Hang on, are you guys talking $1,600 for tires, wheels, and a lift, or just tires and wheels? I'm a little confused. $1,600 seems really, really low.
What do I need to do to run 33s on my TJ?
- Thread starter Wrangler2158
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I have the Zone 4.25" lift running 35's, it's barely enough lift for me but would be great for 33's. Rides pretty well with the hydro shock and for being a $650 lift. With the MML I have no driveline vibrations either. I ended up buying a set of used stock JK wheels with 60% tread 35" discoverer st Maxx tires for another $600. And some 2" wheel adapters that accounted for the backspacing of the JK wheel and 5x5" lug pattern ($200). I can do light to moderate wheeling pretty well all under your budget!
There are qualities of that arm design that would encourage the Jeep to want to fall over backwards. It isn't necessarily the lift height that is the problem.
Agreed. But there is still something to be said for LCOG on steep climbs. At some point, it all comes down to what the math says. The closer to the ground your COG is, the harder it is to put the COG over an unsupported part of the Jeep (IE not within the rectangle defined by the tires). This means you can put the Jeep at a greater angle without rolling over.
Jeep builds really come down to what you're looking to do with the Jeep. If you're just trying to climb steep stuff, you're going to want to keep the COG as low as possible. If you're trying to have a nice Jeep to drive around with on the road and trail ride, you don't need to necessarily worry about COG as much.
I still believe you're making way too big of a deal over COG and your drawings are overly simplistic as they define the problem far too narrowly. As jivw said, there's a lot more than just COG at work when worrying about whether a TJ is going to fall over backwards on a steep climb or tip over when off-camber
I won't disagree with the concept. But translate that into Jeep speak. How tall and what angles are we looking at? I have leaned mine similar to the blue Viking TJ. Once I get over my psychological fear, I eventually realize that the Jeep is fine.
If you view the Jeep at rest, then I don't think there is much more than COG and gravity at play (IE if you lift it up with a forklift to see how far it takes to roll it over). If you are moving (as most Jeeps are when climbing obstacles) there is more at play such as suspension geometry. But COG still comes into affect no matter what suspension geometry you have.
I don't think I'm making a big deal of COG at all. There are different types of wheeling than Johnson Valley. Different types of wheeling require different types of setups. If I wanted to through a giant mud bog, I'd lift my Jeep 10 feet. If I was going to Johnson Valley, I'd set my Jeep up similar to yours. If I lived in Moab, I'd put highline fenders on and run as little lift as possible. Every type of wheeling is different and requires a different build. Simply dismissing COG isn't useful as there are some types of wheeling that need LCOG.
I've also leaned my Jeep over like that. Definitely unnerving if you aren't used to it. But I think that leaning it over is much different than leaning it backwards due to the fact that when accelerating forward on a steep climb, you are essentially asking for the Jeep to roll backwards. You can move forward all you want when leaned over and momentum isn't going to try and roll you over.
On Hell's Revenge, I was trying to get up a climb after stopping on it. My front wheels lifted off the ground and I pivoted around 20 degrees to the left. Whether that is due to suspension geometry or COG, I don't know. But from my experience driving LCOG buggies in Moab, I think it is due to COG.
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People are confusing center of gravity and center of mass.
The center of gravity shifts as the object moves. Specifically, the center of gravity is the point at which gravity acts upon an object.
The center of mass of an object never changes. It’ll remain constant regardless of outside forces (such as gravity).
“Low center of gravity” as it’s being used in this thread isn’t really a thing. “Low center of mass” makes more sense — somewhat — but it’s redundant. Center of mass is center of mass. There are no variables. You can build a TJ with a low COM, but it’s still called COM.
What you’re describing in your trip to Hell’s Revenge is center of gravity, yes. However, you’re combining the two terms (COG and COM).
Your TJ has a COM that remains constant. When your front two wheels left the ground, it was because the COG shifted. That is to say: gravity began to take over. The COM of your TJ remained constant.
I somewhat agree with @Jerry Bransford in that COG is overused, but that’s because it’s used interchangeably with COM — but they’re not the same thing. Building a TJ with a COM that suits you is possible, but the COG will always shift.
I want the place where gravity acts to be as low as possible. Building a Jeep with a "low center of gravity" in mind would result in a Jeep with a low center of mass even if LCOG doesn't exactly fit the definition. COM and COG are identically positioned when at rest. Sure, the COG can shift around, but it for the sake of discussion it doesn't really matter. My argument still remains the same. COM versus COG is really just semantics at this point.
You don't seem to understand that this sentence completely contradicts everything you've written in this thread, and it's because you don't understand the difference between COM and COG.
They are not interchangeable. To claim otherwise is willful ignorance and could potentially be dangerous.
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Ok, say I've never taken basic high school physics before and don't know the difference, explain to me why the difference matters for suspension heights on a TJ (on earth...). I will not argue that COM and COG are interchangeable, but that keeping COG low is the same thing as keeping the COM low. You are making an argument completely based on slightly different terminology, not on the content of the argument.
I'm still confused as to what your argument is about COG (or COM) in a TJ? What are you trying to say?
I'm not sure what the argument is either. However you want to describe it, the desire to not flip over is clearly understood.
I reread the thread and I'm lost (even at my own answers sometimes). I think the point I was trying to make is that COG is fairly important to keep in mind for certain types of wheeling and that it has a large affect on how the Jeep performs. I shared some experiences I had with different suspensions and COG to try and qualify that (I think...).
I'm interested to see how the COM vs COG thing ends up and what that means for the best way to set up a Jeep (according to the physics at least).
Spic
TJ Enthusiast
I wanted 33's but decided with my 3.07 gears and only having a 2 inch BB lift that 32's would be best, I'm happy with the look and it rides great, there's lots to consider when lifting a jeep and changing up tyres, what's it going to be used for, your gears, your wheels and back spacing, but most importantly your budget, I'm no expert as I'm still learning myself, but one thing I have learned over the last 7 months of owning a Jeep is decide what you want, and I mean what you really want and stick with it, anything less will just make you miserable, and your only end up buying things twice. The pic is with 32's 2 inch lift and slight trimmed fenders.
I don't really know how much simpler I can make it beyond "COG and COM are not the same thing and are not interchangeable".
I mean, if you want to keep using the term "center of gravity" incorrectly, go right ahead. I was simply trying to help you understand the difference between the two.
Oh well.
On my 2005 TJ I have Toyo 285/75/17s on a Rough Country 2 1/2 lift. Previous owner put lift/wheels/tires on. Paid about $3300 with labor. According to Toyo's website the overall inflated diameter of the tires is 33.9". No body lift or motor lift. Works fine, no rubbing for what I have done here in FL.
Ok. It still seems like center of gravity is a more widely used term (even in academic reports). And from what I've googled to review my high school physics, the difference between COG and COG doesn't seem have any affect on what I'm talking about.
I'll make this my last post on the topic because it really isn't adding much in terms of knowledge, but I urge you to check out what I've linked below.
https://www.cjponyparts.com/resources/center-of-gravity-infographic