# Rear Cog's Steel, Aluminum, or Ti



## S:Drive (Aug 19, 2009)

I was thinking of changing my rear cog, and I was wondering what material held up the best Steel, Aluminum, or Ti. 

I currently have a Surly 22t, but I think I am ready to drop down a tooth to 21t.


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## cockroach (Jun 12, 2009)

Simple answer....steel.
Aluminium isn't up to it for a rear cog, and while titanium is lighter than steel it's not as strong.
I use the On-One groove armada cogs, super strong cro-mo.


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## Germany_chris (Sep 14, 2009)

my DA cassette is alu and ti it seems to hold up..my SS cog is steel...long term durability steel..but dont rule any out..


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## Cholopolitan (Aug 20, 2007)

*Steel*

I've found aluminum does wear quicker. For fully-geared bikes, aluminum is fine since wear is more distributed. I have no experience with ti.


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## KonaEnduroJC (Jan 16, 2005)

ti and aluminum dont hold up well but are both very light.


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## boomn (Jul 6, 2007)

KonaEnduroJC said:


> ti and aluminum dont hold up well but are both very light.


Ti SS cogs are known for holding up for a _very_ long time. It is a much harder material than aluminum. I would always choose steel over Ti though, but that is simply based on price


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## S:Drive (Aug 19, 2009)

Thanks for the input, looks like I will just stick with the Surly, and get a 21t. Thanks!


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## ShadowsCast (Mar 23, 2008)

I'm sure ti holds up well, but I have a feeling ti longevity has a lot to do with how often people are changing out their chains to keep from ruining an 80 dollar cog...


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## boomn (Jul 6, 2007)

ShadowsCast said:


> I'm sure ti holds up well, but I have a feeling ti longevity has a lot to do with how often people are changing out their chains to keep from ruining an 80 dollar cog...


I don't know the numbers off the top of my head, but titanium is pretty similar in hardness and strength to stainless steel.


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## dkmccandless (Oct 23, 2009)

A bit off topic and certainly not the definitive answer on Ti hardness. Had a Ti seatpost clamp several years ago. Bolt stuck out too far so I grabbed a hardened steel coping saw blade intended for cutting metal. Got absolutely no where trying to cut that bolt. I had always thought Ti was like Al in that it was strong and light, but not necessarily hard. Trying to cut that bolt changed my opinion.


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## cockroach (Jun 12, 2009)

Not directly cog related, but DMR do a titanium axle for their V12 pedals.
From their website:
"Maximum rider weight is not to exceed 185lbs or 85kgs".
But they are 80g lighter than the standard steel.


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## Tone No Balone (Dec 11, 2004)

Here's a pic of an alum cog further on down the thread list!  
steel is real!


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## OldHouseMan (Dec 7, 2006)

I'm pretty sure Chris King stopped making the aluminum cog and only makes steel.


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## weather (Jan 12, 2004)

boomn said:


> I don't know the numbers off the top of my head, but titanium is pretty similar in hardness and strength to stainless steel.


surface hardness is comparable, but elastic and shear moduli are about half as much as 304 stainless.


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## AZ (Apr 14, 2009)

Photo credit to dzm3,


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## scooter916 (Jan 2, 2006)

Germany_chris said:


> my DA cassette is alu and ti it seems to hold up..


actually the carrier is the only thing alloy, the cogs are steel and Ti


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## phlite (May 15, 2007)

Dam, that cog is f'd .. aluminum i presume?


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## Sparticus (Dec 28, 1999)

phlite said:


> Dam, that cog is f'd .. aluminum i presume?


Yes, aluminum.

--Sparty


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## phlite (May 15, 2007)

So, it sounds like steel for the rear cog, but you could go either way for the chain ring? I was looking at the surly steel chain ring, to upgrade my stylo 1.1 ring, in hopes of getting rid of tight places in the chain. But, reading around the singlespeed forum, looks like the surly steel chain ring can get bent fairly easy?

Thoughts on chain ring? Was looking at possibly ISAR alum chainring ... or if not alum, better steel ring from somewhere else? Thanks!


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## Sparticus (Dec 28, 1999)

phlite said:


> So, it sounds like steel for the rear cog, but you could go either way for the chain ring? I was looking at the surly steel chain ring, to upgrade my stylo 1.1 ring, in hopes of getting rid of tight places in the chain. But, reading around the singlespeed forum, looks like the surly steel chain ring can get bent fairly easy?
> 
> Thoughts on chain ring? Was looking at possibly ISAR alum chainring ... or if not alum, better steel ring from somewhere else? Thanks!


Personally I prefer not to run aluminum rings or cogs on any of my bikes (geared or SS) simply because steel outlasts aluminum. I employ Surly rings but my cranks are all 5-bolt spiders which means there's less of a span between ring bolt holes so they're less likely to fold (although I've seen a photo of a folded 5-bolt Surly ring. It may have lost a CR bolt prior to folding, tho.)

ISAR makes aluminum, ti and I think he still offers steel rings & cogs. Until a rich cougar catches me, I'm probably stuck with Surly cuz they're cheap and they work. I put a lot of miles on my bikes, therefore I don't care to invest a lot in wear items. If I was more bling oriented, I'd def be one of ISAR's top clients.

--Sparty


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## p nut (Apr 19, 2007)

I've got a 33T Surly ring with many many miles and seen several cranks. No issues. I'm not sure how people bend these things. Maybe bad chain alignment? Bolts not tight? Don't know. 

I use Surly due to price and availability.


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## alexrex20 (Dec 20, 2005)

i run Salsa rings (aluminum) and have yet any issues with failure or wear. maybe i just don't ride long or hard enough... that just sounds dirty.


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## ISuckAtRiding (Jul 7, 2006)

the ti and steel i use are fairly similar in strength. Close enough to where you wont notice much of a difference in wear life. The ti i use is 6al4v, and the stainless is 17-4ph, both of which are pretty tough aerospace alloys. 
As for aluminum, for chainrings, i think it's fine. You'll probably get at least a season out of it with normal lubing. Sometimes more, sometimes less, depending on where you ride. As far as aluminum cogs go, they do wear out rather quickly, no matter what alloy you use. There is much less chain wrap on a cog than a chainring, so each tooth is getting about twice as much load. I usually say save these for race day.


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## ISuckAtRiding (Jul 7, 2006)

p nut said:


> I've got a 33T Surly ring with many many miles and seen several cranks. No issues. I'm not sure how people bend these things. Maybe bad chain alignment? Bolts not tight? Don't know.
> 
> I use Surly due to price and availability.


It's because they use 304 stainles steel, which is butter soft. 
the yield strength for 7075 aluminum is 73000psi, and the yield strength of 304 stainless is 42100psi.

and for example, the yield strength of 17-4ph stainless is about 145000psi, and 6al4v titanium is 128000psi.

Yield strength is the lowest stress at which permanent deformation can be measured.


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## phlite (May 15, 2007)

Ok, thanks, so Surly rings even 4 bolt, 180mm cranks are probably good for mere mortals hopefully. I was worried about bending, probably worth a shot anyhoo.


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## Sparticus (Dec 28, 1999)

ISuckAtRiding said:


> It's because they use 304 stainles steel, which is butter soft.
> the yield strength for 7075 aluminum is 73000psi, and the yield strength of 304 stainless is 42100psi.
> 
> and for example, the yield strength of 17-4ph stainless is about 145000psi, and 6al4v titanium is 128000psi.
> ...


So will your steel rings last ~3x longer than a Surly steel ring? If so, I might step up. Thanks.

--Sparty


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## ISuckAtRiding (Jul 7, 2006)

Sparticus said:


> So will your steel rings last ~3x longer than a Surly steel ring? If so, I might step up. Thanks.
> 
> --Sparty


Well, i dont make stainless chainrings because that alloy is hard to get in the size needed to make them. It would actually cost more than ti. 
As for the cogs, surly uses an alloy steel instead of stainless, which i think will probably carry similar properties to my cogs. They dont state exactly what alloy they use, so i'm only assuming based on my experiences with the most common types.

Also, yield strength has more to do with the taco issue than wear life. Any steel ring should have a much longer wear life than aluminum.


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## Sparticus (Dec 28, 1999)

phlite said:


> Ok, thanks, so Surly rings even 4 bolt, 180mm cranks are probably good for mere mortals hopefully. I was worried about bending, probably worth a shot anyhoo.


Keep your chainring bolts tight. Everything should work out fine.

--Sparty


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## nuck_chorris (Jun 6, 2008)

cockroach said:


> Simple answer....steel.
> Aluminium isn't up to it for a rear cog, and while titanium is lighter than steel it's not as strong.
> I use the On-One groove armada cogs, super strong cro-mo.


really now, im pretty sure Ti is stronger than steel, look it up, get the facts.

as for the price Ti as you know is more expensive so if you want function over form choose an SS ring


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## Sparticus (Dec 28, 1999)

nuck_chorris said:


> really now, im pretty sure Ti is stronger than steel, look it up, get the facts.
> ...


That's it, Nuck... take him to task for failing to do his homework.

:nono:

--Sparty


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## boomn (Jul 6, 2007)

nuck_chorris said:


> really now, im pretty sure Ti is stronger than steel, look it up, get the facts.
> 
> as for the price Ti as you know is more expensive so if you want function over form choose an SS ring


too generic a statement to make. As ISAR pointed out, there can be a huge difference in strength and hardness between different steel alloys. Some Ti alloys are stronger than some steel alloys and some steel alloys are stronger than some Ti alloys


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## nuck_chorris (Jun 6, 2008)

boomn said:


> too generic a statement to make. As ISAR pointed out, there can be a huge difference in strength and hardness between different steel alloys. Some Ti alloys are stronger than some steel alloys and some steel alloys are stronger than some Ti alloys


fine , ill be more specific , A stamped steel cog versus redline's flight titanium cog. the cog will have greater or equal strength to the stamped cog not less strength with an added bonus, weight savings


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