Not quite. This is what Billy said (you were being selective in your quote. You aren't a journalist by any chance, are you? ). The underlining is my emphasis. Billy’s rule of thumb: “For ideal handling: when sizing a tire for a given wheel, I usually target a tire’s TREAD width to be as wide as the WHEEL width, or 0.5” narrower than the wheel width.”
You have it all figured out, eh? Let me poke a few holes in yours and Billy's theory. Let's start by your way of calculating ideal rim width. You say a 255 should be mounted on a 9", so why is Ferrari using a 9.5"? Let's look at the cars running 245 fronts. Why is the Speciale, Pista, 488, and F8 using a 9"? Clearly they should use a 8.5" according to you. Hm, okay, so the FF and Lusso uses an 8.5". But apparently the boffins in Maranello did not get the memo when designing the Roma, Cali, Cali T and Porto, as they use an 8". And shouldn't the latter also use a 10.5" in the rear? They use a 10". But let's talk tread width for a bit. You are hung up on the idea that the Michelin 315 needs an 11.5" wide wheel for its 11.5" wide tread. But how do you account for the MPS4S K1 having an 11.1" wide tread? Looks like Ferraris boffins messed that up too. What about Porsche? Their N0 MPS4S 315/35R20 has,a tread width of 10.9", and I believe that the BMW is 10.7". So why an 11" and 11.5" on those? Hmmmm Let's look at the 599 GTO shall we? Wheels are 9.5" wide and 11.5" wide. However, the front shoes are 285. Let's hope someone in Maranello got a spanking! Now let's look at the tread width of that 812 again. Look up the width of the 275's. The tread is only 8 9". I guess that 10" is not what Billy wanted. While I'm sure that you got it all figured out and know better than the rest of us, let me leave you with this. What tyre and wheel width combo you choose matters mostly in relation to how you want the car to feel. It is also worth noting that it has the most profound effect on the front. The more you stretch, the stiffer it gets. In some cases this induces understeer and dartiness. I have talked to my contact at bpth Pirelli and Michelin about this countless times, and both agree on one thing. A narrower wheel compared to measured rim width, has a lesser negative effect on handling compared to a wider. When a tyre manufacture designs a tyre within a certain section width, i.e 315, what determines the minimum and maximum rim width is two things. One is whether or not the bead of the tyre seats properly in the rim. The other is whether or not the tyre retains full tread patch. Within this range, the actual traction is not altered, only the feel of the input is. This will of course affect how the car should be driven and set up. If you are a drifter, stretch them. If you prefer neutral handling use measured width or narrower. Go drive a 458 Italia with stock sized shoes and Speciale wheels. It feels a lot different. Now fit a Speciale with Italia wheels and Speciale sized shoes, and it is almost the same. I'm sure you won't agree, but my years of playing around with wheels and tyres have taught me one important thing. You can't generalize like you are trying to do. Tyre sizes are not an absolute. A specific section width puts a tyre within a size range so to speak. But between models, manufactures and types, tread width, section width, shoulder width and diameter can vary a lot. The answer to whether or not a tyre fits is simple. It has to seat properly and it needs full contact patch. Aside from that, what you sense as a driver is what matters. Like with suspension setups, drivers may want different characteristics from the feedback the wheels provide. It is what it is, and like with your 19's there are several ways of doing it right. Sent from my SM-G930F using FerrariChat.com mobile app
Good catch Billy is not wrong. It is however important to stretch it is subjective. Ideal handling and feedback is dependent on what you as a driver prefer. But he is clearly leaning towards neutral which is a good thing for many. He is also making it pretty clear that his advice is his personal preferences. But good article for sure. Sent from my SM-G930F using FerrariChat.com mobile app
Thank you! He wrote this article too which is also illuminating for those of us who don't mess around with tyres as much as you do. https://motoiq.com/not-all-michelin-cup-2-tires-are-created-the-same/
Perfection is in the eye of the beholder Or was it by the seat of the pants?! Sent from my iPhone using FerrariChat
38 PSI seems a bit high. My tire temps start at about 75f and 31 PSI. Get to about 115F and 35 or 36 PSI. I will confirm next time I’m out. Out of interest why do you drive it in Wet mode instead of Comfort or Sport?
IIRC, the manual's chart shows all modes, except for snow, having the same suspension stiffness. Hard to believe, eh?!
just tried them in 2 to 3 inch snow. id say manageable - with a good driver and discretion the tires are certainly capable. Not as bullet proof as snow tires but a good compromise. on paved roads they were totally fine. unless you are in a ski area type environment these tires are certainly capable 365 days a year in a suburb metro area northeast type winter.
i have put a few hundred miles on the tires and not bent rims, that said most of the roads i drive have been freshly repaired and paved so we will see when the potholes re-emerge.
My understanding from the Lusso is there are 3 suspension stiffnesses 1. Hardest- this is in Sport mode only 2. Medium- this is in Sport+ Bumpy Road; also in Comfort and in Wet. 3. Soft- this is only in Snow mode.
Apparently, AZ roads aren’t much better than those in NY. I drove a 2012 FF as a daily for 4 years in KY with no wheel or tire problems but have now suffered two front blowouts on our 2014 FF in the past 3 months in AZ. The stock sidewall profile of 85 mm doesn’t offer enough protection. Image Unavailable, Please Login Has anyone upgraded to the MPS4S in 245/40-20 and 315/35-20 as suggested by Il Co-Pilota? The Michelin website suggests that the stock rims will work, and the 245/40 increases the sidewall profile by 14% to 98 mm - nearly the same as the 103 mm on the stock rear 295/35-20 which seem to fare much better than the fronts. Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login I guess I could simply increase the fronts to 255/35-20 while retaining the stock rears, but that only increases front sidewall profile by 4% to 89.25 mm - not much extra protection. Image Unavailable, Please Login I’d rather not buy aftermarket rims. Ricky suggested switching from Michelins to Contis in the stock sizes but I’m worried that this may not afford enough protection. Any downsides to handling or stability with the 245/40 and 315/35 combo in real world conditions? I run summers year round here in AZ. Not too worried about increased understeer if the 315’s otherwise work well. Thanks!
I’m running 265/35/20 on the front and 315/30/21 on the rears but I have after-market wheels. My tyres’ rolling circumferences are 2% greater than stock front and back. The tyres you’re suggesting are 4% greater at the front and 2% greater at the back. Far be it for me to disagree with Il Co-Pilota (he’s the expert in tyres) but maybe you could try 235/40/20 and 315/35/20 as that would result in a more balanced circumference increase of 2% front and rear. The push back will be that decreasing the front width and increasing the rear will result in even more understeer in and already understeering setup…
I haven’t driven the car a ton but i have not had any issues with the bigger tires. I cant say ive hit any major potholes.
ANOPax, the 245 —> 315 already seems like a lot of stagger. Our 812SF wears 275 —> 315. Your setup with aftermarket wheels is probably the best solution but I’d like to retain the stock FF wheels if possible. Ricky, are you now running Continental ExtremeContact Sport 02 in 255/35-20 and 295/35-20 on the Lusso rims? Do either of you experience any wheelwell rubbing up front with the slightly wider rubber? Does the car handle better? On our Porsche 993TT, I upgraded from the factory 225 front / 285 rear to 245 front / 285 rear on aftermarket Fikse wheels and love it. Much less understeer. Appreciate all the help. I would love to keep using the FF as a daily but have to solve this problem. Truly a dumb setup decision from Ferrari.
Jerry’s Lusso solution is looking pretty logical for our daily driver FF: 245/40-20 front and 275/40-20 rear. Increases the sidewall height from 85.75 to 98 mm front and from 103.25 to 110 mm rear. Maybe dials out some understeer, too? Bummer to go narrower on the back from a visual standpoint, but I’m worried about possible increased understeer with a 245 - 315 stagger. Appreciate any input. Thanks for the help (as always), Jerry. Image Unavailable, Please Login Image Unavailable, Please Login Our FF has also been lowered 18 mm on factory suspension components. Considering raising it back to stock or maybe decreasing the lowering to just 5-10 mm total.
That seems pretty logical. Are the computers happiest with both overall diameters changing by the same amount? Btw, I just posted before seeing your post. Appreciate the input.
The Michelin Pilot Sport 4S isn’t available in a 295/40-20, but both Continental and Pirelli offer it along with a 245/40-20. Pirellis have never served us well on Ferraris. Here’s the Continental Sport Contact specs. Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login The overall diameter would increase by 3.3% from 26.8” to 27.7” front and by 4.3% from 28.1” to 29.3” rear. The front-to-rear stagger would increase by 4.8% or 1.3” stock to 5.7” or 1.6” with 245/40-20 and 295/40-20. Would the computers tolerate this? I think the larger tires could fill up the wheel wells nicely and offer a lot more protection against blowouts. I would definitely raise the car back up. Thoughts? TIA.
