World Superbike Racer
Join Date: Jul 2005
Location: Austin, TX y'all
Thanked 188 Times in 154 Posts
Feedback Score: 12 reviews
Well 525 is a bit wider then 520. Not much, but a hair. However, remember that not all chain kits are created equal. That is what people forget. The stock chain is mass produced and the chain is nowhere near as strong as the aftermarket products that are the equivalent. For example the stock 525 chain won't last nearly as long as the ek zzz 525 or ek mvxz 525 as it's a much better quality. Bikes are mass produced and they need to keep the costs down.
Now, a chain kit (front sprocket, rear sprocket, and chain) are only as strong as their weakest link. All front sprockets are steel and super strong. A rear sprocket can be alum or steel. The chain is steel.
So if you get an alum rear sprocket that is your weak link so you don't needa super super strong chain. However, if you get a steel rear sprocket then the chain is the weak link. So then you get a super strong chain like the ek mvxz or ek zzz and you have a 520 about as strong as the stock 525 chain.
The chain kit will last just as long as it's a better product, it's less weight, and less money. It's just better technology.
The thing people forget is that the quality of the products makes a huge difference. Now if you take the same steel sprockets and an ek zzz chain 525 sure it's a bit stronger then the 520 as it's the same products, but it's over kill for a 600cc bike. Reason being is that not only does abuse destroy a chain kit, but so does time and the elements/weather. If you have a chain kit for say 4 years and only have 2k miles on it I would wager the chain is in very bad shape due to humidity, moisture, etc. I would say the chain likely has rust and is beat up as well. Not by use, but by the time and weather from sitting there. So there is no need on a 600cc bike to run a 525 or 530 UNLESS it's a 100% stunt bike (tons of abuse) or you have a turbo, built engine, etc and are pushing upwards of 200hp to the wheel out of the bike. Then, sure, get a 525 or 530 chain kit.
So with these new superlight steel 520 rear sprockets and the already super strong chain technology that is out there for 99% of 600cc rides there is no reason not to get a 520 chain kit. The only question to ask is "should I get a superlight steel rear sprocket or hard anodized alum" and the answer to that depends on if you want longevity or light weight. The superlight steel rear sprockets weight about 1lb more then the hard anodized alum. Not a lot too notice, but if you're racing or it's a track bike you would probably want the hard anodized alum rear sprocket. If it's a street bike you would probably want the superlight steel rear sprocket like the Driven Evo-Spec superlight steel chain kit we sell.
Any other questions just ask :)