Sprockets: Steel vs Aluminum

Discussion in 'Mechanical & Technical' started by koorbloh, Sep 14, 2008.


  1. koorbloh

    koorbloh
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    Je Fa Fa

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    Ok, so, aluminum wears out faster. Steel is heavier.

    How much faster does aluminum wear?

    How much heavier is steel?


    Street vs Track vs Race vs Dirt


    How much difference does the bike make in what material you choose?




    Sprockets seem to be a hot topic recently....just trying to keep the discussion going and gather info for the future.
     
  2. Wrench

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    I have never been able to tell any handling difference with the added weight of a steel sprocket, but I sure have had better life from them!
     
  3. cobra525

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    If I knew of an option to by AM steel sprockets I would. They last THAT much longer.
     
  4. FastCat

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    I use the Vortex aluminum rear sprockets and I like them. Aluminum sprockets have a hard-anodized coating which is actually harder than steel... the only downside being that the coating is not terribly thick. That being said, I have never had a sprocket fail to outlast the chain - and if you're planning to replace sprockets/chain as a set, the difference in longevity will not matter.

    On an off-road bike where there will be more dirt/sand involved accelerating the wear, it might be foolish to choose an aluminum rear sprocket. ...but on a streetbike that gets somewhat regular chain-attention/service it's not going to matter.

    Of course, with all of that being said, I doubt you could see the "performance difference" between steel and aluminum rear sprockets (all other things being equal) even on a dyno.
     
  5. fastfoodfred

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    Steel is roughly three times heavier than aluminum. At the same weight, let's say a 1/8" steel plate vs. a 3/8" aluminum plate, the aluminum is 1-1/2 times more stiff. Nevermind the price difference in the material.
     
  6. Well, the difference pertaines to your sprung weight versus unsprung weight, but the difference is a matter of... what? OZ's?? Don't think it's going to matter anywhere but in theory ;-)
     
  7. Vigilante

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    Fastfood is right as far as I know... but it totally depends on the type of Aluminum vs. the type of steel used- stiffness too. Typically in regards to weight,

    Density for Al ~ 2 - 3 grams/cc
    Density for Steel ~ 7-8 grams/cc

    Of course there are other factors, some high carbon steels are much less dense that this- metallugists can really change the mechanical properties depending on alloys, manufacturing process, heat treating, hardening... etc.

    Other than just the weight factor, I would think the major difference (if there is one) would show up in rociprocating mass- This is why some race cars use Aluminum flywheels, or aluminum rods (they tend to have less resistance to change in momentum). They don't require as much torque to get spinning to speed. I think this is why the 520 chain conversion is popular on race bikes as well.

    I'm not sure on the wear- I have no experience with Al sprockets.

    As far as the difference in each bike, it depends on what you are going to use the bike for. If you are looking for a little better response out of corners or drag racing from a dead stop, less resistance to change in momentum is better. If you are using your bike as a commuter and it has plenty of performance for you as is, well a mod may not be necessary.

    What is the cost difference between steel and Al sprockets?
     
  8. GixxerPete

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    For a race bike, street or MX/SX, the weight savings is generally considered worth it (YMMV). For a street bike that's well maintained aluminum should be fine. For a dirt bike that's trail ridden, they are pretty hard on chains/sprockets, many prefer steel for durability.
     
  9. vagrant

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    I just got the first black sprocket and gold chain combination I could find - so it matched my bike. The guy on the phone told me "520 kits" were what all the racers use, so I got that so that I can go as fast as Mladin. They also told me that I could fix my not being able to wheelie problem with a 57 tooth rear sprocket, so I got that too.
     
  10. JTR

    JTR
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    I only run aluminum on my dirtbikes, quads and sportbikes get steel fo life!

    rather the longer life and Im getting no trophys or points so its worth it to me
     
  11. tophyr

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    As far as I can tell, this is irrelevant. Regardless of the material, the sprocket will be the same size and probably the same cut pattern. The 1/8" vs 3/8" bit doesn't matter, the sprocket width and tooth size are constant.

    Like someone said above - if you intend to swap sprockets with the chain, get whichever sprocket is cheaper. If you intend to keep the sprocket until it actually wears out, get the steel one, as it will last vastly longer and you won't notice the performance difference.

    There's probably 8oz or so difference between a steel and an aluminum sprocket, with the weight difference centered close to the hub, where it doesn't matter much. For comparison purposes, weight differences with tires can vary by a full pound or even more - and this is at the very outer edge of the wheel, where weight matters the most.
     
  12. vagrant

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    Also, I went 520 and ally to try and compensate for the 15 lbs of chrome on my rims.
     
  13. wsmc831

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    AL sprockets are fine for the street if you don't ride much.

    I've gone through 2 chain/sprocket sets this year, 520/stealth rear steal...520 just isn't worth it on the street, even with marchesini wheels.

    no way I'd ever put an aluminum rear on again.
     
  14. Driftertank

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    a couple manufacturers are making aluminum sprockets with a steel outer ring for the teeth. Sounds great in theory. Don't know if applications for your bike are available. Don't know if differential thermal expansion ratios will affect anything. Haven't read any reviews. Just wanted to point out the existence of such products.
     
  15. Dwntoearth

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    I have an RK 520 conversion on my bike....soon as I can I am switching back to the 530 with steel rear sprocket.

    I have about 4k on this set...its not wearing very well, and yes chain is proper tension and cleaned and lubed properly, just not all that impressed with it is all.never again will I do a AL rear...and a 520 is not meant for two up, though I havent really needed that since I got the combo, but I can just imagine what it would wear like with 2 up....yikes
     
  16. fastfoodfred

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    I'm pointing out that to get stronger than steel, you need a three times the material. A 520 sprocket and sprocket set are always going to be the same width and pitch, so there will be a negative effect on strength. Aluminum is also a softer material. Double whammy. Use it only when performance matters more than cost. On my street bike, longevity rules.
     
  17. tophyr

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    Ah, ok :) I was pretty puzzled, heh!
     
  18. bear600rr

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    I have typically run Vortex lightened aluminum sprockets on my R6 and my 600RR. I also go through roughly one DID 520 X Ring chain every two years and I'm not a wheelie guru..

    Having said this, I just ordered a custom made Titanium II sprocket for my 600RR - guaranteed for life. The longevity was important for me as the RR has Dymag Carbon Fibre rims. My preference is not to have to order sprockets from Dymag in England.

    Any comments re the Titanium option versus Steel or Aluminum?

    http://sidewindersprockets.com/titaniumII-sprockets.html
     
  19. Vigilante

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    Totally depends on the metal composition of each being compared. There is Aluminum that is "stronger" and harder than some steels, and vise versa. Sometimes the material can be much stronger than another, but it may also be too hard/brittle, which can lead to other problems like cracking/breaking instead of wearing out first, but if they don't break they will wear a long time. Here's some numbers for some examples, and I don't know for sure if sprockets are even made of these materials, but you can see the wide range of values for each...

    For 6000 series Al Alloy;
    Tensile Strength, 5800 - 66000 psi, Vickers Hardness, 65.0 - 149


    For low carbon steel (probably wouldn't make sprockets from this);
    Tensile Strength, Yield 20300 - 347000 psi, Vickers Hardness 22.0 - 661


    For high carbon steel;
    Tensile Strength, Yield 39900 - 399000 psi, Vickers Hardness 182 - 848


    There are many properties that should be evaluated, but if someone told me that they bought Al sprockets and they wore out right away, or wasn't happy with them for whatever reason, that means more to me than a sprocket company trying to sell something to me since there are so many things to consider in designing a perfect sprocket.

    Has anyone tried Al sprockets and had comparable results with them as steel ones? Brand name? cost?
     
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