I'm going to replace the stock rear springs on my 89 Formula 305 TPI. I am looking for something stock, geared more towards riding comfort than performance. This car is a weekend cruiser.

I want to retain stock ride height and handling characteristics. It seems like the MOOG CC635 are the only thing that keeps popping up but I am hesitant to put a variable rate spring when the stock springs were constant rate (can someone confirm?). I read a few things about the shocks being designed for a constant rate spring and a variable one can cause issues.

Do you guys have any other suggestions besides the CC635? Any opinion on putting a variable rate spring in vs constant?

 

What springs are the shocks you currently have designed to be paired with.
i wouldn't overthink it, the moog springs will restore the ride height and then some. May have to trim them

 

I have Monroe Sensa-trac rear shocks I put in not too long ago. I am having a hard time finding what spring to pair them with on google though.

I definitely don't want to buy a spring I have to cut. You think the CC635 will sit too high?

 

After a bit more research it seems like the only other option is the Moog 5665 but it looks like it's discontinued. I'm seeing Mevotech makes a 5665 and "some people" on the internet are saying MOOG quality has gone downhill. any thoughts on Mevotech 5665?

I'd be fine with the CC635 but a bunch of reviews on Amazon said it raised the stock ride height 1.5-2 inches and I don't want to cut them. frustrating...

 

Those would be the IDIOTS that fail to realize that their ANTIQUE existing rear springs were already SAGGING 1½ - 2" and the new springs simply RESTORED theior car to its original height.

​​​​​​​[mr_spock] Humans. [/mr_spock]

 

Moog has two rear springs:

5665 is 107 lb/in
cc635 is 104 lb/in variable

The installed height specs are given at different loads, so some math is needed to compare heights at same load. My estimate is the cc365 will sit roughly 1/4" lower within the normal range of sprung weight of our cars.

That happens to be the same split given in the Moog advertised specs because their reference load is in the neighborhood of the actual sprung weight of our cars.

 

I have cargo coils with mustang isolators and it's about three fingers between the tire and wheel arch. Looks perfectly fine. I've even got -1.5" springs in the front, and the rake is minimal.

 

Thanks guys, I'm going to go with the CC635's then. I'll let everyone know how it turns out.

 

I'd love to see a write up on how much sag there is after 40+ years.