Tires...what are you running?

    Quote from Miller Time

    Folks: I will be getting new tires soon and probably will be going with Michelin Pilot Sport 4S. I am torn between the 2 sizes below so you gurus let me know if either of these sizes will fit on my SL (OEM Front: 225-45-18, Rear 255-35-20) without having any ABS, traction, etc, ( nanny issues).


    1. Front: 235-50-18 Rear 255-40-20
    2. Front: 245-45-18 Rear: 255-40-20


    If both will fit, which would you recommend and why? Thx guys.

    Based on a quick look at Discount Tire's Tire Size Calculator (Tire Size Calculator | Check Tire Size Conversion | Discount Tire), I'd expect problems using either set. Generally, changes over about 3% or so will trigger problems with the nannny controls. Your rear tire choice is 7.7% larger than the stock size. Your front tire 235/50-18 would be 4.9% larger and the 245/45-18 is closer to acceptable at 2.7% larger than stock. When changing front and rear sizes, try to change both by the same amount or as close as you can. Since the speedometer/odometer are driven off the rear wheel, the 255/40-20 will actually be turning at 70 mph when the speedo shows 65.
    http://www.willtheyfit.com will also let you see how different wheel/tire sizes will fit/look.
    Here's a pic of the differences -

    Quote from Br4hm4

    New rear tire get's put on today. I am rolling the dice and going with a Nanking NS-20 275/35. Have heard a lot of good things from people that have had them on other performance vehicles. The major gripe seems to be that they wear fast.

    My 4th rear tire was a NS-20 in that same size. Overall, I liked the tire and got almost as many miles out of it as I did with the Kendas. Some folks say the NS-20 has a soft sidewall. The only thing I noticed about it was minor steering wheel movements seemed to make the rear end feel like it was a little loose, but I never felt any problems during quick lane changes such as swerving to avoid debris. Overall, I think it was decent and relatively inexpensive tire.

    Quote from BKL

    Based on a quick look at Discount Tire's Tire Size Calculator (Tire Size Calculator | Check Tire Size Conversion | Discount Tire), I'd expect problems using either set. Generally, changes over about 3% or so will trigger problems with the nannny controls. Your rear tire choice is 7.7% larger than the stock size. Your front tire 235/50-18 would be 4.9% larger and the 245/45-18 is closer to acceptable at 2.7% larger than stock. When changing front and rear sizes, try to change both by the same amount or as close as you can. Since the speedometer/odometer are driven off the rear wheel, the 255/40-20 will actually be turning at 70 mph when the speedo shows 65.http://www.willtheyfit.com will also let you see how different wheel/tire sizes will fit/look.
    Here's a pic of the differences -

    I am not understanding why you think either option will cause him to have an issue with a nanny light? The computer is looking for rolling diameter difference from the front to rear. If you keep the difference close to the same as stock (13.4mm) from fronts to back, all should be good. Speedo will be slightly off, but ABS, traction and stability control will function as if the machine were stock.

    This is why people can run 22/24 setups without lights. Keep the rolling diameter difference close to stock and your are fine.

    See below comment that I posted on the other site...

    No issues with either one. Rolling diameter differences (front to back) below for each combo.... Anyone can do this at willtheyfit.com


    Stock - 13.4mm
    1. 9.9mm
    2. 17.15mm


    5mm difference is .2 inches.


    Not sure why you want those tires though... There are better options with better pricing in a directional type of tire out there.

    Owner of Slingshot #263 that has some stock parts left on it. :D

    Quote from WraithSS

    Correct, I am running the Pirelli P Zero Nero GT all the way around. It is their max performance summer tire and is asymmetric. Here is a pic of the tread pattern to give you an idea:The only issue I have had is an issue any high performance summer tire would, when it's cold the tire loses some traction. As for the front end handling I have done a lot of upgrades to the suspension as well that have made the slingshot handle remarkably well. RRR strut bar, rebound and height adjustable air suspension, DDM sway bar, DDM sway bar mounts, and DDM end links.

    @WraithSS looks to have very similar setup with what we’re having installed. Sling still up at Rev Dynamics, bought tire package off Mitch. Ended up going with 22’s all the way around, had Corbin bags installed too, told Mitch I wanted to go as wide as I could on rear. Went with Ferrada FR1 wheels, after Mitch crunched the numbers (with I think tire calculator and such), had to go with Pirelli P Zero Nero GT instead of Hankook or Toyo. If I recall correctly…


    Fronts: 22 x 9 on P Zero Nero GT 255/35ZR 99Y XL


    Rear: 2 x 10.5 on P Zero Nero GT 305/30ZR 105Y XL




    Also had digital air ride installed. @WraithSS is this setup pretty close to what your running? Haven't seen it yet, gonna wait until we pick it up. Mitch said "been getting a lot of compliments on it in the shop from customers, everyone loves your wheels."

    Quote from WraithSS

    @ThomaSS close, but slightly different.


    Front: 20" x 9" with Nero GT 275/30ZR20
    Rear: 22" x 11" with Nero GT 315/25ZR22

    What I really wanted to ask and I see now I never did with my post. Running air ride, basically same tire/wheel setup. Hoping I'm going to be pleased with this setup from a driving/handling perspective? Thought you may be able to provide some insight there. I understand you have some upgrades to suspension I don't.

    @ThomaSS


    That is difficult to say as your front wheels/tires are much taller than mine and your rear is slightly taller. So, at the same air pressures my Slingshot will sit lower and have a lower center of gravity which changes the handling characteristics a bit. I've also changed the HP rating considerably to make up for the large wheels and added a big brake kit.


    I'm sure it will handle much better than stock as the air ride kits make for a highly adjustable ride from very comfortable to stiff and agile.

    When life knocks you down, calmly get back up, smile, and very politely say, "Is that all you've got?

    I was focusing on the fact that the front/rear tire size changes were not that close. His proposed rear tire was almost 8% larger while the front he was looking at were just under 3% to almost 5%. I go by the rule of thumb that changes under 2% difference are OK, 3-4% differences may work but differences higher than that seem to be problematic. Guess I should have phrased it differently.

    I would like to make sure we provide information that does not push members away from certain tire configurations because of fearing the nanny lights.
    As I have posted before, I have been running a 295 45 18 on the rear with a 275 35 18 on the front. The rear tire has a 4% larger circumfrance than what was on it at stock.
    Checking will they fit shows a difference of 140 mm circumfrance front to rear.
    This configuration does not turn on any nanny lights. I am running this on 2 separate slings with the SL tire size flashed in the ECU.
    The above assumptions have not been proven that I know of. The numbers I share have been proven to work without any issues for over a year.
    I am not trying to get anyone heated about this, but the same theories keep being put out that are not based on anything concrete.

    Again, the only thing that matters is the rolling diameter difference from the fronts to the rear. It doesn't matter if your rear tire has a 10% larger circumference if you pair the correct fronts.


    All you do is....


    1. know that the stock rolling diameter difference on a stock SL is 13.4mm
    2. put in your new combo at willtheyfit.com and see what the difference shows
    3. make the difference on the new combo as close to 13.4mm as possible


    We know for a fact that combos like @slingrazors work. His combo has 36.5mm difference from fronts to rear. We know for a fact that anything above 60mm difference from front to rear is too much and will trigger lights, as I ran a track combo that had this issue.


    What we have been told, is that you can be within 1 inch of the stock rolling diameter difference. This means that the below range should apply...


    -12mm to 38.8mm combos should all be fine (25.4mm either way from stock)

    Owner of Slingshot #263 that has some stock parts left on it. :D

    Quote from BKL

    My 4th rear tire was a NS-20 in that same size. Overall, I liked the tire and got almost as many miles out of it as I did with the Kendas. Some folks say the NS-20 has a soft sidewall. The only thing I noticed about it was minor steering wheel movements seemed to make the rear end feel like it was a little loose, but I never felt any problems during quick lane changes such as swerving to avoid debris. Overall, I think it was decent and relatively inexpensive tire.

    I was a little worried after I got it on...it seemed really slick. I am guessing they over lubed the tire putting it on the rim. After a few quick burn outs, it felt like the traction was better than the Kenda...but I think the overall width is still limiting traction. I think I am going to have to breakdown and buy a wider wheel and tire combo.

    Actively looking for another sling...It is time...

    Just an FYI about new tires. I know it makes sense, since I worked for Goodyear Tire for a few years. The manufacturer recommends that any performance tire be "broken in" for the first 300 miles by NOT spinning the tire or exposing it to excessive heat. Reason being is that the tire making process uses a lot of oil byproducts and they need time to sort of leach out on their own. Adding excessive heat via long distances at high speeds, burnouts or I guess exposing it to the Florida sunlight work against this. They state that traction will improve if this breaking period is followed.


    The issue I have with this "theory" is all race (sticker tires) are bolted on to the vehicle and instantly get excessive heat from long burnouts or high speed racing. So unless the true race tire uses different agents that do not have to cure and leach out of the tire, it would seem that the above theory may not hold true.


    You decide

    Nobody gets outta here ALIVE

    Agree. As track day guys try to "heat cycle" or "scuff" new track tires following a process similar to below...

    Run six to eight laps at no greater than three-quarter speed, then let the tire completely cool down. A second light scuff session followed by storing the tire several days or even a week is recommended, and has proved to be ideal for preparing a tire for competition.



    Scuffing brings the tire up to the lower end of its operating temperature, but not too hot. Do not drive at top speed during the scuff session, STA advises. This will cause the tire to “give up” or “fall off” prematurely in competition.

    Owner of Slingshot #263 that has some stock parts left on it. :D

    Quote from Br4hm4

    I was a little worried after I got it on...it seemed really slick. I am guessing they over lubed the tire putting it on the rim. After a few quick burn outs, it felt like the traction was better than the Kenda...but I think the overall width is still limiting traction. I think I am going to have to breakdown and buy a wider wheel and tire combo.

    The amount of lube used to install a tire does not effect the traction. The mold release and the compounds, as discussed above, are the initial traction factors. As discussed a "break in" period is required to achieve max traction.


    This is a real interesting and informative thread as I am about to buy tires myself. I am looking at putting on tires that have a taller and more flexible sidewalls. I am looking for comfort more than performance. At 70 years of age my hard driving days are behind me.



    LC