03-15-2021, 05:00 PM | #1 |
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Spring rates with gt4 aero kit
I recently added gt4 bumper, splitter, brake ducts, and spoiler. First track event was this last weekend at road Atlanta with the new aero. I’m now having a ton of rubbing. I actually bottomed out enough to brake the backing on the drivers side headlight at turn 10. I have the compression bumped up 4 clicks above recommended track setting. I’m running pirelli dh scrubs 305 front 315 rear on the apex 10” and 11”. Camber is around 3.5 front. I didn’t have any issues with rubbing before the aero was added. Anyone go up to higher spring rates?
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03-15-2021, 05:21 PM | #2 |
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Nice, what kind of laptimes were you running?
You probably have an extra 200 lbs of front downforce vs. the stock GTS coming into 10a at 160+. Definitely need higher front spring rates, though I can't say exactly what. But would probably go for a 50% increase minimum. |
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03-15-2021, 06:25 PM | #4 |
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Are you on the standard KW's? Also, do you have any pictures of the front splitter install process? I'm considering going full GT4 aero on my GTS as well.
Edit, not trying to derail the thread. Just curious about the whole set up. |
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03-16-2021, 09:38 AM | #5 |
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That looks so hot! Damn!
For sure you need stiffer spring rates all around. Likely 850 front and 1200 rear for GTS aero and higher for the GT4 aero!
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03-16-2021, 10:57 AM | #6 | |
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Edit: but my god does your car look good. |
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03-16-2021, 11:02 PM | #7 | |
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I was talking with bimmerworld tech that recommended going to mcs 3 way. This is what they recommended below. Last edited by Docall; 03-16-2021 at 11:05 PM.. Reason: Add pics |
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03-16-2021, 11:37 PM | #8 |
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Did Bimmerworld go over the amount of downforce with you and how much that affects the ride frequencies/damping needs with those spring rates? If I was about to spend ~$9k on parts I'd want to spend some time with someone who'll REALLY do the homework and calculations/modelling to see that it's actually what I want.
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03-17-2021, 07:15 AM | #9 |
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Wow that looks good! Maybe try some packers to reduce the compression travel. If its only touching under braking into 10a, it might be worth a try to keep it simple.
Also, where did you source the GT4 parts? Original motorsport or replica like from the place in England? |
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03-17-2021, 08:30 AM | #10 | |
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03-17-2021, 09:16 AM | #11 | ||
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Is your car still street driven? If it isn't I'd go straight for the minimum GT4 spring rates and take the guess work out of that part of the equation. Even with super stiff springs, though, the MCS dampers are super good at street driving. I have a set on my E92 (800 pound front, 1100 pound rear) and it's easily daily drivable. GT4 spring rates won't be that comfortably but, dare I say it, the car won't be absolutely miserable for the odd street outing either. |
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03-17-2021, 10:58 AM | #12 | |
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When it's your dollars on the line you should "trust but verify."
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03-17-2021, 11:08 AM | #13 | |
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I also took logic class in high school. It doesn't change than unless one has infinite time and resources, going to one of the teams that run and setup these cars is a smart choice and likely drops you off in the sweet spot of performance. From wiki: An argument from authority (argumentum ab auctoritate), also called an appeal to authority, or argumentum ad verecundiam, is a form of argument in which the opinion of an authority on a topic is used as evidence to support an argument.[1] Some consider that it is used in a cogent form if all sides of a discussion agree on the reliability of the authority in the given context,[2][3] and others consider it to always be a fallacy to cite an authority on the discussed topic as the primary means of supporting an argument.[4] Do we all agree that a company that runs 3 M4 GT4 cars has a good idea of how to set these up for track driving? Do we all agree that premium suspensions can take high spring rates but still be reasonably compliant on the street? If you think OP should work with Turner instead I won't challenge that, but to act like people who run that aero package professionally don't have an advantage in knowledge is ridiculous
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Last edited by SYT_Shadow; 04-27-2021 at 11:09 AM.. |
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03-17-2021, 11:10 AM | #14 | |
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03-17-2021, 11:34 AM | #15 | |
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Actually, what I was thinking is why don't I just ship my GTS to one or the other with the goal of finding 3 seconds/lap. Interested in where these GT4 parts are being sourced...
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03-17-2021, 12:05 PM | #16 | |
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03-17-2021, 12:26 PM | #17 | |
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Can we agree that making sure the design intent/priorities of their recommendation follows OP's needs is the right thing to do? Can we agree that seeing the data/calc to justify their recommendation is a good thing?
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03-17-2021, 05:47 PM | #18 | |
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03-17-2021, 06:42 PM | #20 | ||
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03-18-2021, 08:36 PM | #21 | |
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04-26-2021, 11:37 AM | #22 |
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I would also add rear canister disconnects, otherwise i'm not sure how you will get them in the trunk. I have 2Way Remotes with 700/600 and its pretty flat in the corners, but im not on slicks or aero.
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