Tongue Weight Ratings

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turboeclipse

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I am trying to determine how the tongue weight rating affects the weight capacity for a hitch mounted bike carrier. I own a 2010 2-door sport with 3.21 axle ratio.
I understand that for towing the axle ratio primarily determines the tow capacity for the vehicle. The owners manual states for a 2-door sport model with 3.21 axle ratio the towing capacity 1000lbs with a tongue rating of 100lbs. For the exact same model with a 3.73 axle ratio the towing capacity is 2000lbs with a 200lb tongue weight rating. It seems to me that the tongue rating should also be based on the frame and suspension design. I don't see how the axle ratio should affect the tongue rating of the vehicle when all the other vehicle design characteristics are exactly identical. I know that a bike carrier is somewhat of a special case in that the vehicle isn't being used to pull a trailer but the tongue rating is the key factor when determining how much weight can be put on the carrier without affecting the steerability of the vehicle. Does anyone have any thoughts or experience on this?
 
If your just wanting to know about carrying a couple bicycles on the back you will be fine.
 
BLACKJKU said:
If your just wanting to know about carrying a couple bicycles on the back you will be fine.
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They are electric bikes. 50lbs each plus the Thule rack. I estimate the weight at 150lbs. So that is why I am asking. That would be the difference between a 100lbs and 200lbs tongue weight rating.
 
Tongue weight is the downward force the weight of the trailer's tongue on top of the hitch ball. Tongue weight should be 9-15% of the gross trailer weight. The tongue is on the trailer and tongue weight applies to the ability of a vehicle to pull a trailer. Gear ratio effects tongue weight as it applies to a trailer and the vehicle's ability to generate enough torque to get the trailer moving and to get the trailer to slow down.

For example, a 3.21 JK Sport has a lower towing capacity and tongue weight because the gear ratio will put an undue amount of stress on the engine in the lower gears trying to get the JK and trailer weight moving.
The 3.73 and bigger gear ratios have higher towing capacity and tongue weight because of the amount of torque they can generate to get the JK and trailer going.

So, your bicycle rack and its ability to hold a couple hundred pounds of bikes is not a function of tongue weight at all. Hell, I'm close to 300lbs and I stand on my rear bumper all the time to load my roof rack. I could probably jump up & down on the hitch and it wouldn't bother it at all. The capacities are used as safety features. If you took a 3.21 geared jeep and hooked a 3500lb small trailer to it, you'd probably be close to red-lining the transmission thru the first 3 gears just to get it going.
 
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Pretty much what Anybodyhome said. The function of tongue weight has more to do with pulling capacity of a trailer than downward force only on the rear bumper.
 
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It all seems to comes down to driveability. Based on the suspension and chassis design at some load the front end of the vehicle can become unstable affecting steering. The question is for non-towing hitch applications what tongue weight becomes an issue? So taking axial ratio out of the equation my guess is that the max tongue weight rating would be 200lbs. So in my case having 150lbs on the hitch shouldn't be a problem. Thanks for the feedback!
 
turboeclipse said:
It all seems to comes down to driveability. Based on the suspension and chassis design at some load the front end of the vehicle can become unstable affecting steering. The question is for non-towing hitch applications what tongue weight becomes an issue? So taking axial ratio out of the equation my guess is that the max tongue weight rating would be 200lbs. So in my case having 150lbs on the hitch shouldn't be a problem. Thanks for the feedback!
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The steering issue resulting from a load on the rear of the vehicle would occur by changing the COG of the vehicle. Not that 150lbs of bikes on a hitch-mounted rack would likely change the COG enough to make a difference, but the addition of air bags would easily offset the weight. So, if you're concerned that adding even more weight, this might be the way to go.
 
Just my thoughts on it but wouldn't be any different then putting about 300 lbs in the rear trunk section of the jeep.

I carried around 320 lbs of salt bags in the rear of mine for a couple weeks and had no issues.
 
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