First gen bird keeps bottoming out
 

My 1968 firebird 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.

Any recommendations?

Appreciate the input!

50+ year old original springs have probably weakened and sagged.

A stock rear spring replacement might do the trick.

Also, larger (taller) tires. Your 225/60/15's are only 25.6" tall. A 235/60 (26.1") or 245/60 (26.6") would fill the rear wheel well better and add some additional help. The original F70x14's would have been 26.2" tall.

Thanks Champ!

I was looking for a bit firmer spring rate than stock, somewhere between stock and full auto-cross, wouldn't be opposed to swapping the front springs to keep everything balanced if I had to.. I also forgot to mention it's a convertible, so a bit heavier back there.

Do your shocks need replacing?

I went with DSE (Detroit Speed & Engineering) springs front and rear in a 69 bird convertible. Very pleased with the results. I also installed their (DSE valved/adjustable) KONI Red front shocks and their adjustable JRI rears.

Tim john---

Ive got pretty much new stock replacement springs all the way around. Ill measure mine when I get home. I feel like you are a little low. I have Alston subframes and they never rub. Honestly I want to lower mine an inch and a half.