Bike rack - Roof vs Hitch - range difference? Roof details inside

[Proxlamus]

Hey guys,

I have a Model S with a Seasucker bike rack that holds 3. Today I made a short trip to the mountains from Denver to Winter Park carrying 2 downhill bikes on the roof.

Well my 75D should have a range of 260 miles and I commuted 163 miles with only 24 miles remaining when I got home. Ouch! Now it was 96* F out and air conditioning was on, and it was up and down a mountain pass, so I know itll change the range quite a bit.

My average energy was 338 wh/mi.

Anyway, I'm curious how the range is on cars with a Ecohitch and bike rack. I think the roof rack has a massive impact on aerodynamics and I'm *assuming* the hitch wont be as bad and I'm considering making a switch. Any input from those with a hitch rack?

*picture attached is old, carrying 3* (not applicable to today's adventure)

 

[ewoodrick]

I don't know the numbers, but I do know that a number of people highly recommend removing bike racks on ICE vehicles when not in use.
If an ICE vehicle will feel the difference, an aerodynamic vehicle is definitely going to see it.

Noe honestly, the heat is probably going to help. A ground elevation of 12,000 ft is going to be the equivalent of 17,000 ft at 98 degrees. It will require more A/C, but that's mighty thin air and will definitely help reduce the vehicle drag. But the going over the pass didn't help.

Want to get an understanding of how much drag that is? Look at the bikes from the front and guess how much surface area that is. Now cut a piece of cardboard that size and hold it out the window when going 70. Maybe you should start at 30, so you don't break your arm.

 

[Proxlamus]

I'm replying from the hospital now, I tried the cardboard cut out and sticking my arm out the window to hold it at 70 mph and it was like trying to arm wrestle Thor. My arm is broken in 19 places. Remind me not to do that again.

As for the altitude compensation and air conditioning that's an excellent point. I had not considered that.

My biggest question is whether placing the bikes on a hitch mounted rack in the rear of the car where the low pressure drag area is would increase my range . I would assume pulling the bikes out of the majority of the slipstream of the car would help? Or would it make the low pressure in the rear become MORE turbulent and have similar or worse performance.

 

[icefree]

This might help:
New Study Finds That Roof Racks Are a Real Drag on U.S. Fuel Consumption

I have the eco hitch and Kuat bike rack and I love it! Just be sure to use Very High on the suspension when going up any large bump or incline.

 

[Proxlamus]

This might help:
New Study Finds That Roof Racks Are a Real Drag on U.S. Fuel Consumption

I have the eco hitch and Kuat bike rack and I love it! Just be sure to use Very High on the suspension when going up any large bump or incline.
View attachment 315826

Thanks for the link! I wish I had an air suspension! I missed out on the free standard air suspension by like a month after I ordered it. Sad day.

I may have to go hitch

 

[jrtozer]

I tested the efficiency of my Model 3 with and without bikes on a hitch mount carrier and thought you might be interested in the results. Seems like your range experience with the roof rack is similar to mine with the hitch rack.

After multiple runs thru a round trip circuit of highway driving in San Diego at night (70mph, no traffic, no wind, mostly flat, 67 degrees), I found the following averaged results:

257 wh/mile without the bikes
338 wh/mile with two mountain bikes hitch mounted on a 1UpUSA rack

By my calculations, that means carrying the bikes reduces my range by about 25%
(reducing the 310 mile long range battery to 232 miles).

To see if I could reduce the drag (for long road trips), I tried a Yakima hitch bike rack that hangs bikes from the top tube and I removed the front and rear wheels and put them in the trunk (hoping for a dramatically reduced profile). The result is better (but it is a lot more inconvenient removing the wheels).

290 wh/mile with two mountain bike frames hitch mounted on a yakima top tube rack (wheels inside trunk).

Hope this is helpful info for others,
-JR

 

[GlmnAlyAirCar]

I had a hitch rack on a Prius once and it felt like I was pulling a drag chute. About a 25% hit in mileage. I now use a roof rack on my Model S and, while I haven't taken and very long trips with it, I haven't noticed a significant hit in range.