S2000 STR prep resource
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From: Northern NJ
Originally Posted by nmrado,Dec 16 2010, 01:16 AM
What are your camber and toe settings? That's not drastically different than my setup (spring balance and FSB, wise) and I'm considering leaving my '00 RSB attached and softening my modified Saner to eliminate some low-speed push.
0 toe F, +0.25" R
I think dialing out a little of that positive toe in the rear with the 'no rear sway bar' would have helped even more.
I also should note that I was running 18" wheels/tires all year for craps and giggles. Someone had to be the guinea pig!
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From: Austin, TX
Originally Posted by NelsonI,Dec 15 2010, 01:55 PM
Well, I eyeballed those frequencies, so I was a bit high, but figuring something like 650 lbs corner weight /70lbs unsprung, and 900/850 pound springs I work that out to about 3.21 Hz front, 2.94 Hz rear. Those weights are again, just guesses, but probably aren't terribly far off. Within +/- 0.2 Hz, I think.
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Originally Posted by NelsonI,Dec 15 2010, 01:18 PM
Speaking of roll rates--
Nick, it looks like you're running about 1400 lbs of spring roll rate (using wheel rates) and probably another 300 lbs or so from the front bar? I'm assuming that's to limit body roll to the <1.5 degree range or so (maybe more like 1.3 or less, assuming a ~12" moment arm)--is that because of rear bump toe issues? I'd think the camber curves are friendly enough on the S2K to not need the car locked down that much unless there are other issues.
Natural frequencies with those rates must be in the mid/upper 3s, too--maybe it's just for transitional response? Trying to wrap my head around rates that high on ~1.2g capable street tires.
Nick, it looks like you're running about 1400 lbs of spring roll rate (using wheel rates) and probably another 300 lbs or so from the front bar? I'm assuming that's to limit body roll to the <1.5 degree range or so (maybe more like 1.3 or less, assuming a ~12" moment arm)--is that because of rear bump toe issues? I'd think the camber curves are friendly enough on the S2K to not need the car locked down that much unless there are other issues.
Natural frequencies with those rates must be in the mid/upper 3s, too--maybe it's just for transitional response? Trying to wrap my head around rates that high on ~1.2g capable street tires.
F 900lb/in 1075lb/deg 2.7Hz
R 850lb/in 979lb/deg 2.5Hz
A stock front bar adds ~385lb/deg and the rear ~300lb/deg.
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From: Kentucky
So far, I'm really digging using the base model 2006 MX-5 front sway bar as my rear sway bar.
I have to say that I do have a different setup than the norm. The difference (stagger the right word?) in my front to rear spring rate is 800F/500R... (with 650 waiting to be used). I also have a custom Speedway Engineering 1.375" hollow center section of Gendron FSB on full stiff.
The MX-5 FSB can be had for cheap and is not difficult to tweak to make it work, so it might be worth a try.
-Dave
I have to say that I do have a different setup than the norm. The difference (stagger the right word?) in my front to rear spring rate is 800F/500R... (with 650 waiting to be used). I also have a custom Speedway Engineering 1.375" hollow center section of Gendron FSB on full stiff.
The MX-5 FSB can be had for cheap and is not difficult to tweak to make it work, so it might be worth a try.
-Dave
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Originally Posted by NelsonI,Dec 15 2010, 04:18 PM
Speaking of roll rates--
Nick, it looks like you're running about 1400 lbs of spring roll rate (using wheel rates) and probably another 300 lbs or so from the front bar? I'm assuming that's to limit body roll to the <1.5 degree range or so (maybe more like 1.3 or less, assuming a ~12" moment arm)--is that because of rear bump toe issues? I'd think the camber curves are friendly enough on the S2K to not need the car locked down that much unless there are other issues.
Natural frequencies with those rates must be in the mid/upper 3s, too--maybe it's just for transitional response? Trying to wrap my head around rates that high on ~1.2g capable street tires.
I know I'm in the "other" camp now (MX-5) but I've been following your build long enough to know you don't do anything without a reason, so I'm curious.
btw: your wheels are one of my top 2 choices right now...hope to get back to you by year end if they're not sold yet. Just waiting on cash (hoping for a bonus this year).
Nick, it looks like you're running about 1400 lbs of spring roll rate (using wheel rates) and probably another 300 lbs or so from the front bar? I'm assuming that's to limit body roll to the <1.5 degree range or so (maybe more like 1.3 or less, assuming a ~12" moment arm)--is that because of rear bump toe issues? I'd think the camber curves are friendly enough on the S2K to not need the car locked down that much unless there are other issues.
Natural frequencies with those rates must be in the mid/upper 3s, too--maybe it's just for transitional response? Trying to wrap my head around rates that high on ~1.2g capable street tires.
I know I'm in the "other" camp now (MX-5) but I've been following your build long enough to know you don't do anything without a reason, so I'm curious.
btw: your wheels are one of my top 2 choices right now...hope to get back to you by year end if they're not sold yet. Just waiting on cash (hoping for a bonus this year).
Frequencies are in the 2.5-2.3 range. Definitely not up near 3.
I would do everything I could to not use sway bars. I have 1200lb spring sitting next to me that I had planned to try up front with no bar. I'd much rather use low speed compression to support the outside wheel rather than reduce traction on the inside wheel via a sway bar.
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From: Frankfort, KY
Originally Posted by TheNick,Dec 16 2010, 10:38 AM
I would do everything I could to not use sway bars. I have 1200lb spring sitting next to me that I had planned to try up front with no bar. I'd much rather use low speed compression to support the outside wheel rather than reduce traction on the inside wheel via a sway bar.
It would be a nice way to drop 40lbs but i feel it would take one hell of a spring to make it work. Although nascar, F1, rally and every other (car) motorsport uses swaybars. You would think thats for a reason, right?
-Noob input
ps- So I'm totally lost on on this calculations but I saw on here a min ago somewhere a 850 spring/ .7 mr = 600 lb/deg wheel . Im guessing You all took 850/.7 and got 1214 and then divided by 2 to get the "600". From guessing would you just add the 1000 lb/deg of spring divided by 2 and now have a "wheel weight" of 1100 per wheel?
If that above is correct would a 1540lb spring give you the same effect with out a bar?
- So lost but trying to understand
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From: Near Philadelphia
Josh - personally I think you're right, you're not going to be able to get away from using sway bars without having too stiff front springs. However I do think there's some value potentially in lessening just how much front bar you need. The Gendron bar is a huge sway bar, if we could get it down to the point where we only needed a smaller sway bar, that might be better. That was something I was considering trying too.
Also that's a very interesting idea to use more low speed compression to supplement the springs.
Also that's a very interesting idea to use more low speed compression to supplement the springs.
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Originally Posted by alvanderp,Dec 16 2010, 06:21 AM
I still don't see how you are getting to those numbers. I'm getting the same as IntegraR0064(2.61/2.38) What is your wheel rate calculation coming to?
That would put target body roll closer to 2 degrees, which makes sense. Also explains inability to go barless without insanely high spring rates, which further complicates adequate damping at those motion ratios--as I understand it, anyway.
I do find it interesting that with ~0.2-0.4 g more absolute tire grip, the BS S2ks (and CS MX-5s) are still turning faster times with far lower rates. Just goes to show how important minimum speed is in autocross, I guess.
Nick--glad you sold the wheels. Just wish it had been to me. I should have pulled the trigger.
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From: AZ
Originally Posted by NelsonI,Dec 16 2010, 11:54 AM
Looks like I was using the wrong motion ratios--0.82 F/0.77 rear, which appears to be the AP1. AP2 ratios are more like 0.7/0.67? Those low ratios explain the wicked dampers you guys are needing, as well as the very high spring rates. I probably also low-balled total weight at around 2600 lbs. Probably closer to 2800-2850 with driver.
That would put target body roll closer to 2 degrees, which makes sense. Also explains inability to go barless without insanely high spring rates, which further complicates adequate damping at those motion ratios--as I understand it, anyway.
I do find it interesting that with ~0.2-0.4 g more absolute tire grip, the BS S2ks (and CS MX-5s) are still turning faster times with far lower rates. Just goes to show how important minimum speed is in autocross, I guess.
Nick--glad you sold the wheels. Just wish it had been to me. I should have pulled the trigger.
That would put target body roll closer to 2 degrees, which makes sense. Also explains inability to go barless without insanely high spring rates, which further complicates adequate damping at those motion ratios--as I understand it, anyway.
I do find it interesting that with ~0.2-0.4 g more absolute tire grip, the BS S2ks (and CS MX-5s) are still turning faster times with far lower rates. Just goes to show how important minimum speed is in autocross, I guess.
Nick--glad you sold the wheels. Just wish it had been to me. I should have pulled the trigger.