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  #16 (permalink)  
Old 04-11-2019, 03:53 AM
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Thanks Eric, I'll get some U-bolts!
Does this spring rate chart refer to the total weight of the car?
I would assume that is the case, but better to ask, right?
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  #17 (permalink)  
Old 04-11-2019, 07:38 AM
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Quote:
Originally Posted by Bob37pont View Post
Thanks Eric, I'll get some U-bolts!
Does this spring rate chart refer to the total weight of the car?
I would assume that is the case, but better to ask, right?
I can't say for sure, but it certainly looks like they are referencing total vehicle weight with that chart.

Charts I'm used to looking at are just front or rear weights.
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  #18 (permalink)  
Old 04-11-2019, 08:04 AM
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Have you got room to move the hole in the frame for the shackle rearward? Two inches there and slightly longer shackles might do it...

Russ
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Old 04-11-2019, 09:59 AM
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Quote:
Originally Posted by ericnova72 View Post
I can't say for sure, but it certainly looks like they are referencing total vehicle weight with that chart.

Charts I'm used to looking at are just front or rear weights.
Looking at Landrum springs on the Summit site they state the reference is for total car weight. They also list "A" springs for asphalt use, although Summit says they are not for street use. The "A" springs have a 5" arch, while the "D" (dirt) springs have a 6 1/2" arch.
Once I get the car weight I'll call & see why they are not for street use, according to the Summit description.

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Originally Posted by S10xGN View Post
Have you got room to move the hole in the frame for the shackle rearward? Two inches there and slightly longer shackles might do it...

Russ
No, the frame gets narrower behind that hole, that's why I think the sliding shackle suggestion may work better for me.
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  #20 (permalink)  
Old 04-11-2019, 12:41 PM
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Magic Number!

Got the car on a certified CAT scale at the local truckstop.....
She's a not-so-svelte 3,720 pounds!

Landrum lists a 225# spring rate for vehicles weighing 3000 to 3500#.
And a 250# spring rate for vehicles weighing 3600 to 3800#.
These springs with the "A" suffix have a 5" arch.
I checked under the car and with the air shocks at 75# I raise up about 1.5 to 2".
I called Landrum to get the spec on static compression for the weight, but the owner/tech guy is on vacation. I'll call him next week.
My thought is the lighter spring rate might get me closer to my stance without excessive lowering blocks, and still give me a compliant ride.
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  #21 (permalink)  
Old 04-20-2019, 08:27 AM
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More weights

I went back to the CAT scale and weighed both axles with the car set pretty much centered (by eye) on the wheelbase.
Front axle: 1660 lbs.
Rear axle: 1820 lbs.
Total weight using the 2 pads of the scale: 3480 lbs
Total weight using a single pad of the same scale: 3720 lbs
I've not been able to contact the owner/tech at Landrum, I'll try again Monday.
I'm thinking the 3000 to 3500 spring will be right, But I want his opinion.
I've not been able to find a rate calculation for leaf springs based on vehicle weight, as opposed to measuring the springs themselves.
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Old 04-22-2019, 11:59 AM
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So I keep leaving voicemail at Landrum Springs with no call back....
Called tech support at Summit and was told that generally the 'racing' spring for a specific weight is a bit softer than a 'street' spring. Given my axle weights he felt the 225# rated spring would give me a more compliant ride on my Pontiac.
Springs & shackle sets ordered, as well as a set of U-bolts!
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  #23 (permalink)  
Old 04-30-2019, 02:10 PM
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Springs arrived Thursday afternoon, busy schedule kept me tied up until today ( I'm retired, I don't know how that happened!).
Took about 4 1/2 hours, surprisingly no bolts were stuck in place.
As I got the u-bolts ready I realized,after drilling the 7/16" holes to 1/2", the brake line runs tight across the axle, with a welded hold down tab right in the center.
Pretty sure this assembly was not designed for u-bolts.
Quick trip to ACE for grade 8 1/2" bolts and everything went together smoothly.
I ended up gaining 1" of ride height with the 1 1/2" lowering blocks in place.
Put about 40#'s in the air shocks and gained another 1/2", the stance looks good. It's now 2 1/2" higher in the rear that the front, measured at the running boards.
The suspension now has some travel and a smoother ride.
Additional bonus I don't have the jack the car 12" in the air to remove a wheel, the springs don't sag with the weight of the axle!
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  #24 (permalink)  
Old 05-01-2019, 11:49 AM
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To clarify the ride height gain, I actually gained 3" ride height with the new springs over the old springs with no air in the shocks.
Previously I ran enough air the raise the rear 2 ".
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