Some of you might find this interesting. I did not know that aerodynamics would affect FE this much...

A month ago I installed a roof rack for my 2007 HCH...standard stuff made by yakima. I had to use a visor (again, standard yakima product) that directed airflow over the bars due to excessive whistling without it.

At that time, I was getting 62-63 mpg per tank and the weather was still warm. I had a few 70 mpg individual trips and was really excited. About the same time I installed the rack, the weather turned colder;we had some 20 degree days and my FE dropped substantially, around 50 mpg. When the warm weather returned, i still was getting poor (comparatively) FE and could do no better than 50-53 mpg. Last weekend I took a road trip to houston (from Austin) and could do no better than 45 mpg!

Frustrated, I took off the rack this morning and, although temps were in the low 50's I am back to 63 mpg! I wonder how bad the FE will be if I actually put a 75 pound kayak up there!! yikes!

Merry christmas all....

jco

 

Thanks for the great feedback John.

This should help many folks assess whether a roof rack is for them or not.

However we choose to look at it, the HCH-2 is very sensitive to anything that adds drag to its areo-dynamic profile.

It would also be interesting to quantify the amount of drag a rear mounted hitch solution would impose. Theoretically it should be lower but it would still be fun to quantify how much less drag compared to a roof rack.

Would you be able to post some pictures of your setup?

Cheers;

MSantos

 

I'm also interested in pictures and FE stats with the kayak on top.

 

of course! You'll have to give me a few days though, but I'll get them in here.

The rear mount, I agree, probably is better. For my needs though, it just isn't an option for a kayak. Interestingly, my wife has one of those, but it mounts to the trunk. I don't have the patience to experiment with that on my car after my ordeal. It's so easy to install I'll just put it one only when I need it. The bad thing is, the car really looks more "me" with the rack!!

Do any of you know if there is a more aerodynamic solution out there for racks? Anybody with more experience? It seems clear to me that the angle of the visor is the problem. Maybe if the crossbars were an extreme oval shape you could eliminate the visor. Thule makes some but they look to be more football shaped to me.

jco

 

ADAMEK,

you'll have to wait awhile for the FE results. I don't have anything planned within the next month, but when I take a trip i'll post it for you.

jco

 

Interesting. We haven't installed our rack yet since it takes 52" cross bars (the old car used 48"). I am going to try to get them on after the holidaze and I'll see if I have similar results. If so, I'll probably pull them off again unless we are taking a road trip and need the extra storage capacity of the roof box. Like you mentioned about the Kayak, I'm curious to see what kind of effect the box has on FE.

Your trips were mostly highway miles right (I'm guessing based on the high mpg)? I wonder what the impact would be for city driving...

 

that's right, kristian. mostly highway going about 52-60mph. You might actually try your 48" bars. the ones yakima recommends stick out a little far, and we have a few bumps on our heads to show for it. I'm thinking the 48 might work. I'll measure and re-post when I have time.

As far as the kayak goes, I'm thinking city would be better...just my opinion...

jco