25%

Mileage you lose w/roof rack, apparently.

Wonder how much with my bike sideways on a hitch rack?

There's some interesting info on this on the hypermiler sites. (People that are really into measuring fuel efficiency). Apparently if you drive a little gutless car the fuel efficiency is affected far more than if you drive a car with some power.

A guy with the same car I drive measured an 11mpg (37%) reduction in gas mileage with bikes on the roof.

Thus the reason I bought a hitch mount rack, which reportedly doesn't adversely affect mileage at all.

There's some interesting info on this on the hypermiler sites. (People that are really into measuring fuel efficiency). Apparently if you drive a little gutless car the fuel efficiency is affected far more than if you drive a car with some power.

Combustion engines have very defined power vs torque band. I bigger engine running in its optimum rpms
is far more efficient than running the snot out of a little engine.
For instance my my e250 ford pop top camper van gets better mileage than my buddies westy in the same circumstance.
My engine never breaks a sweat , his is bordering on overheating..

Combustion engines have very defined power vs torque band. I bigger engine running in its optimum rpms
is far more efficient than running the snot out of a little engine.
For instance my my e250 ford pop top camper van gets better mileage than my buddies westy in the same circumstance.
My engine never breaks a sweat , his is bordering on overheating..

I wish more people understood this. your over loaded and over worked mini van is not better on fuel then a vehicle designed to do the heavy lifting. that being said a four cylinder pavement ripper with bikes on the roof kicks the shit out of a half ton truck with bikes in the back when it comes to fuel economy. tryed and tested. wagons for the win though when it comes to road trips. bikes inside when your covering miles at high speed.

I wish more people understood this. your over loaded and over worked mini van is not better on fuel then a vehicle designed to do the heavy lifting. that being said a four cylinder pavement ripper with bikes on the roof kicks the shit out of a half ton truck with bikes in the back when it comes to fuel economy. tryed and tested. wagons for the win though when it comes to road trips. bikes inside when your covering miles at high speed.

My 6.2litre gets really good highway mileage. But, city is rough. There is an upside to both.

My bikes are on Ns Rack .
I can sleep 4, cook, shower,poop, (xxx)etc in my ½ ton westy style camper van making mileage irrelevant . Hotels and motels are far more expensive than gas:)

My bikes are on Ns Rack .
I can sleep 4, cook, shower,poop, (xxx)etc in my ½ ton westy style camper van making mileage irrelevant . Hotels and motels are far more expensive than gas:)

Bingo.

I wouldn't argue, self contained units are sweet, hell there is a whole thread about that. but I don't mind sleeping beside my car on a random bush road.

I wish more people understood this. your over loaded and over worked mini van is not better on fuel then a vehicle designed to do the heavy lifting. that being said a four cylinder pavement ripper with bikes on the roof kicks the shit out of a half ton truck with bikes in the back when it comes to fuel economy. tryed and tested. wagons for the win though when it comes to road trips. bikes inside when your covering miles at high speed.

Interesting thread. And yes, bigger engines can be more efficient given the right operating environment - as well as better in the long haul (no pun intended) when it comes to maintenance and servicing over that of a smaller, for instance turbo or super-charged, engine grinding out the same HP and torque with less displacement.

But to the OP, I've said it to so many friends, it's not just bikes - depending on the vehicle's design level and engineering (or lack thereof), even having the windows open for a fun summer blast can create enough drag to have a noted effect on mileage (Bernoulli's Principle). So it goes.

Cool thread.

There's some interesting info on this on the hypermiler sites. (People that are really into measuring fuel efficiency). Apparently if you drive a little gutless car the fuel efficiency is affected far more than if you drive a car with some power.

A guy with the same car I drive measured an 11mpg (37%) reduction in gas mileage with bikes on the roof.

Thus the reason I bought a hitch mount rack, which reportedly doesn't adversely affect mileage at all.

Seems about right. Drove to Marin County last summer with the two bikes on the roof. On the I5 south of Eugene coming home felt like I was driving with an anchor dragging behind the car. Probably cost me 150-200 bux extra on that trip I estimated.

I only really notice the difference on the big straight highway drives. Like the I5 and the Coq where there may be a headwind. Windy Highways not so much

What about Canopys on the back of a truck compared to not?

My understanding is canopies do not offer as much of a benefit as you would think, but are marginally better than an open bed.

Essentially an open truck bed "collects" a mass of air behind the cab which lets the air coming off the cab smoothly reintegrate just behind the tailgate.

When you put a canopy on, you essentially create a giant low pressure area behind the truck which increases drag.

Best solution is a tonneau cover, but it's obviously hard to fit bikes under there.

I did a bunch of reading on this when I had a pickup. Can't find all the articles, but here's one about how aerodynamics work on a pickup.

http://www.nrc-cnrc.gc.ca/eng/achievements/highlights/2007/tailgate_down_myth.html

Interesting article, thanks for posting.

I've got a little 4 banger (2005 Mazda 3 hatchback, 2.3L engine) with 2x Thule sidearms on the roof, one of which is replaced by a ski rack in the winter. I've definitely noticed an impact on MPG, even without bikes/skis but haven't measured it accurately. Probably on the order of 5-10% empty and 20% with two bikes when driving 120km/h with the engine around 3,000rpm in 5th. The car has 190k km on it so it's been losing fuel efficiency due to age as well.

Since I take public transit to work and don't really drive the car during the week I'm not really bothered by it. If I was doing a big road-trip without bikes I would probably remove the racks since it only takes 5 minutes.

Next vehicle/rack will be hitch mounted, not just because of fuel efficiency but because I want to be able to transport 4 bikes.

For those that are curious the Rocky Sprinter, a 3500 170 extended model, has about 90,000kms on it after 2 years and the average economy is around 11.5L/100km. The van is mostly always fully loaded up with 20+ bikes, tents, demo gear, etc.

I did a weekend demo to Nelson and Rossland and back, fully loaded over the Crow's Nest pass[HTML_REMOVED] and maintained 11.5 while mashing the pedal and pulling up hills with only the factory speed limiter (140ish?) stopping us from going faster.

The maintenance fees have been pretty minimal on the van as well. Tires and brakes.