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BIMMERPOST Universal Forums General BMW News and Cars Discussion reason for larger rear wheel and narrower front tire?

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      02-02-2024, 05:10 PM   #23
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Originally Posted by ///MPhatic View Post
It'd help if most every manufacturer didn't set their cars up to be 4x4 height and understeer like pigs. If the suspension came correct from the factory it'd be easy to select tires, but since it doesn't, and most everyone's first priority is to rid themselves of that front gap, any mods become a bad band-aid, including reasonable tire choices. To do it right is to consider the application, then the correct suspension/settings, then everything else, it just doesn't end up getting done that way by most users.
I agree. Unfortunately BMW stopped catering to enthusiasts with the ‘95 e36 M3. Starting with the ‘96 e36 M3, BMW switched to a 225/245 tire setup whereas the ‘95 had 235 square. The e36 M3 also had a reasonable wheel gap. Each generation after the e36, the front tire-to-fender gap has increased. Part of that gap is so countries that require winter chains don’t destroy the front fender when turning. However, I feel BMW has done a good job with the overall tuning of M cars. The M3/M4 is one of only a handful of reasonably price performance cars that can be driven on the track with just a brake pad swap. Can the M3/M4 made to perform better on track? Absolutely. Unfortunately, BMW can’t build a car that pleases 100% of buyers 100% of the time. Until the G8x was released, I couldn’t wait to see what BMW released next. Do I modify them to increase their performance on track? Yes. Why? Because it’s a solid foundation to build on.
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      02-02-2024, 05:21 PM   #24
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Originally Posted by M3SQRD View Post
However, I feel BMW has done a good job with the overall tuning of M cars. The M3/M4 is one of only a handful of reasonably price performance cars that can be driven on the track with just a brake pad swap. Can the M3/M4 made to perform better on track? Absolutely. Unfortunately, BMW can’t build a car that pleases 100% of buyers 100% of the time. Until the G8x was released, I couldn’t wait to see what BMW released next. Do I modify them to increase their performance on track? Yes. Why? Because it’s a solid foundation to build on.
I think a lot of us 'enthusiasts' wish the car was more bent towards the performance end of the spectrum vs the luxury end, but I agree that BMW did a decent job. Not sure about the chains thing since the rear is what drives the car and there is less gap there, but I also haven't researched it. I know BMW recommends 595/600 from 620/620 when purchasing the MPS, but the 2017 Performance Edition that came with the MPS came set up to 620/620.
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      02-02-2024, 05:23 PM   #25
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For the Batmobile look 😂
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      02-02-2024, 05:34 PM   #26
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Quote:
Originally Posted by ///MPhatic View Post
I think a lot of us 'enthusiasts' wish the car was more bent towards the performance end of the spectrum vs the luxury end, but I agree that BMW did a decent job. Not sure about the chains thing since the rear is what drives the car and there is less gap there, but I also haven't researched it. I know BMW recommends 595/600 from 620/620 when purchasing the MPS, but the 2017 Performance Edition that came with the MPS came set up to 620/620.
Chains could contact the fender if the wheel is turned to full lock and you hit a large object that fully compresses the suspension. The ride hight on the outside wheel gets smaller at full lock. If your car is lowered, turn the wheel to full lock and see how close the tire gets to the fender. Then picture it with chains and the suspension fully compressed.
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      02-02-2024, 08:41 PM   #27
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What “turns like shit”? A 992 GT3RS definitely doesn’t “turns like shit”. There are quite a few super/hyper cars that also corner extremely well.
Drag cars with their tall sidewalks.
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      02-02-2024, 10:56 PM   #28
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In the case of the G80/82/87 there are BMW interviews and article/quotes explaining their rationale.

Basically they fit the largest rear tire that still meets the fuel economy and unsprung weight parameters. Then, the fronts have the same rolling diameter, but with taller sidewall to minimize bump/impact harshness. It is as simple as that. 275/35/19 on 9.5" wide wheel and 285/30/20 on 10.5" wheel have the same rolling diameter, but the 35 series in front absorbs impacts better, while the 30 series rear provides less sidewall deformation and therefore more consistent traction into/out of corners, which also makes it easier to program traction control.

No need to overthink.
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      02-02-2024, 11:38 PM   #29
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Quote:
Originally Posted by baron95 View Post
In the case of the G80/82/87 there are BMW interviews and article/quotes explaining their rationale.

Basically they fit the largest rear tire that still meets the fuel economy and unsprung weight parameters. Then, the fronts have the same rolling diameter, but with taller sidewall to minimize bump/impact harshness. It is as simple as that. 275/35/19 on 9.5" wide wheel and 285/30/20 on 10.5" wheel have the same rolling diameter, but the 35 series in front absorbs impacts better, while the 30 series rear provides less sidewall deformation and therefore more consistent traction into/out of corners, which also makes it easier to program traction control.

No need to overthink.
275/40/19 F and 285/40/19 R for F90 M5
245/40/18 F and 255/40/18 R for M440i
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      02-02-2024, 11:50 PM   #30
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Originally Posted by F32Fleet View Post
Drag cars with their tall sidewalks.
Got it. People putting on 17” wheels with even taller sidewalls (rolling diameter larger than stock) could care less about turning. They bought the wrong car to begin with anyway.
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      02-03-2024, 07:07 PM   #31
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Originally Posted by g21 View Post
275/40/19 F and 285/40/19 R for F90 M5
245/40/18 F and 255/40/18 R for M440i
These are not sports cars that people take to the track, so not relevant as the engineering task is much simpler - they are tuned more for road cruising.
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