Well, in fairness, failure of either/ or is timing related anyway, and both result in disaster .
One thing about those pads : the bottom wears out at approximately 2 X the rate of the top ( I still can’t grasp the logic to that, but it’s a well documented fact and very consistently so ..) . The problem is you can’t really see it, unless you remove the variocam assembly, even if you stick a small telescopic mirror in there you won’t have a sufficient view. And I don’t mean to scare anyone here, as either timing belts or variocam pads failures are relatively rare but if and when they happen you’re looking at $ 7,000 - $ 8,000 repair bill, unless you’re a DIY-er, in which case it’ll still be a few thousands. So if you see the top pad with just light traces of the chain tracks on it, and maybe no more than 1mm or so grooves, and also if there are no cracks on the surface , no dryness .. you’re probably fine, but if you have deep grooves on the top and they look brittle or have even hairline cracks, your bottom are near the impending doom category . IMO .
