New arms for wider stance?

[svenakela]

Hi guys,

I have a bus (Vanagon) that is pretty wide already, but I want more and I'm also moving more into "rough road" style. I'm somewhere in between at the moment, it actually runs pretty good on bad forest roads with the SUV tires. Right now I'm repairing a lot of damaged panels and going all in is the only way to go I think.

The plan is to spread the wheels even further apart, about an inch on each side and squeeze in a set of Toyo MT, Toyo Open Country, GY Wrangler or similar. At the moment I'm close to perfect ET according to spec. If I don't remember totally wrong I'm at 35 mm. What I've been told down to ET20 is not a problem (there are standard wheels at ET23) and quite a few German guys are at ET0 claiming no problems at all. With that in mind the easy way would be a set of spacers trimming out the rims. But as you can see above I'm going for wide and big rubbers and that might cause some "interesting" road behavior.

At the same time, the front suspension is far from perfect and has an interval with bad camber. I also use a 012 transmission (Audi A6 Turbo -04) and was thinking that it would be great to use a wheel hub in the rear from a newer vehicle with the same bolt pattern as the shafts that are used on the 012 tranny, so I can run a complete drive train with transmission, shafts and hubs that fit together without modifications.
This means fabricating new wishbones (control arms) in front and a new rear swing arm. I could make more room for the tires at the same time, it's kinda tight as it is already.

What do you think, is it a total overkill with the new arms? Will it be decent handling with spacers?

This is where I am a the moment (image too wide for the forum):
http://1.bp.blogspot.com/-Aiaav8ZafEQ/U ... 723354.jpg

This is a measurement taken from thesamba, Christopher made a serious write down on how bad it turns when the Vanagon is raised. Even if I plan to stay at standard height it's not good and turns worse with wider tires.

(Follow the thesamba link to get more data).

Spacers?
All in and start welding?

[Jadewombat]

The vehicle turning radius will probably be much wider with a wider track unless you redid the front suspension to get more ackerman angle. I ran 5 to 5 adapters on my bus for a while until I could swap over the rear to the correct bolt pattern and just that 1/2" wider on each side it wouldn't turn as tight.

Maybe I missed it, but why do you want to go with a wider track?

[svenakela]

The vehicle turning radius will probably be much wider with a wider track unless you redid the front suspension to get more ackerman angle. I ran 5 to 5 adapters on my bus for a while until I could swap over the rear to the correct bolt pattern and just that 1/2" wider on each side it wouldn't turn as tight.

Maybe I missed it, but why do you want to go with a wider track?

How would the Ackerman angle change with spacers?

There are several reason to go wider. Correct the faulty geometry, avoid heavy steering with the big tires, get more space inside the wheels and at the same time get a better look.
With big tires they tend to look like this:


I prefer this:

[Jadewombat]

The way I understand it, if you move one wheel out (wider) and draw a straight line to the rear wheel, it's not going to cross at the same point. If you moved the wheel out (several feet for instance) eventually the lock to lock of the steering wheel would make an arc with that front wheel that wouldn't even cross the rear wheel.

Either way it won't hold the same turning radius if you add spacers so you'd have to adjust something to get it to do the same turn in. 1/2" spacers doesn't change much, but it was definitely noticeable on my bus when I parked, etc.

https://www.youtube.com/watch?v=ob-FUF0Sh_E

[svenakela]

The way I understand it, if you move one wheel out (wider) and draw a straight line to the rear wheel, it's not going to cross at the same point. If you moved the wheel out (several feet for instance) eventually the lock to lock of the steering wheel would make an arc with that front wheel that wouldn't even cross the rear wheel.

Either way it won't hold the same turning radius if you add spacers so you'd have to adjust something to get it to do the same turn in. 1/2" spacers doesn't change much, but it was definitely noticeable on my bus when I parked, etc.

https://www.youtube.com/watch?v=ob-FUF0Sh_E

Interesting if you have such a big difference with spacers. Then your setup might be incorrect in the first place because spacers are only moving the wheel along the geometrical line that represents the Ackerman angle. I have three different wheel sets, all with different ET and I can't say they are locking up at all. The bigger tires are heavier to turn, yes. But that's just a result of their size and I can still push the bus around by hand on the workshop floor with 235 rubbers.
What model was this problem on?

[Jadewombat]

You're right, I can't explain it either from the ackerman angle on paper because those four points (front 2 wheels, rear axle line, and center of circle) still meet at the same spot along those same lines of trajectory of the front and rear wheels. Still though, if you look at this below to hold the right front wheel along the outer circle and the rear inner wheel on the inner circle, going with a wider track the vehicle would need more turn in.

It's generally well known vehicles with wider tracks take a bigger arc (longer time, whatever you want to call it) to get those outside wheels around through the same circle.

[Jadewombat]

The more I think about it, diagrams like this are pretty ambiguous (if this is what you were referring to). You can widen the track of the vehicle and the line from the center of the turning (yellow) circle to the center of the spindle doesn't change.

However...the diagram doesn't tell you anything about the arc of the circle. How is the arc drawn, middle of the vehicle, draw another line between the two front wheels then back to the rear wheels???

I could narrow or extend the track width as slim as a mini cooper or as wide as a cruise ship and it doesn't tell me in reality how well the car will corner.