I assume you put GM aluminum wheels on it, and not the Roadtrek factory wheels. Offset should be about +27mm.
What you describe in handling is pretty much the classic symptoms of toed out, instead of in. When toed out, they get "twitchy" with small corrections amplified into big movements. You pretty much weave your way down the road. You had the toe in checked, but I don't understand the numbers. Toe in is plus, toe out is minus, so I think you just have the signs switched. If the front end is worn, the slack from the wear adds to the toe out direction, so it could have toe in when checked, but go to toe out while driving. This is a very common mistake that shops make. They should always push the wheels in and out against the looseness to see how much the toe changes, and make sure it doesn't switch to out. As vehicles age, and the front end parts wear, they generally will need more toe in to keep handling well (this is for rear drive). The spec on our 07 one ton is +.1* +/-.2* total toe in. .1 degree is only about .050" in the old school toe in dimensions, which is pretty small for such a big vehicle 1/16" to 1/8" in was pretty common in the day.
The wheel change changes the load on the spring, bearings, etc, as you mention, but it also changes the scrub radius, making it lower. This makes less effort needed to overcome the roadforce put on the tire, so steering gets a bit lighter. It shouldn't make it twitchy, however. It will reduce the affect how one wheel bumps and puddles throw you around, improving that a bunch.
With the wheels moved in, you may need a different tire pressure. Overinflation in the front can make them twitchy also. On a 170 45/50 psi probably would be plenty.
The negative camber is probably because you are low, and if you are on the bumps while sitting, you are VERY low. The normal ride height for the one ton puts the front wheel wells about 35.5-36" from the ground with 245-16-75 tires. Our factory manual shows the 8600# capacity 2500 at only .3" lower. Negative camber will also make them less directionally stable, as you are running on the inside of tire, which can make the effective scrub radius change to the minus direction. Possibly going to the less offset, which reduced scrub radius, and negative camber reducing scrub radius has put you over the edge. Slight positive camber is usually the best for directional stability. Loose wheel bearings also can move you toward negative camber.
The Bill Erb topic has one positive from the Mexican Doctor, and one negative from someone else who got Erb springs, but his shop was not able to get them into the van. So it's a tie, I guess.
You have a big advantage, as you have a 3/4 ton van. It is very likely that if you put the 1 ton springs in it, you may just come out right. I think all the factory springs are about the same free length, and only change in spring rate. Our Tufftruk 5K springs and factory 4300# springs were essentially the same free length. Both could be put in without a spring compressor. The longer springs folks are talking about are because they want to get lower spring rate (softer ride), but still gain the 2" of lift to get back to factory ride height. You then need a monster spring compressor and can get the bowing and interference issue that have been mentioned. If you put the bigger springs we have been using for the 1 tons in your van, you will be very high and harsh, I think. Most of us have at least 4100# on the front wheels.
The fact that the bottom of the van is all banged up is pretty worrisome. Ours would only hit in the middle, if it was high centered, on uneven terrain. It never hit on highway dips or bumps. A good look over over the frame for damage is probably in order. Negative camber is one of the first things that shows up if a vehicle has bottomed out hard and often.
It certainly wouldn't hurt to go down and see Bill Erb, as he does have an excellent reputation, to see what he recommends, and if it makes sense. One thing all the discussions we have had on here have shown is that there appear to very very different results being achieved from some of the same changes It is very hard to understand why that is happening.
What you describe in handling is pretty much the classic symptoms of toed out, instead of in. When toed out, they get "twitchy" with small corrections amplified into big movements. You pretty much weave your way down the road. You had the toe in checked, but I don't understand the numbers. Toe in is plus, toe out is minus, so I think you just have the signs switched. If the front end is worn, the slack from the wear adds to the toe out direction, so it could have toe in when checked, but go to toe out while driving. This is a very common mistake that shops make. They should always push the wheels in and out against the looseness to see how much the toe changes, and make sure it doesn't switch to out. As vehicles age, and the front end parts wear, they generally will need more toe in to keep handling well (this is for rear drive). The spec on our 07 one ton is +.1* +/-.2* total toe in. .1 degree is only about .050" in the old school toe in dimensions, which is pretty small for such a big vehicle 1/16" to 1/8" in was pretty common in the day.
The wheel change changes the load on the spring, bearings, etc, as you mention, but it also changes the scrub radius, making it lower. This makes less effort needed to overcome the roadforce put on the tire, so steering gets a bit lighter. It shouldn't make it twitchy, however. It will reduce the affect how one wheel bumps and puddles throw you around, improving that a bunch.
With the wheels moved in, you may need a different tire pressure. Overinflation in the front can make them twitchy also. On a 170 45/50 psi probably would be plenty.
The negative camber is probably because you are low, and if you are on the bumps while sitting, you are VERY low. The normal ride height for the one ton puts the front wheel wells about 35.5-36" from the ground with 245-16-75 tires. Our factory manual shows the 8600# capacity 2500 at only .3" lower. Negative camber will also make them less directionally stable, as you are running on the inside of tire, which can make the effective scrub radius change to the minus direction. Possibly going to the less offset, which reduced scrub radius, and negative camber reducing scrub radius has put you over the edge. Slight positive camber is usually the best for directional stability. Loose wheel bearings also can move you toward negative camber.
The Bill Erb topic has one positive from the Mexican Doctor, and one negative from someone else who got Erb springs, but his shop was not able to get them into the van. So it's a tie, I guess.
You have a big advantage, as you have a 3/4 ton van. It is very likely that if you put the 1 ton springs in it, you may just come out right. I think all the factory springs are about the same free length, and only change in spring rate. Our Tufftruk 5K springs and factory 4300# springs were essentially the same free length. Both could be put in without a spring compressor. The longer springs folks are talking about are because they want to get lower spring rate (softer ride), but still gain the 2" of lift to get back to factory ride height. You then need a monster spring compressor and can get the bowing and interference issue that have been mentioned. If you put the bigger springs we have been using for the 1 tons in your van, you will be very high and harsh, I think. Most of us have at least 4100# on the front wheels.
The fact that the bottom of the van is all banged up is pretty worrisome. Ours would only hit in the middle, if it was high centered, on uneven terrain. It never hit on highway dips or bumps. A good look over over the frame for damage is probably in order. Negative camber is one of the first things that shows up if a vehicle has bottomed out hard and often.
It certainly wouldn't hurt to go down and see Bill Erb, as he does have an excellent reputation, to see what he recommends, and if it makes sense. One thing all the discussions we have had on here have shown is that there appear to very very different results being achieved from some of the same changes It is very hard to understand why that is happening.
