Careful if putting 599 rims on 612!

The only issue is the standard size tire tread widths are really too narrow for the power this car can generate

Again, as mentioned above, I ran 255 front and 325 MPSS back on HRE rims on my past 612- and with the revised offset they fit Beautifully and were definitely the right performance choice for the car in my experience for both tire selection and size

I'm still running the standard Challenge style wheels/Pirellis on my present OTO car and I can tell you outright they are just not up to the task at hand. The MPSS way outperform the Pirellis in every way- The Pirellis hinder and are the limiting factor to the performance/handling of the car and surely there's not enough tread to handle the power altogether

I have a set of 599 rims w/Pirellis in my garage and was all set to swap out the rears 'til I started to read this thread. Truth is many many people have used 599 setups without issues, and really- What's the chances any of us will really hang tires in the air while street driving?

As far as the front- I can still feel the front is nowhere near as Good as the MPSS. So I'm considering an aftermarket setup again

But- I know I've digressed, so my point- You shouldn't sweat spacers if you need them- It's not a terrible expense because the extra meat on the asphalt is way worthwhile

 

T- The OEM 285/35 20 or 295/35 20 tires fit the 11" 599 wheels with no problems and maintain the factory balance with a very, very slight fade towards understeer because of the stiffer wheel tire combinations and slightly wider 295/35 19s if chosen. The MPSS is available in both sizes.

 

Thanks Moe and Taz.

Yes, not sweating the spacers. I just hope the wheel well is not at risk of a tire rub when I am done here. May pull the shock and swing the suspension to full travel to check and will report back.

 

The 315 won't fit on the 10" Challenge wheels.

Here's an interesting thing to note in regard to tyre width, tread width, and probably grip.

The tread width of the Ferrari spec (599) Pzero 305/35R20XL is 12.1"
The tread width of the Ferrari spec (F12) MPSS 315/35R20XL K2 is 11"
The tread width of the Ferrari spec (612) Pzero 285/35R20XL is 8.5"!!!
Here's the kicker...
The width of the Ferrari spec (FF) MPSS 295/35R20XL K1 is 12"...

I know what I would choose for a 612, the FF reers. That being said, the added diameter of the 315, will of course put more rubber on the road.

Besides, I'm with the others who hate the PZero and love the MPSS.

 

I'm a little puzzled. Did you run MPSS 325/25R20? It's the only MPSS in that width. Those are tiny in diameter compared to the OE rear tyres - 1.4" smaller.

 

Yes you're correct- My error. My point was that there's plenty of room on the rear of the 612. With the right offset of wheels, or spacers, you can do a lot back there with no issues.

I ran 335's on 12" wide rims in the rear-- Never an issue, handling and power transfer to the pavement were Lovely

I was trying to keep it stock this time, but I'm leaning toward this set-up again- Although your point about the FF 295 size is very interesting and appealing- I'm going to check those dimensions as well. I'm just concerned if 295 is wide enough, but with the Michelin's I'm wondering if I just may be Ok

I love the MPSS and the PS2 before them- I swapped out perfectly good tires on many cars whenever I could, just to have them

 

Moe,

Can you provide the the full spec on wheels and tires you had on front and rear for that car, including any spacers?

Also, any pics?

Thanks.

 

Ah, that makes a lot more sense

If you decide to go this route again, why not go the whole way and get 345's, if they'll fit? Then you'll also avoid the "problem" of having Porsche written on your car

The newly released set of MPSS for the Cali T could also be a nice choice for those who would want to run OE size.

 

I have to be honest- I bought the car with the HRE's and sought out the OE wheels & tires later which I relegated to my garage. When I traded the car, I kept the OE wheels.

My recollection is that they were 9's & 12's by 20" diameter.

If my memory serves me- I put 255 35 20 on the front- I know 245 is the number, but I wanted the extra meat on the front and I went on the Michelin site to see recommended rim sizes and it looked Ok

On the rears, I ran 335 30 20--- The tire heights were really close to stock

I cannot comment on offsets because I don't have the car anymore, nor do I ever know what they were- Again, I wasn't the original purchaser of the wheels. But anyone who sells or knows wheels can do the offset math based on factory OE offsets. Additionally there are several websites that will do the math for you.

Rim & Tire Size Calculator. Custom Offsets - Wheel-Size.com

The point again is that you have very much flexibility on the rear of the 612.

Hope that helps

 

According to Michelin specs, MPSS 335/30R20 tyres mounted on 12" wide rims are 0.9" wider than MPSS 315/35R20 tyres mounted on 11" wide rims. When Trygve measured his clearance with 15mm spacers and 315 section MPSS, they left 13mm of clearance. The 599 rims have an offset of 63.8mm(let's say 64mm) and the 612 rears are 51.1mm(let's say 51mm). When installing the 15mm spacers, the 599 rims get an offset of 49mm. The 335 MPSS will need an additional 0.45" or 11.5mm of space on each side over the 315 section MPSS. so in essence, an ET of 49mm should leave 1.5mm of space with the 335's on 12" wide rims. Seeing that the tyres only get this close when the car is completely un-loaded, i.e, airborn or lifted, an ET of 49mm might be enough on the inside. Personally I'd would want a bit more space though. The magic number seems to be around ET 47-45. Next is to find out how much room is on the outside.

 

we do 599 challenge on the 612 all the time. No spacers and the 305 35 20 rears fit perfect.

 

Yeah, but you likely haven't checked for clearance then with the wheels on and the car up in the air. The 315's have about 3 or 4 mm of negative clearance- and that's to the felt covering on the wheel well. There is also a large head phillips which protrudes a further 4 or 5mm so that wan't even really accounted for in my original math.

I'd love to see that same picture I posted with 305's on the car and the car in the air. Please take it and post it next time you put a set on a 612.

Thanks.

 

I'm curious about the 295 size from the FF above where it's mentioned that this tire has more meat on it than the next successive wider sizes

Can someone explain this and if they find this a safer bet on the 612??

I have the 599 rears and I'm going to mount them on my OTO and I suspect they will be fine because people have been doing this for quite sometime without issue. If I have a chance to snap a pic of the wheels hanging I will do so and post, but again- if there is an issue, how many of us will ever get the chance in the real world to entertain that same condition?

 

Likely not. But I will tell you that it is not unheard of for a car to be on a lift and a mechanic to be diagnosing, bleeding F1, etc. and engaging the transmission and turning the wheels. This is not an uncommon use case at all.

 

The easy explanation is this. The size stamped on the sidewall of a tyre, does not tell anything about the specific size of the tyre or its tread. It puts a tyre in a class of sizes, but diameter, section width and tread width can vary greatly. The 295 for the 458 has a tread that is 11.6" wide, as opposed to the 12" of the FF. These tyres are developed in conjuction with Ferrari, so they are made to suit different needs. The 335 made for Porsche, has a wider tread than the normal 345. One of the most extreme examples off the top of my head is the F12 vs. GTO front tyres. According to spec, the MPSS 255/35R20 K2 has a tread width of 10". The 285/30R20 for the GTO has one of 9.5", despite being a 285 section tyre. Tread depth and compound can vary as well. Unfortunately Michelin keeps all of their reasons for this a closely guarded secret, but that's to be expected. The best thing to do, is to ask your dealer if he has an FF and F12 tyre, and then view them side by side.

Why does Ferrari and other companies make these odd differences. It will stand to reason that Ferrari would want more meat on the ground with the more powerful RWD F12. BUT... They may want it be more tail happy(sporty), it's a lighter car, the side wall height etc. also affects how it performs, and they may want the diameter of a 315 section tyre + a larger diameter tyre also puts more tread on the road and rolls smoother.

For us mere mortals that are not allowed access to the great secrets of Ferrari tyre design, trying different combinations based on simple logic and experience, is the only option. Now the MPSS is also out in a 285 size for the Cali, and there are now three MPSS 245/35R20 Ferrari specs to choose from - the FF, the 488 and the Cali. Picking tyres has become "interesting". Some may say "frustrating"...

 

Ok, makes sense, but if what you're saying is true, then the size labels are not true to size unless you get the no brand version of the tire

Good point you have made and I appreciate you bringing this to light

One last question is- How do you denote what version of a tire you are buying- I know there are usually version codes denoting the mfgr, but do the codes extend so far as to denote model as well?

 

As for the size, yes it is the case. Sometimes tread designs also change with size or OEM tyres.

The code that denotes which tyre it is, depends on the manufacture and who it is made for. Michelin/Ferrari uses the K. Now a tyre can be K1, K2, K3 and so forth. That again does not tell what car it is for. That info one has to search out, either by asking their dealer, looking at what is already on the car, or look in the manual(can't remember if it is there).
The difference between K1 and K2 can be explained like this. K1 is the first incarnation of that specific size, speed and load rating of a Ferrari OE tyre. The next tyre will be K2. E.g, the 315/35R20K1 for the GTO came before the 315/35R20K2 for the F12. The matching GTO front is 285/30R20K1. However to denote the fact that the 255/35R20K is for the F12, they also name that K2, so one knows they match the K2 rear, i.e, there is no K1 255/35R20. If a tyre is of a different load or speed rating, it will be a K1 if there are no others. An example of this is the 458 vs. FF rears. The 458 is an SL load rating tyre and the FF is an XL, and they run different front size, hence they are fundamentally different so both are K1 despite them being the same size. Confused?

One of the easier ways to find out what is for what, is simply by using Tirerack.com's search. If you search tyres by car make, model and year it will show the correct tyre with the correct code, i.e, K1, K2 and so forth. They also post most tyre specs.

 

I'm actually not confused, your answer was exactly as I suspected your intent. My only issue is using Tirerack's site. Often when I've inputted sizes over the years it reveals more than one version of a size, but I've never noticed the code extensions anywhere on the search results and although I knew these were manufacture specific sizes, I could never reconcile which was appropriate.

Thank you for the info- It will surely help going forward. At the very least, if I can't figure it out, I'll know enough to contact someone who can.

Thanks again