Since SUVs are subject to rolling during an accident the last thing you want is the spare flopping around inside the cabin. I'm not sure ratchet straps in an x-pattern (much less bungies) over the spare would contain it during a multiple rollover. Perhaps if you weaved the strap through the wheel center hole it would help matters but bolting down is the best way to go.

 

I do not believe the cargo area tie-downs have adequate strength to keep a strapped spare tire secure during an accident. I think the forces exerted on the tire during an accident would cause them to fail.

Also, if a car is in an accident, it's acceleration is not 60 miles per hour. What was calculate earlier was the momentum of a 100# object traveling at 60mph. Instead, you need to look at the impulse force of an object. If the original speed is 60mph, its final speed is 0mph, and it changes speed in one second (demonstration purposes) then the equation for the impulse force would like like this:

m[vx(t)-vx(0)]=integral from 0 to t of Fx(t')dt'

change in momentum is -6000#mile/hour or 8800#ft/s;
if this happened over 1 second then the the right side looks the following

Fx(1)*1second-Fx(0)*0

divide 1 second out from the right side and you get 8800#ft/s^2 for the impulse force acting on the 100# object

 

Ah, yeah... That makes perfect sense...


But i guess the end result is that it has a heck of a lot of force!

 

And when you think about the load rating of a ratchet straps (Example) it still does not look like a good idea, even if the cargo rings could hold.

 

Agreed, the straps don't look like they will hold the force at all. It is simply amazing how much force a relitivly small object can have when travleing at just 60mph.

Just goes to show how much force a 5000 pound truck has at 60mph. That has got to be a scary figure!

 

Part# --- 2615SH

Length ---15'

B.S. ---1,200 lbs

W.L.L. ---400 lbs


but my spare isnt even barely 50 pounds...and if my 4runner does end up flipping im pretty much anyway lol

 

Good idea on making sure your stuff is secured. I'm a fire fighter and I can't tell you how many times a wreck is much more than a fender bender. You always need to think about the worst thing that could happen and then figure out how your going to secure your stuff. This is how I had mine secured in my old rig
and I also built a mount just in case I wanted to save some space in the back
Granted in being able to mount the tire upright you would need the roll bar installed. None the less good idea on making sure your stuff is secured you never know what could happen (not one person has ever thought to themselfs I think today I'll be in a wreck and it will send me into a roll) but just know anything is possible.

 

Yeah but according to the new math even that 50lb tire will have about 4000lb of force in a 60mph crash. but those are way better thatnothing and if yo go in an X pattern it should stop it in all but th worst cases. And if it doesn't then it will take a lot of energy out of it before it breaks lose.

 

Correct. If you have two straps holding a tire in an X pattern, then their combined holding strength is actually 4800#. Each end can support 1200#. My point was more of concern for the cargo rings people are using to attach their straps to. I really do not believe these will hold, although I do not have any data to prove this, I am just looking at it as the weakest link.

 

Yeah, i have never really looked at the rings closely so i can't give any input about that. But that seems like a reasonable thought.

 

Be prepared for a shock when you call the dealer for that cover.Toyota is very proud of their cargo covers.I may have an extra I'd be willing to sell,I'll have to check if I still have it.PM me if interested.
Shubey

 

I think it's time for someone to test the tiedowns. Who is game to strap down their tire and crash their 4runner into a wall at 60mph? It is for a good cause!

 

well to add to the further blah blah and this already way more complicated than it is issue, in a crash the forces on the tie downs more than likely would not be directly straight up. more of a pull from the side as the tire tries to go foward. I say even if a tiedown or strap fails at least it would reduce the velocity of the spare.

 

I guess I am just being a nerd.

But it sounds like a good idea to test the strength of the cargo rings. I will have to see what we can come up with.

 

im actually surprised this topic hasnt been discussed in depth like this before.

also ADH i like your set ups in the back. they look to be very sturdy.

 

wear a helmet

 

You guys are makeing this much too complicated...

Just make your friends sit in the back seat


Seriously though i would be more worried with the spare flopping around while off roading or in a small fender bender and breaking the rear windows

 

Ah but see that doesn't have the drama and cool factor that getting decapitated has!

 

ok thats enough talk about me getting my head freakin taked off by a spare tire.