Offroad Setup - Use Spacers or Offset Rims.

Literally. It epitomizes adding insult to injury.

 

Yes, rubbing is taboo. Nothing says “half-assed” like tires rubbing on things that they shouldn’t. Even in those situations where practically speaking the setup works in spite of the rubbing, it’s got no class. But you do you.

Increasing the scrub radius is bad. Long travel suspension let’s you widen the track without affecting the scrub radius.

 

i guess mentioning the notion of fixing rubs would have added context. i’ll go ahead and keep my peasant build and rub fixes out of the way around here.

fyi - long travel changes the knuckle location effectively changing wheel center line and it’s scrub radius.

 

Please explain.

 

LT control arms are longer which naturally moves the steering knuckle outward.

 

Naturally. But as the steering knuckle moves outward the wheel moves with it. The relationship of the steering knuckle to the centerline of the wheel is unchanged, and so the scrub radius is unchanged.

For visual reference:

 

when dealing with wheel off set you change the radius length.

when moving the steering knuckle you’re dealing with the position of the radius point. though you’re not lengthening the radius you are repositioning it to a point where the sweep or scrub if you will - occupies the same area as a lengthened radius.

 

Maybe I’m misunderstanding you. Referring again to the drawing, the vertical dashed line is the centerline of the wheel. The other dashed line, the one that runs diagonally through the upper and lower ball joints, represents the steering axis. Where the diagonal dashed line meets the ground is the point around which the wheel rotates with steering input. The distance at the ground between the centerline and the steering axis is the scrub radius. Do you mean in the quote above that when you change to long travel suspension that the scrub radius distance is changed?

 

With a LT scenario, the wheel/tire position has moved outward relative to where it sat before in the wheel well.

I think that more outward positioning alone would increase the chances of rub whether it's technically changed the scrub radius or not.

 

When you widen the track of your vehicle with wheel spacers or changes in offset you increase the scrub radius. If you widen the track with long travel suspension, you leave the scrub radius unchanged. Increasing the scrub radius contributes to an increased arc prescribed by the wheel as it turns, and it’s the increased arc, primarily, that causes the rubbing.

Here’s the same drawing as posted above. As the label denotes, it shows a stock 265/70r17 tire on a 7½x17 rim with a +15mm offset:

What if we replace the stock wheel with the very popular 285 tire on the 7x17 rim with the +4mm offset?

Comparing the two drawings, notice in the second drawing that the offset is decreased and the scrub radius has increased.

Looking down from the top, we still see the dashed line prescribing the steering axis. From this view it is apparent that not only is the point of the tire’s rotation on the ground not centered on the tire laterally, it’s not centered front to back either. An effect of this is that as the tire is turned left and right, the leading outboard corner and the trailing outboard corner of the tire prescribe 2 different arcs, drawn in orange.

Now let’s swap out the 265 wheel for the 285.

The arc of the 285 wheel is purple. The arc of the 265 wheel is orange. The 285 wheel fits in the wheel well just fine. So why does it rub? Because the 4Runner is not very tolerant to changes in the diameter of this arc. It’s so intolerant, in fact that just pushing the wheel outboard of the steering axis a scant 4 tenths of an inch, (as occurs when the TRD Pro rims are fitted) causes Toyota to cut the fender at the port. It’s not merely the wheel being pushed outboard that causes the rubbing. It’s the wheel being pushed away from the steering axis that causes the trouble.

 

3D geometry wins every time.

 

i mispoke and didn't articulate my point properly.

what happens to scrub radius aside when changing the length of the control arms, the noted arc radius will be affected since the wheel will be positioned differently. this may not result in the typical rub points on the body, but will definitely rub.