^^^Agree. The spring rates don't seem aggressive at all, the unknown is the shock valving and without dynoing them it is blackmagic. That said, Ride Tech's shock offerings are one of the best reasonably priced pro-touring oriented shocks on the market.

Thanks for the suggestions.

I've got a nitrogen fill setup on the way. When it gets here, I'll get a bottle from the welding gas store and gas up the rear shocks.

I also heard from David Pozzi who's tuned Bad Penny, which has the same front and rear suspensions I'm using, as well as the One Lap Camaro, which uses the same rear suspension.

David's suggesting I leave the rear spring rates alone for now and drop the front springs to 350 lb./in. He noted that 350 lb./in. springs in the 21st Century Street Machine subframe would be equivalent to a 600 lb./in. spring in a stock subframe, which suggests that the 450 lb./in. springs in there now are the equivalent of a 770 lb./in. spring in a stock subframe. In any event, I'll swap out the front springs, leave the rear alone (other than gassing up the shocks) and see where I am.

I'll consider shocks if I can't get it where I want it any other way, but springs are about $70 a set, and gas charged shocks (which I need because they're mounted upside down) are going to be $400-$1,000 plus a set.

FWIW -- I had QA1's on my Nomad --- and switched them out to Strange... which is what Art Morrison uses and sells on his chassis... it was like I built a completely different car... Until then - I had no idea a shock (really a damper) could make that much difference!


The Nomad ran coil overs all the way around.

Interesting...

That's good to know on the QA1's. They were a set I had laying around, so it's not a big deal to replace them.

My first impression when I drove the car was the front was over sprung, over damped or both. I dialed down the shocks, which improved it a bit, but it still felt over sprung (or maybe badly damped with some stiction). I'll swap the springs, and then see where I need to go next.

It may be that the back end will be just fine once I get the front sorted out.

Don't forget though, while you found the relative difference between the spring rate on a stock subframe vs the 21st Century one, you've sort of calculated one back from the other without thinking about the motion ratio and wheel rate. The 450lb spring might be equivalent to 770lb spring in a stock subframe car, but wheel rates are probably closer to 300 and 200. If you had a 550-700 lb spring on the 21st Century frame I would think it would be way too much for what you're doing.

Part of building a car is spending time after its done to get it sorted out to your liking. Even the finished cars around here always seem to be in pieces. Springs are cheaper than shocks though, so if it works for you then you're lucky you only had to make one change. :lol:

I Found my notes.
coil rates are rounded off.

A 300 coil on a 21st century sub has a wheel rate of 156.
A 350 coil = 182
A 400 coil = 208
A 450 coil = 234

A 650 coil on a stock sub has a wheel rate of 156.
A 750 coil = 182
A 850 coil = 208
A 950 coil = 234
You will notice a 50 lb increase in 21st centruy sub = a 100 lb increase in the stock sub.

On a 21'st Century sub, multiply coil rate by .521 = Wheel Rate

Bad Penny started out at 350 went to 450 to 475 for quite a while and I think may have ended up around 500-550.
Steve always wanted to run the car super low, so we had somewhat limited bump travel. We had to go stiffer to make it work. With a higher ride height and more travel, you can run a softer spring. Shocks have a huge influence in this too.

I had the 21st Centry subframe and a Torque arm rear with no bar. I ran 550 lbs front and 325 rear with Bilstein shocks and 1.25 bar .188 wall in 34 inch length. 13 inch sway bar arms netted a rate of 364 lbs.

As stated above, the quality shocks valved correctly, made all of the difference in the world.

I started off with cheap non-adjustible shocks and 350 f and 175 rear with 1 inch solid bar. Quickly went to 450 f and 250 rear. Best ride was above with the best performance. Car rode way better than my wife's M3 she had at the time.

You can guess...you can solicit advice from those who have a similar set up...or you can spend a small amount of time and really calculate what spring the car needs: http://www.ridetech.com/tech/spring-rate-calculator/

This calculator will work for any brand of coilspring or coilover. I'll spare you my personal and shameless recommendation of the RideTech shocks :)

Oh no...I would never do that........:whistling: ....but its gonna cost ya!:G-Dub: