Anyone running 305/30/20 rears? | FerrariChat

Anyone running 305/30/20 rears?

Discussion in 'California/Portofino/Roma' started by Rule12b, Nov 9, 2019.

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  1. Rule12b

    Rule12b Karting

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    #1 Rule12b, Nov 9, 2019
    I’m thinking of having a set of wheels made for our Cali T. I’d like to run 305’s in the rear and 245 or 355 fronts. Anyone running these sizes?
     
  2. Fireman1291

    Fireman1291 Formula Junior

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    #2 Fireman1291, Nov 10, 2019
    I have 315's on my rear. You'll be fine.
     
  3. Il Co-Pilota

    Il Co-Pilota F1 Veteran

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    #3 Il Co-Pilota, Nov 10, 2019
    You can do it. Just be aware that you will increase the wheel arch gap as the wheels have a half inch smaller diameter. Also remember that an increase in rear width in relation to the fronts will make the car understeer more. One thing the Cali/Cali T cars do not need, is more understeer.
    This will be even more pronounced if you decrease offset which moves the rear wheels further out.

    Don't change front wheel offset. It will screw up the steering geometry and roll center.

    Personally i'd go about it slightly different. 9x20 front and 11x20 rear, but with stock offset. Then run 255/35R20 MPSS K2 front, and 295/35R20 MPSS K1 rear. You get wider tyres and wheels, and performance will increase rather than decrease.

    These sizes will also fill the arches nicely.
     
    AD211 likes this.
  4. Rule12b

    Rule12b Karting

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    #4 Rule12b, Nov 11, 2019
    That’s sound advice. It’s my wife’s car and I’m getting rid of the retarded 22’/21 setup on the car, So wheel gap etc. will be variable in change. Point on the understeer.
     
  5. Rule12b

    Rule12b Karting

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    #5 Rule12b, Nov 11, 2019
    Actually after running some calculations based on the 315/25/22 rears and 255/30/21 fronts on the car, it looks like 315/30/20 rear and 265/35/20 fronts will fit and reduce understeer well. I’m going to measure clearances up front to be certain but the rears will definitely fit.
     
  6. Il Co-Pilota

    Il Co-Pilota F1 Veteran

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    #6 Il Co-Pilota, Nov 12, 2019
    That size will not work. Firstly, I don't think that front will fit, but more importantly, the ESC/ABS will not handle the incorrect difference between front and rear tyre diameter. It will put on traction control etc. so that's a no go. If and that's only IF the 265 width will fit, it should be 265/30R20. Unfortunately no suitable tyre comes in that front/rear size combination.

    Another benefit of the 255/35R20 and 295/35R20 is the ability to stick with a Ferrari spec tyre as well as avoiding Pirelli tyres.
     
  7. Rule12b

    Rule12b Karting

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    #7 Rule12b, Nov 12, 2019
    Yes realized I meant 30, not 35. I'm actually trying to make choices based on tire availability, specifically pilot sport 4s' which we like. Hey Fireman, can you tell me your rim size and offset by chance??
     
  8. Il Co-Pilota

    Il Co-Pilota F1 Veteran

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    #8 Il Co-Pilota, Nov 12, 2019
    MPS4S is not available in 265/30R20-315(30R20. Neither is MPSS, or even PZero's.
     
  9. Rule12b

    Rule12b Karting

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    #9 Rule12b, Nov 12, 2019
    265/30 and 305/30 are. 315 would be my choice if we opt for a different tire.
     
  10. Il Co-Pilota

    Il Co-Pilota F1 Veteran

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    #10 Il Co-Pilota, Nov 12, 2019
    What tyre is available in that 265/315 combo? I can't find anything.
    The 265/305 combo yes, but nothing in 315.

    A combo where the front wheel has a diameter of 26.3" and the rears are 27.2" will look tiny on the Cali T. Just something to consider. Really give this some serious though, because you might end up with something that is not what you wanted. You are coming from a set of wheels that have an overall diameter of 27" front and 28.2" rear with your 21/22 combo. You are looking at a big change, even compared to the factory size. which is 26.8/27.9.
     
  11. Rule12b

    Rule12b Karting

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    #11 Rule12b, Nov 12, 2019
    As it stands, under abrupt maximum suspension load, the rears can rub ever so slightly, something which should be eliminated. I think actually a 315/35/20 in a MPS42 would be an ideal rear. When I run that size on a 20x12 rim, it appears that I will be fine as long as the offset allows me to clear the brakes and suspension. Unfortunately, it will fill out the wheel wheel by an additional 6mm versus what is on the car now. (according to the calculations I'm running here: http://www.rimsntires.com/specspro.jsp) So I need to figure out precisely where the rubbing is occurring now and check some measurements on the car itself. That''s for this weekend.

    IF the 315 will fit, then up front, a 255/40 up front would be ideal but would fill out the wheel well by 12 mm more than current. A 255/35 will fit just fine but then I"m not sure if the delta between front and rear (1.7 inches versus stock delta of 1.1 inches) will be too great.

    It's all confusing as hell, as my posts suggest, but I'm the research is worthwhile and will bleed over to the wheels I want to do for my R8 GT. I do appreciate everyone's advice and input. Keep it coming.
     
  12. Fireman1291

    Fireman1291 Formula Junior

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    #12 Fireman1291, Nov 13, 2019
    WHEELS - ADV1 AD05 M.V2
    TIRES - NITTO NT555 G2
    (REAR 315/30R/20 - FRONT 255/25R/20) - No issues with traction/computer calibrations etc
    Image Unavailable, Please Login
     
  13. Rule12b

    Rule12b Karting

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    #13 Rule12b, Nov 13, 2019
    Great looking ride! Do you know your offsets by chance? Admittedly a 25 series tire will undo the ride quality improvements we are shooting for given the sizes we are moving out of (315/25/22 and 255/30/21). Beautiful car and thanks for taking time to respond! That’s 2.5 Inches of delta so that answers a lot of questions right there.
     

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