2015 Ford racing handling pack

[fogus]

Sounds like I need to learn about spring rates. Any suggestions?

What are the concerns with the rear shocks?

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[GTP]

I am not an expert, but I am an ME and I read a lot.

Apparently, there is some consensus on this forum that the factory rear shocks do not have a sufficiently high damping rate for the factory springs. I'll attempt an explanation.

You hit a bump in the road, and the factory spring absorbs it nicely, with enough suspension travel to not "kick your behind" all that hard. BUT, because the shock is under-damped, the ride feels "bouncy" (the exact word used on this forum in other threads). IOW, you may like the soft ride from the spring, but not the couple extra oscillations well after the bump has passed.

What is easy to do is to buy new springs that are stiffer (and lower). At first you may conclude that the ride is better since you feel the road more, faster cornering, etc. But eventually you might notice that the bounciness remains. Only now, the factory shock is mismatched even worse with the new upgrade springs. IOW, the extra oscillations are still there, but they were masked to you at first because they are more closely-spaced in time than before (higher frequency oscillation).

One expert vendor here told me that the PP rear shock is higher damping than on the base car, but it is still not high enough. IOW, better but still not optimal. Furthermore, he quoted me some pretty high spring rates that we can try. (The high rates are bc the rear spring is not coiled over the shock, but much more inboard on the car. The lower arm therefore has a high lever-moment to compress the spring. This explains why the big fat spring goes at the lighter end of the car.)

Next, a related issue is from lowering due to shorter springs. This also exacerbates the problem, because the "softer" factory damper is working with a shorter traveling spring. Note that the resistance to spring (and wheel) travel is proportional to the speed of compression (or extension). IOW, the softer damper is not so effective with a shorter spring and a big bump. It "reacts" too slowly. Again, higher damping is better for this situation.

Also, progressive (or dual-rate) springs are not the end-all either. In effect, the "normal" operating range has been shortened again, which is not good with the factory shock. Then with a big enough bump, you transition into the higher-rate zone on the spring, and the factory shock is not even close as a match for that spring rate.

In short, the expert told me that different (higher rate) rear shocks are as important if not more so, than different springs.

And of course, all this go-fast nonsense comes at the expense of a harsher ride from the stiffer springs and shorter travel. Funny. You upgrade your suspension so you can kick some butt. Then you discover that it is YOUR butt getting kicked by the bumps!

As long as you drive on pretty smooth roads, there is no problem.

 

[fogus]

Thanks a ton GTP. This all makes a lot of sense.

How then does this FRPP handling pack stack up? Perhaps on a scale of 1-10, rate 1) the stock non PP springs/shocks, 2) PP springs/shocks, and 3) FRHP shocks/springs, 4) some other high price point "BA" combo. That would really help me out.

Are struts another name for shocks/dampers? Are those all equivalent?

 

[GTP]

See, what we need is for the guys upgrading their PP suspensions to hand down their take-off shocks to non-PP cars.

 

[TrackpackGT]

In previous FRPP handling packs, they were Tokicos. Folks that race and those who sold them weren't happy with their quality and warranty backing. Hopefully they have stepped up on the 15.

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