Tow bar max weight for bike racks?

Backstory: At some point in the next few months / year we’ll be seriously thinking about changing the car, almost certainly to electric, which means probably an SUV (hopefully just a stop gap until more estate / hatchbacks become available). Which, in turn means that a tow bar bike rack will be more appropriate then the current roof rack solution we currently have.

So, that got me looking. Polestar 2, Tesla Model 3 and Id.3 all have max weight limits for tow bar accessories way under the max trailer nose weight. ie 75kg max trailer nose weight and 30kgs max bike rack weight. Is this just a thing for retractable / removable tow bars? Or are manufacturers realising that a big bike rack with 4 bikes hanging off the back is over stressing their cars. I guess it could relate to handling as well?
I can’t seem to find much about this for ICE cars, but I suspect this is just a newer car thing rather than an electric car thing.

I think some of the larger tow bar bike racks are 15Kgs+ for just the rack, so there’s not much scope for even a couple of burly bikes in addition there, let alone a 4 bike rack. Any thoughts?

My A6 which is the 2011 model specifies different weights for bike racks, so it’s not an entirely new thing, but I suspect that manufacturers are slowly catching up with the fact that towballs are often not used for towing any more. The specified weight reduction isn’t quite as severe as that, although it depends on how far behind the ball the bike rack CofG is.

I don’t know if the lack of an engine over the front wheels means that electric cars are more sensitive to how far behind the back wheels you place the towbar load.

15kg is light for a tow bar rack.

Good point re CofG, although you’d have thought the the extra massive weight of a battery forward of the rear axle would have moved that equation the other way. Probs just slow realisation of what tow bars are actually being used for, as you say.

I think some of the larger tow bar bike racks are 15Kgs+ for just the rack, so there’s not much scope for even a couple of burly bikes in addition there, let alone a 4 bike rack. Any thoughts?

You are correct. One of the reasons we stuck with V70 was the loading on rack (same with Galaxy before). 15kg rack + 4x 13kg bikes = 70kg odd. Remember that some of that weight is also levering out quite a bit – a caravan or trailer is more a push-pull with the weight.

Our Ibiza is only 30kg IIRC.

Many things are factored into nose weights and rack weights. IANAE.

Our Octavia estate has a 75kg limit – pretty much what our rack weighs with 4 old school 26″ hardtails hanging off the back.

The front end definitely feels a bit light on the rare occasions we are fully loaded.

Hadn’t realised this. I’d been looking at a model 3 and wishing it was an estate.
Then I tow bar would be the sort of solution.

This thread may help.

https://teslamotorsclub.com/tmc/threads/tesla-model-3-uk-manual-towbar-accessory-limit-of-55kgs.194522/

The more I’m reading about this, the more I think the reduced weight limit for the bike carriers is about the leverage force the weight dangling off the back will put on the tow bar and it’s attachment to the chassis, not the balance of the car.
Which makes me think that a permanent fit “proper” tow bar would have higher load values than the foldable / detatchable type. I imagine getting that info from a car manufacturer will be difficult.

This is from our kodiaq’s manual. Basically the further out from the ball, the lower the load it can carry, as you’d expect. This was for a electrically retractable coupling.

Edit: ok why is Flickr not working?

Thanks. Interesting the note in the kodiaq book is all about damaging the towing device, as I suspected. 60cm isn’t actually very far away. I assume a 3 or 4 bike rack is longer than that, although the c of g will be closer than the extremity. Equally any bike is going to be at least half a bar width away, so >350 mm?

It doesn’t really matter WHY or how you perceive the numbers.

As a long term tow bar rack user and trailer hauler I would suggest you are wrong on the vehicle balance being a non issue by the way – it’s even covered by someone in this thread in terms of impact on handling of their STW compliant Octavia. If you don’t believe me go and look in a trail centre car park at the overloaded cars doing a ******* dog impression and think about whether that’s likely to affect handling.

That aside, massive amounts of testing and engineering knowledge goes into setting those limits that covers structure, design, leverage effects, flex/fatigue, materials, wider vehicle design parameters such as weight distribution between and beyond the axles etc. There’s always a margin of error of course but that’s not for users to exploit.

The limit is there for a reason and you should stick to it not try and persuade yourself it doesn’t apply to you. To not do so risks parts failure, compromised handling (either of which at the extreme could result in your or someone else’s death from an otherwise avoidable accident), insurance and vehicle warranty invalidity and prosecution. So buy a suitable car for the intended rack or a suitable rack for the intended car.

I drive either a large estate or an MPV because I require certain load numbers to be hit for roof and tow bar loading. I’d much rather have a nice mid sized hatchback. Such is life.

I assume a 3 or 4 bike rack is longer than that, although the c of g will be closer than the extremity.

Yes, but possibly not by a lot. Spacing is typically 19cm, and I’d expect the handlebars of the first bike to be overlapping the towball.

I would suggest you are wrong on the vehicle balance being a non issue by the way

Agreed. It may feel “OK”, but may significantly alter how the care behaves if you have to swerve at speed.

Just my thoughts from having my first car with a towbar rack:

I use a towbar rack and occasionally a small trailer on my Fabia and you notice a bigger detriment in handling with 2 big bikes on the back than a fully loaded small trailer. The trailer is only a small one with a 260kg payload limit but I’ve had it at that limit with bricks and a full boot a few times and each time it’s just slower to accelerate and brake with no real difference to the steering. With 2 bikes on the towbar rack I used to have the car was much more prone to understeer and waywardness in crosswinds. I currently use a single bike carrier and with my Rocket on it (so a 35lbs bike on a 13kg carrier close to the towbar) the steering is similar to a fully loaded trailer. The car is rated for a 60kg nose weight but recommended to keep it below 50kg. No way would I put more than 2 bikes on a rack on it, it just shifts the balance too far rearwards. I’ve got the smallest, lightest engine so would presume a diesel would be better in this regard. The car isn’t unsafe with 2 bikes on the back but it feels very different to normal, Skoda actually recommend no more than 3 bikes on the back with a total weight of 40kgs.

So I looked into this as Tesla M3 is one of the few options for a long range EV at the moment that’s not 80K, until the ID4, MY, enyaq etc come along with a better charging network. I came to the conclusion that 4 bikes on the back was not practical with a 55kg limit listed in the manual. 3 max realistic.

I wasn’t trying to work out why the limits might not apply, just trying to fully understand it.

Interesting points from people driving with tow bar racks. I could take the compromise of limiting to 2 bikes on the back to be honest, if I ever take a 3rd it usually my DJ bike and that can always fit inside the car anyway. Although 2 trail bikes + rack is ~45kgs anyway. So I think the important thing is to understand how far away from the tow hitch the weight limit applies and some how correlate that to where the CofG might be for any installation. On hot_fiat’s skoda diagram above you can have all the nose weight limit ~30cms from the ball, which is probably about the CofG of the rack and one bike.

I’ve had tow bar bike racks for nearly 20 years, and never once did I look/check nose weights. Just checked my car now, and 75kg’s it seems.

My OH has horses and a horse trailer. I cannot physically lift the front of her trailer, when it’s empty, never mind loaded. She once hadn’t parked it properly and the jockey wheel collapsed, I needed a car jack to lift the front.
I’d hate to imagine the actual forces when it’s loaded, and really can’t see how 2-3 bikes on a rack get anywhere close.

I’ve used a Pendle strap on rack in the past on a Saxo, even with one bike it would affect the handling quiet badly. And it was “on” the boot lid rather than hanging off the back of the car.

Another plus for roof mounted systems.