Mileage decrease with bikes on roof?
- Thread starter AaRoMo
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NeilBlanchard
Well-known member
If you are driving at highway speeds, this will have a very large effect. And even at lower speeds, it will have a noticeable effect. Bikes on a hitch rack behind the car would be much better.
SeanNelson
Well-known member
I can't tell you what the effect of roof-mounted bikes would be, but after doing the same 300km trip at the same speeds with and without a hitch-mounted rack with one bike on it I can tell you that it imposed about a 10-22% penalty (i.e., I used about 10 to 22% kWh more with the bike + rack installed). Higher speeds incur a higher penalty - my tests were done at speeds of up to 110 km/h. Efficiency started to drop rapidly around 90 to 100 km/h.
GetOffYourGas
Well-known member
Here's an article where they quantified some of these effects. It wasn't on a Bolt, but it should be very similar.
https://www.menshealth.com/technology-gear/a19482318/roof-racks-hurt-gas-mileage/
And in case you are wondering, they did put an inflated unicorn pool float through the wind tunnel.
https://www.menshealth.com/technology-gear/a19482318/roof-racks-hurt-gas-mileage/
And in case you are wondering, they did put an inflated unicorn pool float through the wind tunnel.
My experience with roof rack crossbars alone, when driving on a long flat bridge on a calm day with cruise control at 65mph:
* Yakima round bars or Thule rectangular bars with nothing (other cars): -8% or so
* Yakima aero bars (CoreBar) with nothing on them (Bolt): too small a difference to be noticeable on the kW use/regen display, though there is presumably some added drag
Obviously, rack accessories and cargo will add more aerodynamic drag compared to just the empty rack. For all of the cars/racks, I remove(d) the rack when not carrying things on it (even the aero bar setup on the Bolt, since the foam pads that I put the boat on are harder to remove and install on the bars than removing the rack from the car).
If you do not want to remove the rack when not carrying cargo, consider the following:
a. Choose an aero bar setup. For Yakima, the less expensive aero bar (CoreBar) does not cost any more than the round bar if you are buying new. Yakima also has a more expensive fancy aero bar (JetStream); Thule aero bars are the more expensive fancy kind. The Chevrolet OEM option is Thule; if there is a Chevrolet accessory sale, it may be less expensive than usual that way.
b. Choose a bicycle carrier accessory with the smallest frontal area.
* Yakima round bars or Thule rectangular bars with nothing (other cars): -8% or so
* Yakima aero bars (CoreBar) with nothing on them (Bolt): too small a difference to be noticeable on the kW use/regen display, though there is presumably some added drag
Obviously, rack accessories and cargo will add more aerodynamic drag compared to just the empty rack. For all of the cars/racks, I remove(d) the rack when not carrying things on it (even the aero bar setup on the Bolt, since the foam pads that I put the boat on are harder to remove and install on the bars than removing the rack from the car).
If you do not want to remove the rack when not carrying cargo, consider the following:
a. Choose an aero bar setup. For Yakima, the less expensive aero bar (CoreBar) does not cost any more than the round bar if you are buying new. Yakima also has a more expensive fancy aero bar (JetStream); Thule aero bars are the more expensive fancy kind. The Chevrolet OEM option is Thule; if there is a Chevrolet accessory sale, it may be less expensive than usual that way.
b. Choose a bicycle carrier accessory with the smallest frontal area.
Pigwich
Well-known member
I put a loaded Yakima sky box on my Bolt last year and did a 1200 Mile road trip. Most driving was at 70. Range dropped to about 160 miles. The difference speed makes gets a lot bigger, obviously.