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HOW TO CHOOSE THE RIGHT SPRING RATE after adding aereo and SEMI FLAT FLOOR IDEA

Hey guys,
Bringing the conversation from Facebook to here. I think this is a better platform for discussion
I 'm adding aero components to my car.
1. SPLITTER :3"FROM THE GROUND , 6" Wider than OEM bumper
2. better Central hood vents ( with the side vents I Have we are talking about 40 lbs DF at 100mph)
3.double fender vents.
4. possible front diffuser ( need to verify clearance first).

  1. So HOW to determine how much DF you generate and HOW stiffer the spring should be?

in this video AJ did a great job explaining some basic numbers.
based on it I did some math.
my current spring rates on my coilovers are 500/600
front left weight is 1104lbs . so unsprung weight is 100lbs ish ( wheel tire rotors calipers and some extra stuff) .so I did 1000lbs/500(spring rate) = 2" of compression.
so assuming 100-150lbs each side of DF ( 200-300 lbs front DF total ) . we should talk abut 20% stiffer spring to maintain the same compression . so 600. ( this is btw 1.85 " and 2.08' depending if 100 or 150lbs of DF each corner) . 20% in the rear will be around 750.
PS.I bought the APR 250 wing to keep the balance neutral.

SECOND QUESTION
Semi flat floor. does it help a little , a lot, nothing at all? in other words, is it worth it?


What you guys think about it?

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I assume 200/300 lbs for all the information I found Around. at 80mph probably not more than 200. AJ new splitter is around 800lbs ( wow) at 100mph. so I hope my assumption is real.
 
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I don't know if this will help you or not, but if you have remote canister nitrogen-charged shocks and struts, you can increase the nitrogen pressure to compensate for some or all of the downforce, and that allows you to run softer springs for more mechanical grip. Just a thought.
 
I don't know if this will help you or not, but if you have remote canister nitrogen-charged shocks and struts, you can increase the nitrogen pressure to compensate for some or all of the downforce, and that allows you to run softer springs for more mechanical grip. Just a thought.
I dont.
I have DA cortex JRi.
I can increase compression but is more related to the speed of compression.
Thanks for the input though.
Ale
 
Hi Ale, I’m in the same place now. I have built a decent splitter and added a wing. What did you learn both theoretically and in practice about spring rates? I want to keep rates as low as possible for mechanical grip but of course don’t want so little spring that the aero overwhelms them. Currently at 450/550 and without aero the rear felt too soft compared to the front. Havent had it on track yet since the wing but I’m sure the rear will feel even softer.
 
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I don't know if this will help you or not, but if you have remote canister nitrogen-charged shocks and struts, you can increase the nitrogen pressure to compensate for some or all of the downforce, and that allows you to run softer springs for more mechanical grip. Just a thought.
Higher gas pressures are for generating the required compression force as they are directly related. Also the higher the gas pressure the higher your cracking force is, or the higher the force is required to begin to see piston movement. You really only want as much gas pressure as it takes to 1) provide your target compression and 2) to prevent cavitation. *Cavitation causes massive hysteresis and while there are times when you might want that its almost never desired on tarmac.
I dont.
I have DA cortex JRi.
I can increase compression but is more related to the speed of compression.
Thanks for the input though.
Ale
tr350_aero1.JPG

tr350_aero2.JPG
tr350_aero3.JPG

DM me, I have everything you are looking for, but be prepared to read a lot.
 
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I see Daytona is starting to get to you... lol
Lol. This was a post of more than a year ago. Np daytona in mind yet. However. Always a great argument to discuss.
I assumed many thing for ma front splitter. And tests even more.
I think the splitter generates 200-300 lbs.
From this assumption
Brian McGreevy helped me with
The right spring rates.
We put on the spreedsheet
DF from splitter
DF from wing
Height and pitch of the car
Sway bars etc
Im sitting 650/800 now. DM me so i can connect you guys.
Ale
 
Higher gas pressures are for generating the required compression force as they are directly related. Also the higher the gas pressure the higher your cracking force is, or the higher the force is required to begin to see piston movement. You really only want as much gas pressure as it takes to 1) provide your target compression and 2) to prevent cavitation. *Cavitation causes massive hysteresis and while there are times when you might want that its almost never desired on tarmac.

View attachment 66946

View attachment 66947
View attachment 66949

DM me, I have everything you are looking for, but be prepared to read a lot.
Awesome! Thanks for sharing!
 

steveespo

Lord knows I'm a Voodoo Child
Moderator
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NY Metro
Steve how did you end up with that much spring up front? Iterative or went straight to that rate? You don’t have a big splitter do you?
No big splitter just the factory PP2. I actually started at 895/1005 which are close to GT4 rates. It was way too much for the TracTive dampers so I backed off 10kg/cm at a time to where I am now. The car does not understeer and turns in like a razor blade. At this time I feel like stepping the rear back up to 895. My APR wing make good downforce and the rear seems to be compressing down under load too much.
 
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No big splitter just the factory PP2. I actually started at 895/1005 which are close to GT4 rates. It was way too much for the TracTive dampers so I backed off 10kg/cm at a time to where I am now. The car does not understeer and turns in like a razor blade. At this time I feel like stepping the rear back up to 895. My APR wing make good downforce and the rear seems to be compressing down under load too much.
The GT4 runs multimatic DSSV dampers which can support a max front spring rate of 1100lbs and a max rear spring rate of 900lbs. Based on that it would seem 1005 is quite a lot of spring for the rear, unless you're making that much more in downforce. With the high front ride rate relative to the rear you've got a lot of pitch, you could add some low speed compression and see if you are still getting an undesirable amount of compression on a long straight.
 
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Vschlag's MCS setup is 800/1100 so all you guys are in the same ball park.

Did you guys arrive at your rates by suspension math and target chassis frequency?

Trial and error testing?

Copied other guys and just went with it?

Some pros use those rates?
 
58
43
Exp. Type
HPDE
Exp. Level
Under 3 Years
TX
Vschlag's MCS setup is 800/1100 so all you guys are in the same ball park.

Did you guys arrive at your rates by suspension math and target chassis frequency?

Trial and error testing?

Copied other guys and just went with it?

Some pros use those rates?

Of the pros I have spoke to, none really use rates that high. Only Vschlag seems to... Although the spring packages are governed more by club/ league regulation(s).

Also in speaking with Penske, JRI, and other suspension engineers they have told me almost no one targets chassis frequencies and that doing so is more in-line with an OEM development pipeline. *edit* This is not to say that "no one" does this ever, it is usually time/resource management which makes targeting ride rates and frequencies difficult.

Teams either tune by track + driver feel or they use a kinematic software which suggests changes based on setup + laptime.
 
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