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finally got my bike back on the road this week. did a 520 conversion and dropped a tooth on the countershaft. even after reading about how happy folks were with lowering the gear ratio, I was unprepared for the amazing difference. it really likes to get the front wheel light now. going to the Sacto area Ducati get together wednesday night was a real thrill when I hit the throttle in traffic while changing lanes. instant wheelie in 4 lanes of rush hour traffic. yeehaw!! this will definitely take a bit of getting accustomed to.
 

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May I ask why you did the 525-520 conversion ?
Save some weight, little less hp eaten by friction, and wear out your chain a quicker...I'm actually going to do it on my track bike when the current chain wears out.
 
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vduc said:
little less hp eaten by friction, and wear out your chain a quicker
Weight saving yes, but regarding wear I thought it was the other way around :think:, 525=less wear vs 520=more/quicker wear :think:

Doc
 

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ditto on that. I turned away from doing the conversion on my 600RR due to the fact it wasn't a dedicated track bike/racer. Feeling any difference would be a stretch, and the cost associated with them wearing out faster wasn't worth it. When I was considering doing it two seasoned AFM racers recommended against it unless the above conditions were present. Dropping the teeth proposal is a good idea though.
 
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That's most probably true jb. I am now on my 3rd set of chain/sprockets on my Multi (including the stock) and the first two were OEM sprockets and chain. I got exactly 17500km out of each and now I have put the DP sprockets and the DP chain (it's an X-ring one) which supposedly will give 50% more mileage.

So far I guess that the above assumption will probably prove to be true cause I only have adjusted the chain twice in the last 15.000km ! while I had to adjust it every 1000-1500km when I had the stock one.

Anyway, I'll be interested to hear your findings with your new sprocket/chain combination.

Cheers,

Doc
 

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vduc said:
...and wear out your chain a quicker...
Doc that's what I said a 520 will wear out quicker. I'd guess if the replacement chain is a stronger higher quality the wear will equal out.
 

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Just how much weight do you think you're saving - 1/2 pound?
 

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with alloy sprockets, it should save 1.5-2.5 lbs, and its reciprocating weight. Remember, the AMA superbikes are using a 520 chain with 220hp. On a race bike, it easily lasts a full season or two, provided you get a good chain.
 

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to be clear, they last a season or two on a club racing race bike, not an AMA bike. those guys probably swap them out every weekend.
 

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Not to cast dispersions on your goal of weight savings, but I hear a lot about "reciprocating mass", inertia, etc.
The real effects aren't as dramatic when you look at it - mass x velocity (in this case wheel RPM x radius of mass centroid). The diameter is pretty small on the sprocket as compared with the entire wheel assembly, so the inertial effects won't be significant. Obviously in racing when one is on the edge of performance, tenths of pounds which can add up to hundredths of a second can actually mean the difference in a race, all other things being equal (which of course they are not).

If you like the look, just say that is why you want to invest the time and money, but don't believe it will make you another Matt Mladin or Neil Hodgson.
 

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I think the chain and sprockets as a whole are considered rotating weight (same as the clutch). And also the rear sprocket and about 90% of the chain is considered unsprung weight (moves with the rear wheel).

The weight difference? Pound and a half or a little more depending on the chain, which is significant either as rotating or unsprung.

Wear? Would a 520 wear any faster than a 525 or 530? Same pitch. Same number of links. Same roller diameter. Just narrower as you go from 530 down to 520. I suppose the difference in width would spread out the forces over a greater area... but I have no direct experience comparing life of 525 vs 520.

Tensile strength would be a bit lower on the narrower chains (all else being equal). Fatigue life is pretty impressive on the best 520 chains these days.

Maybe I'll experiment some day, maybe not.
 

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The mass of the chain is the largest factor. It's resistance to acceleration is high because of it's mass. Pick up a chain and imagine
that weight as a fly wheel. When you accelerate, it must accelerate. the weight saving is very significant.
 

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Where would one obtain the chain and sprockets?
 

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ST4R said:
Tensile strength would be a bit lower on the narrower chains (all else being equal).
No. Tensile strength would be the same, tensile STRESS would be greater :D

Randy
 

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I agree - ultimate tensile strength would be unchanged.

If the pins are the same diameter, and the sideplates are the same thickness, all else being equal the tensile strength of the chain would be the same regardless of the chain width.

The tensile stress on the chain is dependant on the driving force applied to the chain and the resistance to movement of that chain from the weight of the bike. I don't see how the total tensile stress on the chain would change with chain width provided the components were of equal size and shape.

The stress would be spread out over a larger area since the roller/tooth contact area is greater as chain width increases. Is that what you're thinking?
 

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Yes. Same load/smaller area = larger stress (psi).

Interestingly enough, materials have greater specific strength the smaller they get - a microfilament of 4130 steel has an allowable stress similar to its modulus or about 30,000,000psi whereas a normal sized sample would yield 90,000 - 140,000psi (depending on heat treating and sample size).

The size difference of the 520 vs the 525/530 isn't statistically great enough to yield any strength difference. If the links are the same thickness and the only differrence is the roller width, then the contact stresses between the rollers and the sprockets would be greater (remember less area with same load = more stress) by the same percentage as the size difference.

IMHO this is all academic. If you like the "look" buy it.

If the mass difference is of concern, then all things being equal (material, temper), the mass percentage difference would be the strength percentage difference - you end up buying more sprockets and chains.

As in all engineering solutions, everything produced is a compromise - lower weight/higher cost/reduced durability. Still, I am constantly amazed at how much our $ gets these days, even in a Desmosedici!

Randy
 
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