[Closed] How strong are rivnuts?

How often do caravan's fall off a hook ? Never, they flip the car if all goes bottom up.

If worried, jam a wire security loop in the car boot/hatch - usually a good idea anyway to slow down anyone trying to steal the bike.

Towball racks are very reliable. If it starts to rotate off the ball (which it won't) it'll probably fall off rather than just swinging down.

If you're really paranoid add a chain to the towing eye so that when it falls off it doesn't take out the car behind but really, don't bother.

What type of rack? I get where you are coming from but I've never had a problem with our Thule one. I wouldn't worry about the rights, it would be where the number plate screws into the car i wouldnt put any load on.

I know caravans never fall off ,it’s just I don’t trust the science. It shouldn’t work.

I really want to be watching where I’m going not whether my bike is going to fall off.  Normally I only drive 10 miles with it on the back but soon I’ve got to do 200 on a motorway. Just need some piece of mind.

FWIW, I've driven many thousand of miles with up to 4 heavy bikes on a towbar mounted rack. You just have to accept the fact that the rack is NOT going to rotate if it is correctly fitted.

Mind you, every single trip with bikes on the roof, I was worried they'd fall off.

Every.

Single.

Trip.

I’m paranoid about my bike on a tow bar mounted rack.
The bike is never going to fall off the rack , I just don’t trust something gripping a ball.

I understand that, but thousands of these type of rack are used every day, all over the country without issue. If you can swing the rack around its not fitted right.

So I’ve thought of a bit of wood (might be metal once I’ve gone to a mongers) screwed to the number plate bolt holes so that I can attach a strap to stop any potential rotation away from the car.

The issue is probably not the rivnuts - but whatever the number plate is mounted to - 50g v's equivalent of several kg of force. Even a fairly solid bit of bar is pulling on some flimsy metal/ It would be very easy to bend stuff on my car. Even if yours seems rigid - do you turn a simple dunt of the rack on a bollard, high kerb, low wall etc into a new back door?

Most towbar racks sit horizontal even when not clamped up.
If it can pivot downwards on the towball it’s not well designed.

I've never seen a rack fall off a towbar...I can't even clamp mine on if I haven't raised it high enough, the cam just won't close.

Mine doesn't grip the ball, it closes underneath the lip under the ball.

Have you bought the rack and tried it yet to get a feel for it?

Yep, you are over-thinking. It is nothing to be ashamed of, and plenty of people do it, myself included (a lot), but now is the time to accept that a correctly fitted tow bar carrier is the safest and easiest way to carry a bike, and move on.

There are plenty of other things to over-think.

I wouldn't trust the number plate fixings - not without spreading the load on the inside of the tailgate even then it's still only sheet metal and will flex. The manufacturer never designed that panel to take a load like that. Towbar is a far better bet.

It's not friction from being clamped round the ball that stops the rack rotating. When the clamp is done up, it's a full sphere except for a circular hole at the bottom. The stem of the towball fills that hole, so it can't rotate.

What Greybeard said. Think about it - if you were designing a towball rack, would you design it so that it could slip down? Of course not.

Have a look inside the clamp. There's a notch that fits around the neck of the towball so it cannot slip down when it's fully tight. Mine can move side to side a bit of its loose, but never when tight.

The original designers have done a better job than you're likely to be able to bodge on with bits of wood.

You do have to make sure it's lifted up to the right position when you do up the clamp though.

I had a rack like that and used to run a strap round the arms of the rack and then behind the hinges of the boot. Just a normal cam buckle strap. Drove thousands of miles like that, was never needed but gave me peace of mind.

Not all towbar racks are equal. Mine 'could' rotate, but my neighbours is one of the ones that can't. Neither has never failed/rotated.

I fit an extra strap round the bikes and through something solid (I have a loop on the towbar at the moment, but have also used the roof rack or rear tow point. That should stop it falling off and taking out someone else (or give me a defence in court....)

That said, nothing has happened in thousands of miles of use.

Look in the rear view mirror when you leave and take one or two reference points (ie rear screen sticker v bike logo). Keep an eye on it for the first few miles and then check every ten...then twenty.... then fifty... etc

Whenever you stop for fuel etc, check all straps, lights etc...

Gradually your confidence will build 🙂

I have attachment points all over the inside of my van on rivnuts. Managed to pull one out splaying the steel skin. Number plate attachment would be similar.

I really want to be watching where I’m going not whether my bike is going to fall off.

Put the towing ball on the front 😉

Rivitnuts hold my Fianna 3.5m awning on the side of the van*

They also hold my solar panels to the roof* .

*Probably not the same size as the ones holding your numberplate on

How about Plan B?

Plan b for what.

The mechanics don't function as you imagine in the real world

As long as you don't have a flying tiger brand Chinese knock off POS bike carrier made from recycled analogue TV aerials I think Thule et al have spent enough on R&D to make sure their products do what it says on the label before they get sued into oblivion. But yeah using a number plate rivnut......post the pics afterwards

The rivnuts shouldn’t have to do any work in reality.

Only if the bike rack failed, which we know isn’t going to happen. ( possibly)

Really?

What would it take for you to be reassured?

You must have had similar struggles with basic engineering, I dunno, bridges not supporting your weight or similar?

You are trying a Heath Robinson "solution" to a problem that doesn't exist.

I'm going to have to agree with everyone else.

Your instinct is wrong. IF it did go arse over boob a couple of wee rivnuts will turn into bullets when they get ripped out a fraction of a second after.

Trust something gripping the ball. The amount of friction created is more than enough. Your bikes and bike rack are not very heavy at all. they feel heavy to us humans, but us humans are weak feeble things. Steel is very very strong. Immensely strong. Your ball mounted rack is more than enough to support the weight of your bikes and rack so long as you're within all the limitations of your car and axel weight and all that stuff. I used our 4-bike rack loads of times with no issues whatsoever - and sometimes were probably getting pretty close to if not a tad over the noseweight limit of the car. Seriously, you'll be fine. these things are designed with a factor of safety of about 3 so in reality about 3 times stronger than they need to be. This is to allow for people who ignore the weight limits and might not install things properly to give a bit of leeway to ensure safety. Our motorways are not littered with bikes that have fallen off bike racks and I'm sure there are some proper silly donkey's out there with zero technical understanding and little or no ability to follow instructions using these things successfully. You'll be fine.

Do you fly ?

The way I see it is that if the bikes fall off without being rivnutted to the car your bikes will be ****ed. If they fall off and are rivnutted to the car your bikes and car will be ****ed.

You all seem to have lots of faith in tow balls but a few years ago we were cycling on the B road near Loch Ard the car following us braked and turned for a bend in the road. Their caravan overtook us heading for a field. The tow hitch may not have been attached properly, but they are not infalible.

^ I'd put that down to shoddy towbar fitment to the car than the ball failing, probably 😉
For what it's worth I was a tiny bit sceptical about mine before it arrived. Upon fitting though it's absolutely rock solid and carries four bikes with ease. It's a Buzz Racks model from the Roofbox website.

Why should the science not work? It is friction? You apply enough pressure to the clamping force and the friction holds (that is why the tow ball shouldn't be greased)...

It is a very reliable method of clamping and although your paranoia is incredibly high and you are over-thinking this - checks all the online forums for the volume of towball rack failures (I can't think of any off the top of my head)...they are built well and work very well.

Just make sure you follow the fitting instructions, fit the bikes properly and all will be well.

Just put the bikes in the bloody car 😆

OP. Do you trust your brakes to work or do you carry a stick to poke in your wheels?

As an example of how strong friction/clamping force is, remember that that's how the driving/braking force is transmitted between the hubs and wheels on a car.

I have that exact rack - you'll be fine as it is, it's designed for it.

You all seem to have lots of faith in tow balls but a few years ago we were cycling on the B road near Loch Ard the car following us braked and turned for a bend in the road. Their caravan overtook us heading for a field.

How does that relate to the OP? Are you suggesting the towbar snapped? It probably wasn't that, more likely to be incorrect hitching by the operator. Think about how many trailers are towed around all over the country every day. Towing accidents are almost always caused by user error, people don't know how to load trailers or check tyre pressures and so on.

As an example of how strong friction/clamping force is

It's almost certainly not held in place by friction.

I'm also not particularly happy about  my smooth steerer being gripped by my smooth stem.

That interface needs some splines.

Are you suggesting the towbar snapped? It probably wasn’t that, more likely to be incorrect hitching by the operator.

Common cause of hitch snapping is jockey wheel dropping. ...... My old man nearly tore the back end off an Audi 80 and the resulting errant trailer took out a concrete lamppost knocking the top 5ft clean off and left dangling by the cable.... Insurance on that was fun

You all seem to have lots of faith in tow balls but a few years ago we were cycling on the B road near Loch Ard the car following us braked and turned for a bend in the road. Their caravan overtook us heading for a field.

If only it was tied onto the number plate, that would have stopped it!

just to make zippy feel better 😛

How about attaching something to one of the straps then closing it inside the boot. Then tie the other end to the rack.

As an example of how strong friction/clamping force is, remember that that’s how the driving/braking force is transmitted between the hubs and wheels on a car.

Not sure that's helping, now he's going to have to make tethers for his wheels.

Not sure that’s helping, now he’s going to have to make tethers for his wheels.