**i'm getting sick of being bumped!!**

[sonerick]

What? No no no. Obviously some serious misunderstanding as to the purpose of a crumple zone. The frame is NOT a crumple designed component, never. Right, that's why 4Runners > Grand Cherokees. Grand Cherokees have no frame, crumple zones are built into the unibody (in addition to various other components).Crumple zones are designed to absorb impact and prevent the ALL dangerous frame bend that kills people. A bumper, quarter panel, door; these are places that use specifically designed air spaces to create specif ways to absorb energy to LIMIT frame impact. Right again. Who are you arguing with? I never said 4Runners had no crumple zones...

Unibody and On fram constriction impact how this is implemented, no doubt, but it doesn't change the basic purpose. You bet your ass the 4runner has specifically designed crumple zones to keep the frame from bending. When a frame bends, this is when the interior cage of the vehicle is destroyed and means more damage to the inhabitants. Again, never said 4Runners have no crumple zones. I said they have a frame, whereas Grand Cherokees do not. You are really just proving my point.


Now. As to the hitch. Sorry, but hitches bypass a crumple zone. You can ignore it and blame it on Jeeps all you want; but the reality is that when you place a hitch on your truck; the kinetic energy from a rear end collision is taken directly to the frame itself, rather than through the bumper and rear crumple zone. You are correct that hitches attach directly to the frame on our 4Runners and bypass the crumple zones. Grand Cherokees however have no frame. The hitch attaches to the unibody, which has crumple zones integrated into it. In the case of a Grand Cherokee, kinetic energy is not absorbed by the frame, BECAUSE THERE IS NONE. It is absorbed by the unibody's crumple zones, resulting in damage similar to that in the picture above.


The reality is, while a hitch will prevent minor damage in a low speed, low force impact In a 4Runner yes. In a Grand Cherokee, no. Did you read the caption in that picture? That damage happened during a low-speed (5mph) collision.; a high impact crash it can cause substantial frame damage.

Also, this alert from the national Safety Commission kinda sums it up. A hitch alters the impact absorbing characteristics of a vehicle, in turn causing more impact force to a body. A.k.A more whiplash.

The National Safety Commission Alerts: How Receiver Hitches Affect Rear End Collision Injuries

You're misinterpreting what I am trying to say by taking it to the extreme. I understand that the 4Runner has crumple zones to absorb impact energy. I did not say the 4Runner has no crumple zones. It's body has many of them designed to protect the frame and the inhabitants of the vehicle.

What I did say is that the unibody (NO FRAME) construction of the Grand Cherokee has crumple zones built into the rear that likely cause the damage seen in that picture. A trailer hitch on the Grand Cherokee is tied into the unibody, and thus has a more direct impact on the crumple zones in the event of a rear-end collision. A trailer hitch on a 4Runner is tied directly into the frame, which itself has no crumple zones. Had that been a body-on-frame 4Runner, the damage would not have been near as extreme.

I appreciate your enthusiasm for making sure the correct information is being posted on the forum. However, there's no reason to jump down people's throats for no reason. You drew some pretty flimsy conclusions about what I was trying to say from the two sentences in my previous post.

 

[saintbumper]

You're misinterpreting what I am trying to say by taking it to the extreme. I understand that the 4Runner has crumple zones to absorb impact energy. I did not say the 4Runner has no crumple zones. It's body has many of them designed to protect the frame and the inhabitants of the vehicle.

What I did say is that the unibody (NO FRAME) construction of the Grand Cherokee has crumple zones built into the rear that likely cause the damage seen in that picture. A trailer hitch on the Grand Cherokee is tied into the unibody, and thus has a more direct impact on the crumple zones in the event of a rear-end collision. A trailer hitch on a 4Runner is tied directly into the frame, which itself has no crumple zones. Had that been a body-on-frame 4Runner, the damage would not have been near as extreme.

I appreciate your enthusiasm for making sure the correct information is being posted on the forum. However, there's no reason to jump down people's throats for no reason. You drew some pretty flimsy conclusions about what I was trying to say from the two sentences in my previous post.

Great discussion gentlemen but we're off the topic...Forget frame railed and uni-body.

We were talking ball mounts and receiver hitches. A ball mount acts as a lever in your receiver hitch if it is hit. The typical ball mount sticks out about 9" from the rear. More if it is a Pintle type arrangement.

Because of the soft suspensions of passenger cars they dive when they hit something - especially if they apply the brakes right before they rear end you. This downward pressure acting on the ball mount has the potential to wreck your frame - whether it's frame railed or uni-body.

From Archimedes: "Give me a lever long enough and I'll move the earth." The further your ball mount sticks out (or drops down) the greater the risk.

 

[Anonymous4Runner]

That's pretty funny coming from a guy who purposely rammed a brick mailbox post in a fit of rage.

Just sayin'.

:O - Only if you knew the real details behind the incident....

 

[PWGUNNY]

Yep, Bumper Hitch. Mine works even without the ball. The receiver sticks out just enough to leave a 2" square on their front bumper. It's happened to me twice already. No damage to me, but a new emblem on their bumper.

 

[Catfish]

On the flip side of the coin...

Before I had my 4Runner, I had a 2007 Mazda 6. I was parallel parked on a street behind an SUV with a massive, protruding trailer hitch. I noticed it when I parked and even went back and moved my car back a bit to allow PLENTY of room for him to get that thing out of there. When I came back to my car a few hours later, most of my front bumper had been torn off. I could obviously see where the ********* had backed into me, punched through my bumper with that damn hitch, then pulled forward...pulling my bumper off with him as he drove off into the night.

That sucked. Get the hitch, but know what you're dealing with. Don't cost some innocent person several hundred dollars in damage at no fault of their own.