Wednesday, February 16, 2011

What Is OCR And Why Is It Good For Me?

"OCR" stands for Off Center Rim. Velocity produces an OCR version of its Aerohead clincher rim to help wheelbuiders fabricate a stronger rear wheel.
The main culprit for this OCR necessity is Campagnolo as the large amount of real estate their 11sp cassette bodies inhabit within the dimensions of 130mm wide rear hub results in a typically weak bracing angle. WTF is a bracing angle you ask? Picture a triangle with its pointy end being where the spokes meet the rim and the base being where the spokes meet the drive and non-drive side hub flanges respectively. You want that top point to be as centered as possible above the two lower points that form the base.
Campagnolo's drive-side center to flange spacing is very tight on most standard hubsets so what Velocity does is displace to the left their rim on its intended drive side by 4mm. This effectively balances out the pointy part of the triangle more over the center of its base. Take a close look at most rear Campagnolo low profile wheels and you'll notice most employ OCR technology.
Front wheels have no "dishing" ie: the center to flange measurement is equal on both sides of the hub and the rims effectively lives in the middle around it ie: perfect triangle. Ergo, front wheels are almost always more stable (all thing remaining equal).
White Industries labels only their rear for-Campagnolo hubs "H3". Their front road hub and rear-Shimano hubs remain labeled "H2" being their first production model with this hub shell design.
This wheelset is for a light rider so I designed it with a 24/28 spoke count and alloy nipples throughout. I also took some extra steps to ensure the wheel's longevity but those secrets stay here. No soup for you!
Velocity does a fantastic job machining their braking surface as you can see here. Their one claim to disdain is that they "pin" not "weld" their rims together but honestly I've yet to come across a Velocity Rim that was not workable or had a flat spot and the seam so great that I could not bring to round.
These wheels are certainly lightweight and pretty but most importantly they will last an eternity and should require only a minimal amount of maintenance.

A Luxe Wheelworks Production-

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