I have also never seen someone die from having a tree up their ***** but it is pretty safe to assume what the end result will be.... physics and all 
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Motorcycle hitch carrier/towing
- Thread starter alangolding25
- Start date
Motorcycle Mike
Well-known member
Further to the potential damage to the clutch, etc, I simply wouldn't want the extra wear on the rear tire.
Presumably, the reason a person would use such a device is that the area they want to ride in is further than they want to ride to... like the dragon, out West, etc.... but that 1200+km and up is still going on your rear tire -- sure, with less weight, but 100% of it down the center of the tire squaring it off prematurely.
This is how I feel about hitch carriers as well.
The load center of a bike on the carrier would roughly be double what the load center is of a simple trailer hitch ball so you're effectively doubling the torque that's transmitted through the hitch and the farther back your load is the more weight you put on the rear suspension.
It's pretty simple physics but a lot of people seem to gloss over this. I'd consider using a hitch carrier on a full size truck or SUV, nothing smaller.
DoubleJ
Well-known member
Also use a air bag set up on the rear suspension to eliminate any sag. The Escape would be well past its limits. Versahaul has a chart for various vehicles on their site with limitations and recomendations. I now use mine on a '11 F 150 and a '04 3500 Chev Express van. Thousands of klms covered all over north america.
I have a large hitch rated as high as I could find on my 3500 series diesel van.. I regularly tow trailers for work......and if I had a hitch carrier, maybe a 250 lb dirtbike would go on it...or wife's 330 lb Ninja 250 at the very max.
As Caboose stated, the torque multiplication from the bike being located more rearward is way outside the hitch manufacturer's design. You probably have been getting away with it so far because companies over-engineer things to save themselves the liability of failures causing injury and death. Even bridges can withstand roughly twice their advertised load limit before failure in a perfect world. But I wouldn't risk it.
As Caboose stated, the torque multiplication from the bike being located more rearward is way outside the hitch manufacturer's design. You probably have been getting away with it so far because companies over-engineer things to save themselves the liability of failures causing injury and death. Even bridges can withstand roughly twice their advertised load limit before failure in a perfect world. But I wouldn't risk it.
I have also never seen someone die from having a tree up their ***** but it is pretty safe to assume what the end result will be.... physics and all
lol thats funny..
Yeah I have a full size truck.
Could someone who thinks the math is simple do the math. If the math is that simple I would love to see it. I hear you all on your points. I don't disagree, I just want to see the math. I have been using mine for years now with no issues, so its hard to accept something that I found to be untrue (so far).. If it can be proved with science, I will concede. Otherwise my experience proves otherwise.. I mean how do we know for a fact that the hitch was not designed for sustaining this weight. I would love to hear from a person in the automotive industry, who has a true understanding of the materials being used and their structural integrity.
Here is another thread at another forum with wide ranging views..
http://www.advrider.com/forums/showthread.php?t=478968
[url]http://www.sportbikes.net/forums/general-sportbikes/454009-hitch-mount-motorcycle-carrier-comparison-thoughts-reviews-users.html
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BigEvilDoer
Well-known member
Using basic fulcrum theory:
Weight of bike = 400 lbs.
Distance of Bike from Hitch: 20 inches
Length of Receiver: 8 Inches
Total load at end of receiver hitch = 1000 lbs.
Here's a neat graphic I just discovered... Should sort everything out easily for anyone.
Even a class IV hitch with a 24" extension shouldn't carry more than 350 lbs.
Thanks dude.. that graph is perfect. I am going to measure the distance from the hitch next time I put it up.
BigEvilDoer
Well-known member
Don't forget - the weight doesn't include the weight of your hitch mounted carrier.
So bike: 400
Carrier: 75 (estimate)
Total: 475
Well, like I said, a full size truck or SUV is probably adequate for a 400ish lb sport bike on a hitch carrier. Changing the load center as seen by the hitch changes the loading of the hitch and this should be considered when choosing a tow rig and hitch classification. There are two things to consider really, the first is the loading as seen by the rear suspension and the second is the torque being transmitted through the hitch into the frame.
First we can examine the rear suspension loading and we can use my truck as an example. It's a 2005 Sierra crew cab short box. The wheelbase is 143.5" and the distance from the rear axle to the hitch face is 46".
Using a normal receiver with a ball adds approx 8" to the hitch so the load center is 52" from the rear axle or 195.5" from the front axle.
Using a hitch carrier would add approx 24" to the hitch so the load center is 70" from the rear axle or 213.5" from the front axle.
At static equilibrium the force of the tongue weight pushing down on the ball is balanced by the force of the ground pushing up on the rear axle (in addition to the regular weight of the truck without a trailer). The sum of your moments is zero.
A trailer with 400lb tongue weight on a regular ball creates the following:
0 = Fr(143.5") + -400lb(195.5").
Solving for Fr (the reaction force) gives you the additional load as seen by the rear suspension.
Fr = 544lbs
A hitch carrier with a 400lb bike creates the following:
0 = Fr(143.5") + -400lb(213.5")
Similarly
Fr = 595lbs
So realistically the change in loading on the rear suspension is not that big. Any modern half ton truck or full size SUV can handle that.
The second thing to consider is the torque transmitted through the hitch. Similarly at static equilibrium the moment created by the load is balanced by the hitch itself.
A trailer with 400lb tongue weight creates the following:
0 = Tr + -400lb(8")
Solving for Tr (the reaction torque) gives you the torque being transmitted through the hitch.
Tr = 3200in*lbs or 266ft*lbs
A hitch carrier with a 400lb bike creates the following:
0 = Tr + -400lb(24")
Solving for Tr
Tr = 9600in*lbs or 800ft*lbs.
This is where you see a significant difference in loading and this is what you'll need to be certain that your hitch and the rear frame rails of the vehicle can tolerate.
BigEvilDoer
Well-known member
Or, to save on Caboose's calculations, you can go to the website I got that graph from..
Mentions everything that Caboose did and lets you plunk in numbers etc to do the calculation for you.
http://www.visualsc.com/hitch_calc.htm
Mentions everything that Caboose did and lets you plunk in numbers etc to do the calculation for you.
http://www.visualsc.com/hitch_calc.htm
Thank you! I am surprised that all the other trailer hitch threads didn't get blessed with this math to help educate!
Thank you for the link! I bookmarked it just in case.
LOL.. I think this is the most helpful trailer hitch thread GTAM has ever seen.. lol
There is also a ridiculous torque imposed in the plane of the rear of the car while cornering. Normally this would be something like 1500 lbs (trailer weight) * 6" (offset between hitch and ball) * 0.81g (emergency manoeuvre in an escape) = 607 lbft.
With a bike carrier, the math becomes 475 lbs (bike and carrier) * 3' (approximate distance to vertical centre of gravity of bike on carrier) * .81 g = 1150 lb ft. That's double what what the hitch would normally see.
In a similar fashion, the torque when looking from above is close to zero with a trailer (hard to transmit through a ball, but there would be some due to the distance between hitch and ball) and 475*1.66 (distance in ft from hitch to cog of bike)*.81g (emergency manoeuvre) = 640 lb ft with a bike carrier.
The exceptionally bad thing about emergency manoeuvres is they are usually quickly followed by similar forces in the opposite direction, rapidly imposing loads of 500+ ft/lbs back and forth puts a giant strain on everything.
If you get really unlucky, shifting the cog of the vehicle back at the same time as reducing the weight on your front tires (both of which happen when installing a hitch carrier) will make your vehicle push like crazy.
With a bike carrier, the math becomes 475 lbs (bike and carrier) * 3' (approximate distance to vertical centre of gravity of bike on carrier) * .81 g = 1150 lb ft. That's double what what the hitch would normally see.
In a similar fashion, the torque when looking from above is close to zero with a trailer (hard to transmit through a ball, but there would be some due to the distance between hitch and ball) and 475*1.66 (distance in ft from hitch to cog of bike)*.81g (emergency manoeuvre) = 640 lb ft with a bike carrier.
The exceptionally bad thing about emergency manoeuvres is they are usually quickly followed by similar forces in the opposite direction, rapidly imposing loads of 500+ ft/lbs back and forth puts a giant strain on everything.
If you get really unlucky, shifting the cog of the vehicle back at the same time as reducing the weight on your front tires (both of which happen when installing a hitch carrier) will make your vehicle push like crazy.
He lower the price to 950 from 1050 - Motivated to sell, you can probably get it for 850 and that is an awesome price.
If neither you or meme's friend wants it I would be happy to sell my current one and buy this one. I will wait since I have no need for it.
BigEvilDoer
Well-known member
Nah. I leave that to the professionals. ;-)
Funny that I see this thread ... my friend in the states just had his bike fall off the back of his hitch carrier last week. He was only carrying a dedicated dirtbike (Honda XR) on a HF carrier on the back of a Jeep Grand Cherokee (with Hemi). The HF carrier actually snapped in the middle, you can see the metal completely broke off and the carrier came off (luckily) in the parking lot and not on the highway.
I personally would not trust a carrier. I have a trailer
I personally would not trust a carrier. I have a trailer
Where were you when I was looking for trailers :sad3:
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