STR Prep - Suspension and Alignment
03-26-2014, 09:44 AM
#411
Too much front bar is causing corner exit oversteer? I'm not sure I follow. At low speeds, sure, it understeers a bit and is easy to overload the front tires. At high speed though not so much. In fact, every single time I've added more front bar the car is faster and more stable through sweepers at the sacrifice of low-speed understeer. Maybe too much front roll rate for the rear camber I'm running? I recall Glagola having sweeper exit oversteer with his crazy stiff setup.
Those guys running hollow Gendron front bars and no rear bar/miata bar are all softer, but significantly more front roll rate biased. That hints to me that I could go more front biased by stiffening the front or softening the rear. Your setup, however, is more rear biased but yet you run very little rear camber in relation to the front.
My Gendron rear bar has a roll rate of 216lbs/in compared to the Miata base 124lbs/in or the stock CR 348lbs/in. I've seen people run higher and lower rear springs with any of those bars. One nationally competitive car accomplished the same rear roll rate as I have with 550lb springs and a stock CR rear bar; that same competitor ran the Gendron 1.25" hollow bar@6 with a stock rear CR bar and 900#f/650# rear springs for nationals two years ago (more camber though). Another ran the Gendron 1.375"@3 front bar, no rear bar, 700#f/550#r springs at nationals two years ago. Another ran 700# rear springs and a stock AP1 rear bar. All of these people I respect and have demonstrated success with those setups. People aren't contributing to the community as much lately so I have no idea where people are at now.
Those guys running hollow Gendron front bars and no rear bar/miata bar are all softer, but significantly more front roll rate biased. That hints to me that I could go more front biased by stiffening the front or softening the rear. Your setup, however, is more rear biased but yet you run very little rear camber in relation to the front.
My Gendron rear bar has a roll rate of 216lbs/in compared to the Miata base 124lbs/in or the stock CR 348lbs/in. I've seen people run higher and lower rear springs with any of those bars. One nationally competitive car accomplished the same rear roll rate as I have with 550lb springs and a stock CR rear bar; that same competitor ran the Gendron 1.25" hollow bar@6 with a stock rear CR bar and 900#f/650# rear springs for nationals two years ago (more camber though). Another ran the Gendron 1.375"@3 front bar, no rear bar, 700#f/550#r springs at nationals two years ago. Another ran 700# rear springs and a stock AP1 rear bar. All of these people I respect and have demonstrated success with those setups. People aren't contributing to the community as much lately so I have no idea where people are at now.
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03-26-2014, 10:06 AM
#412
^^^ well the tune would def have something to do with it as well i would think. Also have you tried lowering the rear pressures ? i would back off the rear bar to make it softer as well. small adjustments would make it easier to track down whats causing the problem.
03-26-2014, 12:56 PM
#414
Your front bar stiffness is compensating for the higher rate of the front bar. Basically I guess to make it simple you are compensating for the rear bar by stiffening the front and likely the tires are not sufficient for the heavy rate of the bars/springs. I don't think any Str guys are running the monster front bar. Most are running hollow. I would try to lower the bars to softest setting on front and rear and try see how it handles
I'll set the rear bar to the softest setting (a hair stiffer than the Miata bar) for this weekend since that is a known change. If I have time at the TNT, I can mess with the front bar, or even springs, and rear tire pressure. Eventually I'll try the overall softer setup.
03-26-2014, 12:59 PM
#415
I also think you have too much front bar. Some people have the monster bar but they're running it on settings 2 or 3 which is the same as the stiff end of the smaller bars. The 4th setting is a huge jump over 3, 200 lb/in on the monster bar.
I have noticed that when I put way too much stiffness in front it can cause the car to randomly oversteer. I'm not sure exactly what the mechanism is.
Generally the fix for corner exit oversteer is to either decrease rake, lower front rebound, increase rear compression, or be more gentle with the throttle.
But it's really hard to get the S2000 to put power down well at high speeds especially without a wing.
I have noticed that when I put way too much stiffness in front it can cause the car to randomly oversteer. I'm not sure exactly what the mechanism is.
Generally the fix for corner exit oversteer is to either decrease rake, lower front rebound, increase rear compression, or be more gentle with the throttle.
But it's really hard to get the S2000 to put power down well at high speeds especially without a wing.
03-31-2014, 07:48 AM
#416
We had a little time on Friday before the Texas National Tour to measure everything on the car. The alignment has changed a bit since I last measured it so what I found was a bit of a surprise. The car has been on the back burner for the past 1.5 years so the fact that it was off was not a surprise.
Car: 2006 S2000 AP2
Ride height: 13.0"f/12.5"r hub center to metal fender edge
Shocks: Moton Clubsports
Springs: 900f/650r
Front Bar: Gendron bearing 1.375"x0.25" @4
Rear Bar: Gendron bearing 1.0"x0.95" @1
Alignment: -2.8f/-3.1r camber*, 1/16" total toe OUT front, 1/8" total toe IN rear
Tires: 255 square BFG Rivals @35psi
Differential: off-the-shelf OS Giken
*I'm still verifying camber with multiple grassroots tools.
While somewhat wonky on paper, the car was good for a 1-2 finish over the weekend. The surface at College Station, for those that don't know, is concrete of better quality than Lincoln (no tar). The course on Saturday favored those that could hang onto the car through high speed maneuvers and the car excelled there. Sunday's course paid dividends for those that found rhythm and kept distance to a minimum. The car did well on Sunday, too, but we struggled to find the rhythm; the 3 shifts into 3rd didn't help either.
Before the test-and-tune we reduced the rear bar from 3 to 1 to cope with the power-on oversteer we'd experienced in prior events. The TNT had a 270* sweeper which really exasperated the on-throttle oversteer. Due to the speed of the competition courses, and the concrete surface, the car was a little different but I cannot attribute it directly to the rear bar change. The Rivals this weekend were very predictable and easy to coax into anything. The steering wheel can overload the front tires while cornering and throttle can overload the rear tires. This placed priority on throttle steering over steering input adjustments, speed maintenance over acceleration. The overall neutrality and stability made it really easy to attack everything on course.
With that out of the way, my next setup is going to be a touch softer: 800f/550r, 1.375@3f/1.0@1r, -3.0f/-2.7r.
Car: 2006 S2000 AP2
Ride height: 13.0"f/12.5"r hub center to metal fender edge
Shocks: Moton Clubsports
Springs: 900f/650r
Front Bar: Gendron bearing 1.375"x0.25" @4
Rear Bar: Gendron bearing 1.0"x0.95" @1
Alignment: -2.8f/-3.1r camber*, 1/16" total toe OUT front, 1/8" total toe IN rear
Tires: 255 square BFG Rivals @35psi
Differential: off-the-shelf OS Giken
*I'm still verifying camber with multiple grassroots tools.
While somewhat wonky on paper, the car was good for a 1-2 finish over the weekend. The surface at College Station, for those that don't know, is concrete of better quality than Lincoln (no tar). The course on Saturday favored those that could hang onto the car through high speed maneuvers and the car excelled there. Sunday's course paid dividends for those that found rhythm and kept distance to a minimum. The car did well on Sunday, too, but we struggled to find the rhythm; the 3 shifts into 3rd didn't help either.
Before the test-and-tune we reduced the rear bar from 3 to 1 to cope with the power-on oversteer we'd experienced in prior events. The TNT had a 270* sweeper which really exasperated the on-throttle oversteer. Due to the speed of the competition courses, and the concrete surface, the car was a little different but I cannot attribute it directly to the rear bar change. The Rivals this weekend were very predictable and easy to coax into anything. The steering wheel can overload the front tires while cornering and throttle can overload the rear tires. This placed priority on throttle steering over steering input adjustments, speed maintenance over acceleration. The overall neutrality and stability made it really easy to attack everything on course.
With that out of the way, my next setup is going to be a touch softer: 800f/550r, 1.375@3f/1.0@1r, -3.0f/-2.7r.
03-31-2014, 02:44 PM
#419
I have a video of my third place day 1 run but I dropped my tablet on day 2 and it was randomly starting and stopping solostorm as a result so I didn't get any more data or video. I had to edit the length a little and that seems to take youtube some time to accomplish with its editor. As soon as youtube puts it up I'll link it.
Thanks for sharing the setup and great driving both of you. Is this Jon or Robert?
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX Added to the STR video thread XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXhttps://www.s2ki.com/s2000/topic/925480-str-prep-events-and-videos/page__st__275
Thanks for sharing the setup and great driving both of you. Is this Jon or Robert?
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX Added to the STR video thread XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXhttps://www.s2ki.com/s2000/topic/925480-str-prep-events-and-videos/page__st__275