You know what, you're right, I was mixing things up. The longer lowers will add caster angle, which is why I suggested the OP extend his earlier.
Is yours wondering too?
I need some advice
- Thread starter jmharris23
- Start date
You know what, you're right, I was mixing things up. The longer lowers will add caster angle, which is why I suggested the OP extend his earlier.
Is yours wondering too?
Excellent point, Jeff! Lockers pit left axle shaft against right axle shaft when external forces are attempting to rotate the wheels in opposite directions. Off-road on dry, sticky rocks, that happens a lot. On dirt or even pavement it's very infrequent. The only time I've seen it happen with locked diffs on the road is when a vehicle spins out of control. If the entire vehicle ends up rotating around an axis that lies between all four contact patches (in that rectangle), the inertial forces work to turn the wheels in opposite directions, and that can break axles or locker components.
Everything is relative. So, relatively speaking, for what it is, tire size, aerodynamics worse than a cinder block, it handles fantastic. Just a little bit more required steering input than what would be ideal. All fresh components up front. Tire pressure at 26-28psi.
Could very well be our shitty roads. Virtually every road has a crown to it.
Although I've never personally witnessed it, I've heard of locked 35's breaking on the road. And it's not about the axles rotating in opposite directions, it's about rotating at different speeds. Hit the rear locker in a high traction situation and make a sharp turn - the outer axle shaft wants to rotate faster than the inner shaft, and pop...
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Are you talking wonder or extra effort to turn the wheel? Wondering could just be the nature of a solid axle vehicle if everything else is in good condition. Extra steering effort could be too much caster, or at least more than necessary.
Road condition also factors in.
That's what caused my stock 35 spider gears to grenade and crack my carrier. Too much traction while attempting to overcome that traction, i.e. a burnout.
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And 8" or 10" wide wheels? 10" wheels are pretty squirrelly without lots of caster.
Another great post. I'd like to add an explanation as to why caster is important. The blue line represents a line drawn from the center of the wheel through the center of the contact patch. The red line is the axis about which the knuckles rotate (a line drawn through the centers of the top and bottom ball joints). The tractive force of the road on the tire acting over the distance between the point where the blue line intersects the road surface and the red line, measured perpendicular to the red line, creates a torque that can be either clockwise or counterclockwise. Automotive engineers realized over a century ago, that if that distance is zero, the vehicle will hold a steering angle, even if you take your hands off the steering wheel. That's an over-simplification, and in reality it doesn't quite work that way, but from a basics standpoint, it's helpful in understanding caster. In reality, neutral caster just feels odd.
Now, when you do have some caster, positive vs. negative is very important because the direction that the tractive force wants to turn the knuckle changes when you switch from positive to negative because as the wheel turns, that force moves off the steering axis and generates a torque that affects steering. The farther you turn the wheel, the farther away from the axis that force moves, and the torque increases.
With negative caster and with your hands off the wheel, instead of the vehicle holding the steering angle, the tractive force wants to turn the vehicle even more, and that increases the steering torque generated even more, turning it more, generating more torque, turning it more, etc., until the knuckle is at the steering stop bolt. By then, which happens very quickly, you're completely out of control - unless you kept your hands on the wheel and were counteracting that steering torque generated by the negative caster, which is a natural tendency.
On the other hand, positive caster does the opposite. When you start a turn, the torque generated is in the opposite direction, so it's actually wanting to reduce the steering angle. All vehicles (except maybe rear-steer vehicles and circus vehicles) have positive caster for that reason - take your hands off the wheel, and the vehicle straightens up. You actually have to keep force on the steering wheel to make a turn.
Of course, in reality, there are a lot of other factors affecting steering dynamics, so it's not quite as simple as what I described above. However, here's the general spectrum of caster from unrealistically high negative caster through unrealistically high positive caster:
- Unrealistically high negative caster - once you start a turn, the torque is so high that you are not strong enough to counter it, and you crash immediately by spinning out of control (probably rolling the vehicle in the process)
- Realistically high negative caster - you get tired arms while driving because you are constantly counteracting the torque, and it's constantly changing direction; you're also mentally fatigued because "I can't take my hands off the wheel!"
- Moderate negative caster - no tired arms, but you are mentally exhausted from concentrating to keep the TJ "between the ditches"
- Neutral caster - steering feels very light and a bit odd, but you don't really know why; you notice that it will maintain a corner with hands off the wheel
- Moderate positive caster - steering feels light and a bit odd, but less so than neutral caster; with hands off the wheel, TJ slowly corrects itself
- Realistically high positive caster - like realistically high negative caster, you get tired arms, but for a different reason - because it takes an abnormally-high amount of force on the wheel to make a turn
- Unrealistically high positive caster - I hope you like going straight, because you aren't strong enough to turn the wheel!
Another excellent point here, but it's not the width of the wheel that's the problem. Rather, its the change in the perpendicular distance between the steering axis and the center of the contact patch in the left/right direction caused by the 10" wheel's center being offset from the center of a stock wheel. The TJ steering was originally designed with the contact patch at a specific location - dependent on the wheel. Change that enough, and the change in steering dynamics will be noticeable. The simplistic explanation above doesn't take that distance into account.
They better! The crown is what keeps you from hydroplaning every time it rains. A 2% crown is standard for road designs around these parts. That works out to about 1/4" per foot.
I once had a well known axle builder show up on the forums whereupon he set about bragging over how perfect he and his crew were able to set the inner Cs when they were welding them up. It was a great point of pride that they were able to get them both perfectly lined up with each other. I asked why they were not dialing in any cross caster.
I shit you not- he asked "what's that and who does that?" I pointed out that every TJ front axle ever made had a small amount of cross caster built in to compensate for road crown. It went to hell in a handbasket from there but I was surprised that an axle builder with a ton of experience would not understand such things. I know better now but my expectations were much higher back then.
From what is available to buy,wheel width is all i (or the O.P.) need to know to find what I'm looking for.
You are as likely to confuse as to help with the long posts.and certainly make this take much longer to deal with than it needs to be.
Keeping things simple and to the point are all that's necessary. Helping people on forums is already like herding cats with adhd!
Thank you for the opinion. I believe in teaching a man to fish, not handing him a fillet-o-fish. You can always place me on ignore. Trust me, I'm not easily offended.
If somebody is bragging about using an angle finder correctly you already know they ride the short bus
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