10-06-2022, 11:32 PM | #1 |
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Tire diameter/gearing compromise
My Michelin All Season 3+ tires have served me incredibly well. I drove from Maine to Alabama and back on them almost three years ago. They’ve gone 25k miles total, which is pretty good for the way I drive. I’ve even done a full track day on them. It’s time to get new shoes though and the Michelin All Season 4’s beckon — however, there is a problem. The available sizes are whack for this tire. No 235/35 or 235/40.. not even a 245/35.. only 225/40 or 245/40 and I just can’t do a square setup with 225’s. So I’m seriously considering the 245/40 r18 on my APEX ARC8 18x8.5 wheels. I have camber in the front and I know they will fit but I’m concerned that the car will feel noticeably more sluggish with the tire diameters being so far off. Does anyone rock this setup? Thoughts?
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10-08-2022, 06:22 AM | #2 |
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I have done the change to 245/40 instead of 245/35 for my winter tire setup (PA4s, rear, the also didn't offer the OEM size)). There is a noticeably difference in thrust of the longer rolling diameter.
I changed the final drive ratio of my LSD to get more thrust and fun when revving my 6speed. Its perfect for my summer tire set up. The 4S I am running have 840 revs/mile in 245/35 but only 809 revs/mile if I would go to 245/40. That's 3.7% less thrust when you are running 245/40s and less smiles per miles - because I love to rev the engine . I wouldn't want to go 245/40 outside the winter season.
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10-08-2022, 05:26 PM | #3 |
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Lmao thinking we could sense or feel the difference of 40 wheel revolutions per 5,280 feet of travel!...
Just sayin! Although we definitely could sense the softer ride with a higher sidewall along with softer material in winter rubber |
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10-09-2022, 08:19 AM | #4 |
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Perhaps I am just more in tune with my car and how it feels.
That said, I am loosing the equivalent of 13.5 hp in my M2 tuned M235i (3.7% of 365 hp). And you get the 3.7% throughout the entire rev band. Back in the days of naturally aspirated engines guys would be all over such an increase in power. Think of it like a 3.7% salary raise. Would you not take it if all you have to do is select the right option?
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10-09-2022, 08:26 AM | #5 |
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How much of that difference is actually the weight? I'm leaning towards that being the culprit and not only rolling diameter. Swapping from winters to summers for example, my wheels are noticeably heavier even with 225s on them. Not dismissing the diameter but that isn't the only factor.
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10-09-2022, 08:55 AM | #6 | |
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Weight of the wheel and tire is 40lbs for my setup. So a 2.5 % difference. Its unsprung weight though. Can you feel it in cornering. Likely.
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10-09-2022, 11:15 PM | #7 |
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Good food for thought here. Thanks.
I’m now thinking of going with Bridgestone POTENZA RE980AS+ - SIZE: 245/35R18 square. I’ve read good things about them. Seems like it’s kind of the only option for a decent all season with compatible dimensions. 24lbs each in that size on my Apex arc8’s bring them to ~42lbs per corner.
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10-11-2022, 01:41 PM | #8 |
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Since my original post, Tire Rack has added all the sizes for the Michelin Pilot Sport All Seasons to their inventory. 235/40 and 245/35 in particular.
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10-15-2022, 07:35 AM | #9 |
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I'm having the same problem per se, i can't make up my mind on tire size. I'm running stock 225/40, they are way too small as we all know. I want to keep stock square and i guess 235/40 is the way to go but it's not enough of a difference in size. Enter the 245/40 but i've been down this road before on other vehicles and yes, again as we all know it reduces torque multiplication which translates to a slightly slower car which is against what most of us are after. Usually i'm decisive, not on this subject at the moment.
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10-15-2022, 09:35 AM | #10 |
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Not gonna lie, I’m seriously considering just getting a Bootmod3 license and running a stage 1 tune with the 245/40 tires and calling it a (expensive) day. I don’t track this car anymore and I’ve been steady on 3-5k mile oil changes so it would probably be fine and just make up the difference in torque from going with larger tires. Still deciding.
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10-15-2022, 01:57 PM | #11 | |
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10-15-2022, 03:26 PM | #12 | |
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If you are running A/S tires that is already a huge compromise in dry summer performance. And on winter tires losing a bit of torque is probably not something you will notice, you probably make it up from the colder charge air. Last edited by Kernel Kurtz; 10-15-2022 at 03:31 PM.. |
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10-15-2022, 06:29 PM | #13 |
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Fair point...
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10-23-2022, 11:36 PM | #14 |
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I went for the 245/40/18 Michelin All Season 4’s. Happy with the choice so far. Seems to handle about the same as the All Season 3+’s. It does drive like there’s a restrictor plate on the throttle but it’s not as big a deal as I thought it might be — it’s very subtle. Still pulls strong once it gets going. I may flash Bootmod3 this week to see if that makes up the difference.
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