Nissan IFS geometry?

[winkosmosis]

I was walking by a previous generation Frontier yesterday and the wheels were turned so I could see the suspension arms. It was one of the models with a taller than normal suspension.

The angles of the control arms was really weird. The downward angle of the UCA was actually steeper than the LCA! This would mean that as the suspension compresses, the tire tilts outward. That's the opposite of what should happen-- the tire lean into the turn like a motorcycle, stay perpendicular to the road (like with a solid axle), or at least stay more perpendicular than the vehicle (most IFS).

With this design, the proper camber change doesn't happen during suspension cycling until after the arms reach the horizontal position.

I thought it must be an optical illusion, but then I realized that Nissan lift kits include longer UCAs, which would match the geometry I saw.

The only explanation I can think of is that in the original OEM design, both upper and lower arms are parallel to the ground, so when you (or Nissan) cranks the torsion bars the shorter UCA is forced to angle downward more and pull the top of the tire in. So you (or Nissan) replace it with a longer arm but you're still left with the same geometry issue.

Why did Nissan design their IFS this way, especially considering they themselves sell vehicles with "lifts"? The solution would be to have the frame mounts closer to each other than the knuckle mounts, so that no matter what the tire will gain positive camber as it moves down (or when you lift) and negative camber as it moves up (when the suspension compresses).

 

[davidshourd]

I have had 3 nissan trucks, 87' (2.5" lift), 03' (1.5" lift) and now an 07' (3.5" lift). the 87' and 03' were nearly identical to each other in regards to front suspension and steering and probably what you observed. the Nissan IFS in the 1st Gens (pre 05') was nearly impossible to get any real good lift out of without heavy mods up front, of course you then put your drive shafts at a steep angle and wear out joints, not to mention the steering components. I think what they did in the 05'+ helped (coils in lieu of torsion bars), but I think their primary market was on road with occasional off road, IMO. fortunetly for the 05'+ Xterras and Frontiers the titan front suspension just bolts on (swap out drive shafts as well) and you gain (I think..) 2" more of travel (up and down?) with the longer arms and a better geometry for the drive shafts. IFS will always have its limits for travel, alignment and shaft geometry, at least on a stock set up. but it also has its advantages to a certain degree.


There are some guys in this forum (MCM) who probably know way more. please tune in.

Though I do not recall either the 87 or the 03 Arms being "near level" when they were stock. more like your lower picture at stock then twice as bad lifted.

here are a couple old pictures from my 87' with about 2.5" of lift, I got most of the camber out with alignment, but I woudl rotate often to keep wear as even as possible. note the picture from straight on that the passanger tire is on a slope.

 

[winkosmosis]

It looks like in your pic the passenger side tire is cambering the way it should, which doesn't match what I thought. Or maybe that's an optical illusion.

When you lifted it, were the bottoms of the tires pulled inward or pushed out?


On the way home I walk by a current gen Frontier with a body lift every day so I can see the upper arms. I think the geometry is completely different. I'll have to look more closely next time.

 

[davidshourd]

when first lifted (without an alignment) the top is leaning towards the frame. but then the upper arms connect to the frame with a spindle arm that goes through the upper arm bushing. they can then be shimmed off of the frame where they bolt to to push the tops out. I think I had mine like 1/2" to 5/8" of shim, longer bolts required. you can barley see the shims (washers) behind the front bolt and then the bolt head just behind the yellow shock on the close up picture. In other words its possible to align this suspension, but not the easiest.

 

[winkosmosis]

OK, so that does match what I thought.

So once you have it shimmed so the camber is vertical, suspension compression causes the tire to tilt outward then tilt back inward again. I guess that's no problem driving straight, but it can't be good for cornering. But I thought IFS was supposed to handle better than a solid axle.

 

[Strizzo]

OK, so that does match what I thought.

So once you have it shimmed so the camber is vertical, suspension compression causes the tire to tilt outward then tilt back inward again. I guess that's no problem driving straight, but it can't be good for cornering. But I thought IFS was supposed to handle better than a solid axle.

well, its supposed to ride better, but the best SFA design up against the worst ifs design and its a crapshoot.

on my 96, the bars had been cranked and the lower arms were pointing down about 10 degrees iirc. the tops of the tires also tilted outwards.

 

[Hootowl]

There really has not been any problem on camber adjustment to OEM specs after doing a suspension lift on the W21/WD21 Hardbody/Pathfinder, the W22/WD22 first generation Xterra/Frontier or the 2nd generation Frontier/Xterra. One goofy thing that they did on about the 2006+ Frontier/Xterra is that they quit installing the camber adjustment bolts at the factory so you have to buy the OEM or aftermarket camber adjustment bolts to retrofit them onto the truck.

A consistently limitting factor, as one of the other folks mentioned, is the angle of the the front drive shafts increase with a suspension lift and after a point of lift, put the CV's into a bind that wears on them pretty good. Some folks will reduce this bind by dropping the transfer case some using excentric mounting bushings and thus reducing this angle and resulting bind. With the coilover front suspension with the OEM suspension on the 2nd generation Frontier/Xterra, they are not really limited on CV angle up to about a 3 inch suspension lift increase.

 

[winkosmosis]

There really has not been any problem on camber adjustment to OEM specs after doing a suspension lift on the W21/WD21 Hardbody/Pathfinder, the W22/WD22 first generation Xterra/Frontier or the 2nd generation Frontier/Xterra. One goofy thing that they did on about the 2006+ Frontier/Xterra is that they quit installing the camber adjustment bolts at the factory so you have to buy the OEM or aftermarket camber adjustment bolts to retrofit them onto the truck.

A consistently limitting factor, as one of the other folks mentioned, is the angle of the the front drive shafts increase with a suspension lift and after a point of lift, put the CV's into a bind that wears on them pretty good. Some folks will reduce this bind by dropping the transfer case some using excentric mounting bushings and thus reducing this angle and resulting bind. With the coilover front suspension with the OEM suspension on the 2nd generation Frontier/Xterra, they are not really limited on CV angle up to about a 3 inch suspension lift increase.

Well the camber seems like no big deal to me, but what bothers me is that as the suspension cycles upward, the camber goes the wrong way. So you're leaning going around a corner and the wheel is leaning even more. Bad for traction, the opposite should be happening-- leaning into the corner like a motorcycle.

I'd imagine that if you were really desert running in your Desert Runner, you'd be able to get the outside tire to roll over onto the sidewall.