I bought a new Shimano FC-M171 crank for a low end hybrid bike mostly because it had a chainline of 47.5 mm. and I didn't want to spend more than the bike was worth for a new crank.

The teeth seem to randomly vary in size, not in any systematic pattern. Some are shorter. Some are longer. Some are pointed. Some are more rectangular.

Is this just really, really crappy made-in-China quality or am I missing something?

See jpeg:

Click on the image for a hi-resolution image.

This may be the most asked question. Your chainring is perfectly normal. The cut down and differently sculpted teeth are "shift gates" which improve shifting. Essentially they make the glide in Hyperglide.

It is not a defect or poor workmanship. It is designed that way to enhance shifting performance. If you look at the cogs on the rear, the teeth are not all the same on those either.

Thanks!

You know, at some time in the deep dark past I might have even trashed a crank for the broken teeth that didn't look too different from this. Live and learn.

which of course begs the question, what makes the "hyper"?
;-)

(very good use of the words to explain it btw, just couldn't resist)

Actually, I alternate, sometimes saying it's the hyper in ...

If I remember, it started with Uniglide, then Superglide, now Hyperglide. All used cut down teeth of some sort or another,though the exact shapes evolved over the years.

Uni, Hyper and Inter are all cassette/freewheel cog profiles

Uni: twisted teeth
Hyper: Sculpted teeth and outer cog surfaces
Inter: Hyper features on the backside of the cog

Super: Hyper concept applied to chainrings

ya I remember (ish, vaguely) but what I was trying to do was come up with an ADD joke or something about hyperactivity, but it werent happening....

seems to me my old touring bike (around 1990) had some sort of "glide" going on, but dont recall the name.

Welcome to the World of "preworn" Chainrings and cogs I mean ... "shifting aids" .

Well, if "preworn" means they only last 40,000 to 50,000 miles, I'll take them. The difference in shifting performance between the old style "flat" chainrings and the newer shaped, ramped and pinned chainrings is night and day.

We get this question routeenly too. I tell the person to look 180* acress the "broken" tooth for the other one and then ask how that could happen. This second tooth is often behind the crank arm in a well protected location.

BTW this tooth profiling on rings started with Shimano's "W" cut in ,maybe, 1982. A pair of teeth were about half height, in two locations, on the big ring. This evolved into superhyper teeth. I have done this to a number of traditionally symetrical profiled toothed rings to help their shifting with very good results. All it takes is a few well controled file strokes. Andy.

It's All aboput the Quality of the Material Hillrider, you know that. Campy Chainrings of yore were "regular" as it can get , but seemed to last and last and last If the OP gets 40-50,000 miles out of his cranks , Great for Him !!!!!

Sure I know it. Campy rings "of yore" may have indeed been durable but so are their new ones and so are Shimano's. That 50,000 miles on a set of chainrings was referring to me, not the OP.

its engineering at work .they got boats to buy and houses to pay for..

That's Wonderful durability Hillrider I then wish Shimano would make 110 BCD chanrings for All of their cranksets, even the ones from the 80/90's . But now everything is so model and year specific, it's silly. That Shimano apparently plans to make parts obsolete is a major reason I do not choose many of their parts. I use their rear and front derailleurs only, and even those are now long "obsolete" to them.

So what do you buy, Campy? They change their components and obsolete older ones at least as often as Shimano and charge more for the privilege.

Sugino originated the 110BCD and still makes chainrings in that size. They even leave off the shifting aids. Isn't life good?

Good, if you never shift under load or in a hurry. Been there, done that, newer works better. Also, Shimano makes their compact cranks in 110 mm BCD and doesn't off-set one bolt like Campy does so you can use any make chainrings, not just proprietary ones.

I choose Sugino Cranks, and I started using them since the early 80's with the AT, and now the XD I left the Shimano/Campy thing long ago.

I choose to have a in-dependent drivetrain. No shift aids, no indexing etc. I don't buy into "systems" ...lol.... it's like joining a club ! I don't do those either

There's lots of cranks to choose from these days, and that's a very good thing.


The beauty of life and cycling is that for whatever one hungers for , there's a way to fulfill it. Infinite choices. There are No rules ...never will be .... just as there are no rules to the Imagination

Above All .... enjoy the Ride !!!!!!!!!!!!!!