04 June 2014

Next Attempt

Newly-mounted WickWerks 50/34 compact road double chain rings
So far as I know, WickWerks rings are machined, rather than forged; this is not a point in their favour when considering their probable length of service.  On the other hand, if you look at the upper right, you can see that there's a relatively thick rim in the ring design, which ought to help retard bending.  The rings themselves are a bit thicker than the norm; enough so that I had to adjust the front derailleur.  So that might be helpful.  WickWerks also rates them for tandem use, and the (forged, marginally better-shifting) Praxis rings, which have so far bent the least, are not.

I clamped a laser to the downtube and spun the empty crank, and if it's out of flat it's by a very small amount.  This is pretty strictly down to me pushing too darn hard at this point in time.

There's a 50/34 set of Surly stainless steel rings coming for the Experiment, since I have some hope those will last without bending.  (They will likely also shift like urgh, but everything is tradeoffs.)  And the Experiment is what I'd be riding if the particular horror of being sixty kilometres into a planned three hundred kilometre tour when the big front ring goes non-serviceable happens.  (And, hey, last time took out the small ring, too, nearly; enough top ring bend to interfere with any gear but least and next-least.)


Janice in GA said...

I'm kind of in awe of your ability to bend chainrings. I'm neither very large nor very powerful. I simply can't imagine the force it would take to do that!

Of course, I'm still riding a 1991 Trek hybrid with almost all original equipment. It's getting a little ramshackle and noisy, but still shifts and brakes well. ::knock wood::

Graydon said...

I don't feel like I'm powerful; I haven't been decently strong since my middle twenties. It's more that I'm not in the design space.

I'm, well, I'm increasingly middle-aged, but (as I understand it) bike stuff is mostly designed for people who are 150 pounds, maybe a bit more; I'm a hundred pounds heavier than that and I can still do the one-foot-on-a-high-thing-and-step-up, so I've got to be able to generate a kilonewton or so of downforce per foot. Into longer than normal cranks. Nobody seems to make shifts-nicely rings that are meant to deal with this.

(I am starting to dream about getting one of those electron-beam 3D printers that do complex metal parts and making chain rings in really robust aerospace nickel-cobalt alloys.)

Long may your Trek shift and brake well! and the rattles are usually subject to a bit of tightening here and there, or getting a good mechanic to be nice to the bearings.

orc said...

Maybe switch to a 130 bcd crankset so there's more spider and less ring there? (possibly a 130/74 triple with the outer ring replaced by a bashguard -- you could get a 50/30 double out of that and a < 1:1 alpine gear.)

Graydon said...

That's a much more practical suggestion than my desire to get a serious metal parts additive machining device (at a mere quarter million or so the each) and start making robust 110BCD rings.

I suspect it would work, too, especially if I could solve the shifting issues. I've been trying to avoid 130BCD because that means junking two custom cranksets. Certainly it's the tabs down to the spider that fail with the decent (Praxis, WickWerks, Carbon-Ti) rings. (Blacks pure and the SRAM rings just folded.)

Graydon said...

Sigh. "Blackspire", of course. Not "Blacks pure", which is at best some kind of dire blended whiskey.

orc said...

Don't let the sunk cost fallacy drag you down, though; at the amount of money you've put into getting custom rings you can get a 130/74 crankset and see if it works better.

If a 130/74 does work better, you can store the custom cranksets for a rainy day (or the day you decide you want to put a 42/34 alpine double on one of your bikes and spin your way up the bluffs around Lake Ontario.

Graydon said...

The problem is the 195mm crank arms; I know that works. I know with great confidence that I go faster and hurt less. (Leg cramps two hours after getting home when I forget to take ibuprofen, lie there and stiffen, and then move abruptly is *way* better than leg cramps that happen while riding and make getting home seem highly unlikely.)

So, yes, I could try the standard 175mm cranks in 130/74 pretty easily, but I more or less already know that crank arm length doesn't work, and indeed hurts. So trying 130/74 means a High Sierra order, a long wait, and exceeds prudence with present cash flow even more than the last couple ring purchases have.

So, yeah, something I should try. But it'd be nice to keep some >50km bike capability in the meantime.