how to measure if axle is centered under truck

[concretejungle]

I want to be sure that my axles are properly centered under the truck. I guess an alignment would tell me, but if i wanted to do it, how would I?

here is what i was thinking. Using a right angle with measurement marks on it, mark a line on all four wheels (outside) exactly the same height from the ground. Hang a plumb-bob from the frame and measure from the string (frame) to the line on the tire using a straight edge (level) placed across the tire to get a straight line. Do the same on each corner.

If it's properly centered the two distances from the frame to the center line of the two tires should be equal? No?

 

[Hayes]

Isn't it pretty much certain that a lifted truck will NOT have the axles aligned exactly down the center--unless you've corrected it with new panhard rods?

Hayes

 

[Nay]

You don't have to measure - with OME and stock panhards, it isn't centered. You can tell visually.

 

[shocker]

Maybe easier would be to park on as level of ground as possible, put a level on top of the tires, hang a pumb-bob from the ouside of the flares/fender panels, and measure the level distance from tire to flare/fender panel.

I would assume that both flares/fender panels are fairly equdisdant from the frame, at least close enough for axle centering.

 

[T Y L E R]

What about rotor surface to frame?



TY

 

[landtank]

I just measured the outside of thetire to the frame. Just be sure to use a similar lug on the tire. With my lift a standard tape measure passed over the tire and contacted the frame rail about mid center. Attached is a pic of the rear, the front is a little more challenging but you get the idea.

 

[concretejungle]

Thanks rick. I will do the same, but i'll use a straight edge across the tire to ensure that both sides are measured equally.

Reason i'm wanting to do this is i am having a little pull to the right, along with some strange wear on my rear tires. I want to see how far off the rear axle is from center. This could be causing all my pulling problems and strange wear. I have felt for any play in the rear wheel bearings and have none.

 

[landtank]

this method is only so accurate and I don't think the straight edge would really yield anything more accurate but go for it.

 

[concretejungle]

Holy BLEEP! I just went out and measured same way rick did. I'm off an inch. RR frame to ouside tire = 14 9/16 inches, LR frame to ouside tire = 13 9/16 inches.

 

[landtank]

LOL, you ought to see it after 4" of lift. Left tire was damn near touching the frame.

 

[concretejungle]

Could this be a contributing factor to my pull to the right? I know i have a little tire pull. There is one tire that if i put it in the right front, truck pull bad to the right. If i put it front left, it still pulls to the right, just not as much. Feels more like the truck pulling due to the crown in the road in that case.

 

[landtank]

I'm not 100% sure but I've always thought that this sort of thing shouldn't cause a pull. Maybe someone in the know can answer it definitively. But it does seem that you have a bad tire there.

 

[concretejungle]

OK, maybe someone higher up the ladder will chime in.

Yes, i agree it's a bad tire. But i bought them from 4wheelbuttholes so they told me there is nothing they can do except sell me another tire at full price, plus shipping, plus pallet fee, plus one butt ream without lube. So i've just delt with it.

 

[shocker]

Did you try putting the tire on the rear of the vehicle?

 

[alia176]

4wheelbuttholes ? That's damn funny!

 

[sleeoffroad]

Not sure if it would cause a pull, but people do report that centered axles drive better then non centered ones. Also, turning left and right would be different, understeer vs oversteer.

Do not measure in reference to the body. The body is not necessary square on the frame. Measure from any common part on both sides of the axle (like rotor) to the frame. This must obviously done at ride height. Could be with tires removed, if axles are on axle stands.

 

[landtank]

The one thought I've had is that the truck, until recently, has not had the panhards adjusted and the PS birf is worn way more than the DS one.

 

[OGBeno]

If you lift the truck on a lift where the axles are able to hang by themselves, you will see just how far you are to either side. Actually, a good way to tell is to look at the front of the front control arms (while vehicle wieght is on it) and you should see it 'lean' on the inside of the bushings towards one way or another.

Once you see it, then you can adjust panhards as needed--usually lengthening them to re-center under body.

Cheers.
-onur
Akron, OH

 

[Nay]

You can also do that whole pythagoreom theory thing. The panhard to axle connection creates a triangle. A squared + B squared = C squared, with C being the length of the panhard rod, A the axle length between panhard mount points, and B the distance between frame mount and axle (straight down).

Lifting will increase B. Therefore, A must decrease (this is the pull of the axle to the side). So take your measurements, and then decrease B by 2.5" and solve for A (C does not change). That is the amount of axle movement.

Nay

 

[T Y L E R]

You can also do that whole pythagoreom theory thing. The panhard to axle connection creates a triangle. A squared + B squared = C squared, with C being the length of the panhard rod, A the axle length between panhard mount points, and B the distance between frame mount and axle (straight down).

Lifting will increase B. Therefore, A must decrease (this is the pull of the axle to the side). So take your measurements, and then decrease B by 2.5" and solve for A (C does not change). That is the amount of axle movement.

Nay

Nay doesn't C change .. by adjustment of the panhard rod?


TY