@BasedGod baseline your car as YOU see appropriate, which may or may not include rod bearing service. How much documented history to you have? Do you know the previous owner? How confident are you with a wrench? How long do you plan to keep your car?
I am 36,000 miles, post replacement, without going BOOM. My car never went boom, I just believe in maintenance.
It is really unfortunate that too many people are getting into these cars without fully understanding the level of commitment -- and dump them for pennies with looming deferred maintenance.
It is my opinion, after nearly 300,000 miles of driving m5s over 3 generations, that rod bearings are wear items and should be serviced as any other wear item: clutch, suspension/LCAs, wheel bearings, yada, yada, yada...and, as items wear from use/time/dry rot, they need to be serviced. The quicker people make the connection, the longer your s85 will last.
I replaced my s85 bearings at 84,000 miles because my Pb levels were high.
http://www.m5board.com/vbulletin/e6...cussion/290497-rod-bearings-84-000-miles.html
http://www.m5board.com/vbulletin/e6...e-rod-bearings-replaced-17-000-miles-ago.html
http://www.m5board.com/vbulletin/e6...e-rod-bearings-replaced-30-000-miles-ago.html
My decision was a no brainer. I understand it might not be as clear cut for other people.
Today, I am 36,000 miles POST preventive replacement, with about a dozen track days and no signs of wear. I plan on pulling them again in 14,000 miles for 5h1ts and giggles. I also let my warranty expire, unused, at 50,000 miles. Now, I'm at 120,000 miles on the odo.
My s85 is also my third (s38 and s62) ///Motorsports engine. The s38 was/is known for timing chain tensioner guide rail wear at about 80,000 to 100,000 miles. Not all s38s needed new chain tensioner guides. But, as an s38 owner, you have two choices: 1) replace the guides and timing chain as a maintenance item, or 2) wait for your chain to slip and face catastrophic failure. Personally, I went for a full rebuild (and stroker) as my preventative maintenance route.
My s62, I was tracking at 180,000 miles, on original VANOS and rod bearings. As was mentioned before, s62s had "issues" as well. My s62 was a healthy factory freak, while my s38 and s85 needed normal maintenance that is part and parcel to ///M ownership.
When the s62 was developed, ///M enthusiast b1tch3d and b1tch3d and moaned about the s62 "only" being an off-the-assembly-line modified m62 and not a hand built bespoke (s38) race engine. The next time around, ///Motorsport listened and gave us the bespoke s85: F1 inspired and exotic v10. Make no mistake, bespoke and high strung NA ///Motorsports engines require greater attention to detail and diligence.
Nothing has changed from the first m88/s38/s14 to the s85. ///Motorsport has always given us high maintenance engines.