Stock rear SL rim - how wide of a tire?

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  • So the 285/30/20 works on the stock rim? Did it jack with speedo or traction control. I have been looking at tire threads all morning and was about to order the Nitto 255/35zr-20 and then saw this thread :-)

    My tire guy told me that some brands of the 285/30/20 will work, 275/35/20 is better. It comes down to how the tire sits on the shoulder of the wheel. With this being said, the 285/30 will sit lower by almost a half inch vs the 255/35. It will spin faster so the speedometer will read higher than you are actually going. Should not interfere with the nanny system on the Slingshot.

    CO D12


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  • My tire guy told me that some brands of the 285/30/20 will work, 275/35/20 is better. It comes down to how the tire sits on the shoulder of the wheel. With this being said, the 285/30 will sit lower by almost a half inch vs the 255/35. It will spin faster so the speedometer will read higher than you are actually going. Should not interfere with the nanny system on the Slingshot.

    I also looked at the 275/35/20 as I continued to read. I did find a tire sizing site so I could actually see the difference you were talking about. Thank you for explaining it! I think I am going to go with the 275/35/20 Nitto 555 G2 for my rear and leave the stock on the front until I need another back tire :-)

  • It never caused any fault lights to flash and speedo error is within range. You can't get too focused on that. If interested, read what I have to say about that below


    Ok, what size tire can you run and keep the speedometer accurate? Who's saying it's accurate now? When is it accurate? Basic math leads to the following explanation.


    Let's say you have the factory rear tire on your slingshot and it comes from the factory with 9/32" of tread. Ok so far? So you wear it down to the tread bars which show up at 2/32" remaining tread. So how much tread have you worn off the tire? If you said 7/32" you're only partially correct. Your speedometer is calibrated by the effective gear ratio as well as the overall tire height. So when your tire is worn out and at the 2/32" remaining tread, and you put it side by side by the identical new tire, the difference in height is 14/32" (or almost 1/2" difference). So your speedometer on your slingshot is accurate sometime during the life of your tire. Replacing it with something close, makes it also accurate, but at a different point in time. A taller tire will be accurate when it wears down some, a shorter tire is more accurate when it's new. Just food for thought. I always run with my GPS on and it displays current speeds and the difference from that and the speedometer varies from identical to a mile or two off depending on speed. It's one of those factors to consider when buying the tire, but as long as you're close, don't worry too much about it. Two miles per hour off isn;t going to save you from that speeding ticket. Ask Kenny_H about how that works out in GA

    Never be held prisoner to your past. It was a life lesson - NOT a life SENTENCE

  • It never caused any fault lights to flash and speedo error is within range. You can't get too focused on that. If interested, read what I have to say about that below


    Ok, what size tire can you run and keep the speedometer accurate? Who's saying it's accurate now? When is it accurate? Basic math leads to the following explanation.


    Let's say you have the factory rear tire on your slingshot and it comes from the factory with 9/32" of tread. Ok so far? So you wear it down to the tread bars which show up at 2/32" remaining tread. So how much tread have you worn off the tire? If you said 7/32" you're only partially correct. Your speedometer is calibrated by the effective gear ratio as well as the overall tire height. So when your tire is worn out and at the 2/32" remaining tread, and you put it side by side by the identical new tire, the difference in height is 14/32" (or almost 1/2" difference). So your speedometer on your slingshot is accurate sometime during the life of your tire. Replacing it with something close, makes it also accurate, but at a different point in time. A taller tire will be accurate when it wears down some, a shorter tire is more accurate when it's new. Just food for thought. I always run with my GPS on and it displays current speeds and the difference from that and the speedometer varies from identical to a mile or two off depending on speed. It's one of those factors to consider when buying the tire, but as long as you're close, don't worry too much about it. Two miles per hour off isn;t going to save you from that speeding ticket. Ask Kenny_H about how that works out in GA

    Thanks for educating a tire idiot! You guys rock and are the reason I keep coming back to this place. That and I think I finally found a group of folks as crazy as I am!

  • It never caused any fault lights to flash and speedo error is within range. You can't get too focused on that. If interested, read what I have to say about that below


    Ok, what size tire can you run and keep the speedometer accurate? Who's saying it's accurate now? When is it accurate? Basic math leads to the following explanation.


    Let's say you have the factory rear tire on your slingshot and it comes from the factory with 9/32" of tread. Ok so far? So you wear it down to the tread bars which show up at 2/32" remaining tread. So how much tread have you worn off the tire? If you said 7/32" you're only partially correct. Your speedometer is calibrated by the effective gear ratio as well as the overall tire height. So when your tire is worn out and at the 2/32" remaining tread, and you put it side by side by the identical new tire, the difference in height is 14/32" (or almost 1/2" difference). So your speedometer on your slingshot is accurate sometime during the life of your tire. Replacing it with something close, makes it also accurate, but at a different point in time. A taller tire will be accurate when it wears down some, a shorter tire is more accurate when it's new. Just food for thought. I always run with my GPS on and it displays current speeds and the difference from that and the speedometer varies from identical to a mile or two off depending on speed. It's one of those factors to consider when buying the tire, but as long as you're close, don't worry too much about it. Two miles per hour off isn;t going to save you from that speeding ticket. Ask Kenny_H about how that works out in GA

    Good explanation. From what I am seeing, the speedo on SSs are relatively accurate. I got use to having the spedo on my Kawis and Wing read 5 to 10 high. Good reason to have a GPS on board.

    John
    '15 Nuc 'em 'til they glow orange
    '15 Ram 2500
    '16 Denali 289 RK
    '17 Mazda 3 HB


    :ORANGESS:


    SOG supporter

  • I got to the point on my Suzukis that I just automatically multiplied whatever the speedo showed by .9 to get me real speed. An indicated 61 mph was 55. 70 was really 63, etc. It became automatic after a bit.

    It's so bad on some bikes they had to come out with the "speedo healer". I had to run one on my Kawasaki Z1000. Like you, mike was off like 9.2%. It was really cool if you wanted to make your rider shit their pants on the highway, I adjusted mine one day to display 199% of factory speed and took a "friend" out on the interstate. I opened it up full throttle and had her look at the speedometer. She couldn't believe that she was holding on while going over 200 mph in high gear.


    I had to fess up when we got home though

    Never be held prisoner to your past. It was a life lesson - NOT a life SENTENCE

  • So, I’m think’n. The Nitto NT 555 G2

    Is 255 35 20. Will the 305 35 20 fit the stock rim? If so, no hiccups with the Speedo?

    Lastly, would there be any driving (control) issues with the a wider tire?

    See - https://www.nittotire.com/pass…ra-high-performance-tire/. Technically, Nitto recommend at least a 10.5" wide rim for the 305/30ZR20 555 G2 tire. See this site for speedometer impact - https://www.discounttire.com/learn/tire-size-calculator. Just enter the relevant tire info. http://www.willtheyfit.com will provide a visualization to show the impact of different tire & wheel impacts (including different offsets), but the speedo impact is not as accurate as the DT Tire Size tool. Using these two sites, you can get a pretty good idea on fitment issues and speedometer operations. I have a 2015 base model SLingshot and have had tires ranging from the stock 265/35r18 to a 295/30ZR18 on the rear. I now have two rear tires I use. One is an Achilles ATR Sport 2 305/30R18 tire on a Circuit Performance CP32 18 x 1.5" wheel with 35 mm offset that I wanted to test since the tire and wheel only cost me a little over $250. I also have a Nitto 555 G2 315/35ZR17 tire on an American Muscle 10th Anniversary Cobra Style 17 x 10.5, 28 mm offset Mustang wheel that combined set me back less than $400. I still haven't decided if I'll stay with the Achilles/Circuit Performance combo yet, since I'm waiting to see how many miles I get from that combo. The Nitto/AM wheel combo has already given me 11000 miles and still has more tread left. Both offer reasonably acceptable levels of traction under boost.

    Edited once, last by BKL ().

  • So, I’m think’n. The Nitto NT 555 G2

    Is 255 35 20. Will the 305 35 20 fit the stock rim? If so, no hiccups with the Speedo?

    Lastly, would there be any driving (control) issues with the a wider tire?

    I have ran the Nitto for years now and love them. I have ran the 305, 315 and I ran a 345 (aftermarket rim). You do get a little more spin as the smaller side wall causes it to break loose, however I had great grip in turns. I am currently running the 315 on my 2018 SLR LE, but on aftermarket rim.

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  • I went with this one....if I remember correctly I picked it because it fell into the height of the factory tire. I didn’t want Speedo or light issues...


    https://www.carid.com/nitto-ti…-255-35zr20-96238751.html

    I have a set of those on mine, same size rear. Great grip. I’ve got about 12,000 miles on them. Not worth a crud in the wet. 😕. On warm/hot days WOW! Like it’s on rails.

    John
    '15 Nuc 'em 'til they glow orange
    '15 Ram 2500
    '16 Denali 289 RK
    '17 Mazda 3 HB


    :ORANGESS:


    SOG supporter

  • I have a set of those on mine, same size rear. Great grip. I’ve got about 12,000 miles on them. Not worth a crud in the wet. 😕. On warm/hot days WOW! Like it’s on rails.

    Almost any wide tire like this isn’t too good in wet or snow..

    Right now it’s just on my rear...I’m still burning up the second set of factory tires on the front.


    One of the other biggest reasons for picking this tire is it starts with 11/32” of tread depth.


    I’m never going to buy a new tire with less tread to start with.

  • I went with this one....if I remember correctly I picked it because it fell into the height of the factory tire. I didn’t want Speedo or light issues...


    https://www.carid.com/nitto-ti…-255-35zr20-96238751.html

    A 285/30/20 Toyo Proxes T1 Sport is almost the same size as eom and has no issues with abs or lights


    https://www.ebay.com/itm/Toyo-…462c99:g:1eUAAOSw5AhcQxfY

    Never be held prisoner to your past. It was a life lesson - NOT a life SENTENCE