Wheel/Tire question for Base Slingshot

    Quote from MiM

    Stretching has been discussed @BKL... @lrobbi did it, but @WraithSS somewhat frowns upon it...


    I'm swisterzland... But if you do end up going this route, keep us updated! Especially if you do this here locally in Houston... :thumbup:

    Actually what I "frown upon" was using a huge wheel spacer to correct your offset. You're confusing what I said.

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

    If I can get the Base model 17 x 7" wheel widened to 10.5", I shouldn't need any spacers since the front offset (42mm) is only slightly less than the rear offset (45mm). I plan on emailing Weldcraft Wheels to ask about the entire process. I still have plenty of tread on my current 275/35R18 tire, but I would definitely like a larger tire once I get the turbo installed after the swing-arm recall is completed. I found a front wheel on EBay for $150 shipped (never used, customer put on SL wheels before taking delivery).

    Edited once, last by BKL ().

    Just a heads up your rear wheel would not be centered.


    You are adding 3.5" to the wheel = 88.9mm, split that in half and you get 44.45mm. The offset difference between the front and rear wheels is only 3mm.

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

    Quote from MiM

    This confuses me, but what would his new offset be?

    Think of it this way. If your rear wheel is a +45 offset it sits nice and centered on your back end of the Slingshot. Any material you add will go towards the swing arm side. The wheel will look off center to the right. He would have to add a spacer to push the mounting surface of the wheel back to the left.

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

    Couple things: Stock base rear is 18" - seems like all the talk is centered on a 17" for the rear ?! The offset is important in the rear for clearance issues, not so much in front but good idea to stick close to the factory amount. If you are installing larger diameter tires make sure the size ratio is the same as stock for traction/stability control. Also when installing a larger diameter tire on the rear you can have the ecu changed to the SL tire size setting so the speedo will be closer to correct. :thumbup:


    As for rim size clearing calipers the stock rim sizes will clear Alpha's Big Brake Kit calipers (which are bigger than stock) - so anything bigger will be no problem.


    When buying tires if they offer a buy 3 get one free - get and extra rear. :rolleyes:

    2JZ Swap - 400+ WHP - Custom Hood - PRP Seats - Cerwin Vega Stereo - AccuAir - Foose Wheels - Hankook Tires - LiteTheNite LED's

    17" was referred to because @BKL found them on the cheap and is trying to utilize a lower price point. The offset difference between the front and back wheels is only 3mm which is not a deal breaker since he was planing on widening them anyway and a spacer would be necessary.


    Larger diameter tires do not have to have the same size ratio as stock, but they do need to be close to the same front/rear ratio as to not throw a code as that is what the nannies are calculating off of.

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

    Ahh that would make sense. Going smaller in the rear could potentially change gear ratio (if overall smaller diameter) and mean a little quicker acceleration, although we fight for traction now - putting any more torque to the wheel wouldn't help. There are a lot of options (tires) for 18, 19, and 20") for the rear. We're a Tire Rack dealer and I've gotten my Hankook Ventus V12's for just over $100 per front and about $175 for the rear I think. Lots of options though that are less than that and still good tires. Depends on if you want longer life or traction. I prefer sticky tires that don't last long... :rolleyes: Currently on a 3 rear tire+ per year plan and a dedicated set of track day tires/rims. :whistling:

    2JZ Swap - 400+ WHP - Custom Hood - PRP Seats - Cerwin Vega Stereo - AccuAir - Foose Wheels - Hankook Tires - LiteTheNite LED's

    Quote from MiM

    This confuses me, but what would his new offset be?

    @MiM If you add 3.5 inches to the "ugly" side of a rear wheel then you have to somehow "scoot" it over toward the pretty side half of what you added to keep it centered.


    In @BKL s case he is considering adding 3.5" to a 7" rim making it a 10.5" rim.
    So if he was starting out with a 45mm +offset rear wheel he would need a "spacer" half the width of 3.5".
    3.5"x.5 = 1.75"
    1.75" = 44.45mm
    But he is starting out with a front rim with a 42mm +offset so his rim would have been 3mm off toward the pretty side to begin with so he can subtract 3mm from the above calculated spacer so...
    44.45 - 3 = 41.45
    1.632" = 41.45mm is the required spacer


    An easy way to remember, when referring to rim offsets, which way is negative or positive is to think of the "negative" impact a wheel hanging out away from the vehicle (deep dish) would have on the drivetrain and handling for that matter.
    The following is a short clip explaining wheel offsets
    I hope this helps. :thumbsup:


    @Slunglow... Thank you for taking the time... You're a good man! I'm treating you to something whenever I finally meet you...


    I'll probably still ask dumb questions and not get some things that are stated by others, but those calculations and video did help me (and will probably help others)! Thank you!

    Quote from MiM

    @Slunglow... Thank you for taking the time... You're a good man! I'm treating you to something whenever I finally meet you...


    I'll probably still ask dumb questions and not get some things that are stated by others, but those calculations and video did help me (and will probably help others)! Thank you!

    No problem brother I'm not the brightest rock in the pile but I have had alot of fellow members help me with questions and I'm just trying to pay it forward. :thumbsup:

    Ok, now I'm confused. Either I never understood this, or I'm going buggy after doing tax pre work all day. If you ass 3" to the ugly side of the wheel, don't you have to use the same 3" to the pretty side via a spacer and not half that amount? As an example, lets just say the actual numbers were that the original wheel was 7" wide and had it evenly spilt 50/50 for a zero offset. Now you add 3" to the inboard side, wouldn't you have to add three inches to the outboard side (with a 3" spacer)? I need a beer and some sleep

    Nobody gets outta here ALIVE

    Quote from funinthesun

    Ok, now I'm confused. Either I never understood this, or I'm going buggy after doing tax pre work all day. If you ass 3" to the ugly side of the wheel, don't you have to use the same 3" to the pretty side via a spacer and not half that amount? As an example, lets just say the actual numbers were that the original wheel was 7" wide and had it evenly spilt 50/50 for a zero offset. Now you add 3" to the inboard side, wouldn't you have to add three inches to the outboard side (with a 3" spacer)? I need a beer and some sleep

    Phil the whole idea is to add an equal amount to both sides so the wheel stays centered. But since it is much easier to "stretch" a rim on the ugly side you have to add a spacer half the width of the stretch to get half of it on the other side. Make sense ? ?(:(:)

    Quote from MiM

    When are wheel/rim dealers/websites going to do this?!? Frustrating and time consuming trying to find pieces that work for us... :cursing:

    If you find a Forgestar rim you like and call in your order, the guy there knows all the Slingshot sizes that fit(rim/offset/bolt pattern...) ;) They are custom, so they can taylor any design, you just can't get Super concave with stock brakes.

    Thanks to everyone who has helped clarify my situation. I confess to having confused myself regarding offset and the need for spacers. Originally, I assumed I would need a spacer, but I became confused as I tried to research the situation. That was why I ordered the OE Wheels 17 x 10.5 rim so I could actually put it on and see for myself how things looked, both from caliper clearance on the inside of the wheel, but also what might need to be done to center the tire.
    I also admit that when I was researching larger tires, cost became a factor as I was not looking to pay $300+ for a tire that wasn't going to last as long as less expensive tires. I realize that having a single rear tire will place more wear on a tire compared to a conventional four wheel vehicle, but I would hope that I would see around half the tread-life, especially for tires that have a significantly higher UTQG.
    Folks typically seem to look at going to larger tires when looking for more performance/traction. I did the same thing when I started looking for the largest tire that would fit on my Base rear wheel (295/30R18). While searching online after seeing other folks using 305s, 315s or even up to 345 tire widths, I somehow stumbled across some 315 17" tires that seemed remarkably low-cost compared to equivalent width tires in larger wheel sizes. Using my favorite tire comparison tool from Discount Tire (Discount Tire), I realized that a 315/35R17 tire is only slightly larger that the OEM 265/35R18 tire (and should be running just under 66 mph at an indicated 65 mph), if I can find a 17" wheel that will clear the brake caliper. A little more research showed the Slingshot has the same rotor diameter front and rear, so the front wheel should hopefully fit on the rear. I still haven't actually tested this by swapping the front for the rear. Given the low temps we are currently experiencing in the Houston area, I may wait a few days until we're back in the 70s, maybe 80s, next week!

    Edited 3 times, last by BKL ().