Rain cover for bike including on floor and car

[LittleGreyCat]

Not the best description, but anyway.

I started out wondering if it was worth getting a cover for when my bike was left outside (not at home).

Plenty of cheap and cheerful covers around a tenner.

When the bikes are on the roof rack I don't bother and I think wind resistance could be an issue.
However I now have a Thule towball rack and this will put the bike down amongst the road crud so I was wondering if this justified a cover.

None of the easy search hits suggest they are suitable.
Other searches seem to find USA based products.
None seem to acknowledge the UK rules about number plates and lighting which require a trailer board for most tow bar fittings (which don't include lights).

Online discussions seem to conclude "why bother".
My main concern is exposure to road salt in the winter.
I don't tend to ride my bike sideways at 60 mph in the pouring rain on motorways so there is no direct comparison with pootling along country lanes in the dry with the occasional puddle.

Does anyone use and can recommend a cover?

[rotavator]

Have you seen this one: Oxord bike cover?

http://www.oxfordproducts.com/bicycle/brands/oxford/cycle_covers/stormex_1_bike_cover_single/

I don't have one but have seen them in action on tow ball racks.

[mattsccm]

Cheap ones keep the muck off as well. If anything flaps it will eventually rip.
Better still don't bother and wash the bike at home.
Lights, trailer board etc surely a red herring unless you happen to have some magical bike that doesn't obscure lights number plate etc on the car.

[rmurphy195]

Airflow over the top of the car will hit the bike on the rack - if you put a cover on it will be like a parachute, putting extra strain on the towball mounting and whatever you use to hold the bike on the rack. May even rip it off! Unless its on the back wall of a motorhome of course!

On the motorway imagine a 70mph wind hitting the bike and its cover sideways more if you are driving against a headwind ...

[LittleGreyCat]

Cheap ones keep the muck off as well. If anything flaps it will eventually rip.
Better still don't bother and wash the bike at home.
Lights, trailer board etc surely a red herring unless you happen to have some magical bike that doesn't obscure lights number plate etc on the car.

The comment about trailer boards was because some seemed to claim that they were transparent so you could see the lights on the car.
This was mainly the US ones, mind.
No good in the UK.