Tow Bar tongue weight

Forums › Transport (cars, bikes and boats) › Tow Bar tongue weight

KrazyKid

1238 posts

Uber Geek

#306945 6-Sep-2023 11:33

I've got a tow bar with a 50kg Tongue weight rating.

I want to get an bike rack and put a couple of e-bikes on the back of my car.
The combined bike rake and ebike weight would be about 60-65KG.

Is there an easy option on increase the tongue weight rating to support the extra weight?
Is it as simple as welding a brace for the tongue of the towbar?

Thanks

johno1234

2793 posts

Uber Geek

#3124136 6-Sep-2023 11:38

Personally it would not worry me one bit. That rating is likely to have a large safety margin to allow for people incorrectly loading trailers or towing overweight trailers.

BlakJak

1275 posts

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#3124139 6-Sep-2023 11:45

How many people do you know who've stood on their towball from time to time? I'd agree it's not something i'd worry about much.

It is an interesting thought though, with e-bikes typically being much heaver than conventional bikes, tongue load hasn't been a huge concern before.

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MikeAqua

7773 posts

Uber Geek

#3124147 6-Sep-2023 12:11

I would take the sticker off the towbar and chuck the bike rack on there without any concerns.

Tow bar tongue ratings are often ridiculously low.

The rule of thumb for towing is 10% of the gross trailer weight.

My towbar is rated for 3,000 gross trailer weight, but only 250kg downward weight.

Mike

coffeebaron

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#3124148 6-Sep-2023 12:18

Can you get a hitch option - i.e. does the towbar come out so you can insert a hitch bike bar?

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Senecio

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#3124149 6-Sep-2023 12:24

50Kg is a crazy low tongue weight? The standard when towing is to keep ~10% of the total weight being towed over the tongue. That would indicate the car could only tow ~500Kg.

Regardless, for a bike carrier only I would ignore it.

richms

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#3124152 6-Sep-2023 12:41

It's not just the weight, but where it is in relation to the rotation of the vehicle as it goes over bumps etc.

Bikes are up about a meter from the towbar and will result in quite a bit of force on the bar that a trailer would not put on it. Just have to look at those idiots in Aussie folding their utes with loads well away from the center of rotation to see how bad it can be.

Standing on the towbar is no way near the force of accelerating 65kg with a 1 meter long lever on the connection.

Richard rich.ms

RunningMan

8953 posts

Uber Geek

#3124206 6-Sep-2023 15:33

To add to @richms it really depends on the towbar design and how it's attached to the vehicle. Not really possible to say from just the number, but a bike rack puts very different loadings on to a trailer, and you need to consider the peak loads under sudden stopping or steering etc. which will be vastly more than the the static load of a person standing on it.

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KrazyKid

1238 posts

Uber Geek

#3124210 6-Sep-2023 16:04

It's an old Honda Civic and is only rated for 500Kg towing. - hence the 50kg tongue rating.

If i go ahead I'll probably get one of those standing racks for 2 e-bikes from Thule or Torpedo 7.
I've put one bike on a pole tow rack and the bike swayed like no tomorrow. Way to much mass.

Sound like I will need to visit a towbar installer as I would need them to look at the whole thing.
Short trips should be fine, but if I'm taking bikes 2 hours away for a ride I would rather be sure of things :)

Another simpler option might be to remove the batteries for the ebikes - that would get the total weights down to about 55kg or less so should be fine then.
That should be close enough to the 50kg limit...

mclean

581 posts

Ultimate Geek

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#3124212 6-Sep-2023 16:20

Some observations (from a mechanical engineer):

1. No manufacturer will put a 50 kg tongue weight rating on a towbar without reason. I'm guessing it's a very light car and the rating is determined by the attachment to the car.

2. The vertical shock loading from a concentrated mass over the towball might be more than a trailer rotating about it's axle.

3. Be wary of ignoring a design safety margin simply because you know it's there.

Senecio

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#3124213 6-Sep-2023 16:32

Removing the batteries is good call.

shrub

775 posts

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#3124233 6-Sep-2023 18:10

You can also install tether straps to the boot/hatch lid lock

MadEngineer

4271 posts

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#3125467 9-Sep-2023 21:32

^ that

Does this bike rack you’re looking at include them? The one I’ve got does and I was concerned about attaching the little hooks to the lip of the boot but they don’t do any damage at all.

Is the car already rear heavy or front light?

What does your car manual say out of interest?

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scuwp

3885 posts

Uber Geek

#3125628 10-Sep-2023 13:25

When we had our tow bar fitted they added extra bracing to minimise the 'bouncing' you can get with heavy bikes. It worked well.

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