@Slunglow if you run the calculators it shows that 11 is the minimum you want on a 345.
By the way I found out from another SS rider that the aftermarket shocks will not work with a 345 unless you use a spacer or adjust the offset in the rim when made.
Just keep that in mind!!
Wait, what? I have Alpha JRI 2-Ways... A 345 rear won't work just like that? Need more stuff?
Man... What's the next step down but above 305? 
According to this site - Toyo Proxes T1R 345/25R20, the recommended wheel width for the Toyo 345 tire is 12-13". An 11" wheel might be a little narrow. In case you have trouble opening the site, here's the info -
A...................B.......C......D.........E........F..........G..........H............I.........J.............K.......L.......M
|
345/25ZR20 104Y RD BSW |
26.8" | 13.6" | 12-13" | 12.5" | 10mm 3/32" |
Reinforced | 1984 lbs | 50 psi | (Y) 186 mph | 35 lbs | Black | 776 |
A - Size
B - Diameter
C - Tire Width
D - Rim Range
E - Measured Rim
F - Tread Depth
G - Load Range
H - Max Load
I - Max psi
J - Max Speed
K - Tire Weight
L - Sidewall Letters
M - Revs/Mile
I couldn't stand the way the Data table displayed so I edited it for easier reading. (By the way, formatting data is a PITA if you want it to maintain columns! At some point, I lost the dividers between the columns in the table and had to re-edit all of the....)
I placed a Nitto Motivo 97W XL on my rear wheel.
Love how it holds in standing water soooo much better now. Stock sucked on the rear, but the front ones are holding out fine. Still on after 32000 kms.
I placed a Nitto Motivo 97W XL on my rear wheel... Still on after 32000 kms.
So, that's like, 42 miles or something in North America?
So, that's like, 42 miles or something in North America?
It's just under 20000 tyvm 
Some seriously deep tread on the Nitto 555 G2. My rim really needs a 305 width tire but it will run the 285 width. Nitto only makes the 555 up to 285 so that was what I put on it. I had the Toyo 305 Proxies +4 on and they sucked..
Everybody knows what the stock Kenda tires look like. I thought I'd post a picture showing my worn Sumitomo 295/30R18 (still on the rear wheel) next to the Nankang NS-20 275/35R18 tire (unmounted). To the naked eye, I feel they both look about the same width even though the Nankang is only a 275 compared to the Sumitomo 295. As I stated earlier, the Nankang NS-20 tire feels fine during rapid lane changes like a quick change from the right lane to the left and back (as if swerving around an obstacle), yet feels a little loose during minor, normal, steering corrections when going down down the Interstate. At least one reviewer said the NS-20 tire had soft sidewalls. I now have about 3000 miles on the tire and don't really notice it now.
I have managed to make the NS-20 break-free and spin a little during more energetic acceleration, but I am relatively happy with it considering that I ordered it with free shipping thru Discount Tire Direct and paid to have it mounted at Discount Tire for less than I paid to replace the original Kenda 265 with another Kenda 265.
Note - As the directional arrows show, I had the Nankang tire backwards in the picture.
I'm running the 285/30/20 on the stock 20X9 whhel and that's the largest you can go. It actually should be on a 8 1/2, but Discount Tire says it's ok on the 9 inch. But the tire tread even at that size varies a lot from company to company. The widest tread for that size (that I found) was a Toyo Proxes T1S. Traction was ok
AND tirerack also lists the range of the reccomended rim width and the width they tested the tire with.
Here is one that we use on a pretty regular basis -
Online Wheel and Tyre Fitment Calculator. Offset, Tyre Stretch and Speedo Error | Will They Fit
@V-SHOT, followup to our discussion today. You should bookmark this thread.
I've now got around 4000 miles on the Nankang NS-20 275/35R18 rear tire and have pretty much gotten used to the way the Slingshot handles with the tire. I occasionally still notice some minor squirelly feeling from minor steering wheel movements, but have had no problems when I've executed high-speed, abrupt lane changes. I might even consider putting NS-20s on the fronts to replace my OEM Kendas that now have almost 31000 miles and still look good for more miles. I think I will probably move up to a 225/45R17 size, though.
Some seriously deep tread on the Nitto 555 G2. My rim really needs a 305 width tire but it will run the 285 width. Nitto only makes the 555 up to 285 so that was what I put on it. I had the Toyo 305 Proxies +4 on and they sucked..
@rabtech what is the width of your rear rim?
I'm about 3500 to 4k miles on my rear 555 and love it I will be installing 555 on the fronts when the kendas wear out, total mileage is around 9800. The new has wore off so I'm expecting milage will be lower on the next tire lol.
Only con I can even think of is damp roads, super slick.
Quote from rabtechDisplay MoreAnd the winner is ...... 18x8.5" on the front and 20x10.5" on the rear.... I'm putting new meat on all three 245 on the front and 285 on rear
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Never mind, I found it...
I've been posting my experience with trying to find an inexpensive way of getting the widest tire possible on my Base Slingshot. Here's the thread - Wheel/Tire question for Base Slingshot. Since you guys have been talking about the Nitto 555 tires here and have mentioned less than stellar performance in rain, I thought I'd ask about Nitto Motivos (I'm looking at a 315/35R17 on the rear. The Motivos are rated just below the 555 G2 for dry performance, but just above the 555 G2 for wet performance. I like the significantly longer treadlife (up to 60K miles on the Motivos) and would also like some good wet road performance since the wide rear tire might exacerbate hydroplaning.
Any body have any experience comparing the two?
As far as the Sumitomo HTR series goes, there is a big tread pattern difference between the Z II and Z III tires. I don't usually spin the rear if I can avoid it and I only got 5000 miles from my HTR Z III 295/30R18XL (300AAA rating) on my Base model Slingshot compared to the 10000 miles I got out of each of the two Kenda stock tires I've had. I'm now running a Nankang NS-20 275/35R18 on the rear. It's slightly larger than the stock size which means it should be turning a little over 66 mph at an indicated speed of 65 mph. It feels a little squirrelly in response to minor steering corrections just driving down the Interstate at 65 mph (at least 1 review I read felt it had soft sidewalls), but when trying a quick lane change from right-to-left lane and back at speed on the Interstate, the Slingshot still seems to handle fine. I now have around 3000 miles on the NS-20 and am interested in how long it lasts, especially after I get my Hahn Turbo kit installed. I bought a Kenda 265/35R18 here locally (Houston, TX area) for around $136, installed, and ordered the NS-20 from Discounttiredirect and paid Discount Tire for the install and the combined cost was cheaper than the Kenda, IIRC. I wish Nankang made a NS-20 in the 295/30R18 size, but the 275/35R18 (360AA rating) is the largest 18" NS-20 tire they make, although they do make a 285/30ZR20 (240AAA rating). I can make the NS-20 spin, but it still seems to provide decent overall traction. I do not normally go out if rain is expected, but I do occasionally get caught in rain.
I am also considering trying a Goodyear Eagle F1 Asymmetric All Season 285/35R18 size, which should be turning just under 66.5 mph at an indicated speed of 65 mph. It has a 500/AA/A rating with a tread life warranty of 22,500 miles when used in a non-rotatable setup. According to the Goodyear site, it should run around $245 installed + tax, making its operational cost comparable to the Kenda and Nankang tires on a per mile basis, but hopefully offering better overall traction/performance..
I have been wearing the Goodyear Eagle F1 since my first month of ownership. Outside of perfect weather, the Kendas were scary to me. Probably 20k miles on the fronts, and looking great. The rear, I replaced early unnecessarily for a track day, and it probably had much more life left. Now that I don't do burnouts all (seriously all) the time, the rear still looks great with maybe 10k miles on it.
2 minutes into riding with Goodyears, you will go, yeah, this is a lot better. Can't compare to other options... Much improved in rain, rear still sucks in snow...
I've been posting my experience with trying to find an inexpensive way of getting the widest tire possible on my Base Slingshot. Here's the thread - Wheel/Tire question for Base Slingshot. Since you guys have been talking about the Nitto 555 tires here and have mentioned less than stellar performance in rain, I thought I'd ask about Nitto Motivos (I'm looking at a 315/35R17 on the rear. The Motivos are rated just below the 555 G2 for dry performance, but just above the 555 G2 for wet performance. I like the significantly longer treadlife (up to 60K miles on the Motivos) and would also like some good wet road performance since the wide rear tire might exacerbate hydroplaning.
Any body have any experience comparing the two?
Wouldn't any increase in tire width increase susceptibility to hydroplaning?
Never mind, I found it...
That is awesome. I forgot I bought those.... 
That is awesome. I forgot I bought those....
Are those not the rims you are running now?
Wouldn't any increase in tire width increase susceptibility to hydroplaning?
Increasing the tire width does also mean it might increase chances of hydroplaning, given the lightweight of the Slingshot. I feel I need a wider tire once I install my turbo and hope using a tire with improved resistance to hydroplaning will reduce any chances of hydroplaning.
Nitto markets the Motivo as an All-Season Ultra High Performance tire and the 555G2 as a Summer Ultra High Performance tire. Here are the specs on the 2 tires -
Motivo - 560 A A Dry Performance 4/5 Wet Performance 5/5 Comfort 5/5 Quietness 5/5
555 G2 - 320 AA A Dry Performance 4.5/5 Wet Performance 4.5/5 Comfort 3/5 Quietness 3/5
The Motivos cost less than 10% more with longer expected treadlife and better wet performance, comfort and quietness ratings.
