Hi all,
I am sure this question has been asked a million and one times but i cant seem to find an answer,I tried search too! So I have a fj with a 3" spring lift from toytech. What size tires can i run?
Thanks,
B
Lifting only affects tire clearance as the vehicle just sits there in the parking lot. The normal articulation of the suspension puts the wheels up and down in and out of the wheel wells no matter what their starting position is. Tire fitment (for functional suspension systems) is about the wheel well, not the lift. Lifting is for ground clearance.
If you put a tire that doesn't fit, you'll get rubbing. The lift might reduce the frequency of rubbing, but it can't eliminate it unless it also stiffens the suspension to the point where it physically won't move that much anymore.
In order to fit tires that wouldn't work without modifications, the modification to do is open the wheel well by removing unneccessary material, and potentially by reshaping the sheetmetal.
One of the hidden problems of tire fitment is that the backspacing of the rim affects what can fit into the front wheel well.
Imagine looking down from above at the front wheel as the steering wheel is turned fully to the right and fully to the left (lock to lock). The wheel will be rotated in an arc around a center point which is the hinge mechanism in the steering knuckle. That center point is actually inward from the inside of the wheel by a few inches. This means that the position of the outside edge of the wheel (relative to that center point) defines the size of the circle arc that the farthest points of the wheel travel through. If the rim is designed to inset deeply into the wheel well, it will be a smaller arc. If the rim is designed to stick out, it will be a bigger arc.
The bigger an arc, the more stuff there is for the edge of the wheel to touch.
Tire fitment is thus a matter of optimizing the tire choice, the rim choice, and the amount of wheel well modifications one is willing to do.
Lifting only affects tire clearance as the vehicle just sits there in the parking lot. The normal articulation of the suspension puts the wheels up and down in and out of the wheel wells no matter what their starting position is. Tire fitment (for functional suspension systems) is about the wheel well, not the lift. Lifting is for ground clearance.
If you put a tire that doesn't fit, you'll get rubbing. The lift might reduce the frequency of rubbing, but it can't eliminate it unless it also stiffens the suspension to the point where it physically won't move that much anymore.
In order to fit tires that wouldn't work without modifications, the modification to do is open the wheel well by removing unneccessary material, and potentially by reshaping the sheetmetal.
One of the hidden problems of tire fitment is that the backspacing of the rim affects what can fit into the front wheel well.
Imagine looking down from above at the front wheel as the steering wheel is turned fully to the right and fully to the left (lock to lock). The wheel will be rotated in an arc around a center point which is the hinge mechanism in the steering knuckle. That center point is actually inward from the inside of the wheel by a few inches. This means that the position of the outside edge of the wheel (relative to that center point) defines the size of the circle arc that the farthest points of the wheel travel through. If the rim is designed to inset deeply into the wheel well, it will be a smaller arc. If the rim is designed to stick out, it will be a bigger arc.
The bigger an arc, the more stuff there is for the edge of the wheel to touch.
Tire fitment is thus a matter of optimizing the tire choice, the rim choice, and the amount of wheel well modifications one is willing to do.
Excellent and clear answer, as usual.
The concept of what a suspension "lift" actually does is something that is so often lost: as you state, it's just changing the "resting" angle within the normal sweep of the IFS (i.e. it's the pivot points on the upper and lower control arms that determine the range of the travel, and those points are not changed by the lift) and the stiffness within that sweep range.
On the tire fitting, this is why the arguments go round-and-round: what tire you can fit after you move away from stock depends so much on the tire, the wheel, and what you've done to your wells, trim, mud-flaps, body mount.
AND what ends up limiting you progressively changes as you remove each incremental obstacle (get rid of the body mount and the next thing you hit is mud flap and trim, etc.) This isn't an endless process, though (tire size cannot go to infinity). At some point, you get frame interference problems, and then that determines the max size. Actually, your willingness to accept rubbing on the frame limits your tire size (since it's a rare, full stuff, full turn limit).
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