[NordicX3]

Hi, I’ve had an iX40 for a bit more than a year now and like the car a lot despite the recalls, freezing frameless windows in winter and incredible loud fan noise at below -5 celsius/23F(does anyone else have that problem?). But as we are skiing some weekends a year I’m considering buying a roof box now. But as i did not want to wait for the iX50 with a longer range and delivery time I’m now stuck with the shorter range which makes the range vs roof box question a bit more critical. :-) So I’m wondering if anyone has experience what a roof box on an iX will do with the range/consumption?

Ps. I tried the search function but did not manage to find a suitable thread so please point send a link if there is already such a thread.

[sor]

This is tough to say. I have a ski rack which I load up occasionally, which provides a similar extra drag but I imagine a roof box would be less, unless it sticks out over the windshield.

The issue I have in characterizing it is due to several things changing at once. In October I was regularly getting 300-320mi total range or 33-34kwh/100mi. Then the temp dropped and I put on my rack AND put on winter tires and non-aero wheels. Now on really cold days where I don’t prewarm the car and do a round trip to the ski resort I do maybe 42kwh/100mi (250 miles) and on warm sunny winter days the round trip to the resort is maybe 37kwh/100mi (280 miles).

I have no idea what just adding the rack would do by itself but hopefully this gives some sort of insight. As a rough guess maybe it accounts for half the change between my good October range and my good winter range, ~2kwh/100 miles increase?

[ggalanis]

Originally Posted by NordicX3

Hi, I’ve had an iX40 for a bit more than a year now and like the car a lot despite the recalls, freezing frameless windows in winter and incredible loud fan noise at below -5 celsius/23F(does anyone else have that problem?). But as we are skiing some weekends a year I’m considering buying a roof box now. But as i did not want to wait for the iX50 with a longer range and delivery time I’m now stuck with the shorter range which makes the range vs roof box question a bit more critical. :-) So I’m wondering if anyone has experience what a roof box on an iX will do with the range/consumption?

Ps. I tried the search function but did not manage to find a suitable thread so please point send a link if there is already such a thread.

It will of course vary depending on many factors, but you are looking at being in the ballpark of a 30% loss of efficiency compared to your vehicle without the rack and box installed.

Here is a test done by out of spec reviews.

[hugo_nz]

We saw around a 15-20% impact on efficiency and range with a roof box. Not as bad as I was expecting though.

[ixDriver]

Tesla comparison tests showed ~16% range loss with the roof box, as a rough guideline

[sor]

If these numbers are right, nearly all of my range loss is due to the roof rack and not the wheel or winter tires, I guess

[ggalanis]

Originally Posted by sor

If these numbers are right, nearly all of my range loss is due to the roof rack and not the wheel or winter tires, I guess

Makes sense since it seems normal to me that it has a bigger impact on the vehicle aerodynamics than the wheels do and aero contributesAs it has always been the case, you should remove the box and even the rack when you don't need it. With an EV, if you have cheap charging at home, perhaps the cost is no longer super significant, but if that is not the case, or for a gas car, it is an expensive choice to leave it there at all times.

[NordicX3]

Thanks lot for the replies, very insightful. I think I will buy one for the next season.

Need to buy a tow bar bike rack as well for the MTB for the summer. Any experience on the range loss on a tow bar bike racks? :-)

[sor]

Ok, I did an actual test today, just because it’s the weekend and I was bored.

Note this is just one data point and the actual rack/box will make a difference, as well as air density differences are not inconsequential at 5k elevation vs sea level.

It’s 45° and sunny. I did a 22 mile loop at 75mph in efficient mode - all freeway with my roof rack, one pair skis, winter tires/wheels. Car was pretty well warmed up on my way to the starting point. Then I took off the skis and rack, put them in the back of the car, and did the loop again. The numbers are a bit different from what I see in practice just because it’s a pure freeway test, I think.

With rack - 39.3kwh/100 miles. Theoretical total range is 270 miles.

Without rack - 32.8kwh/100 miles. Theoretical total range is 320 miles.

Bigger difference than I’d have thought!

[NordicX3]

Originally Posted by sor

Ok, I did an actual test today, just because it’s the weekend and I was bored.

Note this is just one data point and the actual rack/box will make a difference, as well as air density differences are not inconsequential at 5k elevation vs sea level.

It’s 45° and sunny. I did a 22 mile loop at 75mph in efficient mode - all freeway with my roof rack, one pair skis, winter tires/wheels. Car was pretty well warmed up on my way to the starting point. Then I took off the skis and rack, put them in the back of the car, and did the loop again. The numbers are a bit different from what I see in practice just because it’s a pure freeway test, I think.

With rack - 39.3kwh/100 miles. Theoretical total range is 270 miles.

Without rack - 32.8kwh/100 miles. Theoretical total range is 320 miles.

Bigger difference than I’d have thought!

Fantastic! Thanks a lot for doing this! Incredibly helpful!

[mcl]

Originally Posted by sor

Ok, I did an actual test today, just because it’s the weekend and I was bored.

Note this is just one data point and the actual rack/box will make a difference, as well as air density differences are not inconsequential at 5k elevation vs sea level.

It’s 45° and sunny. I did a 22 mile loop at 75mph in efficient mode - all freeway with my roof rack, one pair skis, winter tires/wheels. Car was pretty well warmed up on my way to the starting point. Then I took off the skis and rack, put them in the back of the car, and did the loop again. The numbers are a bit different from what I see in practice just because it’s a pure freeway test, I think.

With rack - 39.3kwh/100 miles. Theoretical total range is 270 miles.

Without rack - 32.8kwh/100 miles. Theoretical total range is 320 miles.

Bigger difference than I’d have thought!

While I haven't done as rigorous a test as you (mucho gracias, BTW!!), anecdotally, after doing a ski trip 1-2 times a week for the last two months, I'm also seeing 15-20% range reduction with roof rack and ski mount. Not sure how much more/less it would be with the box as I don't have that mounted.

[02601_33859]

For those interested:

https://www.consumerreports.org/fuel...-fuel-economy/

https://www.consumerreports.org/fuel...-fuel-economy/

(hitches on top, bike racks below)

[Paladin1]

I'm guessing BMW engineers went to the trouble of designing aero tires, trimming the fat from door frames with frameless windows, slicking up the exterior with quirky vents, folds and creases, and stuffing the car with CFRP for specific reasons (that we all love to criticize - "Ugly front!" "Frameless windows, WTH!"). But the farther we get from that design, the more we pay in electric range (although for function, often willing to pay it). My daughter, my ducats! Physics is a fickle bitch sometimes.