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Old 05-05-12, 05:48 PM   #1
Asi
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Chairings - why aluminum? why not steel?

I looked at my chainring from time to time and i could see that is wearing out a bit too fast. I searched the market for a new one and see that is somehow a bit pricey (I mean I ride a 1989 steel bike all original, all dura-ace, and a proper chainring costs half of the price I paid for the bike).
I made a good use for a laser cutter I got at work, and made myself a chainring (a steel one).

The real question.. why most of them are aluminum? Aluminum chainrings and steel chain wears a lot faster, also titanium cogs on some cassettes.
I see steel chainrings only on very low grade stuff. (and not sold seperatly, and not that i would want one of those, I made one from a steel plate 4mm thick, and some beveling on a lathe, but that's another story). The weight issue is almost non-existing, steel can be much thinner than Al. Yet for weight weenies I understand, but the normal way should be steel and the niche class should be Al-Ti-Mg-Carbon fiber stuff - stuff that the main advantage is weight (density to be specific) and the rest are disadvantages (especially price for Ti and carbon stuff)

Is there any argumentation on using improper materials? (Al chainrings, Ti-cogs, Ti-chains, anodized Al for rims, etc)

I guess there are some B-class engineers at work in the bike department... The A-class is into aviation/automotive.
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Old 05-05-12, 06:04 PM   #2
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Steel would last longer, but not as much longer as you seem to expect. In any case, bike specs are driven by weight, and it wold be hard to justify steel rings on anything but the lowest entry level bikes (where they are used).

It should be noted that not all aluminum rings are created equal. There are numerous grades of aluminum, and some are incredibly wear resistant. Also consider that, excepting the smallest granny rings used for mtb which are usually steel, most chainrings tend to hold up fairly well, and tend to outlast chains and cassettes by a big factor. In over 100k road miles I have never replaced a chainring, including one pair with well over 50,000 miles on them (and believe me, I don't baby my bikes).

All in all, it would be very hard to justify using steel rings as an improvement. The added life would not be enough to justify the weight penalty.
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Old 05-05-12, 06:14 PM   #3
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Most people don't complain if they get 23 yrs of life from their aluminium chain rings.
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Old 05-05-12, 06:43 PM   #4
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There are some touring/trekking triple cranks that use steel for wear resistance, particularly on the smaller rings which get used more. Two that come to mind are the Shimano Deore LX 48/36/26 (M583?) and the Sugino XD300. I think the Sugino is all steel while the Shimano used Alu for the big ring. While these certainly aren't top-of-the-line cranksets, they aren't department store grade either.
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Old 05-05-12, 07:38 PM   #5
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Steel granny rings are fairly common but the larger chainrings, particularly road rings, last so long with any decent care that improved longevity would be a non-issue.
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Old 05-05-12, 07:44 PM   #6
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I've seen worn chainrings, so now that I think about it, they must have worn from use of insanely worn chains. Of course, these chainrings were not on MY bikes.

In other words, FBinNY is right: chainrings don't wear out, but maybe they do, only if you abuse your bike. Replace your chain when it starts to wear.
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Old 05-05-12, 07:50 PM   #7
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The last chainring I replaced had slightly over 90 kmiles of use. A steel one would presumably have lasted longer but with a tradeoff of greater weight. Since I can get a replacement for about $40, the cost is about 0.04 cents per mile, or one extra penny on each 23 mile ride. Don't think I'm ready to accept a heavier chainring for savings of that magnitude.
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Old 05-05-12, 07:59 PM   #8
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Well steel would be likely as good I have several that are steel in my collection. The thing is steel is a lot harder on chains and much less forgiving on gearing setups. Plus as others have said they last longer than most bikes I have alloy rings with several thousand miles on them that are 30 years old or better with no prolblems.
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Old 05-05-12, 09:20 PM   #9
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+1 Weight savings is why they use Al rings. The durability factor just isn't justified. FWIW:

Shimano 48T Biopace aluminum: 77g
Shimano 48T Biopace steel: 220g

So on a standard double you might be looking at a 250g weight penalty, which is over half a pound.
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Old 05-05-12, 09:39 PM   #10
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Suley's take on their stainless steel chainrings.

On a drivetrain with a steel chain and steel cogs, why wouldn’t you want to use a steel chainring? Most chainrings on the market are made from aluminum, which is 35% softer than stainless steel. A softer metal means a shorter lifespan. Enter the Surly Stainless Steel chainring, made from 304 grade stainless. You can now have an all-steel drivetrain that will love you long time. Stainless, as it’s name implies, is a rust and corrosion-resistant alloy steel that is known for it’s toughness. Like all things mechanical, it will eventually wear out. When it does, simply flip the chainring around and you’ll get another lifespan out of it. Our chainring is ideal for single-speed, fixed gear or tandem timing chain applications. It is not ramped or pinned for shifting assistance, so shifting will be a bit slower if using these with a front derailleur. Check out all the sizes we carry:
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Old 05-05-12, 10:01 PM   #11
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Quote:
Originally Posted by GeoKrpan View Post
Suley's take on their stainless steel chainrings.

....Most chainrings on the market are made from aluminum, which is 35% softer than stainless steel.....:

Just like a coin which has 2 sides, there are two ways to look at the chainring material argument.

Yes, steel rings may last longer, but given what you're spending per gram to save weight, the higher cost of replacing rings sooner than you might otherwise is still one of the cheapest ways to save weight.
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Old 05-06-12, 01:31 AM   #12
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There is no point in having steel chainrings in sizes over 34t.
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Old 05-06-12, 02:31 AM   #13
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Well, maybe 23years lifespan seems ok, but the point is:

1989 - dura-ace - shaved (the chain was replaced from time to time, and the rear cassette is in very good condition with no visible wear on cogs, so the weak part was the chainring itself)
1962 - xb3 (some russian thing, steel) - like new, and I still use it as a fixie.
1974 - xb3 - Steel, it has some wear, but i have plenty of lifespan remaining
197? - stronglight - steel, still usable, some wear may be noticed
First two are 53t (but the BCD, and number of bolts is different, otherwise I would just put a like new xb3 that I have around)
the rest are 50-51t

And another thing: On a bike 20-30-40-50years old that is in working condition and at low price (50$ or so).. you don't change parts ,more expensive than the bike itself (on some occasions you may).
So in terms of old bikes, most of them that are all steel, are still on the road. (not referring only to the chainring) - and yea, I don't like Al on gears and other important moving parts like crankshafts, drive-shafts, bearings - and you don see them made out of Al in cars/motorcycles/industry, wonder why? But you see them in bike industry. Weird.
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Old 05-06-12, 08:36 AM   #14
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35,000 unbabied miles on shimano 600 chainrings, both the 40 and the 53
usually using the 40

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Old 05-06-12, 10:22 AM   #15
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Quote:
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The weight issue is almost non-existing, steel can be much thinner than Al.
The thickness of the chainrings is the same regardless of the chainring material (the chainring thickness is correlated with the inside width of the chain).
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Old 05-06-12, 10:30 AM   #16
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7075t6 alloy is quite long wearing, it must be machined,
the softer alloys lend them selves to punch presses, so production costs are lower.

For Single speed and IG hubs, I have found Surly Stainless steel chainrings very nice.

20 years ago,
I did find and install steel chainrings, on my cyclo-camping tour-bike,
50,38,24
and my winter, studded tire, old mtb,
48,36,22
weight matters less, on those rigs.
and drivetrain is simplified for durability, friction bar end shifting
and 6 or 7 speed freewheels,
so latest shift pins and ramps features, absence is not an issue.

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Old 05-06-12, 10:38 AM   #17
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hypothesis: it is cheaper and easier to machine chainrings from aluminum.
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Old 05-06-12, 10:46 AM   #18
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hypothesis: it is cheaper and easier to machine chainrings from aluminum.
Which goes a long way toward explaining why low end OEM cranksets have steel chainrings, while pricier cranksets have aluminum chainrings.
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Old 05-06-12, 11:13 AM   #19
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I don't like Al on gears and other important moving parts like crankshafts, drive-shafts, bearings - and you don see them made out of Al in cars/motorcycles/industry, wonder why? But you see them in bike industry. Weird.
I guess you've never changed a timing chain on an older small block Chevy. Nylon teeth on an alum hub for the timing chain. Supposed to be quiter than a steel gear.
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Old 05-06-12, 11:14 AM   #20
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Which goes a long way toward explaining why low end OEM cranksets have steel chainrings, while pricier cranksets have aluminum chainrings.
It doesn't completely kill the hypothesis, since other cost variables may be involved for manufacturing low end vs higher end crank rings. Is it easier to stamp something out of softer steel than to manufacture using some other technique, with more exacting tolerances and other specs? I suspect so, but it's just a hypothesis.
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Old 05-06-12, 11:28 AM   #21
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Which goes a long way toward explaining why low end OEM cranksets have steel chainrings, while pricier cranksets have aluminum chainrings.
Now that's funny. I like aluminum because I'm such a spode they last forever.
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Old 05-06-12, 11:31 AM   #22
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See 1:37 for how it was done "back in the day"
http://www.youtube.com/watch?v=ZPLRF5F5SZY

See 10:43 for the "British" method
http://film.britishcouncil.org/how-a-bicycle-is-made

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Old 05-06-12, 11:51 AM   #23
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I just wore out a 32T aluminum middle chainring on a triple. I had installed a new chain at the usual wear point. Everything worked like a charm on the workstand, but when I tried riding the bike, the lower portion of the chain "stuck" to the chainring, jamming against the underside of the FD. Closer examination revealed the teeth had taken on a slight "hook" shape. The worn-out chain had a large enough pitch for the links to slip off the teeth, but the new chain "stuck" in the hooks when pedaling under load.
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Old 05-06-12, 03:32 PM   #24
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Originally Posted by GeoKrpan View Post
Suley's take on their stainless steel chainrings.

On a drivetrain with a steel chain and steel cogs, why wouldn’t you want to use a steel chainring?
Yeah, baby!

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Old 05-06-12, 05:28 PM   #25
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It doesn't really make a difference to me. If the bike came with aluminum chainrings I use them until they're worn out, same with steel.

But, if I have to buy new cranks or chainrings and there is a steel option at a comparable price, I will get steel, it lasts longer.

I ride 15,000 miles a year, it makes a difference.
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