Balancing Aero and Unsprung Mass

[squriellord]

A challenging question: When replacing OEM wheels, how do you balance aerodynamics versus reducing unsprung mass?

The issue, as it is, it that many aftermarket rims look very nice but my understanding is that their thin spokes and larger diameters do not promote great airflow around the wheel well, with exposed areas creating turbulence as the wheel rotates.

This is partially alleviated by shopping for a diameter the same as stock but selection is more limited. (maybe could even re-use my functional tires...)

Hybrid's, cars generally more optimized for better aero by the factory, have rims which may be light, but generally leave little 'open' area, such as the Honda Insight and mid-2000's Civic Hybrid, which I assume a flat rotating rim with few openings=more aerodynamic than an open rotating rim with many openings. Even the Prius's wheels have funy aero bends near the lip despite their more conventional appearance.

My real issue is that my current vehicle for the foreseeable future uses 5x114 and 70.2mm bore. Aero rims I've looked at such as the Honda Civic Hybrid's (which are 5x114 but must be bored out) do not weigh significantly less than my stock alloys but would provide better aero.

Dredging google has brought up the Civic Aero rims as about 16lbs, while my stock weight somewhere around 19lbs I think.

Yet at the same time, if I'm going to bore rims to fit my hub, why not go for really lightweight stuff? I can get 5x114 15'' rota slipstreams which weigh <13lbs but due to their open design would suffer from worse aero. There were articles on the benefits of torque and lightweight rims but that was more for drag racing, not FE.

In terms of cost, its only a little more expensive for the Civic aero rims than ultra-light 15'' 5x114 aftermarkets by various companies.

Anyone have any advice?

-Squriellord

[jdgFirefly]

Buy the light rims and buy or make aero hub caps, best of both worlds

If its one or the other than it depends on where or how you drive. lighter is better for acceleration aero is becomes more significant at higher speeds like on the highway.

The gains for aero hubcaps has been tested by people on this site. Lighter rims however is harder to quantify because it totally depends on how much time is spent accelerating

[Bicycle Bob]

Lighter wheels are also a boon to rolling resistance on bumps, so they matter more if you tend to replace shocks often in your area.