjusted then.

Bending steel derailer hangers is apparently a moderately common thing. Park Tool even sells a tool for adjusting them, and, of course, adjustable wrenches are a fairly common tool for hackers and shadetree mechanics. I’m not going to run out in a hurry to get a replacement derailer just yet (unless I decide to tweak the aged Simplex derailer I got with my gaspipe frame discovery into shape [it’s clean, but the idler pulleys are shattered; replacements are difficult to find, so I will probably need to ream out a pair of Shimano-style pulleys to fit around the somewhat chunkier bolts that hold the idlers to the shifter cage]) because it would be a shame to get a fancy new derailer just in time to have the bicycle vote to become a fixie.

David Parsons Mon Jan 31 22:31:12 2011

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