Rear Spring Rate Advice
#16
Race Director
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Looks good Greg -- I piece I was missing in your setup was the fact that you run a staggered tire setup, which does contribute a little to understeer.
This past weekend, I was at Thunderbolt / NJMP. A former student hopped in for a ride. He has a similar setup as my car, but with a bit firmer spring rates up front (450) and just helper springs and stock torsion bars in the rear, as well as M030 sways front and rear. Where his car was giving him lots of understeer (in the Octopus), he commented that my car had lots and lots of front end grip. I think the 400 lb sprigs up front (vs. his 450's), plus the bigger Welt rear swaybar was the difference. I also run 245-45/16's at all four corners on 8x16 wheels, and prefer a slightly oversteering attitude for the track.
Suspension setup has a lot to do with driver preference as well as how the car is driven. For example: late brakers / trail brakers may prefer a more understeering car. Slower entry drivers may want some power-on oversteer and set up their cars appropriately. And then there's the AX gang...
Suspensions aren't rocket science, but they are also not 'one size fits all.'
-Z-man.
This past weekend, I was at Thunderbolt / NJMP. A former student hopped in for a ride. He has a similar setup as my car, but with a bit firmer spring rates up front (450) and just helper springs and stock torsion bars in the rear, as well as M030 sways front and rear. Where his car was giving him lots of understeer (in the Octopus), he commented that my car had lots and lots of front end grip. I think the 400 lb sprigs up front (vs. his 450's), plus the bigger Welt rear swaybar was the difference. I also run 245-45/16's at all four corners on 8x16 wheels, and prefer a slightly oversteering attitude for the track.
Suspension setup has a lot to do with driver preference as well as how the car is driven. For example: late brakers / trail brakers may prefer a more understeering car. Slower entry drivers may want some power-on oversteer and set up their cars appropriately. And then there's the AX gang...
![Big Grin](https://rennlist.com/forums/images/smilies/biggrin.gif)
Suspensions aren't rocket science, but they are also not 'one size fits all.'
-Z-man.
#17
Race Director
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I fully expected understeer for two reasons. First, my track tires (Toyo RA1s)are staggered (235s up front and 255s in back). Second, I went with a combined rear spring rate (t-bars plus coilovers) that is probably no more than (and probably less than) the 400# fronts. Conventional wisdom says this is an understeering setup.
Turns out the car is very neutral.
Turns out the car is very neutral.
Here you are going flat out yet the rear is still a bit high.
![](http://i124.photobucket.com/albums/p11/gcirillo/Track%20Picks/QF1M4210.jpg?t=1220924923)
Here I am going flat out at 6000 rpm in 3rd.
![](http://944spec.org/944SPEC/images/stories/AZ/2007/OctPIR/img_4209.jpg)
Here in these two I am going flat out at the top of 4th gear.
![](http://members.rennlist.org/m758/20080613_SP944-94_001r8.jpg)
![](http://members.rennlist.org/m758/20080615_SP944-91_001r8.jpg)
You can see the slight rear end low attitude power on.
#18
Drifting
Join Date: Jan 2008
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If/when I'm ready to go to the next level, I'll get the t-bars done and dump the springs. But at that point, I might just sell and buy a fully prepped track car. For the foreseeable future, my track car needs to be street legal and usable as a third car.