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Discussion Starter · #1 · (Edited)
Background from another thread - After paying twice as much and getting half the miles on my Sumitomo HTR Z III 295/30R18 compared to what I was getting on the stock Kenda 265/35R18 (5000 miles vs 10000 miles, respectively), I'm seriously thinking about trying another low-cost, similarly-rated tire, the Nankang N-20 275/35R18. Slightly larger, but not enough to mess with the speedo and safety systems. At an indicated 65 mph, it should be doing just under 66 mph. Discount Tire Direct is offering them with free shipping for just over $100 each. They're actually rated with a slightly longer tread-life estimate than the Kendas. Getting ready to visit my local Discount Tire.

Called my local Discount Tire and was told they didn't know how quickly they would get the Nankang tire. I ordered online from Discount Tire Direct who showed the same store as a local installer and was told the tire should hopefully get here in a couple of days. Tire 275/35R18 tire was priced at $128 w/free shipping, $3 for a new valve, $13 for Road Hazard replacement and Texas sales tax. Guess I'll find out what happens next.

Tire was delivered one day after I received an email that it had shipped and telling me I could get tracking info in 24-48 hrs.:rolleyes: Had it mounted and balanced a couple days later at my local Discount Tire for $16 + disposal fee and tax.

I have attached a PDF file with some pics of the Nankang and the old Sumitomo tire. Overall, I was happy with the Sumitomo tire, except that it cost twice what the Kenda did and only lasted half as long. The Nankang is rated for 20% longer tread-life compared to the Kenda (360AA vs 300AA, respectively) and is an All-Season tire labeled M+S. The Nankang has good looking water evacuation grooves. When I initially had it mounted, the roads were still damp from a rain a few hours earlier and the tire spun easily on the damp pavement. I assume this was due to any chemicals left on the tire from the manufacturing process. Once I got a few hundred miles on the tire, it has offered decent grip during straight-line acceleration on dry pavement. I haven't experienced any wet roads since the initial install. The Nankang is also rated at 40,000 miles, so considering it can't be rotated, it should still be rated for around 20,000 miles.

In most ways, I like the Nankang tire, EXCEPT for the following - Just going down the road, the rear tire feels like it is soft, with routine, minor steering corrections seeming to produce much more leaning compared to what I experienced with the OEM Kendas and the Sumitomo. The feeling reminds me of driving one of the old Detroit "boats" as if the rear is barely making contact with the road surface or my suspension is just way too soft. This feeling bugs me to the point that it almost makes me uncomfortable. The really odd thing about this is when I try making a quick lane change at 55 - 70 mph the Slingshot seems to do fine with no more lean than I would expect due to such a rapid maneuver.

I had read a review where the user was very unhappy with the Nankang's sidewalls, saying they flexed too much, but there were enough more positive reviews that I discounted that review. Now, I'm not so sure about the Nankang tire. While it was priced competitively with the Kenda, and I think the tire looks good and like its straight-line, dry road acceleration, I'm just not sure if I can get used to the way the tire makes the Slingshot's rear end feel. It just seems really odd that the tire feels strange during normal steering corrections, yet feels comfortable during high-speed, abrupt lane changes.
 

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Thanks for being the guinea pig! Please report back in 3 months (or 3K miles, which ever first) and give overall impressions. :D

Any takers to bet which comes first? 3K or 3mo? hahahahah
 

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Discussion Starter · #3 ·
I've had my Slingshot since June 22, 2015 and currently have around 27,000 miles, so 3,000 mile should be here pretty quickly. Sadly, I'll be away from my Slingshot for the next 3 weeks or so.:(
 

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Tires are the foundation of your SS, I would never sacrifice quality for price. If an accident were ever to happen because of the tire causing you to loose control the cost of your savings just went out the window. I also don't run any tire bald like some do for the same reasons. This is just how I roll and its only my opinion, like azzholez, everyone has one.
 

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I'm huge in Japan...
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The Lexus Forums love them. I almost went that route because I found so many positive reviews from Amazon, TireRack, and a few other places. I would love to see the feedback on a SS.
 
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Discussion Starter · #6 · (Edited)
Tires are the foundation of your SS, I would never sacrifice quality for price. If an accident were ever to happen because of the tire causing you to loose control the cost of your savings just went out the window. I also don't run any tire bald like some do for the same reasons. This is just how I roll and its only my opinion, like azzholez, everyone has one.
I would tend to agree, especially about using bald tires. However, just because something costs more does't guarantee quality. As @Br4hm4 posted, some folks on the Lexus Forums love Nankang tires. The Sumitomo I had previously was also rated as a good tire by a Forum Member for his Corvette. In my case, I am simply puzzled how the Nankang tire can seem to respond well to a rapid lane change in an emergency situation, yet feel like it's barely gripping the pavement during casual steering wheel corrections.
 

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Discussion Starter · #8 ·
To be honest, I've now ridden three times on the Nankang (a little over 300 miles, I think) and still haven't checked the pressure. The guy at Discount Tires said they used the pressures shown on the frame sticker, so that should be 32 psi for the rear.
 

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Discussion Starter · #9 ·
I've now put about 4000 miles on my Nankang NS-20 275/35R18 rear tire and have pretty much gotten used to the minor squirrelly feeling I referred to in an earlier coment. The Slingshot still seems stable when I try a rapid lane change. The tire doesn't really look like it has any wear. I might even try some on the front, but probably in the 225/45R17 size.
 

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The guy at Discount Tires said they used the pressures shown on the frame sticker, so that should be 32 psi for the rear.
There could be the problem. Why do people insist on using the frame/door stickers pressure on a different brand Tire. Always use the tire manufacturers pressures.


LC
 

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Discussion Starter · #11 ·
@LargeCar, I agree. Unless I encounter unexpected wear that can be traced to sir pressure, I tend to rely on the manufacturer's suggested tire pressures.
 

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There could be the problem. Why do people insist on using the frame/door stickers pressure on a different brand Tire. Always use the tire manufacturers pressures.


LC
The door sticker inflation pressure is used to maintain the maximum contact patch for the weight of the vehicle.

The tire manufacturer doesn't know the weight/weight distribution of the vehicle, and therefore lists the maximum pressure the tire was designed for.

Being very light, the Slingshot runs a lower pressure than a car or small truck that might run the same/similar tires. In theory, you could put a tire on that holds a max. pressure of 44lbs (instead of 32psi), but the weight of the Slingshot doesn't change, therefore the "pounds per square inch" of contact patch remains the same at 28psi, the pressure on the contact patch doesn't go up to 44psi (without changing the shape of the contact patch).

If you figure the Slingshot weighs 1,900lbs with driver and has 3 wheels with roughly equal weight distribution, that's
(1,900lbs / 3wheels) = 633lbs per wheel
supported by each tire,

at 28lbs/sq.inch (suggested tire pressure) the contact patch is
(633lbs / 28lbs/sq.inch) = 23 sq.inches.

If the front tires were 8" wide that would be a contact patch of
23sq.inches/8inches=3" so 8" x 3",
and a 10" wide rear tire would be
10" x 2-3/4".


At 44psi (pounds per square inch) of inflation the contact patch would change:
Front: 8" x 3" => 8": x 1-3/4"
Rear: 10" x 2-3/4" => 10" x 1-1/2"

That's a 35% reduction in rubber on the road.

How does that affect braking? Let's say there's lots of rubber on the road--braking is great! Let's say there's no rubber on the road--huge problem! So the more rubber you put on the road the better.

Tires are like balloons though, if you over-inflate them the contact patch isn't 10" wide in the rear and 8" in the front because the tire bulges in the center, so lets say the width is reduced to 6-3/4" in front and 9" rear. The center of the tire bulges more than the edges, so the center wears faster, creating a bald stripe in the middle of the tire as the result of over-inflation.

Under-inflation is the exact opposite, where the center of the tire takes less weight than the outside of the tire and it "folds in" so to speak. The tread will look newer in the center of the tire and worn on the outsides.

tire-inflation[1].gif


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