09-28-2020, 07:12 AM | #1 |
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M2C Mid-Corner / Corner Exit Issues
So I finally got the M2 Competition out on track after the mods, and I am having issues with the vehicle mid-corner to corner exit behavior.
The car has the Ohlins R&T with the Ohlins recommended spring rates, Ground Control Camber plates, 265/295 Yokohama A052 tires. The front has 0 toe, rear has total 1/8th toe in. -3 camber front, -2.1 camber rear (drivers side), -2.7 camber front, -1.7 rear (passenger side). The track I visit most often is mostly all right hand turns, hence the setup being as this. Front rebound is set at 7 clicks, rear at 12 clicks (was originally 7 at rear but softened the rebound after) The rear of the car starts letting loose from mid corner to corner exit on right hand turns. It is more prevalent on longer sweeping corners. I am a pretty seasoned driver, and it does the above mentioned over steer with no jerking of the wheel, or rough application of power. In fact if you hold throttle steady and keep the steering angle steady the back ends up coming around. All nannies are off, so its not a matter of the electronics throwing the car off either. I was out on track on Wednesday, and back again yesterday (Sunday). On Sunday we took cross temps on tires and the rear can use more camber, front wasn't so bad. I thought with the amount of stagger running with the tires the car would actually understeer from mid-corner to corner exit, however I can't even apply any power since there is way too much yaw. I would appreciate anyone who has experience with the F87 chassis to chime in. |
09-28-2020, 07:30 AM | #2 |
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Your alignment doesn't make sense to me, I've never heard of anyone running that way it's not NASCAR. Set both rears to -1.8 with stock toe in. The Ohlins are over sprung and under damped in stock form, the f8x kit is disappointing in my experience. Try softening the rear dampers to add more grip to the rear.
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09-28-2020, 08:25 AM | #3 | |
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Actually on a race track where you have 80% of the turns that are right hand turns, and 20% are only left hand turns, the stagger on the camber makes perfect sense. Think about it, the reason why you are using camber is to maximize the contact patch on the corners, and a car has 4 tires. When you turn right, the camber on the right hand of the car actually does not help you with the contact patch, so by compromising a little for the left hand turns, you run less negative camber on one side and your contact patch is increased for 80% of the corners on that given track layout. Also your recommendation of running less camber in the back again does not make sense, we did cross temps on tires, and the rear is asking for more camber. I appreciate you trying to help though. |
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09-28-2020, 09:40 AM | #4 |
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Do you oversteer on exit in both left and right turns?
I typically like a loose car. But when it gets too wild softening the rear and/or stiffening the front usually does the trick.
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09-28-2020, 10:47 AM | #5 |
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The left hand corners on this track aren't really long turns, but the rear is very sensitive to steering input on the right hand turns.
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09-28-2020, 10:58 AM | #6 |
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The first thing I’d try is equal alignment settings on both sides just to test that change before playing with the dampers. An easy test.
Other than that, it sounds too stiff in the rear. |
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09-28-2020, 11:01 AM | #7 |
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The toe is equal, the camber is not. But the camber will only negatively impact the corner grip if they are equaled out.
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09-28-2020, 11:04 AM | #8 | |
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I’ve also had a car dialed in that behaved poorly on track (-3F, -2R, 0.04 deg toe in F, 0.28deg toe in rear), and come to find out afterwards the alignment was out of whack. Probably from hitting a pothole or something on the way to the track. Re-aligned and everything was back to normal. My gut tells me the issue is the rear is too stiff, but double checking and trying diff alignment is easy to do as a test. Last edited by ZM2; 09-28-2020 at 11:12 AM.. |
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09-28-2020, 03:02 PM | #9 |
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How's the usable range in stroke on the rear shocks with the Ohlins? I know they screwed up in designing the coilovers on the rear of the S2000 so if you lowered it an inch you would have only about an inch of shock travel. Most people have settled on a little extra preload in order to achieve ride height and keep it from bottoming out.
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09-28-2020, 03:20 PM | #10 | |
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The way it works on the M2, is you need to set the ride height with the preload adjustment (so the perch on the spring), then match the ride height adjuster (shock length) according to that. This might sound weird, but I am using the terminology from their own manual, which kind of can be mislading, because the ride height adjustment only adjusts the shock/dampener length which by itself will not adjust ride height unless you change the preload. |
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09-28-2020, 07:44 PM | #12 | |
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Also, I suggest you try 1.8 to 2.0 degree rear camber, irrespective of what your pyrometer is telling you. That’s where most F8x guys end up after some experimentation. |
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09-28-2020, 09:46 PM | #13 | |
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Ever since Wednesday, the day I had it on track, I've actually shortened the shock length by two turns and after reading what you just wrote I went out to check the amount of rod the shock has before the bump stops. Obviously Ohlins USA is closed now to see if under 2 inch of shock travel is sufficient, but this could have been definitely the cause of the erratic behavior of the car. Just check out the video of the lap and a bit which I posted on Youtube, you'll see how wild the car was. |
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09-29-2020, 02:04 AM | #15 | |
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I'd be reluctant to make a handling balance assessment in those greasy conditions. However, from what I could see & hear, the rear was breaking traction before it was stepping out which is a throttle application issue, not a suspension problem. What F&R tyre pressures are you running? |
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09-29-2020, 07:31 AM | #16 | |
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I was on track for another four hours, and it dried out. The problems I was experiencing that described on my OP is more evident in this short clip. Steering input remains the same, extremely light and smooth throttle application and the rear comes around on exit. |
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09-29-2020, 08:41 AM | #17 |
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I personally don't like the non linear throttle in sport modes. Very touchy with minimal input. Would take some getting used to on the track for sure.
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09-29-2020, 04:58 PM | #18 | |
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09-30-2020, 08:00 AM | #20 |
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09-30-2020, 10:35 AM | #21 |
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Just an update on this.
We've been talking to Ohlins about the issue with the vehicle dynamics. Did some measurements of the suspension, droop length, rear shock shaft measurements etc... It looks like unfortunately their instruction manual and the setup guide is quiet a bit off. The car doesn't have enough droop, preload is way off too. As per the setup from the installation manual, the preload is set more than what it is supposed to be which could also be contributing to all of this. I have a busy week this week, but we are going to make the changes Ohlins has recommended and report back. |
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09-30-2020, 10:37 AM | #22 |
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I assume in the hands of a novice driver, it would definitely be scary. To me it was just more annoying than scary. Losing a lot of drive out of the corners because of this.
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