Snap oversteer
01-15-2010, 02:26 AM
#1
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Snap oversteer
Ok, I've spent an hour or so trawling through older threads and it would appear that most think that snap oversteer is the preserve of poor drivers or is just a myth.
I'm relatively new to the S (3 months) and my previous car of 4 years was a Miata NA 1.6 with a 15 PSI turbo conversion, bigger sway bars, Tein coilovers, Toyo R888's on 15" rims and a retrofitted Torsen Type I diff.
During 4 years of ownership of the Miata I only experienced snap oversteer the once and it happened at 20mph or so and, most notably after I'd just fitted the Torsen and the surface was damp with cracked rear tyres (with good tread depth) Snap oversteer in that situation resulted in a 180 degree spin that today I honestly can't remember any of it - it really was that sudden.
My reason for bringing up this subject is that in the UK over the past month or so the weather has been either very wet, icy, snow or whatever. In the the short time I've owned the S I can count on both hands the number of cars that have been written off, and that is of those that contribute to the UK sub forum of S2ki.
In all cases the rear has broken loose in a straight line and at moderate speeds. All have have good tread depth on the rear tyres and only one was in VTEC (1st gear) at the time the rear decided to give way. All bar 1 were owners with less that 6 months ownership of the S, but the common and widely used explanation is that they 'were a passenger'
My view is that the characteristics of the torsen and the way it apportions the torque between the rear wheels when it detects slip is the main contributor to the cars behaviour especially in wet conditions.
This is my definition of snap oversteer;
[media]http://www.youtube.com/watch?v=ECo60jFqKFQ [/media]
Yes the driver appeared to lift and unsettle the car, but the car's behaviour thereafter would have caught out 99.99% of drivers out there.
My question is;
what can I do to ensure that I do not become another statistic with this car. My car is MY00 with 04+ 17's and Koni yellow/stock springs and a front lower arm brace.
Cheers and thanks for reading.
I'm relatively new to the S (3 months) and my previous car of 4 years was a Miata NA 1.6 with a 15 PSI turbo conversion, bigger sway bars, Tein coilovers, Toyo R888's on 15" rims and a retrofitted Torsen Type I diff.
During 4 years of ownership of the Miata I only experienced snap oversteer the once and it happened at 20mph or so and, most notably after I'd just fitted the Torsen and the surface was damp with cracked rear tyres (with good tread depth) Snap oversteer in that situation resulted in a 180 degree spin that today I honestly can't remember any of it - it really was that sudden.
My reason for bringing up this subject is that in the UK over the past month or so the weather has been either very wet, icy, snow or whatever. In the the short time I've owned the S I can count on both hands the number of cars that have been written off, and that is of those that contribute to the UK sub forum of S2ki.
In all cases the rear has broken loose in a straight line and at moderate speeds. All have have good tread depth on the rear tyres and only one was in VTEC (1st gear) at the time the rear decided to give way. All bar 1 were owners with less that 6 months ownership of the S, but the common and widely used explanation is that they 'were a passenger'
My view is that the characteristics of the torsen and the way it apportions the torque between the rear wheels when it detects slip is the main contributor to the cars behaviour especially in wet conditions.
This is my definition of snap oversteer;
[media]http://www.youtube.com/watch?v=ECo60jFqKFQ [/media]
Yes the driver appeared to lift and unsettle the car, but the car's behaviour thereafter would have caught out 99.99% of drivers out there.
My question is;
what can I do to ensure that I do not become another statistic with this car. My car is MY00 with 04+ 17's and Koni yellow/stock springs and a front lower arm brace.
Cheers and thanks for reading.
01-15-2010, 02:45 AM
#2
Registered User
The usual suspects - _proper_ tires for the weather (summer tires need not apply for cold weather), alignment, driver input, etc. I've had the car for >9 years in Rochester, NY where we get 90-100" of snow a year and cold temps from Nov. through March and have never spun the car on the street. I've had it get loose due to excessive speed for the conditions (hit a patch of packed snow or ice) and had an interesting experience that turned out to be caused by a broken front swaybar link. I use all-season tires for the winter rather than snow tires and drive according to the available grip rather than making assumptions - I actually test traction to determine the limits by applying power and brakes.
There's nothing magical here. I submit that most problems are due to driver error, perhaps because we've become insensitive due to FWD. I enjoy steering the car with throttle but there's an awful lot of drivers (not just S2k drivers) who really don't have a clue even with FWD. Now, put them in a RWD car and the problem increases exponentially. I scared myself shitless when I first got the car from the stories on this forum with "snap oversteer" and multitudes of crashes. It turns out that one can't be at the limits of adhesion in a turn and then have VTEC kick in very successfully - physics sucks. I'm not saying this is the problem here but the overall concept fits. Drive according to traction/conditions in a properly maintained car and you will have very few problems.
There's nothing magical here. I submit that most problems are due to driver error, perhaps because we've become insensitive due to FWD. I enjoy steering the car with throttle but there's an awful lot of drivers (not just S2k drivers) who really don't have a clue even with FWD. Now, put them in a RWD car and the problem increases exponentially. I scared myself shitless when I first got the car from the stories on this forum with "snap oversteer" and multitudes of crashes. It turns out that one can't be at the limits of adhesion in a turn and then have VTEC kick in very successfully - physics sucks. I'm not saying this is the problem here but the overall concept fits. Drive according to traction/conditions in a properly maintained car and you will have very few problems.
01-15-2010, 06:00 AM
#3
The driver in the video lifted at about 0:09, being a bit tentative about the traffic in front of him perhaps. In that case, and in most cases, "snap oversteer" doesn't just HAPPEN. Events precipitate it.
The early AP1 is particularly sensitive to what most would consider very minor mistakes on the part of the driver. Part of it is rear roll stiffness bias, and another part is rear toe change with bump.
Before I bought my '01 S, I'd had tons of experience tracking my modded 240Z, which for a long time was tuned for quite a bit of oversteer. But the car was always benign when the back end came out.
After I bought the S, I took it to Watkins Glen, which I'd had several events' worth of experience at with the Z.
My first hot lap in a car much slower than the Z, I kinda feathered the throttle a bit entering the top of the esses, and damned if the back end didn't try to step out. And with only a very subtle lift, and not at maximum possible speed for the car at that part of the track. Next time around I kept in it and was gentle with steering inputs, and learned that the car wants to oversteer initially, but then handling becomes neutral as the body rolls and the outside rear toes in (and the inside rear toes out).
Basically, my observation is that the early S requires very subtle inputs at the steering wheel, and is prone to trailing-throttle oversteer if you back off while cornering.
The AP1 setup almost seems specifically DESIGNED to catch out inexperienced drivers! Rear roll stiffness bias gives great steering responsiveness and initial oversteer, then the outside rear toes in and returns handling to neutral. BUT, if you LIFT, not only do you unload the rear tires, losing you rear grip, but the outside rear toes OUT, all but ensuring that you're going for a spin!
As for what you can DO, first thing I'd suggest is try to get experience driving at the limits of adhesion at autocross events and/or track days.
Regarding the car, always ensure that you have sticky tires in good condition, and always ensure that the rears are at least as sticky as the fronts! A bigger front sway bar will reduce the car's general oversteer tendencies. Or you might even consider removing the rear sway bar, which would increase body roll, but bias more roll stiffness to the fronts (giving more rear grip).
The AP1 suspension is kind of a funny setup. It's quite surprising that the Japanese have now tried at least three times (2nd gen RX7, NSX, AP1) to have the rear toe geometry change with bump as if that were in any way good for performance, predictability, or safety. In the end it's bad for all three! They "fixed" that with the AP2 (at least in the States).
The "rear toe change with bump" idea was never a good one, but once you get *used* to driving the AP1 at the limit, it's not a big problem. I've since put 16 track days on my stock '01 and only managed to spin it once (knock on wood!).
The early AP1 is particularly sensitive to what most would consider very minor mistakes on the part of the driver. Part of it is rear roll stiffness bias, and another part is rear toe change with bump.
Before I bought my '01 S, I'd had tons of experience tracking my modded 240Z, which for a long time was tuned for quite a bit of oversteer. But the car was always benign when the back end came out.
After I bought the S, I took it to Watkins Glen, which I'd had several events' worth of experience at with the Z.
My first hot lap in a car much slower than the Z, I kinda feathered the throttle a bit entering the top of the esses, and damned if the back end didn't try to step out. And with only a very subtle lift, and not at maximum possible speed for the car at that part of the track. Next time around I kept in it and was gentle with steering inputs, and learned that the car wants to oversteer initially, but then handling becomes neutral as the body rolls and the outside rear toes in (and the inside rear toes out).
Basically, my observation is that the early S requires very subtle inputs at the steering wheel, and is prone to trailing-throttle oversteer if you back off while cornering.
The AP1 setup almost seems specifically DESIGNED to catch out inexperienced drivers! Rear roll stiffness bias gives great steering responsiveness and initial oversteer, then the outside rear toes in and returns handling to neutral. BUT, if you LIFT, not only do you unload the rear tires, losing you rear grip, but the outside rear toes OUT, all but ensuring that you're going for a spin!
As for what you can DO, first thing I'd suggest is try to get experience driving at the limits of adhesion at autocross events and/or track days.
Regarding the car, always ensure that you have sticky tires in good condition, and always ensure that the rears are at least as sticky as the fronts! A bigger front sway bar will reduce the car's general oversteer tendencies. Or you might even consider removing the rear sway bar, which would increase body roll, but bias more roll stiffness to the fronts (giving more rear grip).
The AP1 suspension is kind of a funny setup. It's quite surprising that the Japanese have now tried at least three times (2nd gen RX7, NSX, AP1) to have the rear toe geometry change with bump as if that were in any way good for performance, predictability, or safety. In the end it's bad for all three! They "fixed" that with the AP2 (at least in the States).
The "rear toe change with bump" idea was never a good one, but once you get *used* to driving the AP1 at the limit, it's not a big problem. I've since put 16 track days on my stock '01 and only managed to spin it once (knock on wood!).
01-15-2010, 08:43 AM
#4
The S2000's handling is a double-edged sword.
My favorite video (that I can't seem to find) is a Best Motoring vid where they take a race-prepped tuner S2000 driven by a professional. Then they take the winner of an "amateur racer" contest and let them drive the race-prepped car around the track.
One guy spun the car three times and almost put it into a wall. He was abrupt and imprecise in his steering inputs and his heel-toeing. At speed, that's enough to overcome the grip of the tires.
The answer? Slow down and get smooth.
It was a striking contrast that the car set up for "optimal handling" was too much for even a "decent amateur racer."
Kind of like a blade 2-iron for a mediocre golfer.
Yes, going from a Torsen to a Clutch-type diff does reduce the "snappiness" and makes the rotation and corner exit more predictible. But it's a trade-off and other handling concessions need to be made to prevent some of the understeer issues that can occur with a fixed torque axle breakaway.
My favorite video (that I can't seem to find) is a Best Motoring vid where they take a race-prepped tuner S2000 driven by a professional. Then they take the winner of an "amateur racer" contest and let them drive the race-prepped car around the track.
One guy spun the car three times and almost put it into a wall. He was abrupt and imprecise in his steering inputs and his heel-toeing. At speed, that's enough to overcome the grip of the tires.
The answer? Slow down and get smooth.
It was a striking contrast that the car set up for "optimal handling" was too much for even a "decent amateur racer."
Kind of like a blade 2-iron for a mediocre golfer.
Yes, going from a Torsen to a Clutch-type diff does reduce the "snappiness" and makes the rotation and corner exit more predictible. But it's a trade-off and other handling concessions need to be made to prevent some of the understeer issues that can occur with a fixed torque axle breakaway.
01-15-2010, 08:52 AM
#5
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Originally Posted by ZDan,Jan 15 2010, 08:00 AM
The driver in the video lifted at about 0:09, being a bit tentative about the traffic in front of him perhaps. In that case, and in most cases, "snap oversteer" doesn't just HAPPEN. Events precipitate it.
That was a lot of 360's!
01-15-2010, 09:04 AM
#6
Registered User
The best tool to prevent that is your right foot, 'cause like everyone is staying, snap oversteer doesn't just happen (usually)-- it is normally caused by a wrong reaction from the driver. 
01-15-2010, 09:36 AM
#7
Former Moderator
Here's my experience of inexperience
maybe having something other than a torsen may have helped or the fact that I was on the stock RE050's. Whatever the problem seems like it may be I think it always boils down to inexperience. If I had done things differently I would have been fine but I chose to stay off the gas too late in to the corner which caused this.
Do I want to change this charcteristic of the car? Most definitely
Here's the right video[media]http://www.youtube.com/watch?v=lCE60j6gL5Y [/media]&feature=youtube_gdata
maybe having something other than a torsen may have helped or the fact that I was on the stock RE050's. Whatever the problem seems like it may be I think it always boils down to inexperience. If I had done things differently I would have been fine but I chose to stay off the gas too late in to the corner which caused this.
Do I want to change this charcteristic of the car? Most definitely
Here's the right video
[media]http://www.youtube.com/watch?v=lCE60j6gL5Y [/media]&feature=youtube_gdata
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01-15-2010, 10:18 AM
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Now compare the characteristics of the S to a Miata NC
[media]http://www.youtube.com/watch?v=cqlYXdVPPoA [/media]
Could it be the FMR layout of the S that causes the pendulum effect or is it just one of the quirks of the car.
I'll definitely take your advice and enrolled in driver tuition.
[media]http://www.youtube.com/watch?v=cqlYXdVPPoA [/media]
Could it be the FMR layout of the S that causes the pendulum effect or is it just one of the quirks of the car.
I'll definitely take your advice and enrolled in driver tuition.
01-15-2010, 10:36 AM
#10
Former Moderator
For the S it's an off throttle issue. The car is supper easy to control while on the gas.
This is one of the reasons I think it's super hard to track on oem tires. The fronts are way to skinny and to be able to turn the car in you have to transfer some weight but the experience will tell you how much.
[media]http://www.youtube.com/watch?v=kYZjY56glo4 [/media]&feature=youtube_gdata
This is one of the reasons I think it's super hard to track on oem tires. The fronts are way to skinny and to be able to turn the car in you have to transfer some weight but the experience will tell you how much.
[media]http://www.youtube.com/watch?v=kYZjY56glo4 [/media]&feature=youtube_gdata