heckler
July 24th, 2009, 11:32 AM
I used to use roof mounted racks for my bikes all the time. I noticed a real drop in gas milage when they were up there- worse with the bikes, not surprisingly.
Two things changed. I got into kayaking, which meant different racks on the roof at different times, and my commute stretched to about 40 miles each way. I decided to ditch the roof bike rack and get a hitch rack. I figured if it were out of the wind, how could it mess with milage.
Well, it does, hence the question!
With the rack installed, even without bikes, I see 1-2 mpg drop. With bikes it gets worse. Worst case so far has been one bike way on the back (of a 4 bike rack). Quick highway speeds and I dropped almost 5 mpg!
Any aerodynamicists out there? As a roadie I understand drafting, both in first and second position. Both riders benefit- the lead rider by the wind not whirling back in behind him essentially causing suction. Does it makes sense that the same thing could be going on with the bikes out back of the car? The further back, the more the slipstream would be messed with?
Just curious.
Two things changed. I got into kayaking, which meant different racks on the roof at different times, and my commute stretched to about 40 miles each way. I decided to ditch the roof bike rack and get a hitch rack. I figured if it were out of the wind, how could it mess with milage.
Well, it does, hence the question!
With the rack installed, even without bikes, I see 1-2 mpg drop. With bikes it gets worse. Worst case so far has been one bike way on the back (of a 4 bike rack). Quick highway speeds and I dropped almost 5 mpg!
Any aerodynamicists out there? As a roadie I understand drafting, both in first and second position. Both riders benefit- the lead rider by the wind not whirling back in behind him essentially causing suction. Does it makes sense that the same thing could be going on with the bikes out back of the car? The further back, the more the slipstream would be messed with?
Just curious.