Side steps, Running boards, Nerf bars etc. Aero or not?
 

I was doing a lot of reading on trailers and campers and the emphasis on good radius on edges all round was emphasized for both aero & crosswind stability, got me thinking about my vehicle shape.

The lower body between the wheels curves down from mid door to the underside, till it hits the sidesteps which result in a trapped wedge of air, the wheel guards stick out both front and back.

Now they can be handy if you are lowering skirts on the sides, but I don't intend to do that. They are Ally, so weight is not an issue and they do not protrude beyond the wheel guards, so no frontal area benefit. The only benefit they provide is step in convenience and some panel protection from stones coming off front wheels, I could deal with both of these issues though.

I did a bit of searching, although info was scant, some advised removal but no definitive data, just heresay, some say they help smooth airflow from wheels keeping side flow seperate, others say they are a drag.

The other thing I thought of is the discussions of high mpg concept vehicles and how high off the ground they are, if I removed the steps it would look more like that and in addition they exposed both above and below to the airflow, doubling effect.

So any idea, are they a benefit or a drag?

Bump,
No ideas, comments??

They add frontal area and certainly they aren't smoother, so I'll vote for them being an aero hindrance.

running boards
 

If they don't extend beyond the outside of the tire faces and have no flat plate end caps,front or rear,they may perform as a flow fence,helping the prevent comingling of air at different pressures or velocities which might induce some vorticity/turbulence.Roger Clark of GMC Truck Division may have commented on running boards in the Pop Sci Taurus/Silverado comparo.

Mine are integrated into the design and do not protrude beyond the tyres, the only thing was the way the body curves in creating a significant depression on the sides, just made me wonder if it was a source of turbulence.