ZOEPER: Why? Because you didn't ask before you took it appart.
I also bet you never looked at the owners manual for any "be carefuls" either. Although to be fair, I haven't seen many warnings about issues like this in ANY owners manuals. If you're like some folks I've seen, I suspect you may have torn into it like a kid ripping open Christmas presents and may have screwed up more stuff than you even suspect as a result.
The OD chevrons orient the bearings so that if the faces that have been offset ground for preload, they are properly oriented at installation. If some hack did the offset grinding and didn't mark the chevrons, your guess is as good as any as to the proper assembly procedure. You have a 1 in 3 chance of installing them properly if you blindly guess at the procedure.
Roundess and eccentricity are NOT the same thing. A wheel can be perfectly round but if the hole that mounts on the rim to the spindle pin is off-center, it will rotate in an eccentric manner. All the balancing in the world won't fix it either.
In the days of less than concentric raceways to OD/s and ID/s, the chevrons and 'pip' marks on the inner race sides denoted the eccentricity high points. By mounting the spindle bore eccetricity high point opposite the bearing eccentricity high points, you could minimize the amount or even the need to grind the ID after installing bearings to bring the ID concentric to the axis of rotation established by the ball paths.  |