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Discussion Starter · #1 ·
My 1968 convertible keeps slamming the subframe connectors on every little bump as they are the lowest point. I know I should look into the BMR subframe connectors but I don't want to re-route brake & fuel lines at the moment and concentrate on the rear springs.

Currently I have BFG 225/60/15 on all 4 corners with the fenders about 25.5 inches off the ground in the front and 25-3/8 in the back. From receipts I believe the 5 leaf rear springs are original. Napa 277-1154 springs in the front, 328 ftlb spring rate.

I think I need some firmer springs in the rear, but it seems all the higher rate springs are lowered an inch or 2 which I don't think would work with the front springs, though I would swap the fronts to keep them balanced with the rears. I had read that the rear leafs are around 125 ftlbs spring rate, so I think 150 might be a good neighborhood for me.

Any recommendations?

Appreciate the input!
 

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Every once in a while a BMR rep gets on here. Hopefully he will chime in. Maybe your body bushings are not compatible with the BMR stuff? Maybe solid is what you need with their product?
 

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I did a full coil over conversion on all 4 corners with Ridetech 4 link and BMR subframe connectors 255/40-18's & 325/30-19's and I still scrape mufflers sometimes.. ... I blame the crappy roads.
 

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What subframe connectors do you have? A pic of ground clearance would be useful. Generally 5” guarantees no road contact.

I would have guessed the front springs need a higher rate, not rear, but real fix is likely different connectors or higher ride height.

Don
 

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Discussion Starter · #5 · (Edited)
Found the instructions in the receipt pile, the subframe connecters were from Heidts, I will measure ground clearance tonight when I get to my garage, I am guessing 4 inches from just a look. I would still like to replace the rear springs as they are 50+ years old.

Thanks!
 

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Discussion Starter · #6 ·
ok, looks like I am 4.5 inches from the bottom of the subframe connectors to the ground and 6 inches from the floor of the 68. Seems like at close to 5 I would only bottom out in certain instances but its every tiny bump I hit over 20mph.
 

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ok, looks like I am 4.5 inches from the bottom of the subframe connectors to the ground and 6 inches from the floor of the 68. Seems like at close to 5 I would only bottom out in certain instances but its every tiny bump I hit over 20mph.
Sounds like maybe you need some new shocks. What’s on there now?

Don
 

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Discussion Starter · #8 ·
I believe they are AC Delco's, I will double check when I get over to my shop. I don't recall any bouncing so I don't think they are shot, but I should probably upgrade to some higher performance ones, just have to figure out which ones.
 

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It’s hard for me to visualize subframe connectors with 4.5” of ground clearance hitting the ground at 20 mph with good shocks. Are you sure that’s what you are hearing? Are there witness marks on the connectors? I think posting some pics would be useful.

Don
 

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Discussion Starter · #10 ·
Good idea, will post some after I get to the shop this weekend. Thanks!
 

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Discussion Starter · #11 ·
Ok, drove it this weekend. I have AC Delco premium shocks which seem in good condition, they seem firm and only did the down and up once on the fat guy bounce test. Took some pics and its definitely hitting the subframe connectors, seems like the right hand side more so than the left, I did notice the right hand side is half an inch higher and receipts say the right hand spring was removed and repaired back in 2016.

I also made note of when impact occurred and it did seem to happen not when the fronts hits a bump, but when the rear wheels do. I have been searching for stock height leaf springs with 175-200 ftlbs spring rate to no avail. Been through a few old posts of people putting in some 1 inch drop ones that actually raise the car a bit so I might go for front and back 1 inch drop.

Wood Water Automotive lighting Tints and shades Darkness Wood Water Table Flooring Tints and shades Automotive tire Wood Grey Rim Automotive exterior
 

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Those subframe connectors suck big time imho. There are better options out there.

Don
 
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