Join Date: Dec 2003
Location: Austin, TX y'all
Stealth or renthal for 520 is like water and oil. Two very very different sprockets. One is alum and one is steel.
As z06 said a superlight steel rear sprocket in 520 with a high end chain can last as long as stock. Stealth rear sprocket, Driven evo spec superlight steel, Vortex superlight steel, etc would fall into this category. You go with a 520 chain kit with a good chain and these sprockets and 20-40k is what you should see for mileage if you take care of it.
Many 1000cc owners run alum rear sprockets and get 7-20k miles out of it depending on how they take care of it. I would say the average is 10-12k miles though.
If you're a street guy I would recommend the superlight steel 520 chain kits.
More importantly then anything though is taking care of it through proper chain slack and cleaning/lubing the chain. I've seen super strong 530 kits not last 1k miles with bad maintenance and i've seen some weak 520 alum kits run over 20k miles. Maintenance is the #1 factor in the life of your chain kit no matter what.
BTW if you want super long lasting with a steel rear sprocket then snag the ek zzz chain. Longest lasting street 520 chain on the market right now, but it's a bit more money. For a bit less money and about 5% less life you can get the ek mvxz or rk gxw chain.