Wheel/Tire question for Base Slingshot

    Looking for affordable wider rear tires for my 2015 Base model Slingshot. 295/30R18 is about the largest size tire I can mount on my Base rear wheel. Those tires also get relatively expensive. I realized I might go wider and save some money by replacing my wheels.


    I found a couple of affordably priced candidate tires on Summit Racing-
    MickeyThompson 6278 Street Comp Ultra High Performance Radial Tire315/35R17 for $165 w/free shipping. Summit also lists the Nitto 555G2 in 315/35R17 for $195 + $10 shipping. Both tires are rated 300AA as are the OEM Kendas.


    Both tires would require me to replace the OEM rear wheel with a 17 x 10.5wheel, which, when combined with the tire sizes above should still be compatible with the speedometer gearing for my 2015 Base Slingshot.


    Onthe JEGS website, I found some wheels for older Mustangs that come in17 x 8 +29.5 offset and rear spacing of 5.66” along with a 17 x10.5 +27 offset and rear spacing of 6.81”.


    According to the Rimsntires.com Wheel/Tire Size Comparer (Custom rims, wheel tire packages for your ride - RIMSnTIRES.com), I should be able to fit 17 x 8 wheels with a +29.5 offset to replace the front wheels on my Slingshot using the stock size tire (205/50R17). Further research shows I should move to a 245 tire with the 17 x 8 wheel size. Rimsntires.com also says I can use a 17 x 10.5+27 offset wheel to replace my rear wheel/tire using either of the tires listed above with acceptable clearance and the rear wheel's actual speed at an indicated 60 mph should be 60.8 mph. One of my concerns about this info is I don't know how the rear spacing referenced above might affect the fit and the Rimsntires.comcalculator doesn't allow for that measurement. :cursing:


    Should I be concerned about any negative impact from the Rear spacing measurements mentioned above?


    I'll also be posting on The Dark Side to try and get maximum exposure.

    Edited 2 times, last by BKL ().

    Watch the rear brake caliper clearance... I've personally tried wheels which had the proper offset but did not clear the stock rear brake caliper. Often, wheels which are advertised as "big brake compatible" have more clearance for wider brake calipers with the same offset. A 17" wheel may prove more difficult in this regard compared to the stock 18" wheel size. I used 45mm offsets on my rear wheels.

    Quote from MiM

    I've been looking at getting wider as well @BKL... I thought offset for rear needed to be +45mm, otherwise your rear wouldn't be centered?

    That's correct. The Rimsntires tool is assumes you have a wheel/tire mounted in a typical fenderwell and only looks at clearance issues compared to whatever base wheel/tire info you provide.

    Quote from gearhead

    Watch the rear brake caliper clearance... I've personally tried wheels which had the proper offset but did not clear the stock rear brake caliper. Often, wheels which are advertised as "big brake compatible" have more clearance for wider brake calipers with the same offset. A 17" wheel may prove more difficult in this regard compared to the stock 18" wheel size. I used 45mm offsets on my rear wheels.

    I am still researching clearance. I know that the 17" front wheel on my 2015 Base Slingshot clears the 298mm rotor used on the front and rear, just not sure about the caliper.
    I was thinking about ordering a 17 x 10.5 94-04 Cobra wheel to see how it mounts, but the vendor seems to be out of stock. OE Wheels has the standard "Bullitt" Mustang wheel in-stock, but I'm researching other manufacturers.

    So far I think I found a good set, with similar rolling distances and matched offsets for about $1600...


    17s and a 19 rear with 325 wide... Rear replacements at $260 and fronts at $100.


    If I can sell my base wheels/tires and SL wheels/tires, maybe $1000 is all it'll cost me... We'll see...

    Quote from MiM

    So far I think I found a good set, with similar rolling distances and matched offsets for about $1600...


    17s and a 19 rear with 325 wide... Rear replacements at $260 and fronts at $100.


    If I can sell my base wheels/tires and SL wheels/tires, maybe $1000 is all it'll cost me... We'll see...

    That's awesome news @MiM. What do they look like?

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

    What's the 325/??R19 going to do to the speedometer reading?
    I ran the numbers using the Rimsntire calculator and a 30 profile tire will read 63.4 at an indicated 60 mph. A 35 tire will read even higher at 66.3 mph. Having been pulled over for 74 in a 70 zone, I'm reluctant to vary more than about 5%.

    Edited once, last by BKL ().

    Guys. Check out this site as it will allow you to plug in offsets as well. Online Wheel and Tyre Fitment Calculator. Offset, Tyre Stretch and Speedo Error | Will They Fit


    I posted on the dark side a table that shows the different rim/tire sizes that would keep you close to spec. I believe someone has done it on this forum as well.


    Keep in mind if you are going with aftermarket shocks you will need a little more space f you go with a 345

    Proud Member of SOG!!!!!!!

    2015 SL (Yellow) Traded becuase it kept melting

    2018 SLR LE with DDM SuperCharger!!! I guess the gray ones are faster...

    Quote from MiM

    Thanks @MACAWS! Might be awhile, but going to go with textured gunmetal... Really like bronze, but that would require a color scheme change ala @WOLF style...

    I have seen bronze on different colored vehicles and it looks good on a surprising amount of them. The Chrysler 300 uses a very muted bronze on many colored 300s. ;) You can do what ever you want my friend, it will be unique and good looking.


    Quote from BKL

    I am still researching clearance. I know that the 17" front wheel on my 2015 Base Slingshot clears the 298mm rotor used on the front and rear, just not sure about the caliper.I was thinking about ordering a 17 x 10.5 94-04 Cobra wheel to see how it mounts, but the vendor seems to be out of stock. OE Wheels has the standard "Bullitt" Mustang wheel in-stock, but I'm researching other manufacturers.

    Update - I ordered a 17 x 10.5 OE Wheels wheel from JEGS. The wheel looks nice, but when I test-fit it on the rear hub, a piece of cardboard less than 1/16" (.0625") thick barely fit between the inside of the wheel and the outer edge of the brake caliper. The interior of the wheel measured measured just under 14.375" when I measured the inside diameter of the wheel with my measuring sticks laying against the wheel's mounting surface that goes against the brake rotor. While the wheel technically fits, I'd like a little more clearance than just under .0625", so it looks like I need to return the wheel to JEGS. That's too bad because it would have cost me less than $375 to replace my Base wheels with the 17 x 10.5 " rear wheel and 2 - 17 x 8" front wheels.
    I then removed one of my Base model 17 x 7" front wheel and measured the interior diameter at the mounting surface that goes against the brake rotor and got a measurement of 15.125", meaning there should be clearance of .375" between the inside of the wheel and the outer edge of the brake cylinder. This means I should be able to buy a surplus 17 x 7" base front wheel and have it widened to 10.5" for around $500, allowing me to mount a 315/35R17 Nitto 555 G2 tire while maintaining my stock wheel look.