Car roof box

[ProfJohnL]

We have a large Halfords box bought for £30 on eBay a few years ago.
Use of a step to load/unload when on top of the Freelander is definitely recommended.
Not noticed any significant difference in fuel economy when towing. In fact quite the opposite as it seems to run a few hundred RPM's less when cruising on an A road or motorway.

???? This does not make sense. Assuming you are using the same gear and speed for your comparison, then engine RPM will be exactly the same.

If you using less RPM, then you are traveling slower. which will use less fuel.

 

[RogerL]

???? This does not make sense. Assuming you are using the same gear and speed for your comparison, then engine RPM will be exactly the same.

If you using less RPM, then you are traveling slower. which will use less fuel.

If the transmission is a torque converter automatic without lock-up, then reducing the aerodynamic drag will reduce the rpm.

 

[ProfJohnL]

If the transmission is a torque converter automatic without lock-up, then reducing the aerodynamic drag will reduce the rpm.

I hadn't considered the torque converter boxes...

And my original comment related to driving without a caravan. It is possible that under some conditions that a car roof box might improve towing performance by pre diverting the air flow before it encounters the caravan body

However there are so many other variables which could cause a change in the perceived load, such as wind strength and direction which would have almost as much effect when towing.

 

[Hutch]

I hadn't considered the torque converter boxes...

And my original comment related to driving without a caravan. It is possible that under some conditions that a car roof box might improve towing performance by pre diverting the air flow before it encounters the caravan body

However there are so many other variables which could cause a change in the perceived load, such as wind strength and direction which would have almost as much effect when towing.

Without going into a wind tunnel, to get true aerodynamics of a top box, I would imagine the side turbulence immediately behind the top box before the air gets to the caravan will not be smooth. But you never know.

 

[Beachball]

Your choice and if buying from Halfords I wish you all the luck in the world. 👍
😀

Halfords is the nearest shop for trying these roof cross bars on my car and i wanted to see how they go on but thanks for your input