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      07-11-2019, 07:54 PM   #1
blackbeast06
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295/30/19ís feel unstable on oem 437ís

After being fed up with grip issues I decided to size up the rear tires. I put PS4S 295/30/19 on the stock rims. While there seems to be more grip it also seems to have less stability. The car almost feels like the sidewalls are mushy from being crammed onto the rim. Has anyone else experienced this sort of feeling from that size tire? I kept the stock front size.
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      07-11-2019, 08:06 PM   #2
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I realize that this won't answer your question...but I put 285/35/19 PS4S on my OEM 437s and they are leagues better than OEM- so much so that it's almost less fun in terms of all the grip making it not 'slide' around low speed corners as much (if that makes sense)
I did consider 295/30s but the best results seem to come from 285/35s for the 437s for reasons I'm not going to get into (there's a whole thread on this some where on here).
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      07-11-2019, 08:29 PM   #3
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Maybe I’ll have to go with 285’s next time around. The 295’s just feel squishy and wobbly on high speed cornering. I’ll have to try and find that thread.
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      07-11-2019, 08:36 PM   #4
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I have actually done 4 wet / dryish track days on 295/30/19 PS4S on 437 rears, 275/30/19 fronts. On the street they wander a bit but on the track they are sound.
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      07-11-2019, 08:48 PM   #5
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Try increasing your tire pressure from 32 to like 34-36 PSI to increase stiffness.
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      07-14-2019, 05:24 PM   #6
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I recently went to 265/35/19 up front and 295/30/19 in the rear MP4S. I agree it does feel a bit more wobbly like sidewall flex in the corners but my grip is loads better than the MPSS. It could just be better grip causing the sidewalls to flex more in turns rather than the MPSSs which would just slide. But it is a definite improvement over MPSS.

I read extensively that the 30s in back and 35s up front would confuse traction control but after several weeks it has not...maybe at extremes of traction on a track it is noticeable, but If anything my DSC is interfering less.
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      07-15-2019, 06:46 PM   #7
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Quote:
Originally Posted by blackbeast06 View Post
Maybe I'll have to go with 285's next time around. The 295's just feel squishy and wobbly on high speed cornering. I'll have to try and find that thread.
Def go 285 next time. The 285 is made for a 10" wide wheel and the 295 is not. Plus, I don't think you are gaining much contact patch with the 95 vs 85.
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      07-15-2019, 07:37 PM   #8
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I went with 285/35/19 PS4S on stock rear rims. Didn’t want to go with a 30 series rear tire. I wonder if the reduced rolling diameter in the back compared to the front is impacting the handling feel.
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      07-16-2019, 09:35 AM   #9
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I just put a new pair of 295/30ZR19 Conti 5Ps on the rears and moved the stock 275/35ZR19 from rear to front. My traction improved a good bit, and there's no sidewall flex at 35PSI. I did install the tires on a new set of BBS CI-R 9.5/10.5, but having wider rims should allow me MORE sidewall flex than you. Installing on a more narrow rim should pull the sidewall in a little and tighten up the flex.

Always check tire pressure in the mornings when coldest, and only top off cold. Remember that heat expands tire air/nitrogen, and also softens rubber, so measuring PSI cold is important (rims cool to the touch, or hose them down if you can't wait). I suggest not to use the factory 100MPH inflation (37-40 depending) so you don't wear out the center of your treads too fast.

My 2 cents. Enjoy!
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      07-16-2019, 09:40 AM   #10
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i run this setup and wonder why the tire shop inflated the fuck out of my tires...maybe ow i know why,

i run 275-295

front/rear tire pressure please?
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      07-16-2019, 04:06 PM   #11
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Quote:
Originally Posted by G35POPPEDMYCHERRY View Post
i run this setup and wonder why the tire shop inflated the fuck out of my tires...maybe ow i know why,

i run 275-295

front/rear tire pressure please?
G35PMC,
I recommend starting with 35PSI front, 36PSI rear.
-TopJimmy
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      07-18-2019, 06:10 PM   #12
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The main reason that you feel this "wobble" is because the OEM 437 10" wheel is not wide enough to offer proper sidewall support for a 295mm tire, regardless of sidewall height.

This lack of sidewall support causes something known as "sidewall deflection", this happens as the tire "rolls" underneath the rim and onto the sidewall under hard cornering.

The video at the link below shows exactly how the tire deflects under load:

Tire Sidewall Deflection

The sidewall of a tire is not designed to carry the lateral loads experienced during heavy cornering. This contributes to the mushy feeling that you are experiencing. If you mounted this tire to an 11" wheel, you would notice much less of this deflection occurring.

- Max
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