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  1. #1
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    mileage with bike on top vs. inside

    I took my Matrix "04 SRX up to Mammoth in Sept. with road bike on top and the mt. bike inside. I figured that the skinny profile wouldn't effect the areo to much.

    I got onlly 30 mpg on the way up, same as my BMW 3 series with roof racks
    so on the way back via Yosemite and Fresno, I put both bikes inside but left the rack on.
    I got 42 mpg from Mammoth to Fresno. I didn't really think that the one bike on top would effect my mileage that much! Now my rack are for looks only, bikes are always carried inside.

  2. #2
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    That's the Ticket!!!!!!!
    mountain biking is not a crime, so quit giving me dirty looks before I bunnyhop your car

  3. #3
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    Is one way up hill and other down hill? I know i see a big difference when i go up to winter park and when i come back down.

  4. #4
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    I took a different route back, but it still had probably 100 miles of additional steep uphill. its really not a fair mileage test but for that much difference in miles per gallon i was surprized

  5. #5
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    I am going to go out on a limb and say that NO WAY was there that much difference in milage just from the bike.
    Is one way up hill and other down hill? I know i see a big difference when i go up to winter park and when i come back down.
    going to winter park and back for my explorer might change gas milage from 20 mpg down to 16 going up. That is a 20% decrease.
    Besides gravity, milage decreases at higher elevations also.

    A bike has nowhere the resistance that gravity does when climbing up into the mountains, and yet the difference in milage from 42 to 30 is about 29% decrease. I would suspect that of that 29%, 26% was due to gravity and elevation differences, and the other 3% due to wind resistance (and maybe some other unknown factor having an effect).

  6. #6
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    Quote Originally Posted by nagatahawk
    Now my rack are for looks only, bikes are always carried inside.
    If you really want the best mpg, ditch the rack completely. My racks are never on any of my vehicles, unless needed. I'm a cheap SOB, and I want the best mpg I can get.

  7. #7
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    Quote Originally Posted by crashtestdummy
    If you really want the best mpg, ditch the rack completely. My racks are never on any of my vehicles, unless needed. I'm a cheap SOB, and I want the best mpg I can get.
    I may leave the rack on because I like the way the car looks with them up. Most of my daily driving is inner city, but I will probably remove them for any highway long runs.

    smilinsteve,
    your probably right Like I said this was really not a fair or scientic test,
    because I took al totally different route back. there was a lot of low gear climbing up to 7000 feet going thru Yosemite. but the thing is I still got 42 mpg and the bikes were inside! I the car is rated at 31 mpg on the highway, so I'm happy.

  8. #8
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    When I used to drive for the GT Cycling team we had a VW Passat wagon (1.8T) that would get 30 mpg with nothing on the top and 4 guys inside, but would only return about 20 mpg with 4 bikes on top.

  9. #9
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    throughout all vehicles and roof racks that i have owned:

    '92 v6 camry - 32mpg w/o bike...28 w/bike...approx 12% difference in mpg...
    '96 4cly camry - 34mpg w/o bike...28 w/bike...approx 17% difference in mpg...
    '99 volvo awd wagon - 27mpg w/o bike...24w/bike...approx 11% difference in mpg...

    keep in mind that i run a fairing with two fork mount racks...generally hauling one 22" kona coiler deelux and sometimes paired with a med wsd cannondale...

    i did this summer haul two bikes on top and w/two bikes on a trunk rack hangin on my hatch, four dudes and four dudes' gear for four days for 900mi round trip...prairie-mountain-prairie terrain...average 22.9mpg during the trip...not bad for a 140k mile old volvo v70...!!!

    assuming one were to average out my roof rack w/bike change in mileage i only paid an add'l $15 round trip when haulin my buds and our bikes for 900+miles...ultimately well worth the 15 bones for the convenience to store crap within the confines of the wagon...
    Bikes + Wedding = Less Bikes

  10. #10
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    I didn't get any worse or better with the racks and bike on top of my '05 BM\W 328.

    On my Matrix SRX there is no bottom end and mid. I have the rev the crap out of the motor to get the car up to speed. Although the motor is rated at 175hp at 8,2000 rpm. and it doesn;t really come in until around 6'000 rpm. I believe the torque is rated around 140 at 6000 or 7000, not a good torgue curve application for hauling bikes.
    the wind really affects the mileage of this car because of the low torgue.

    I'm thinking a '10 Subaru Outback non turbo 4 cyl. with 6 sp manual with 8 inches of ground clearance may be a better choice! And with the bikes inside! that or a VW Jetta wagon TDI. I'm always dreaming my next car, and bike even after I get the next one!

  11. #11
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    +1 TDI wagon

  12. #12
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    subie outback baja was on my list prior to the volva...

    so was the mazda 6 wagon, jetta tdi, passat w8, audi a6, audi all-road, and subie forester...volva won b/c of locale...
    Bikes + Wedding = Less Bikes

  13. #13
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    If you try to squeeze out every last mile per gallon and never exceed 65 or accelerate too fast, you might not see a HUGE difference with a rack, but you will still see a difference. Lots of people claim they can drive in this way, and for very short periods of time they usually can, but it usually flies out the window pretty fast under real-world conditions/driving habits.

    Bottom line, it's a lot of drag and the faster you go, the more drag it is. Some vehicles suck to start with and are like pushing a brick through the air, so if you get 22mpg to start with you may only see it move down to 19-18 or something, whereas if you get 35mpg you might see it move down to the twenties. It's also not just the frontal area of the bike causing drag, there's profile drag, interference drag and seperation-drag from sharp corners. Bottom line is that it's a lot of parasite drag and parasite drag increases as a function of velocity squared. Twice as fast = 4x the drag. This is going to cause a difference.

    I've done the math and my T2 has more than paid for itself. Factor in the fact that you usually don't remove a roof rack so it's costing you some money all the time (if you drive faster than 45mph) and the roof rack continues to cost you more money, whereas the hitch pays for itself in terms of the dollar difference. I can't really understand how someone would "like" the look of a roof-rack, but by all means put a roof-rack on there, a luggage-rack on the trunk, etc, but I can't see any reason to mess up the clean lines of a car with something that's going to add drag. About the only thing I'd ever want on top of my car is one of those aero-boxes for moving stuff across the country, but a lot of people around here don't take those off either.

    I think back in the day the only realistic choice was a roof rack. Only the roof racks had decent security in terms of the bike staying in one place while driving (not swinging) and the hitch-racks were ones where the bikes "hung" from the top, they weren't even that easy to "tilt" for hatch access. Now things are different with all the great hitch-racks on the market. I can't even imagine lifting my bike up to the top of my car, it would get old and dumb real fast. It's probably worse having a car that has some guts because then with the bikes on top you can still go fast, but you wouldn't believe the fuel consumption at those speeds (due to the drag).
    "It's only when you stand over it, you know, when you physically stand over the bike, that then you say 'hey, I don't have much stand over height', you know"-T. Ellsworth

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  14. #14
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    I get 70 MPG with the bike on the inside on highway trips.

  15. #15
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    There is no way that the mileage difference is that much between bike on car and off.

    I routinely drive between the Rockies (Vail) and Minneapolis. I usually get much, much better mileage on the way back. It's simple - Vail is at 8000' and Mpls is at 1000'. You have to lift all that mass 7000' up hill on the way out and you get it all back on the way back.

    I have a local route I drive all the time with and without bikes. On my BMW 530XIT wagon when I average it out, the difference is about 2mpg.

    J.

  16. #16
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    Put 5 bikes on the roof of your wagon and put the cruise control at 70 mph and you'll notice a lot more than 2 mpg.

  17. #17
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    Quote Originally Posted by Jayem


    I've done the math and my T2 has more than paid for itself. Factor in the fact that you usually don't remove a roof rack so it's costing you some money all the time (if you drive faster than 45mph) and the roof rack continues to cost you more money, whereas the hitch pays for itself in terms of the dollar difference. I can't really understand how someone would "like" the look of a roof-rack, but by all means put a roof-rack on there, a luggage-rack on the trunk, etc, but I can't see any reason to mess up the clean lines of a car with something that's going to add drag. About the only thing I'd ever want on top of my car is one of those aero-boxes for moving stuff across the country, but a lot of people around here don't take those off either.

    I think back in the day the only realistic choice was a roof rack. Only the roof racks had decent security in terms of the bike staying in one place while driving (not swinging) and the hitch-racks were ones where the bikes "hung" from the top, they weren't even that easy to "tilt" for hatch access. Now things are different with all the great hitch-racks on the market. I can't even imagine lifting my bike up to the top of my car, it would get old and dumb real fast. It's probably worse having a car that has some guts because then with the bikes on top you can still go fast, but you wouldn't believe the fuel consumption at those speeds (due to the drag).
    I usually keep the speed down around 65 on the Matrix. the car seems to like this speed better probably because of the low torque motor.

    The top mount is not my ideal set up, but I had the racks left over from my BMW sedan. so I transfered the trays over and traded in the racks at my local bike rack shop. This set up fit my budget at that time. My first bike weighed in at 21lbs wheel off, so lifing it up was no chore. My current 33 lb. with 20mm wheel on is a bear to lift up but with a small stool it's manageable.

    I normally drive in town during the week so my speed are way below 45 mph. Further, I do like the look, otherwise my Matrix would look like all the other gunmetal grey Matrixs running around. I have a Gary Fisher sticker on the air foil which looks cool. My tribute to the founding father of Mt. bikes. Yes my next car may have a hitch mount. Although they don't look as cool. just kidding!

    Then again I may not use racks at all and continue to transport inside out of site. I have cablelock and u lock to secure the bikes inside.

  18. #18
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    Put 5 bikes on the roof of your wagon and put the cruise control at 70 mph and you'll notice a lot more than 2 mpg.
    Nope.

    Did just that (4 bikes though) with my wife's volvo XC90 back and forth to CO. Mileage difference was between 2 and 3mpg difference than when we drive out there smooth.

    And that was driving faster than 70mph - heck, the speed limits in places is 75.

    J.

  19. #19
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    I found this test someone did:

    The (not very rigorous) test: "A-B-C" ...

    I did these roof rack runs as part of the warm-up for last year's side mirrors experiment.



    The comparison was between:


    A - no roof racks

    B - empty roof racks

    C - a mountain bike on the roof racks

    It should be said this wasn't a rigorous test. I only did one bi-directional run for each of the B and C conditions. So, while the results were dramatic, you'll have to take them with a grain of salt large enough to require roof-top transport.

    Conditions ...


    Air Temperature (ATMP).. 67.6 F / 19.8 C; Aug 23/06; 7:30 - 8:30 PMWind Direction (WDIR)... N ( 0 deg true )Wind Speed (WSPD)....... 6 kts (11.1 km/h / 6.9 mph)Wind Gust (GST)......... 7 kts (13.0 km/h / 8.1 mph)Pressure (IN) .......... 30.01
    Results ...

    @ 88 km/h (54.7 mph)

    A = no roof racks
    B = empty roof racks
    C = mountain bike in roof racks

    A/B/C ... West ... East ... Average MPG (US) / L/100 km / MPG (imperial)

    A ..... 55.0 ... 55.3 ... 55.2 / 4.26 / 66.29
    A ..... 55.5 ... 55.5 ... 55.5 / 4.24 / 66.65
    A ..... 54.8 ... 55.3 ... 55.0 / 4.28 / 66.05
    B ..... 49.3 ... 47.3 ... 48.2 / 4.88 / 57.89
    C ..... 40.2 ... 40.0 ... 40.1 / 5.87 / 48.16




    Average of all 'A' runs: 55.24 mpg (US)


    Just adding (empty) roof racks reduced fuel economy to 48.2 mpg (US), or -7.0 mpg / -12.7%.


    Putting the mountain bike on the rack absolutely destroyed the mileage! Down to 40.1 mpg (US), or -15.1 mpg / -27.3%

    http://metrompg.com/posts/roof-racks.htm

  20. #20
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    Quote Originally Posted by smilinsteve






    Average of all 'A' runs: 55.24 mpg (US)


    Just adding (empty) roof racks reduced fuel economy to 48.2 mpg (US), or -7.0 mpg / -12.7%.


    Putting the mountain bike on the rack absolutely destroyed the mileage! Down to 40.1 mpg (US), or -15.1 mpg / -27.3%

    http://metrompg.com/posts/roof-racks.htm
    Makes sense, logically and from a physics point of view. Unfortunately, arguing about mpg is an exercise in futility. There are very few drivers that accurately record gas usage and miles driven.

  21. #21
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    On the original post, Fresno, CA is at 296ft elevation. Mammoth is at around 8000'. It's all downhill from Mammoth to Fresno. That will have a huge impact on the mileage. You want to know what it is supposed to be you need to make sure that you drive both ways at the same speed with the same configuration and average the two and account for any surface wind difference.

    J.

  22. #22
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    your right, I left mammoth at around 7000 feet dropped down then went 50 miles north to Yosemite, climbed up into the Tioga pass at around 7000 feet then dropped back to Freso. I was just sharing my extreme mileage with you good folks. No this was not a scientifice mileage run. Even so, the bikes were inside and I achieved 42mpg, my highest ever! I will try it again next summer, LA to Mammoth with bikes inside and no racks on top. But I like the look, it keeps me from looking like a soccer mom type car.

  23. #23
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    Quote Originally Posted by nagatahawk
    your right, I left mammoth at around 7000 feet dropped down then went 50 miles north to Yosemite, climbed up into the Tioga pass at around 7000 feet then dropped back to Freso. I was just sharing my extreme mileage with you good folks. No this was not a scientifice mileage run. Even so, the bikes were inside and I achieved 42mpg, my highest ever! I will try it again next summer, LA to Mammoth with bikes inside and no racks on top. But I like the look, it keeps me from looking like a soccer mom type car.
    Well, here's the thing - I get that kind of mileage from my wife's SUV driving from Vail to Denver. Going the other way it's a whole different deal. Literally driving from Denver to Vail is 3/4 a tank of gas. Going from Vail to Denver is 1/4 tank of gas. Has nothing to do with the bikes at that point. Has everything to do with basically being able to coast downhill for 120 miles.

    That all said, my son and I just did a swing of colleges for his college visits. We had two mountain bikes on top so we could do some riding in some interesting places. We drove about 750 miles over a weekend (all in the midwest) and got pretty close to 3mpg less on my BMW wagon - 22mpg vs 25mpg or about a 12% decrease in gas mileage. Not a big deal. That, for what it's worth, about matches the same drop on the Volvo SUV. All that driving was done at around 70mph.

    J.

  24. #24
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    In my '05 Honda CR-V Manual tranny, if I drive my daily "normal" driving (combination of City and Highway) I get about 24 mpg on average. If I do this with my Yakima Roof Rack with 2 mounts on, that drops my mileage by about 1-1/2 mpg pretty consistently. If I drive 65-ish with 2 bikes on the roof, I am pretty lucky to break 21 mpg. If I drive over 75 with 2 bikes it is more like about 19 mpg. Normal "clean roof" driving on a road trip at the 75 range will get me about 23 - 24 depending on hills, etc... Strangely enough, the best MPG I have ever gotten for distance in that vehicle was about 27 driving from Scottsdale to the Bay Area with a Thule Atlantis 1800 cargo carrier on the rack. Held a steady 65 - 68 mph all the way, rockin' the tunes and being mellow. Me, one other person, 3 bikes inside and a lot of other people's gear in the car and rooftop case.

    I keep the bikes inside for security and bike protection as much for aerodynamics. Bikes in a 70 mph stream of bug-filled and sometimes rain-filled air, can require a lot more cleaning and maintenance. Especially in STI road levers, etc... Inside they are safe from all of that and won't get accidentally driven into a parking structure, or creamed if you get rear-ended, etc...
    R.I.P. Corky 10/97-4/09
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  25. #25
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    No good My Civic sucks gas with bikes on top!! 33 down to 22

    My Civic gets 33mpg back and forth to work, 20 mile mix of some city, mostly freeway.

    We went camping with 2 bikes on top, full trunk and ice big ice chest in the back, and the mileage plummeted to 22mpg trying to go 80mph on the freeway from Arizona to New Mexico and back.

    We now have an Element and put 2 bikes on a receiver hitch rack, and even loaded with 2 big dogs, and lots of camping gear we get 24mpg going 80mph.

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