Front Coil Spring Clearance Problem

[JohnIL]

I've run into a weird clearance problem on my '65 C10. See the pictures below for a visual explanation.

Here's the scenario.

When I bought the truck, the PO had installed a set of LMC 2" drop coils on the front. Occasionally, whenever I unloaded the front suspension over uneven ground, I would hear one of the front springs twang. I assumed it was just because the springs are shorter than the originals.

Fast forward to today. I'm approaching the end of a power brake conversion project. While I had the front suspension apart, I did the common caster correction mod. I moved the lower control arms 3/4" forward to add more caster. As you would expect, this mod adds a minor angle to the springs. I had the truck back on the street for the first time tonight and the driver side front spring twangs every time I hit a pebble. With the truck back up on blocks, it's clear that the driver side front spring is making contact with the front edge of the upper spring pocket. The passenger side spring, however, is nicely centered in the upper spring cup, with about 3/8" of clearance.

You can see the difference in the pictures below. The first picture is the passenger side spring with plenty of clearance. The second picture is the driver side spring, clearly making contact with the front edge of the spring pocket. I verified that both springs are centered in the upper spring pocket and lower spring cup. I verified that that ends of the coils are seated in the indentions the lower spring cups. As far as I can tell, the springs are properly seated.

I thought maybe the driver side lower control arm might be further forward than the passenger side. I measured the position of the control arms from fixed points on the frame rails. They measure exactly the same.

So, I'm stumped. I would expect the springs to vary a little bit from side to side, but this seems pretty extreme. Is it possible the springs are that much different from each other?

I appreciate any wisdom you can share.

John

[Richard]

Originally Posted by JohnIL

I've run into a weird clearance problem on my '65 C10. See the pictures below for a visual explanation.

Here's the scenario.

When I bought the truck, the PO had installed a set of LMC 2" drop coils on the front. Occasionally, whenever I unloaded the front suspension over uneven ground, I would hear one of the front springs twang. I assumed it was just because the springs are shorter than the originals.

Fast forward to today. I'm approaching the end of a power brake conversion project. While I had the front suspension apart, I did the common caster correction mod. I moved the lower control arms 3/4" forward to add more caster. As you would expect, this mod adds a minor angle to the springs. I had the truck back on the street for the first time tonight and the driver side front spring twangs every time I hit a pebble. With the truck back up on blocks, it's clear that the driver side front spring is making contact with the front edge of the upper spring pocket. The passenger side spring, however, is nicely centered in the upper spring cup, with about 3/8" of clearance.

You can see the difference in the pictures below. The first picture is the passenger side spring with plenty of clearance. The second picture is the driver side spring, clearly making contact with the front edge of the spring pocket. I verified that both springs are centered in the upper spring pocket and lower spring cup. I verified that that ends of the coils are seated in the indentions the lower spring cups. As far as I can tell, the springs are properly seated.

I thought maybe the driver side lower control arm might be further forward than the passenger side. I measured the position of the control arms from fixed points on the frame rails. They measure exactly the same.

So, I'm stumped. I would expect the springs to vary a little bit from side to side, but this seems pretty extreme. Is it possible the springs are that much different from each other?

I appreciate any wisdom you can share.

John

Reading this it seems like you measured to the frame mounting point on the arms. Springs are further out to wheels than that. Maybe measure to outer point on arms like center of ball joints and see if the same on both sides. Maybe something crazy like two passenger side lower arms installed?

[JohnIL]

Originally Posted by Richard

Reading this it seems like you measured to the frame mounting point on the arms. Springs are further out to wheels than that. Maybe measure to outer point on arms like center of ball joints and see if the same on both sides. Maybe something crazy like two passenger side lower arms installed?

Richard,
Thanks for the idea. I measured from fixed points on the frame to the lower ball joints. Both sides are the same. And, the shock mounts are on the rear side of both control arms.

The difference appears to be in the springs themselves. Any other ideas?

Thanks.
John

[leegreen]

Are tops of springs fully seated over the centering ring?
Is compressed spring length same both sides?

What parts did you change, just spindles? Ball joints fully seated in CA and spindle? lower CA bushings in good shape and shafts still straight? Holes in cross member for lower CA still nice and round?
maybe some old collision damage - Flanges at ends of crossmember still parallel to each other? CA themselves bent?

Or a bad spring

[JohnIL]

Lee,
Thanks for the feedback. I checked most of this already, but you've given me a few more things to measure.

The springs are definitely fully seated. This was my first thought. I checked the tops and bottoms multiple times.

I replaced the spindles, ball joints, lower control arm shafts, and bushings. The ball joints are fully seated. I checked that last night too. I measured the control arm shafts to verify their the same from one side to the other.

It's difficult to confirm the control arms are straight, but they do measure the same to fixed points on the frame. If there is a difference between the left and right lower control arms, it is in the 1/16" neighborhood.

I haven't measured the compressed spring height and the crossmember flanges. But, I definitely will.

Thank you for the leads.

John

Originally Posted by leegreen

Are tops of springs fully seated over the centering ring?
Is compressed spring length same both sides?

What parts did you change, just spindles? Ball joints fully seated in CA and spindle? lower CA bushings in good shape and shafts still straight? Holes in cross member for lower CA still nice and round?
maybe some old collision damage - Flanges at ends of crossmember still parallel to each other? CA themselves bent?

Or a bad spring

[JohnIL]

I'm thinking about swapping the springs from one side to the other to see if the problem follows the spring or it stays on the driver side. Before I commit to all that work (disconnecting the ball joints and shocks to release the springs), I'd like some feedback. Does this make sense or am I just wasting time?

Thanks.
John

[leegreen]

if you can't find anything out of whack with a tape measure I think taking the springs out for a look is next.

Switching them side-side makes some sense, you may have swapped them during the brake upgrade and they have a 'set' for the other side that made this worse. (any chance the noise switched sides?) But if one spring is different than the other new springs might be a consideration.

[Richard]

Originally Posted by JohnIL

Richard,
Thanks for the idea. I measured from fixed points on the frame to the lower ball joints. Both sides are the same. And, the shock mounts are on the rear side of both control arms.

The difference appears to be in the springs themselves. Any other ideas?

Thanks.
John

The difference at the ball joints may be able to be compensated for with an alignment. Next I would measure to a point on the spring pockets in lower arms.

[JohnIL]

You make a good point about alignment adjustments. I measured from a fixed point to each of the drainage holes in the bottom of each spring pocket. Assuming the holes are stamped the same on both control arms, they measure the same. I will take more careful measurements tonight.

It's almost like the spring sits differently in the pocket on the right side than it does on the left side. I know that's partially true, because both springs are wound the same direction and both lower spring pockets both "index" toward the center of the truck. The lower tails of both springs are on the inside (center side) of the spring pocket. That puts the upper tails on opposite sides from each other. The upper tail on one side faces the front of the vehicle. The upper tail on the other side faces the rear of the vehicle. But, if this were the problem, then every one of our trucks would have the same problem.

Originally Posted by Richard

The difference at the ball joints may be able to be compensated for with an alignment. Next I would measure to a point on the spring pockets in lower arms.