Improve rear end grip in corners - remove oversteer

[Skiy]

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.

[NickyC]

What a beautiful car.

[K8_M235i]

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.

[Skiy]

Originally Posted by NickyC

What a beautiful car.

Thank you 🙏

[Skiy]

Originally Posted by K8_M235i

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.

What about the zcp front sway bar? I do like the reduced roll the rear provides and removing it will require to drop subframe again.
I dont have camber plates so adjusting camber will be difficult in front. But wont more camber improve front grip in cornering?

[M 4 FUN]

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.

[K8_M235i]

Originally Posted by Skiy

What about the zcp front sway bar? I do like the reduced roll the rear provides and removing it will require to drop subframe again.
I dont have camber plates so adjusting camber will be difficult in front. But wont more camber improve front grip in cornering?

The front camber was more of a general note, probably won't help in this situation, but you will want to have about a degree more front camber than rear camber.

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.

[jfritz27]

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/

[TractionControlDelete]

Originally Posted by jfritz27

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/

These articles are excellent! Thank you - definitely bookmarking these

[jfritz27]

Originally Posted by F82KPowers

These articles are excellent! Thank you - definitely bookmarking these

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.

[Skiy]

Originally Posted by K8_M235i

The front camber was more of a general note, probably won't help in this situation, but you will want to have about a degree more front camber than rear camber.

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.

They dont make regular cup2 in that size hence i went for the ZP version. They have a cup2 R I believe but thats a different tire as well

[Skiy]

Originally Posted by M 4 FUN

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.

Its tuned and a manual. I stiffened the rear because i was getting a lot of understeer on stock tire sizes, i guess i improved it more then i thought it would as its not that much thicker of a bar.

[Skiy]

Originally Posted by jfritz27

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/

Thank you for these articles. They explain it all well. It depends on my speed but fast corner i notice it starts to swing out at the very beginning. If i use throttle a bit i can make it swing out even at lower speeds towards end of corner. It gives me a feeling as if i put plastic crates under my rear tires and just driving around on ice and the rear keeps swinging out when u turn. Its obviously not that dramatic but it feels like the rear has some momentum always behind it now and i gotta be aware to keep it planted when before i had to just worry my speed isnt too high into corner entry or i will plow forward. It definitely feels more nible and fun. I will try the zcp front sway bar as its an easy swap and hopefully it stiffens the front a bit and reduces roll

[F80RN]

There's a plethora of Information here. Thanks to the OP and everyone else who contributed. Going to read this all tonight

[David0ff]

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

[Skiy]

Originally Posted by David0ff

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

The one that i got for rear was from a mustang gt350. Not sure if r or not. I think its from the R. The guy said he got the performance set of wheels and this one was from the front. Its the 180 thread wear and not the newer 240. It actually is the track connect version and not just the connect one. Is this the correct gt350r tire that your talking about?
Pics of what i have

[Skiy]

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

[Skiy]

I also swapped a ZCP front sway in today and will report if that helps.

[David0ff]

Originally Posted by Skiy

The one that i got for rear was from a mustang gt350. Not sure if r or not. I think its from the R. The guy said he got the performance set of wheels and this one was from the front. Its the 180 thread wear and not the newer 240. It actually is the track connect version and not just the connect one. Is this the correct gt350r tire that your talking about?
Pics of what i have

This is a pic of 8/20 tires from last season

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

[Skiy]

Originally Posted by David0ff

This is a pic of 8/20 tires from last season

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

I cant find the 305 98y on tirerack. Is it not there?

[Skiy]

Originally Posted by David0ff

This is a pic of 8/20 tires from last season

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

Just double checked and mine is the 102y version but 180 tw. What tw is the 98y?

[Skiy]

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?