Thule or Yakima cargo boxes?

i personally own a thule box (evolution 1600) and i must say that i have never had a problem with one at all. i also work at a shop which sells them and put them on peoples’ roofs all the time. i cannot recall one time that i have had a problem installing them. the quick mount system on the thule racks is also so easy i can put a box on in 3-5 mins. i have no experience with the yakima racks.
p@uL

John, while I’ve never used their boxes I can’t say enough good things about the Thule system. I’ve used their gear for a long time, toting everything from bicycles to kayaks to lumber. The nice thing is that the oldest pieces still fit on the newest bars, making them solid longterm investments. The hardware and the coatings hold up well.

This is not to say anything negative about Yakima, I’ve simply not used their stuff.

If I were to get a cargo box I’d personally avoid a dark one because I’d want to cook the stuff inside as little as possible. It’s also worth investigating the aeordynamics from a gas mileage, wind noise and crosswind stability perspective. I have no idea how to get past the marketing lingo and get the facts here.

Thanks for the comments. I went with the Thule Cascade 1500 XT. I was also looking at the Yakima BlackPro 16s (16 cu ft vs Thule’s 15) and it does have some more convenience-oriented features but the styling of the box (with the broad arch of the top) seems to limit its utility for fitting bulky items (ie smaller boxes, jerry cans, etc). The Thule is shorter and more squat than the alpine-type cargo boxes but seems to fit most of my gear pretty good.

For the basic rack, I went with the Yakima because the towers adapt more easily (cost efficiently) than the Thule towers. I’m also under the impression that the round crossbars are stronger than square crossbars.

Has anbybody ever done an aerodynamic study of these carriers, or an impirical study to find out which carriers have the least impact on gas mileage? With cost of gas so high (it’s had a significant impact on our hiker visitation in New Hampshire, which is not a big state) I think that would be useful information.

i have never done a scientific test with the thule boxes but from personal experience i can honestly say that i didnt see a huge difference in milege per gallon. i have driven from Buffalo, New York to Whistler, British Columbia and back on 3 seperate occasions. i was driving a VW Jetta TDI(turbo diesel) although there most likely a difference i didnt really notice one.

I have done a preliminary mileage test with my new Cascade box + 90 lbs of ice climbing/ winter camping gear.

This is roughly equivalent to my daily hwy commute mileage with a 175 lb passenger aboard. Take into consideration that I have snow-tires on so mileage is already adversely affected.

2001 Toyota Corolla S
1.8 L 1ZZ-FE engine
87 octane Shell Bronze gas (not gasohol crap from PetroCan)
Manufacturer mileage spec: 5.3 L/ 100 km hwy, 7.2 L/ 100 km city

Commute mileage with passenger/ no rack
6.1L/ 100 km (ave. of 10 tanks)

Commute mileage with rack + Cascade 1500 XL and 90 lbs gear
6.4 L/ 100 km (ave. of 2 tanks)

These are essentially highway miles with snow-tires but in the summer I get around 5.5 L/ 100 km on the hwy with all-seasons.

My advice, there is little if no impact on mileage so go for utility and get the bulkier/ less stylish Cascade boxes instead of paying for aerodynamic styling of the Evolution or Spirit boxes. I doubt you will see a difference in lost mileage.

There is some perceivable wind noise, but only above 110 km/h and the effects of crosswinds seem minimal but might differ with higher side profile cars (like SUVs and minivans). YMMV (pun intended).

Had a long Post on Friction in Automobiles, Engine Performance characteristics and parasitic losses in engines, Aerodynamics and Drag written, but deleted it in favor of this one (thanks M.A. for helping me come to my senses).

Work the numbers on those fuel consumption figures – nearly 5%. A less aerodyanmic carrier will cause a bigger hit in fuel economy – especially at highway speeds. Personally, I consider 5% a big hit. If one must add a roof-top carrier, especially a poorly designed one (from an aero standpoint), just reduce the speed the vehicle is traveling and fuel economy will be regained. Aero is a very fascinating subject and things are NOT always as they appear to the eye.

“Personally, I consider 5% a big hit”

I think its all relative Paul. You have to consider what that 5% penalty buys you. 5% is a bigger hit with a less fuel efficient vehicle. Take for example, if one were driving a Chevy Suburban (late model) which has a posted combined mileage of 13.7 L/ 100 km. A 5% hit on that would boost consumption by 0.7 L compared to 0.3 L for my smaller gas sipper. In Canada that’s roughly 70 cents more per 100 km (box penalty) vs 30 cents… but in a small car the payoff is an increase in trunk space of 125% vs 50% (or less) in the larger car.

I guess what I’m trying to say is that the economics of a roof-top cargo box work more in favor of it being atop a small car vs a large car/SUV.

PS. I’m extremely skeptical of the claim that a 3500 small block V8 in a 6000 lb vehicle can get you 13.7 L/ 100 km combined.

John, Good point on the small vehicle – that point was in my long, never-made-it-to-press post. BTW, I drive a ’98 version of your car, and my daughter an ’02 version of it. Great little commuter.

My point, which I probably wasn’t clear on, was a less aero designed box will be worse than the 5% by at least another 2% but probably much more. Research by GM, more specifically Chevrolet, in the late 90’s showed that in many automobile designs, even a simple rear deck lid spoiler can improve fuel economy by 2% or more (even up to a 2mpg improvement on a 28-30 hwy mpg vehicle) – even a relatively simple looking design change can have a very positive (or negative) effect at higher speeds. Look at the proliferation of spoilers on Semi’s cabs nowadays. Even with their parasitic drag, they still improve aero enough to be beneficial.

Just to illustrate “aerodynamic drag”, I’m always amazed to see people driving on our highways with a mattress strapped to the roof of their car. It often has its front half “standing up” or even partially folded back (actually better aero than “upright”) over on itself by the wind rushing over it. These vehicles often can’t do much more than 64kph – barely above the minimum speed allowed on many of our highways. Hey, they had no problem driving out of the store’s parking lot, but now that they want to cruise at highway speeds, it’s another story. This HP (horsepower) sapping drag is the cause. Remember, aero. drag is a second order function that increases as the square of the increase in velocity. So, the drag at 60kph is NOT twice the drag experienced at 30kph, it is FOUR times the drag at 30kph. Double the speed; quadruple the drag. At 120kph, the drag is 16 times what it was at 30kph. It takes a lot of HP ot overcome the increased drag (HP, obviously comes from “burning” fuel and releasing stored chemical energy). What’s even more ridiculous is that the guy often has his left arm out the window, holding onto the mattress – at least he “thinks” he can hold the mattress on should his ropes come loose. Hopefully, he won’t loose a few fingers, only the mattress, if the ropes don’t hold.

[Note:Oh…regarding your “P.S.”…quite possible…just make sure you’re going downhill ;) Seriously, is that one of those variable displacement engines that runs on fewer cylinders on lighter load/cruise situations? Actually, if the velocity was low enough, it could get that fuel economy. I had an ’01 Audi A6. A somewhat “porky” looking vehicle, but it was actually one of the most aero. designed vehicles sold in the USA that year with a very lo Cd (coefficient of drag) due to its gentle curves (air has mass and so doesn’t like to drastically change direction – ‘a la Newton’s First Law of Motion). It’s Cd was actually very close to that of a Chevrolet Corvette. Aero is sometimes tough to “eyeball”, especially to a non-Aero. designer/engineer. Anyways, that Audi would just require 8.4L/100km at ~89kph. It weighed nearly 4200lbs with two people and fuel and had a 2.7T twin-turbo V6 engine with greatly modified/increased turbo boost and other mods, resulting in nearly a ~50% increase in HP, plus fuel curve mapping changes in the ECM (engine control module) – hence the much better, ~15% improvement, in all speeds cruise (not acceleration) fuel economy than the Mfr/EPA rating – a win/win situation for me. It’s the Cd of the SUV/Truck that makes the fuel consumption figure skeptical, but it might be possible. Ok…enough cars (my love for cars and auto racing rivals hiking and backpacking – but, ne’er the twain shall meet – sort of a Jekyll and Hyde personality at work here, especially with the recent Enviromental Threads being discussed)…now back to our regularly scheduled topic.]

Paul,

Ok, just to keep slightly on topic. We are discussing the aero effects of cargo boxes on small cars and big gas guzzlers and how that mileage number can affect the environment that we all use and love.

now slightly, ot.

[To my knowledge, the Suburban does not have a variable-displacement engine. It is a 5.3L V8 claiming 13.7 L/ 100 km combined which I submit is “impossible”. I’m confident of this because my parents have a 02 Lexus RX300 with a 3.0 L DOHC V6 that has a better aero number, weighs less, and gets 12.9 L/ 100 km comb under a light load, conservative driving regimen. I’ve been looking at Bio-fuel research as a career move and to be honest to the point of grating on your nation’s farmers… gasohol and E85 is the biggest nonsense I’ve heard yet in a State of the Union address. Field inputs, tillage maintenance, and getting the raw stuff from 8% to azeotrophic to 99.x% will put you in the energy red-zone. There was a published research communication from Cornell that concluded that 1.3 gallon equivalents of gasoline would be needed to make 1 gallon of neat ethanol (which has half the calorific content of gas). Now if you apply the same formula to the production of bio-diesel fuel it looks a little better. A deisel engine is 30-40% more efficient than an Otto cycle 4-stroke + diesel fuel is hydrophobic hence not azeotrophic, and non-oxygenate so like the gasoline of old it has a long shelf life. IMHO North America should be working on updating diesel quality standards and promoting diesel hybrids instead of promoting energy-robbing, engine/pocketbook-rotting schemes like ethanol.]

So, if you don’t need the carspace for your camping gear (and who has THAT amount of gear) there are funner ways of lightening up your wallet as you lighten your pack.

John, Good post. It has such good info, I’m adding to a file I have on Auto related matters. Thanks for posting it. Agreed on some of the fuel issues you mentioned. We experience something similar to what you are speaking of already in the northern climes of the USA with our so-called federally mandated “winter” gas. My 90% hwy/10% city ~38.5 mpg commuting fuel economy in warmer months becomes ~34.5 mpg from december on even w/o warming up my car (which, depending upon the source, is to be discouraged – but that’s another subject). Decades ago, the automotive industry pulled one over on the Fed. Gov’t. with “air pumps” for “reducing” (sic) emissions. The Fed. Gov’t apparently hasn’t learned its lessons yet. But, maybe that’s standard where politics are concerned.

Oh…not that it matters much, nor will it account for the facts, but that Suburban might just be a RWD and not an AWD version (like the Lexus). As you are undoubtedly aware, generally speaking, AWD, by its very design, will reduce fuel economy somewhat vs a 2WD version of the same vehicle. They often play these games – half disclosure of the facts.