Roof Rack and Gas Mileage

[jimmy z]

Will the addition of a roof rack (Yakima with deflector) affect the gas mileage of my auto? I know it may be a long shot of a question but I'm curious if anyone has compared the before and after fuel consumption.

I just bought a new ride that came with a roof rack which hasn't been installed yet. I'm trying to decide whether to use it or to make a hitch mount rack. The idea of a roof rack scares the hell out of me when it comes to pulling in the garage.

Thanks in advance....

[TimD]

Anything which adds aero drag, including driving with your windows open, is going to reduce your fuel mileage.

Note a hitch rack may increase your aero drag, depending on the shape of the rear of your vehicle and what measures the manufacturer has taken to reduce drag at the rear.

[jthurow]

Alex Wetmore over on the iBob noticed that the roof rack on his VW golf reduced gas mileage by a little less than 10% when there were no bikes on it but it reduced it 25% when one bike was on it.

jimi

[Ken Robb]

I read a report that said a deflector did nothing to reduce drag and that surprised me.

[Blue Jays]

The deflector likely did a great job of reducing perceived noise, though.
Interesting that it didn't benefit mileage too much, compared to a plain roof rack.

[Polyglot]

On my VW Passat station wagon, the cross pieces of the roof rack increase fuel consumption by about 5-8%, the cross members and bike or bikes increases it by about 10-15%. Strangely enough I have not noticed much difference whether I fit 1, 2 or three bikes on the roof. Luckily on the Passat, it takes less than 3 minutes to install or remove the roof rack, so I only run with it when I absolutely need it. For the rest it sits in my garage. BTW to fit one bike on the tailgate affected the fuel economy in virtually the same way.

[mistermo]

sorry, I don't know how to delete this post that I made in error.

[SoCalSteve]

Alex Wetmore over on the iBob noticed that the roof rack on his VW golf reduced gas mileage by a little less than 10% when there were no bikes on it but it reduced it 25% when one bike was on it.
jimi

And, if you use one of those bra protector thingies, the mileage goes down even more. Had this happen when I used 2 of these on 2 bikes on a roof rack on my wife's CRV. On a long freeway trip it made a huge difference (lower) in gas mileage.

Needless to say, on the way home we managed to fit both bikes in the car and never used the bra protector thingies again.

Your mileage may vary (pun intended). :banana:

Steve

[mtb_frk]

Sure it makes a difference, but does it look as cool without it? :banana:

[Onno]

I drove across the country 2 summers ago in my Passat with 3 bikes on the roof, and on average it reduced my mileage by about 25%. It felt very significant. Since I can get a continuous readout of mileage in the car, heading into the wind at about the speed limit I'd look down to see about 20 mpg a lot of the time. OUCH.

With 1 bike it's about 15%. In fact, if I had to do it again, I'd figure out a way to stuff the bikes in the back, and try to squeeze luggage in their too, with excess in the rocket box, which reduces mileage about 10-15%. Or I'd buy a hitch-mount, which has to effect mileage less!

[nikedunksb]

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[palincss]

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this handbags price is 179usd,hope can get some discount next time.

Serotta_Pete, your mailbox is full. More spam for the chopping block. Any other moderator able to axe this?

[Charles M]

depends on car and rack and I can't find the study, but I remember a range, averaged, of 7% decrease at highway speed. They used a test track in AZ and used two cars and two suv's...

The large air deflector actually harmed milage I believe. It created a far larger frontal area than the rails alone and harmed airflow over the vehicle as well.

[RPS]

Will the addition of a roof rack (Yakima with deflector) affect the gas mileage of my auto?Any drag will increase fuel consumption, but it will affect cars differently. Much depends on car size, engine size, gearing, aerodynamics, how fast you drive, etc…. It comes down to incremental required power caused by the bike(s) on the roof and the vehicle’s BSFC. Since you can’t know all this, you’d have to compare similar vehicles driven in a similar manner to get meaningful data.

When I drive my CR-V with a tandem on top I slow a bit to reduce vehicle drag enough to offset the bike’s added drag – unless I’m in a hurry. Even with the tandem on top, I still get better MPG than driving a larger van that fits the tandem inside.

[jimmy z]

Wow - great info from all...thanks!!!

I like the idea of being able to take the roof rack off when not needed but I don't think my rack can be removed as quick as mentioned in Polyglot's earlier post. Even if it's a 15 minute change...that would be the best way to go.

I didn't mention it in my original post but I have an 03 Jetta TDI. I would think the aero drag caused by a rack would affect a smaller car with limited power.

Thanks again,

Jim

[William]

I've got a rack on my cruiser and I don't really notice a difference in power or mileage. I think the air that gets deflected from the front of the vehicle and windshield sends it over the rack for the most part.

When bikes are mounted in the rack it's a whole different story. I can definitely feel the difference at speed and it's obviously affecting my mileage as well.





William

[Ray]

Nothing but trouble. In addition to the fuel consumption (which is pretty significant), keeping the bikes on the roof exposes them to bugs (unless you get that bra-protector thing which hurts mileage even more, as noted above), bad weather, theft when in a restaurant or staying in a hotel overnight, and garages, which are the WORST. And, perhaps, more important, all of those possibilities cause me to spend more time WORRYING about the bikes when traveling. Since I ran some bikes into a garage about ten years ago, I've never used a roof rack and I've made two car-buying decisions since with the expressed goal of being able to fit two bikes inside comfortably. Which is not all that hard to do if you're not focussed on performance cars (tough to get a bike in a Porsche). Much easier on the bikes and on my peace of mind.

-Ray

[dnades]

Saab 95 wagon with thule rear mount hitch rack. 3 bikes. Fully loaded down with camping gear. I get a 15% reduction in highway mileage. Usually get 32mpg with nothing in the car or attached. 27mpg loaded down with gear and bikes.

[Spinner]

after a trip about ten years ago with three bikes on the roof and an inconvenient hail storm. the sound of the hail stones (3/4 - 1 inch diameter) hitting the bikes was arrrggggggggg.

nonetheless, when using a roof rack on multiple road trips, i did experiment by wrapping the frame with plastic wrap or putting masking tape on the leading edges. both of these techniques did work to eliminate the bug problem.

i still wonder about the impact on bearings when you drive for extended periods in rain with the bikes on the roof. maintenance aside, it can't be good.

[William]

About 98% of the time my bikes ride in the vehicle. But when we go camping and bring the kids bikes along, bikes go up top and gear goes in the basket.



William

[RPS]

Nothing but trouble. In addition to the fuel consumption (which is pretty significant), keeping the bikes on the roof exposes them to bugs (unless you get that bra-protector thing which hurts mileage even more, as noted above), bad weather, theft when in a restaurant or staying in a hotel overnight, and garages, which are the WORST. And, perhaps, more important, all of those possibilities cause me to spend more time WORRYING about the bikes when traveling. Since I ran some bikes into a garage about ten years ago, I've never used a roof rack and I've made two car-buying decisions since with the expressed goal of being able to fit two bikes inside comfortably. Which is not all that hard to do if you're not focussed on performance cars (tough to get a bike in a Porsche). Much easier on the bikes and on my peace of mind.
-RayI agree that it’s nice to have the option to carry bikes inside. Making vehicle choices based on our cycling needs may seem a little over the top to some but personally I think it’s warranted if the compromises are not excessive.

In my case I gave up valuable storage space and angled the corner of a shelf to make it easier to swing a tandem in and out of the side door. I could have fabricated or bought a rack to carry the tandems behind the van (which I often do with single bikes) but on road trips I prefer to place bike(s) inside when I have room because I never know what kind of weather I might encounter. And as you say, they are more protected from theft and damage while inside. Either way -- whether inside or behind -- they don’t affect the van’s mileage so I don’t make the decision based on fuel economy.

[Ray]

I agree that it’s nice to have the option to carry bikes inside. Making vehicle choices based on our cycling needs may seem a little over the top to some but personally I think it’s warranted if the compromises are not excessive.
Yeah, I agree. But, other than just wanting a really high performance sports car, I think it usually doesn't involve a lot of compromise. Rather, it just narrows down the choice of vehicles. In the small, economy car world, there are a few that work well, a few that work less well, and some that don't work. So I chose from the ones that worked. For a family hauler, I'd look at a mini-van (even a really small one like the Mazda 5 rather than a sedan. But even most sedans can carry a bike in the trunk if you fold the rear seats forward. SUVs and full size mini-vans and full sized vans are easy. Pickups too if you get a removable cover for the payload area.

There will be times when you can't carry the bike(s) you want AND more than one other person simultaneously, but those usually aren't for riding-centered trips anyway. That's when a trunk mount strap-on rack is a good enough fall-back. And I don't take my nicest bikes on those trips anyway, so I don't worry a lot about them in transit.

-Ray

[harlond]

Wow - great info from all...thanks!!!

I like the idea of being able to take the roof rack off when not needed but I don't think my rack can be removed as quick as mentioned in Polyglot's earlier post. Even if it's a 15 minute change...that would be the best way to go.

I didn't mention it in my original post but I have an 03 Jetta TDI. I would think the aero drag caused by a rack would affect a smaller car with limited power.

Thanks again,

JimFWIW, my hitch rack takes one minute to put on or off. I had a roof rack before, but I much prefer the hitch rack, and gas mileage is only one reason.

[jimmy z]

FWIW, my hitch rack takes one minute to put on or off. I had a roof rack before, but I much prefer the hitch rack, and gas mileage is only one reason.

I have to agree with you....I think a hitch mount makes a lot more sense for me. I may use the parts (fork mounts and trays) from the roof rack to make a hitch mount rack. Another huge benefit...I can swap the hitch mount rack between my Jetta and my wife's SUV

[Elefantino]

I have four racks up top on the minivan.

It does hurt the mileage, but it makes it easy to spot my car in the parking lot.

[BumbleBeeDave]

Just too many friends I've seen who have used one and forgotten they had a bike up there, pulled into the garage, and WHAM! Several people at Serotta have told me that's their most frequent reason for frame repairs.

BBD

[torquer]

Making vehicle choices based on our cycling needs may seem a little over the top to some but personally I think it’s warranted if the compromises are not excessive.
Just for the sake of comparison, look at all the truck/SUV ads that boast how big a boat you can haul (or used to, anyway). How many time a year do you need to move a boat, anyhow?

[RPS]

Just for the sake of comparison, look at all the truck/SUV ads that boast how big a boat you can haul (or used to, anyway). How many time a year do you need to move a boat, anyhow?In fairness to them it’s a little different because on that one day that you need to pull that big boat out of the water you’d better have the right truck or you’ll end up looking silly. Or if pulling a small horse trailer that would be tough to pull with a Honda Fit. :rolleyes:

The thing with bikes is that we do have options so that we don’t have to end up driving a 6,000 pound truck or SUV all the time in order to have the capability to infrequently carry three or four bikes inside. With proper packing you can put four bikes in a minivan, or place them on a roof rack, or a hitch rack, or a combination of these, and still have space to haul the riders in a relatively small vehicle that won’t be wasteful the rest of the time.

In my case the van is already a 50% downsize of the vehicle it replaced so the fact that it can carry bikes inside or off the receivers is just a bonus. I was not trying to justify large vehicles in general, but rather vehicles that are just large enough to meet their intended use.

[Ray]

Or if pulling a small horse trailer that would be tough to pull with a Honda Fit. :rolleyes:
The Fit is remarkably spacious. I could probably get a horse in there. Couple of ponies, easy! :cool:

-Ray

[RPS]

The Fit is remarkably spacious. I could probably get a horse in there. Couple of ponies, easy! :cool:

-RayNot to change the subject, but on most of my regular rides I go by a miniature horse ranch where many of their horses would easily fit in your Fit.

OK, back to racks.

[WadePatton]

NOT directly on point, but to the issue of fuel consumption:

IN response to $5 per gallon fuel, I improved my fuel mileage 15% in daily driving and much more on the highway by simply reducing my "cruising speed". I was getting 17-18 and it jumped to 20-21 locally. The trip to Indy netted 22.5. That's over 100 "free" miles per tank.

Calculated figures-no guesstimations.

And that's not too shabby for a 7200# 4x4 pickup with redneck tires and over 200k on the mill.

Let me connect the dots. The less aero the shape-the easier to benefit from reducing drag-which is a function of the _square_ of velocity. IOW you don't have to slow down much to see benefits.

Bikes in the bedmo.

[RPS]

And that's not too shabby for a 7200# 4x4 pickup with redneck tires and over 200k on the mill.

Let me connect the dots. The less aero the shape-the easier to benefit from reducing drag-which is a function of the _square_ of velocity. IOW you don't have to slow down much to see benefits.Diesel?

[WadePatton]

of course, and

for the ultimate balance of efficiency and performance... :D

[torquer]

The thing with bikes is that we do have options so that we don’t have to end up driving a 6,000 pound truck or SUV all the time in order to have the capability to infrequently carry three or four bikes inside. ... I was not trying to justify large vehicles in general, but rather vehicles that are just large enough to meet their intended use.
Actually, that was my point: we require fewer transportation trade-offs accomodating our toys than most other folks, so no justifications are needed.

[Kervin]

I like the idea of being able to take the roof rack off when not needed but I don't think my rack can be removed as quick as mentioned in Polyglot's earlier post. Even if it's a 15 minute change...that would be the best way to go.

It takes a while to put it on the first time, but after a little pratice, I'm sure you could do it in less than 15 minutes.

[android]

Sure it makes a difference, but does it look as cool without it? :banana:

HA!! We set up my wife's blue WRX wagon the exact same way, backward rack and all. Hope we don't end up in the same parking lot!

[android]

Just too many friends I've seen who have used one and forgotten they had a bike up there, pulled into the garage, and WHAM! Several people at Serotta have told me that's their most frequent reason for frame repairs.

BBD

This is just dumb. People with RV's, campers, any kind of specialty truck all are capable of keeping track of what they're driving under and how tall their vehicle is.

If you have a remote, put it in the trunk when you put the bikes on the roof if you're a moron and don't think you'll remember. Very easy.

Better yet, fill your garage with bikes and scuba gear and park on the driveway.


On the PT Cruiser or WRX, we lose about 2 or 3 mpg with 2 bikes on the rack.
If we're expecting rain on the trip, I will remove the chain, put on seat covers and zip tie the crank arms to the chain stays to keep them from spinning.

Bugs wash off pretty easily if you get to them promptly after taking the bikes off the car.

With smaller cars, we can't really jam 3 people a 75lb standard poodle, 2 bikes and luggage *inside* the car for a trip. I'd prefer the daughter and poodle on the roof, but the wife says no.

[WadePatton]

This is just dumb...
aye, but common. My racing partner pulled under his carport with bike on rack after a long, brain-numbing event last year. The air in the fat tires and flexibility of his camper shell prevented damage to the frame. It was only a few inches too short.

Ask at the LBS 'bout how many times they hear the tale and see the destruction.