In anticipation of a holiday later in the year, I recently fitted a roof box to my Fabia Saloon. This was mainly done to assess the ease or otherwise of fitting and whether there were likely to be any ill-effects,in terms of handling.

My experience was quite the contrary.

The handling seemed to improve, and no wind noise ! I took it for a test drive, suitably weighted with a dummy load . My route included suburban roads, fast windy "A" roads, motorway and hilly sections. There were no problems. I couldn't believe this !.

Even the real-time M.P.G. was showing no difference to consumption at across the speed range compared with the values I usually get with the car with no roof box ?

Mind you the wind conditons were fairly subdued on Friday evening.

Even more troubling is the fact that he box is far from aerodynamic. Its a cheapo Italian polyproplene job, with a blunt front end, measuring 14 inches in depth, 4 foot long and 3 foot wide and when mounted on the Fappa roor bars, the underside edge sits at east 5 inches above the vehicle roof line.

Again, I couldn't believe there would be no problems !

I wonder if the box is acting in a similar way to the spoiler you see fitted on the cabs of artics ?

Any body else had a similar experience ?

Regards

Nick,

25/05/08

IMO, the extra weight so high up on the car should be detremental to the handling?

Sounds like the opposite though...

IMO, the extra weight so high up on the car should be detremental to the handling?

That's would have been my understanding and expectation too ! Whether your car driving or motorcyclying or flying, to maintain good handling the rule is "Keep the weight and therefore the COG, central and low-down in the structure|".

Ok, probably only had 1/3 full load on board when I tested (The box takes up to 50 KG) - and anyway,in practice I would put all the light camping stuff uptop - sleeping bags, tents, matts etc.

My puzzlement was that the container didn't do anything untoward in terms of aerodynamics - and I took it up t the motorway speed limit.

Nick,

25/05/08

I think probs feels better because the car is sitting a tad lower and mainly because the extra weight is damping down the ride somewhat.

Ours 'feels' more sure footed with a lot of extra weight aboard.

Ordinarily extra weight so high up will be quite detrimental to C of G and handling and roll-over 'point' etc.

Are the cars not a bit over sprung and a bit under damped?

The higher CoG won't help, but maybe the mass helps the suspension a bit

I estimate Roof box and bars weigh about 25lbs, plus a further 10lbs of test load.

Nick,

25/08/08

Aerodynamically, the difference should be quite noticeable. It certainly is with a roof learner board. There is no way the car will be as economical with the box on top. As for handling, it may feel OK, but at the limits, you would probably notice it. As speeds go up, the effect of a higher up centre of pressure could induce high speed understeer as well.

Chris