Mountain Bike Reviews Forum banner
1 - 11 of 11 Posts

·
parenting for gnarness
Joined
·
6,251 Posts
Discussion Starter · #1 ·
I recently got a Yakima HoldUp, and had hitches installed on my 2 small cars. The hitches weigh about 30lbs each, the rack about 50. On the car I drive most often, I've noticed my recent mileage improved by 1-1.5 mpg. No other changes to my normal maintenance, fuel choices, driving style, A/C etc and its almost always just me in the car. I've probably gone through 3 tanks since I got the rack, and its no fluke! The rack has been on the car ~30% of the time (folded up = no drag), the bike maybe 10%. Obviously the weight and drag from the bike will hurt mileage, but, is it possible that the weight of the rack and hitch is serving to hold the backend of the car down and improve mileage? The car is an Acura TSX (nee Honda Accord) and its been pretty consistent at ~26 mpg for 3 years.

My other car is a Prius (wife's car), but I don't drive it enough under consistent conditions to have established any patterns - every time I've driven it, its had the bike on it, and often more people in the car. My wife drives it a lot and carpools in it so no data there is consistent.

:confused:

fwiw, i've driven my truck about 6 miles in the past month since I got the new rack. thinking of putting it up on blocks, so i can really embrace my white trash roots. :p
 

·
Registered
Joined
·
1,901 Posts
That's surprising, and kinda counter-intuitive.

Reminds me of the an episode of Mythbusters, where they debunked the myth that leaving the tailgate down on a pick-em-up truck improves gas mileage. They concluded that the with the tailgate up, a high pressure bubble is created behind cab and this forces the turbulance over the length of the truck. They theorized that with the tailgate down the turbulance landed on the bed of the truck, where the down pressure created drag. I've only seen this episode once, so maybe what they debunked was reestablished.

Confused? Yeah me too; its just part of living in a U2metoo world.
 

·
Registered
Joined
·
159 Posts
sounds counter-intuitive. If more weight in the back helps, then take the rack off and load your trunk with 50lb of cinder blocks. :) Sounds weird that additional weight would help aerodynamics though.

-Kevin
 

·
PMP,TAN,LAUNDRY
Joined
·
4,344 Posts
Not sure about mileage but my truck definitely handles better with my Thule hitch rack especially in windy conditions. I've heard people tell me to throw sandbags in the back of my truck when driving on ice for better traction, bricks would do the same thing.
 

·
just 1 more
Joined
·
1,153 Posts
u2metoo said:
That's surprising, and kinda counter-intuitive.

Reminds me of the an episode of Mythbusters, where they debunked the myth that leaving the tailgate down on a pick-em-up truck improves gas mileage. They concluded that the with the tailgate up, a high pressure bubble is created behind cab and this forces the turbulance over the length of the truck. They theorized that with the tailgate down the turbulance landed on the bed of the truck, where the down pressure created drag. I've only seen this episode once, so maybe what they debunked was reestablished.

Confused? Yeah me too; its just part of living in a U2metoo world.
They just revisited that myth and this time used a flowmeter in the gas line. Best mileage was with one of those tailgate net things. Next best 2 were tailgate up and bedcover. Worst was tailgate down and tailgate off.
 

·
Elitest thrill junkie
Joined
·
39,565 Posts
It is possible that a rear rack could be serving somewhat as a vortex-generator and inducing more turbulent flow at the rear of a vehicle, this may help to fight the seperation of airflow that often happens near the rear of vehicles. Laminar flow is the least amount of drag, but usually only occurs at the beginning of an object, and as the air flows around it, it transitions to a more turbulent flow, and then when you have objects with sharp corners (like at the rear) you get seperated flow, which has the highest drag of all.

But, it's still a stretch. Not going to say it's impossible, but it's probably more likely that the heat+humidity is decreasing the usefull power of your car, and your accelerations and such take a little longer, and burn a little less fuel, as is typical in the summer. The influx of humidity would increase that effect.
 

·
parenting for gnarness
Joined
·
6,251 Posts
Discussion Starter · #10 ·
hmmm...wheelbender6 and Jayem's ideas of slower acceleration make the most sense. I do drive more gently on surface streets where i might otherwise be burning a lot w. acceleration. thanks y'all!
 

·
Sup?
Joined
·
639 Posts
not driving like a bat out of hell is probably it.. If I keep my foot out
of it (Honda Element) and drive like Grandma going to church on
Sunday AM I get *WAY* better mileage. Problem is, I cant
really stand to drive this way.

I've noticed that more folks are slowing down a bit around town
(taking off from lights, etc:) these days.
 
1 - 11 of 11 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top