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      12-07-2021, 02:49 PM   #18
McLaren720s
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Drives: 2024 M4 Competition X
Join Date: Jun 2019
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Quote:
Originally Posted by beachBmmr View Post
Quote:
Originally Posted by Mrspeed636 View Post
How did the new setup do on track!? I know it was only yesterday but I know we are all curious to hear.
1. Definitely more mechanical grip up front. The added camber basically increased the contact patch significantly.

This is verifiable with lateral G-force increase, and faster corner speeds that demonstrates that the car was performing better in the corners.

Turn 6 is a sweeper, I pulled 1.25@90mph vs 1.10@88 mph
Turn 12 is uphill, I pulled with plates 1.25g@52mph vs 1.16g@50mph

I was able to improve my lap time by 1.03 and my maximum lateral Acceleration to 1.31g from 1.28.

PR went from 2:09.53 to 2:08.51
On my last lap I was 1 second faster pace from the 2:08 into the second to last turn when fuel reserve cut my engine power...GODDAMMIT can be heard from my recording.

2. While I wasnt able to get temps, the wear "look" pretty even. I did 125 track miles / 50 laps and the shoulders look good, with no rolling over. I also ran 34-36 hot pressure @ 200 degrees.

So I was able to get more performance out of the tires, which is verifiable and wear seems to be a bit better on the fronts, but only time or probe temps will prove it.

Now the rest of the story...

This car has a staggered setup for a reason. With more grip in the front the ass was moving noticeably more. Now I also increased the negative camber in the rear from -1.7 to -2, but the car really rotated a bit easier on corner entry, and I felt had more of a desire to step out on me on acceleration, in places I normally did not feel it.

I talked with some experienced guys at the track, who run M2CS racing, M2C instructor cars and drive NASA Spec Boxsters. They all told me the latest BMWs do not react well to more grip in the front without compensating for it in the rear. The car now needs to move weight rearward to deal with more grip in the front, as well as adding more tire to the back... McLaren720s Your squirrellyness under heavy braking could be related to lowering changing your rear grip, because under braking, the ass was dancing more than before. Might want to try taking some rake out of the car to keep more weight rearward. If I had HAS, I would do that.

The guys calling for 285 or 305 square setups on the G80s are going to be very upset with what they do to the car based on how its reacted to this small change in suspension that changed the front grip.

One might even say, the guys in Germany actually know what they're doing.
Awesome analysis!

My problem is that I haven't done any changes to my car. The rear was loose under max braking both stock and now with MSS HAS. And the HAS actually added more squat in the rear than stock.

Also, have you considered adding aero in the rear (aka wing) to increase downforce on the rear axle?

And what if you just add more rubber in the rear? Maybe 305s?

Another thing to consider is rear axle kinematics
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2024 BMW M4 Competition XDrive - Tanzanite Blue/Kyalami Orange - AST HAS - RaceChip
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