08-13-2022, 08:45 PM | #1 |
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Improve rear end grip in corners - remove oversteer
I am wondering whats next step to remove the oversteer that i now get on my f80.
current suspension mod list 2016 m3 6mt base Rear ZCP sway bar EMD springs front tension arm mono-ball upgrade Diff mount with dual oem poly bushings 19x10 and 19x11 apec arc8 wheels 285/35/19 cup 2 ZP on front - it looks like a semi slick 305/30/19 cup 2 connect in rear 2.0* front camber 2.2* rear camber I used to run Swift spec R springs and car was stiff but handled fairly well, few years later ride got bumper and harsh. I swapped to EMD springs and front control arm mono-ball bearings and it felt much more comfortable but front became a bit lower then on the Swift springs. I noticed a lot more understeer but i was on all season tires on stock 19' wheels. Next mod was rear sway bar and diff brace along with trans mount upgrade and it removed some understeer. Car became more neutral again and even a bit more tail happy, take corner too fast and rear end throws itself out a bit even without much throttle. Search for grip continues, I get wider wheels and choose the stickiest street tire i can get, i wanted to run as close to oem diameter in front so went with a 285/35/19 cup2 ZP, its from a C7 z06 so really wide, 11.2" thread width. Car now has more grip overall but front has immense grip now, probably a bit due to the wider even more aggressive rubber then the regular Cup2 tire. If i push car now the rear end tend to start sliding, its fun but i feel its a bit too aggressive how it steps out and with the amount of front grip i have it feels like it can get me i trouble. I have the digital M performance steering wheel and it shows above 1.3g lateral in corners and ramps and I feel there is more left in the car but rear end tends to start stepping out. Sometimes tho the rear end starts stepping out even at around 1g lateral force. What would help? Im thinking also doing front ZCP sway car but the CS models use the base front one Maybe rear control arm toe links? Before car would never have oversteer, it would just understeer when pushed hard. I can of course just drive it within its means but it'd be nice to have more rear lateral grip. |
08-13-2022, 10:30 PM | #3 |
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Some things that would help:
-More front camber -Matching tires, the zps are much different than regular cup 2s -possibly switch back to stock rear sway bar. Sway bars are a tuning tool and you feel oversteer less rear bar is the way to go.
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1998 S54 E36 M3 BMWCCA Club Racing #532 CM 1995 E36 M3 Sunbelt S52 |
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08-13-2022, 11:44 PM | #5 | |
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I dont have camber plates so adjusting camber will be difficult in front. But wont more camber improve front grip in cornering? |
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08-14-2022, 03:06 AM | #6 |
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Everything you have done to stiffen up the rear end makes it worse. By using the ZCP rear anti roll bar you are increasing front end grip and not rear end grip. By using stiffer bushes you will not get any sense of when the car is on the way to loose grip until it suddenly brakes loose. Personally i would never mix different types of tires as they work different at different temps.
I don't know if your car is auto or manual or tuned but by using torque reduction you can make it muchmore driveable by adjusting torque in each gear. These cars have so much torque that it becomes a problem on track, especially on manual cars, and especially if they are tuned. Also by using the GTS diff sofrware you will have a differential that is less aggressive when it starts to lock up. |
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08-14-2022, 09:32 AM | #7 | ||
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Adding the matching front sway bar would help with the balance of the car. First step for me would be to put regular cup 2s on the front so you have matching tires. From there you can start tuning the suspension.
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08-14-2022, 11:04 AM | #8 |
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You didn't mention your rear toe settings -- if you don't have any rear toe-in then that's an easy intervention to start with.
Otherwise, can you be more specific about when the oversteer seems most pronounced? Beyond the toe-in, how you would address it I think in part depends on the scenarios where it's happening. You may be limited in what you can do with stock suspension, but in general as others have noted, you generally want to soften the end of the car that lacks grip. But how much you do this via damper/ride height adjustments vs bars will depend on the scenarios when it's happening (is it more under lateral load/steady state conditions vs when weight transfer is happening front/back). Not an expert here, but I've been recently trying to brush up on suspension basics and these are some things I'm learning. Check out: https://suspensionsecrets.co.uk/how-...nd-understeer/ Also: https://speed.academy/how-to-fix-und...-setup-tuning/ |
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08-14-2022, 12:05 PM | #9 | |
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DSC, you say? Never heard of it
https://youtube.com/@tractioncontroldelete |
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08-14-2022, 02:17 PM | #10 |
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No prob... yes I think these are great resources. I particularly like the suspension secrets one as it lays out an algorithmic approach based on a few questions about how the car is behaving. At some point I (or someone else) should put all that into a flowchart figure.
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08-14-2022, 04:56 PM | #11 | |||
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08-14-2022, 04:57 PM | #12 | |
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08-14-2022, 05:11 PM | #13 | |
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08-15-2022, 09:40 PM | #15 |
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Problem is your rear tire compound.
The vette ZP cup 2 is a super sticky, fast warming co pound. The rear connect is a more tamed down version of it which does not have the same ultimate grip and warmup characteristics. Try looking for a 305 or 315 in 19" from a mustang 350r or GT. The mustang 305 is as wide as the vette 285. Suggest the 315 to match your front. Compound and warmup is almost identical to the vette tire How I know: I spent last season tearing Cup2s on my lapping car, I delaminated about 12, tried about 20 in all. Good luck
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08-15-2022, 10:30 PM | #16 | |
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Pics of what i have |
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08-15-2022, 10:35 PM | #17 |
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Other issue with running the 305 in front is its taller. 26.3" vs 25.8" for the vette zp version. I already had to trim my fender to bumper joint as it was running and it slightly rubs on rear side of front left fender liner in one spot. I added some jb weld on the fender liner so it will wear that vs make a hole in my liner and its been holding up. Half an inch taller tire will rub even more when turning.
Also not sure why it rubs on one side and not other. Nothing is bent in suspension and alignment is good |
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08-15-2022, 10:39 PM | #19 | ||
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The top 4 are 285zp vette like yours The bottom are 305 98y mustang like you need, there is also a 315 which comes on some mustangs which looks like the 305s & 285zp The 305 you now have in the rear is a tamed down version of the sticky 305 98y which comes on the mustang 350r I'm quite sure
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08-15-2022, 10:46 PM | #20 | |||
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08-15-2022, 10:48 PM | #21 | |||
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08-15-2022, 10:53 PM | #22 |
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I see the difference. Then outer thread block has less cut outs on yours and the first grove looks shallower and thinner. I have not ran into the ones that you have yet. Can you post a link to that tire? Does it work well with the zp fronts?
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