Engine angle and IRS Angle

[chicane67]

Different solid axles geometries (and of course IRS) make for different settings, but the point is that optimum traction and braking behavior settings are usually not the same as the best vibration and u-joint settings.

I agree with that. But.....

All suspension designs will have some pinion change throughout travel, it is virtually impossible to move the axle through a 6" travel and have 0 pinion change. Minimal perhaps but you can't say *no* change.

And that was the point that I was trying to convey. You will induce pinion angle change with links as short as this, with this set-up (AME 4-bar). Now, with links in the 65 inch range you might get closer to zero angle change at 6 inches of articulation, but even that is being greatly optimistic.

And this is where we could (unnecessarily) start splitting hairs...........



(and no I am not inciting any cc.com, knockdown, hardcore tech challenge at this one. my typing skilz will most likely get me spanked)

[parsonsj]

John, I fail to see how pinion angle has an impact on AS. AS is determined by the SVSA, which has no bearing on pinion angle (well maybe an inch or 2 but not enough to be a determening factor).

All suspension designs will have some pinion change throughout travel, it is virtually impossible to move the axle through a 6" travel and have 0 pinion change. Minimal perhaps but you can't say *no* change.

Sorry, I wasn't being all that clear. In the real world, it's the other way around. Setting up the SVSA for AS will change the pinion angle. Change the lengths or connection points of the linkage arms of the suspension, and most likely you'll change the pinion angle. This will be true unless you can rotate the housing mount points around the centerline of the axle ... which doesn't occur in the real world.

There is no change in pinion angle using the AME 4 bar. The upper and lower control arms are equal length and parallel. The connection points on the housing and the crossmember are equi-distant, and parallel. They form a perfect parallelogram. The SVSA is infinite. The pinion angle does not change through 6" of travel, and wouldn't change through 12" of travel (if that were possible in the real world).

jp

[dennis68]

Sorry, I wasn't being all that clear. In the real world, it's the other way around. Setting up the SVSA for AS will change the pinion angle. Change the lengths or connection points of the linkage arms of the suspension, and most likely you'll change the pinion angle. This will be true unless you can rotate the housing mount points around the centerline of the axle ... which doesn't occur in the real world.
jp

Well, were getting a little off topic but for future reference purposes I'll explore this a little. Shortening SVSA for improved AS does have to increase pinion angle. On stock pick ups yes, but if you are building from scratch there is no reason SVSA has to have any affect on pinion angle at all. Just change where you weld the mounts to the housing or the frame.

Or run a full floater birdcage...