Monday, June 6, 2016

Replacement air springs for the GMC

OEM Firestone air springs are no longer available and the aftermarket oem springs don't get a lot of positive recommendations. Mark Grueninger made a set of adapters to use a current Firestone 9294 spring. His post is here.
Thanks to Mark I set out to make a set like his.

From Ebay I got steel discs for $10 each and combined shipping of $16.
I already had a section of 3x4x12 rectangle tube with 1/4 wall to use for standoffs.
Milling a 1/4" over 6" taper on a standoff.
Offset the spring mount to bogey 1/2" to clear the wheel well. Spring maximum OD specs at 10.7" from Firestone's data sheet.

 R&S Leafspring had the best price on the springs.

test fit all the way up

test fit all the way down
Painted and installed at normal ride height.


  1. Wally, I stumbled upon this from a related post, then went back to read the Grueninger notes from his photos. Interesting that:

    a). you did an offset on the brackets.
    b). your bolts to the boogie arms look to be the same size.

    I have a '78 with original bags. I have a fab shop and will have them make a set of these up. Any revisions or updates you've added since this writeup?

    PS, there are many very interesting posts on your blog. The megasquirt and Arduino stuff is very interesting. You have fantastic metal working skills.

    Mark Grady | northern IN | '78 Kingsley

  2. This comment has been removed by the author.

    1. A. I offset the brackets because I read some had to do that so the bag cleared the wheel well liner.
      B. All four bolts are the same
      If I had it to do over the plates could be thinner than 1/4"