In our case, it's only two bikes, on a tilting carrier, so no need to remove them to get in the boot.
The carrier is locked to the tow ball.
The arms that clamp to the cross bars have locking knobs.
I then travel with a length of heavy duty chain* from B&Q (cut and sold by the metre, if I recall?) wrapped around/through bikes and carrier. I think I got the thickest they had. Think the links are 8mm thick steel? Took some cutting in the shop... any thieves would need the very big/heavy bolt croppers at least!
To stop the chain falling off, I attach one of these...
Alarm off when actually travelling, then set it when parked up out of sight/overnight etc.
We also have a "normal" bike lock for each bike, but rarely use them on the carrier. I did put both through everything when overnighting in a French hotel though, so that meant two bike locks plus the alarmed chain that needed cutting to get them off!
* Our chain is "plain", without any form of protection, so it does scratch the bikes. Not too bothered as they are fairly cheap bikes, and a few scratches look less appealing to others! You can get various chains in sheaths or plastic coated, if required.
As for the weather, the only things that matter are the seats.
I have a memory foam seat, and when it looked dry, I sat on it to find it was almost like sitting on a sponge! It wasn't as dry as it looked!
We've actually bought (but thus far keep forgetting to use!) some really cheap, tacky, plasticky, elasticated shower caps.
Think they were 95p for a pack of ten, from some cheapo shop next door to poundland!
Really must try and remember to try them, to see if they are any good!
I must point out though... I have yet to have the alarm go off on site, or even give off the warning beep. I like to think that is down to camping amongst decent folk, but it's still nice to make things a little more "inconvenient" for any would be thieves!
Lock them to your car if you are tenting. We have 2 long lengths of bike cable linked together. Like a chain only rubber coated so it doesn't scratch and chip everything. Then a good d lock once it's threaded through all 4 bikes.
You only need a mild deterrent as most don't lock their bikes at all from my experience.
Like the chain and locks and alarm when left on your car.
Our bike rack, when camping, cannot tilt as we have a removable tow bar and a trailer actually on the tow bar as well as the bike rack. (If you do not believe this do Google it - a witter one!)
Unless it is a biking holiday we take our older hybrid bikes, purposefully leaving the expensive jobs at home. Sad that we have to think that way, but we do, despite them being insured!
We tend to chain them to a big tree if there is one next to our tent once they are off and as well as fastening them to the tree we lock them all together with big covered security chains, using 3 or 4 in total.
We do the same when they are on top of the car - hard to remove all three together without making a big noise.
Do you have the
A. 'We can go faster than you' bikes?
OR
B. The 'we can cycle all day' bikes?
We have the 'I've had enough NOW children' after about an hour or so. Though to be fair last time we went out ds (7) went over the handle bars and had a mouthful of mud. It was down hill in a mixed woodland with lots of tree roots.
I think ours are the latter Frazzle. We take them into Cambridge a fair bit along the river path so are not precious at all about them.
We have other bikes too for speed/distance but wouldn't risk those on a normal camping trip. Our use as a family wouldn't warrant them really though as our 9 year old can only manage 10 miles (with breaks) before we have earache from all the moaning!
We would look like 'all the gear and no idea' on the swisher ones at kid speed .
If you have bikes, chances are you have old inner tubes lurking around in the shed or garage. Cover the chain in lengths of the aforementioned inner tube to prevent it scratching your bikes.
Amazing family weekend with old steam engines, classic car displays, market stalls, and full catering and bar. And camping on site - Save £25 by booking in advance.
Topic: Bikes on site for whole family
We take them into Cambridge a fair bit along the river path so are not precious at all about them. 
