Increasing rear grip...options? - Page 2 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 10-05-2013, 12:38 AM   #21
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I already have a 12mm rear bar on the car and 28mm on the front.
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Old 10-05-2013, 01:01 AM   #22
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Disconnecting an end link is the least rear bar of all.
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Old 10-05-2013, 04:56 AM   #23
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Every time someone suggests removing the rear bar on a track car, I cry myself to sleep.
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Old 10-05-2013, 10:18 AM   #24
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Every time someone suggests removing the rear bar on a track car, I cry myself to sleep.
Me too.

I still don't think he has checked into whether he is running out of rear suspension travel mid-corner.
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Old 10-05-2013, 11:27 AM   #25
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Me too.

I still don't think he has checked into whether he is running out of rear suspension travel mid-corner.
Unfortunately I can't as it's a track only car so I'm going to make a change before I go to the track again. Most likely I'm going to switch rear shocks between the 2 cars and replace the NB top hats with ISC top hats for a bit more travel. Just bouncing on the back of the car the setup currently on the track car is softer than the one on the street car.
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Old 10-05-2013, 12:59 PM   #26
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Less rear ride height, less front rebound. Don't bandaid it with toe changes. When was the last time the car was cornerweighted and/or aligned? What does the tire pyrometer say?
Shouldn't that be *more* front rebound? The reasoning being - on corner exit you're unwinding the wheel and adding more power... the car derolls and squats, so nose comes up, and more low speed front rebound will reduce front grip and thus reduce oversteer?
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Old 10-05-2013, 05:05 PM   #27
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I swapped the shocks today. The 325# springs went on the street car and the 350# went on the track car. I also added the ISC top hats. I took the street car for a ride and it's apparent that the shocks that were on the track car are valved softer than the ones that were on the street car. After the switch the street car now kinda glides over rough pavement. Hopefully the increased rebound will help keep the rear planted better coming out of corners on the track car.
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Old 10-08-2013, 06:49 PM   #28
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Originally Posted by JasonC SBB View Post
Shouldn't that be *more* front rebound? The reasoning being - on corner exit you're unwinding the wheel and adding more power... the car derolls and squats, so nose comes up, and more low speed front rebound will reduce front grip and thus reduce oversteer?
More front rebound will keep the nose down on exit and increase front grip. Let the nose rise and weight shifts to the rear tires on exit as it should. Hence less front rebound (at least IMO).
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Old 10-08-2013, 10:01 PM   #29
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Originally Posted by Savington View Post
More front rebound will keep the nose down on exit and increase front grip. Let the nose rise and weight shifts to the rear tires on exit as it should. Hence less front rebound (at least IMO).
Doesnt weight shift irregardless of body roll.
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Old 10-08-2013, 10:15 PM   #30
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In talking with a friend he said that in dirt track racing that they'd use a soft rebound shock on the right front and a stiff rebound shock on the left rear to increase rear traction coming out of a corner. Since we have to turn both ways on a road course you'd tune both shocks on an axle the same.
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Old 10-08-2013, 11:24 PM   #31
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Originally Posted by wannafbody View Post
In talking with a friend he said that in dirt track racing that they'd use a soft rebound shock on the right front and a stiff rebound shock on the left rear to increase rear traction coming out of a corner. Since we have to turn both ways on a road course you'd tune both shocks on an axle the same.
You should race dirt track. Problem solved for us.
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Old 10-09-2013, 11:16 PM   #32
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A dirt track Miata would be cool.
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Old 10-10-2013, 08:48 PM   #33
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So do you know if you were on the bumpstops exiting the corner or did you just guess you were?
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Old 10-10-2013, 10:57 PM   #34
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So do you know if you were on the bumpstops exiting the corner or did you just guess you were?
Just a guess, I'm headed to the track Sunday so I'll find out if I've solved the issue.

I was talking to a guy today who told me that the local dirt track was having a race this weekend with a $50,000 purse. No wonder dirt track racing is so popular.

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Old 10-11-2013, 12:32 AM   #35
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Mine is very well balanced with the fm front barand stock rear bar. Much better than with no rear bar. The car it's extremely predictable.

I've got the nb tophats, fcm bumpstops. I think the rear bumpstops may be cut in half, id have to check.

Maybe slightly less front bar?
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Old 10-11-2013, 09:00 AM   #36
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Originally Posted by djp0623 View Post
Maybe slightly less front bar?




The balance of any car between oversteer and understeer is a function of weight balance front to rear versus spring rates front to rear (and the sway bars are springs). If a setup has so much rear spring that a rear sway bar is unnecessary to achieve balance, then you have too much rear spring or not enough front spring (including sway bar). This is a bit of a simplification for the sake of illustration as there are a few other mitigating factors involved as well. Such as, the rear suspension bottoms out causing the car to behave as if the rear spring rate has suddenly skyrocketed (thus causing an abrupt onset oversteer condition).
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Old 10-13-2013, 11:25 PM   #37
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Update, took both cars to Nelson Ledges. If you aren't aware, this is probably the bumpiest track in North America. The track car felt better, I didn't feel as if the rear was going to slide out at the touch of the throttle. So the changes that I made by switching shocks and springs and tophats seemed to improve grip. Incidentally, switching shock and springs to the street car didn't seem to have a negative impact. The 1.6 is definitely lacking power but the car is able to put that power down quite effectively. For some reason it seems to hook a little better than the track car(maybe the cage plays a role). My friend took me for a few laps and about scared the crap outta me. I was seriously impressed that despite throwing it into the corners it didn't break traction despite the tires howling in protest. That being said, after driving both cars, I'm coming to the impression that the Yoke AD08's are a more forgiving tire than the Star Specs on track.
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Old 10-14-2013, 12:25 AM   #38
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I would be willing to bet your problem is shock travel, **** bump stops, greasy tires, bad driving, and unpredictable diff engagement combined.
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Old 10-14-2013, 09:22 AM   #39
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I would be willing to bet your problem is shock travel, **** bump stops, greasy tires, bad driving, and unpredictable diff engagement combined.
Yeah, but if you take all of that out of the equation there wouldn't be a problem.
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Old 10-14-2013, 11:11 AM   #40
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Oh, I'll readily admit that I'm not the best driver, I'm fairly slow but I am focusing on being smooth and increasing speed. My friend who is a good driver has said that the street car seems to stick better as well.

One thing I noticed last time I was at the track, we swapped the Hoosier R6s on the track car and the improved grip helped. I was actually able to get the car to understeer by turning the steering wheel quickly.

Maybe the VLSD is the difference between the 2 cars.
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