Coil overs on backdrafts

[Steve Gallegos]

Backdraft owners, how hard is it to replace the shocks and springs in the rear with coil overs? I have car #595.

[spdbrake]

There is some info in this thread. Thread size rear Spring Adjuster

Be aware that setup is relying on the Shock bolt (single shear) to support the the suspension as well. I'm not fond at all of single shear in critical areas and definitely not in boosting the load of a fastener designed for shock loads to one that supports the vehicle. Thoughts of going through a sweeper at speed and the bolt breaking is enough to prevent me from doing that mod.

[FredG]

I do believe the RT4 comes with rear coilovers. Completely different rear suspension mounting system.

[spdbrake]

I still haven't seen any pics of an RT4 suspension.

[Mike_Gr]

I know this is an old thread but I am currently having Vintage motorsports modify my rear shock mounts to put bolts in double shear both upper and lower. I converted my rear to true coilover. Will update the thread with pics of the mounts once I get the car back. They have already finished just waiting on a few other things.

[russdana]

I like all of that set up except for the bottom mount. It just seems like a weak design for the load as stated. They should have fabricated a "U" brace for the bottom mount to distribute the load evenly and destress the fastener.

[Mike_Gr]

Originally Posted by russdana

I like all of that set up except for the bottom mount. It just seems like a weak design for the load as stated. They should have fabricated a "U" brace for the bottom mount to distribute the load evenly and destress the fastener.

That is somewhat temporary. I was planning to buy one that is just a threaded rod like the camber arm but they didn’t have them in stock. This arm is used by a lot of the bmw folks with good success so should work until I get the one I want. Issue is they are a plan to instal and need to unbolt diff and slide it back to get the inner control arm bolts out.

[Mike_Gr]

Originally Posted by russdana

I like all of that set up except for the bottom mount. It just seems like a weak design for the load as stated. They should have fabricated a "U" brace for the bottom mount to distribute the load evenly and destress the fastener.

I just re read this post and realized I think you were referring to the lower shock mount on the spindle, I thought you were referring to the blue upper control arm vs the stock piece.

The fabrication being done is not shown yet as I have not gotten any pictures. The pictures in the thread are just showing the shock mocked up to the stock mounts. VMS is fabricating (or has at this point) new upper and lower mounts that will put the top and bottom mount in a double sheer orientation so like the U you are describing exactly.

[Mike_Gr]

New lower mount in place, This looks like it will be plenty strong. Bracket welded to one side of spindle and spacer welded to the other with ARP bolts.

[Mike_Gr]

Upper mount with similar design. Thanks VMS!