Drag Penalty for Bikes On Roof? - Escape Trailer Owners Community

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Old 09-29-2014, 09:07 PM   #1
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Drag Penalty for Bikes On Roof?

Does anyone have any reasonable comparisons for fuel mileage with and without bikes on top of the car (Highlander in our case) when towing an Escape? There is a definite drag penalty for bikes on the roof under normal highway driving, but I'm wondering if it's that much worse compared to the big hit already incurred from towing.

We have a great Saris rack that fits in the receiver on the Escape, but it's really heavy. That and the two bikes add more weight back there than I'd like. If it's not too big a mileage hit, I think I'd move the bikes to the roof of the car, but I hate to invest in more bike rack stuff just to try it.
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Old 09-29-2014, 09:22 PM   #2
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We often have kayaks on the roof of the Ridgeline. The mileage penalty is 1-2 mpg without the trailer. It tends to drop to 16-17. With the Escape hooked up and the kayaks we seem to drop about 1 mpg from the trailer with no kayaks. With the kayaks and trailer it's about 10 to 10.5.

I think we get drag from the kayaks or the Escape, but it doesn't double when we we add both.
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Old 09-29-2014, 09:28 PM   #3
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Quote:
Originally Posted by bisonbill View Post
I think we get drag from the kayaks or the Escape, but it doesn't double when we we add both.
That's what I was hoping to hear. Towing, I'm generally driving a little slower, which also helps with the drag situation. I really appreciate an actual comparison with numbers. Thanks.
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Old 09-29-2014, 09:40 PM   #4
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Maybe you should compare it both ways? Yes there will be added weight on the rear, which means your tongue weight will decrease and maybe require the shifting forward of cargo, but there would be almost no wind resistance mounted on the rear. Maybe its a wash?
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Old 09-29-2014, 09:47 PM   #5
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That's what I'm trading off. The rear rack keeps them down out of the wind. They do get really crudded up from road grime, but that's not terrible. It just always feel wrong to load that heavy steel rack and then two bikes that far behind the axles, even if things balance out okay, statically at least. Dynamically, that's a lot of weight in the wrong place. But then we've towed them several thousand miles that way, so maybe I have a solution looking for a problem.
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Old 09-29-2014, 10:01 PM   #6
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Yeah, I dunno. As long as handling and stability aren't affected. Was just thinking about the gas mileage.
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Old 09-29-2014, 11:05 PM   #7
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Perhaps this may be of help. On my former Escape 19, I carried two bikes that weight a total of 66.4 pounds and the Thule rack was 23.1 pounds, total of 89.5 pounds. The tongue weight was reduced by 40 pounds, from 360 to 420 lbs, when carrying the bikes.
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Old 09-29-2014, 11:15 PM   #8
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We have not carried bikes on the roof, but we have carried a large canoe and (not at the same time) used a Thule rooftop carrier box with and without our current trailer (which is roughly as tall and wide as an Escape 19'). Without the trailer the canoe and box both certainly add drag, but with the trailer the canoe or box makes little if any difference to fuel consumption. Bikes are terribly shaped compared to this box or even the canoe, but maybe in front of the trailer they won't matter much?
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Old 09-29-2014, 11:24 PM   #9
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Although rearward weight shift (seen as reduced tongue weight) is one result of adding mass to the back of the trailer, it is not the only effect. Adding mass out at the ends is bad for stability, and just adding more mass to the front to restore the tongue weight does not counteract the adverse effect on stability.

Although it is not desirable to have bikes in the airstream - for drag, or for the bikes - the tug's rooftop seems to me like a better place for them than the back of the trailer.

We have not carried bikes with the trailer; we have with our motorhome, in a rack on the back, but in that case on the back is the only reasonable option - the roof is certainly out of the question.
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Old 09-30-2014, 05:23 AM   #10
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I've carried two bikes and a swagman rack on the back of our previous 17 and had the same result as above - tongue weight was 40lbs less. I added weight ( water jugs with sand, so I could adjust easily). I drove 12k miles or so overall with them on, and never noticed a problem with stability.
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Old 09-30-2014, 09:51 AM   #11
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I have had bikes up on the roof with the spandex covers to keep the bugs off the forks and bars and its like a sail. Noticed a drop in fuel mileage and could alsp notice a difference in power when passing on the highway. I have two styles of racks, one that you remove the front wheel and mount the fork to the rack and these are not as bad but I tried some that mount the bike with both wheels on and that really puts the bike up there along way to catch alot of air. I have also used a yakima sky box on the truck @ times. without the trailer its about 1-2 mpg penalty with the trailer theres no difference.
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Old 09-30-2014, 10:08 AM   #12
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I've also had experience with two bikes on top with the spandex covers. I once tried this on a Prius when my son and I left for the starting point of a week-long ride. The bikes knocked the mileage in half! Needless to say, I switched to a hitch mounted rack. I'm thinking of racks that lock the forks down without the front wheel, and probably turning the bikes backwards so the rear tire get the first shot at bugs and such. If this works, I'll make up something to hold the front wheels on the rear bumper of the Escape. I'm happy to hear there is very little additional drag penalty after taking the big hit with the Escape. That seems to be the consensus.
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Old 09-30-2014, 11:09 AM   #13
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I used to leave the crossbars in place on the Yakima rack on my Tacoma. Then I read a Consumer Reports article that stated just leaving racks in place can cost 1-3 mpg on average. I tested that and found it to be very true in my case. The racks came off! Those were just the cross bas, I can't imagine what the loss would be for those folks who leave their snowboard and and bike racks in place year-round.
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Old 09-30-2014, 03:17 PM   #14
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Quote:
Originally Posted by Chapitre View Post
I drove 12k miles or so overall with them on, and never noticed a problem with stability.
Good - but just be aware that you have less margin of stability than without the bikes. When a tug/trailer rig is at a speed near the limit of the trailer's stability, it will feel fine, but sway could be started by an emergency avoidance maneuver or a gust of side wind. It's hard to know how much margin is available - I don't know how fast our van could tow our current trailer before it became unstable, and my concern it that I unknowingly come too close.

(Although I have had the trailer at a too-high-to-mention speed once, so I'm not so concerned )
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