tire width vs. drag (Cd)

[ngrimm]

If I have two bicycles with the same tread but one with wide tires and the other with narrow tires, would doing a coast down comparison be a fair test of the theory?

[aerohead]

Originally Posted by ngrimm

If I have two bicycles with the same tread but one with wide tires and the other with narrow tires, would doing a coast down comparison be a fair test of the theory?

My opinion is that it would take a wind tunnel with extremely accurate load cells to be able to pull out the difference.Your own body is the largest drag contributor and its interference drag would play into at least the drag of the rear tire.
Technically however,the narrow tire would tunnel out with the lower CdA.

[tjts1]

There are several MB models where they specify different CD numbers for the base skinny tire version vs the optioned up big engine big tire version.
C220 coupe 0.24
C350 coupe 0.27

[aerohead]

Originally Posted by tjts1

There are several MB models where they specify different CD numbers for the base skinny tire version vs the optioned up big engine big tire version.
C220 coupe 0.24
C350 coupe 0.27

Yeah,my CRX was that way.Porsche 911s ditto.Trans Am Firebird.
One caveat.The wider tire may get it flush with the flanks of the car,reducing some turbulence,buying back some gain over the increase in frontal area.

[trooper Tdiesel]

comparing 33"X12.50X15 to 33"X9.50X15 tires on a older SUV with about 100hp.
the tires had the same tred lay out, and where very aggressive about 20/32" of tread.

there was on average a 3 mpg difference


0.01C