08-01-2020, 03:19 PM | #1 |
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Can 4 PSI make that big of a difference?
Gentlemen (and I use the term loosely), wanted to get your thoughts and experiences with regard to tire pressure.
Recently changed my rear tires to General G-Max RS 275/35/19 from MPSS 265/35/19. Immediately felt like the car was unsettled and twitchy when pushed. Really, really did not like it at all. Thought, "Oh well, that's $340 wasted. Gotta go buy the MPS4S's now." But, then, randomly did some reading online and came across several articles about tramlining and tire pressure - articles seemed to indicate that one way to potentially reduce the tramlining is with lower tire pressure. https://www.tirerack.com/tires/tiret....jsp?techid=47 Sure enough, I checked my tire pressure, and the installers had it all the way up to 39 PSI. Brought the rears back down to 35 PSI, and all seems right with the world again. It went from, "I can't stand these F***ing tires," to "Oh, gosh, daily driving, I can't tell the difference between these and the MPSS." So, question for you all is: "Is this all just my imagination? Like, placebo effect? Or does 4 PSI make that much of a difference???" |
08-01-2020, 03:26 PM | #2 |
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I think so yes. Some are better at feeling a difference than others.
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08-01-2020, 03:26 PM | #3 |
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Absolutely. 4 PSI can make the world difference.
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08-01-2020, 03:50 PM | #4 |
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Yes, it makes a difference. Just like not having four MPS4S makes a difference.
This makes me wonder why you didn't consult your brethren before purchasing tires? Don't you trust us, impulse buying at the local Walmart, honeymoon with the car over, sleep walking... again, covid brain fog, ate too much cap'n crunch, cptobvious? |
08-01-2020, 03:56 PM | #5 |
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Yes, it can, and the LIGHTER the car, the more the difference. I once had an installer put 35/35 in my Exige tires that should be 23/25 and the entire ride home I thought the car was trying to kill me. I'm surprised I kept it on the road. Lowering the pressure turned it right back into a go-kart, instantly.
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08-01-2020, 04:16 PM | #6 |
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yes that is a significant defference and you can feel it if you push it even a little bit. The chassis will communicate to your ass.
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08-01-2020, 04:33 PM | #7 |
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Yes, absolutely. I can tell when my tires lose pressure, it drives differently. And usually when I check, its off by 4-5 psi
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08-01-2020, 05:51 PM | #8 | |
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Too funny! Since you're giving me stick, here was my rationale: 1. Rear tires wore out, but my front tires are still in really good shape 2. Also, wanted to play around with tire size 3. If I experimented with MPS4S's, that would have cost me ~$640 + tax 4. So, instead, decided to experiment with the General tires, and they only cost ~$340 + tax 5. I think I've come to the conclusion that I prefer OEM sizing - figure the engineers knew what they were doing with regard to vehicle dynamics, so why gainsay them? 6. Now, plan is when the front tires wear out, I'll get all 4 MPS4S's OEM size, having conducted my experiment to my satisfaction Come on! I'm a man with a plan! |
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08-01-2020, 05:52 PM | #9 |
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So this begs the question.
What tire brand, F&R size and pressures are you running? Maybe, I should change? MPSS 245/265 35/35 per jamb sticker. Last edited by omasou; 08-01-2020 at 06:14 PM.. |
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08-01-2020, 05:53 PM | #10 | |
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08-01-2020, 06:04 PM | #11 | |
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My understanding is that tread width is ultimately most important with regard to DSC? But, I could be totally talking out of my A** and happy to be corrected! |
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08-01-2020, 06:14 PM | #12 | |
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08-01-2020, 06:15 PM | #13 | |
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08-01-2020, 06:29 PM | #14 | ||
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Well, in any event, once the front MPSS wear out, I'll be getting all MPS4S's in OEM size. |
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08-01-2020, 06:45 PM | #15 |
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That's about an 11% deviation, and would be regarded as significant. From an experience perspective a 2psi difference is noticeable. It's likely tire dependent to a degree, but 4psi is substantial.
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08-01-2020, 08:02 PM | #16 | |
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However, RAKE is super important to some driving systems, so choosing a taller sidewall in just the front or the rear can have a terrible impact on how the car loads each tire, which can confuse all sorts of systems. |
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08-01-2020, 08:45 PM | #17 | |||
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08-01-2020, 08:50 PM | #18 | |
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08-01-2020, 08:57 PM | #19 | |
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I know one thing a lot of people like about the M2C is it's loose rear end, or what we like to call 'playful.' I personally wish I could get a little more grip than slip. In this regard . . . 1. Has anyone switched from PSS to PS4S and feel the dry pavement grip was noticeably improved? Overall ride quality noticeably different, better or worse? I have experience with both tires, but not on the same vehicle so my bias toward the PS4S is more opinion than validated. 2. I have never looked up the recommended PSS psi for the M2C. I am assuming my psi are set at recommended. Has anyone dropped the psi 2 or 3 below recommended on stock (PSS) tires? My suspicion is this might give a little more road grip I am after, as well as less firm ride quality. 3. I assume the tire pressure 'alert' does not go off until the reading is +/-4 from recommended? Can anyone verify the 'alert' range? Thank you ///AVM Last edited by ///AVM; 08-02-2020 at 02:33 PM.. |
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08-01-2020, 10:05 PM | #20 | ||||
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08-01-2020, 10:21 PM | #21 |
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AVM - Folk have switched to the 4S's, at various tire sizes. I basically agree that the playfulness of the original tires is fun, and it appeals to reviewers of high skill like Chris Harris. However, I know I'm not at his skill level, I daily the car in rain and shine, and I was interested in seeing how the car would work out with more grip, even if it sacrificed a little playfulness. Cup 2's were right out because of the sheer number of wet days I have to drive this car on.
I went to Apex EC-7 wheels running PS4S 265/30's and 295/30's. It's made a the car a bit more serious, but I'm connecting with it more, skill-wise and just with what I want out of the car. It's more predictable and I'm very much enjoying it's behavior off the line with the increased grip. The PS4S's are quieter and they transmit a lot less vibration into the cabin. I don't know how much more "grippy" they'd be at OEM sizes...at least a bit, I'd think. |
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08-01-2020, 10:36 PM | #22 |
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it seems like most people have answered the question but take this into consideration.
When your tires heat up it increases tire PSI, so carefully think about when you measured your tire pressure. Did you do it after driving it for a bit? If you did, and then adjusted it then, it means you like your tire pressure at around 32ish PSI give or take cold. tire PSI gets pretty nuts in the autocross group. People get obsessed down to the psi when they do runs. and even measure after every run. |
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