11-04-2020, 09:55 PM | #1 |
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ZCP Tire Specs vs. GTS Questions
So on doing research about a new wheel, tires, and suspension setup I did some research and found out that the BMW M4 GTS unsurprisingly runs a different setup then the BMW M4 ZCP. My question is the GTS runs 19 x 9.5 fronts on 265/35/19s and 20 x 10.5 fronts on 285/30/20s, while the standard ZCP runs 20 x 9 265/35/20s and 20 x 10 285/30/20s, why would they make the wheel wider? Isn't the tire just stretched more with the wider wheel and the wheel is heavier? I also know that the GTS runs Michelin Sport Cup 2's which obviously don't run super stretched like the MPSS. The only possible reasons for this I can think of is so they could camber the wheels for cornering? I'm no expert but the other conclusion I've come to is that 19 in the front will allow better cornering while 20 rear will extend the length of the contact patch.
Furthermore, I'm currently debating a new wheel and tire setup, where I took inspiration from this setup and planned on getting the V-FF 103's from Vorsteiner in 19 x 9.5 with 275/35/19R MPS4S and 20 x 10.5 305/30/20R MPS4S, I'm by no means an expert and have a lot of learning to do but this should give better straight line performance while still breaking sideways when I want it to and cornering better, additionally the wheels would be lighter. I'm currently on stock 20" ZCP setup. I'm lowering on Swift Spec-R's all though KW HAS is alluring as I'd like that rake look the GTS has and I don't think the wheels will provide it. Source > https://bimmertips.com/oem-bmw-f82-m...l-style-specs/ P.S the CS also runs 19 front 20 rear but the same width as ZCP - Callan |
11-04-2020, 11:07 PM | #2 |
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I have 763M wheels with PS Cup2s that came on my M3 ZCP as a factory option. CS and 763M set up is the same tire sizes as GTS, but narrower wheels by 0.5 inch.
I think the CS setup works amazing. I feel that smaller front wheels allow for improved ride and feel, while the large/wide wheels in the rear help reduce oversteer and increase grip (maybe also improve handling/rear feel). I feel the CS/763M has the ideal set up but many may not like 19” front and 20” back. I love it though and wheels look great. And to finally answer your question... I think they are cambering the tire sidewalls for cornering to improve turn in response. I remember the old E46 M3 ZCP had really aggressive sidewall setup with PS2 (stock) and I felt it was for improved turn in at the price of harshness. It might help to slightly reduce tire walls from moving during cornering (just a guess, not an engineer anymore). |
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11-05-2020, 07:02 AM | #3 |
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In general terms, for a given tire, a wider wheel will offer crisper handling response at the expense of ultimate grip, while a narrower wheel will offer more grip at the expense of handling crispness.
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11-05-2020, 07:30 AM | #5 |
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11-05-2020, 09:56 AM | #6 | |
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Back in the day me and my friend went back and forth with this for days.... There is the law of diminishing returns and and optimal set up. All things being equal. |
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11-05-2020, 03:55 PM | #8 |
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This setup seems to be working great on my M4cs. Note that the new G8X M3/4 are also equipped with this type of staggered setup.
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11-05-2020, 04:07 PM | #9 |
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11-10-2020, 05:51 AM | #10 | |
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However, do you have empirical data on identical tires showing a decrease in maximum cornering force with increase in rim width (staying within the TRA rim width window for the tire size of course)? I've only seen the opposite of that, so I'm curious what data you're referring to.
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11-10-2020, 07:27 AM | #11 | |
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If there were only performance advantages to stretched tires (wider wheels for a given tire size), we would see all sports, super and hyper cars on super stretched tires, which often is not the case. Like everything else in life, it is all about the desired compromise.
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11-10-2020, 07:39 AM | #12 | |
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11-10-2020, 08:31 AM | #13 | |
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A tire that is more stretched over a wider wheel will be more likely to "skip" over minute bumps on the road surface and lose grip in the process.
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11-10-2020, 08:50 AM | #14 | |
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11-10-2020, 09:04 AM | #15 | |
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11-10-2020, 09:20 AM | #16 | |
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On the street, there a huge range of OE considerations from ride comfort, rim protection, fender clearance (especially in the EU), etc. Wider wheels reduce all of the above.
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11-10-2020, 11:56 AM | #17 |
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the wider tire will give you more cornering grip. I would go with the 10.5 or 11.
As another example the 997.1 GT3 ran a 305 rear section tire on a 12" wheel. The 997.1 Turbo ran a same sized 305 rear section tire on an 11" rear wheel. It made a huge difference in the shoulder shape and how it could take camber on hard cornering etc.
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