BIKE RACKS AND CARRIERS FOR CARS MEGATHREAD - all questions asked and answered here

puffmoike

Likes Dirt
What do you think puts less stress on a tow bar. Platform or vertical rack?
I’m no engineer but I’d guess platform (EDIT: VERTICAL ) would cause less stress over corrugations, potholes, etc (primarily vertical forces) but more under emergency braking (horizontal forces)
 
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Knuckles

Lives under a bridge
What do you think puts less stress on a tow bar. Platform or vertical rack?
Vertical overall, the further out from the attachment point the load is, the more leverage force is placed on the litch area. Vertical might undergo more torsional twisting when loaded with 5-6 bikes but as the main load is pretty much directly over the attachment theres not much if a fulcrum. It's pretty much moot anyway, if you have a decent, up to reg towbar, neither will be a problem.

The rack will fail a million times over before the towbar even notices it's loaded.

it's a nice bridge...
 

moorey

call me Mia
Vertical overall, the further out from the attachment point the load is, the more leverage force is placed on the litch area. Vertical might undergo more torsional twisting when loaded with 5-6 bikes but as the main load is pretty much directly over the attachment theres not much if a fulcrum. It's pretty much moot anyway, if you have a decent, up to reg towbar, neither will be a problem.

The rack will fail a million times over before the towbar even notices it's loaded.

it's a nice bridge...
250kg max at the hitch could pretty quickly be reached with 4 ebikes on a platform rack hanging 4 foot back, I’d reckon. For the second time today I’ll point out physics isn’t my forte.
 

Haakon

Keeps on digging
Also bear in mind 100kg on the rack for example will be more than that when hitting a big bump in the road - you need a fair margin, although the towbar rating probably already has that margin built in.

*also not awesome at physics…
 

Knuckles

Lives under a bridge
250kg max at the hitch could pretty quickly be reached with 4 ebikes on a platform rack hanging 4 foot back, I’d reckon. For the second time today I’ll point out physics isn’t my forte.
Ball mass is about the steering and suspension geometry of the tow vehicle.

Exceeding the maximum ball mass rating, in either direction + or - and you will introduce sway and yaw to both the tow vehicle and load, ultimately introducing yourself to being jacknifed, upsidedown, in a table drain, once you hit crusing speed. It is not the strength rating of the hitch itself.

it's a nice bridge...
 

Sheepie

Likes Bikes
Vertical might undergo more torsional twisting when loaded with 5-6 bikes but as the main load is pretty much directly over the attachment theres not much if a fulcrum.
This is why sway straps are so important for vertical racks over 4 bike, for $10 worth of ratchet straps from Bunnings it secures the whole thing and reduces a lot of dynamic stress.
While we’re on straps, a lot of the verticals are designed for shuttling so only have bungees on top, I’ve found the grunt cam straps (also from Bunnings) are a cheap insurance policy for long / high speed / extremely rough trips.
 

moorey

call me Mia
Ball mass is about the steering and suspension geometry of the tow vehicle.

Exceeding the maximum ball mass rating, in either direction + or - and you will introduce sway and yaw to both the tow vehicle and load, ultimately introducing yourself to being jacknifed, upsidedown, in a table drain, once you hit crusing speed. It is not the strength rating of the hitch itself.

it's a nice bridge...
Your.
 

komdotkom

Likes Bikes and Dirt
250kg max at the hitch could pretty quickly be reached with 4 ebikes on a platform rack hanging 4 foot back, I’d reckon. For the second time today I’ll point out physics isn’t my forte.
But if you have 4 e bikes on the back
A) you deserve it
B) you can afford to get a decent tow vehicle
 

Dales Cannon

lightbrain about 4pm
Staff member
Ball weights are a static load, dynamic loading can be up to 2 or 3x that momentarily. Hitch and towbar design takes that into account and works on that load being applied at a set radius from the bar mounting points. The ball weight both puts a vertical load on the back of the vehicle as well as creating a bending moment on the bar frame and chassis. Moving the loading point further from the factory position reduces the allowable load accordingly. For example if the hitch was 50m long you wouldn't fit in the garage.
 
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