I replaced my kumho ASX all seasons (245/40/18) with kumho SPT summers, same size. They're just a bit louder than the all seasons, but still quieter than either the stock turanza's that came on Cheryl's 04, or the goodyears that came on my 05. The tires seem to be be a bit more firm, but not detrimentally so. There is less tramlining and steering wheel kickback, but neither has been elimenated.

I don't know how they're wearing just yet. I've put a little over 1k miles on them in two weeks. My asx's wore out in about 16k miles or so. I'm running higher pressure on these new tires, and I'm going to have a realignment performed, which I believe were the two primary factors in the excessive wear on my previous kumhos.

Wet traction is fabulous. Better than the all seasons, and even better than the stock goodyears. Straight line traction is also pretty good; though the differences here amongst the three sets of tires I've used is minimal.

The all seasons would tend to flat spot in the winter when parked over night. After a few miles, they would return to normal. These summer tires do the same, even in 80 degree weather. I'm apprehensive about how badly they will flat spot in the winter.

Lateral traction is also improved over my previous two sets of tires. Quite a bit better than the all seasons, and marginally better than the goodyears.

Now here comes the harsh part, and I must admit that I'm confused. When I read reviews on tirerack, I saw plenty of mention of a soft sidewall. This trait appears to be common to kumho's in general; so I was expecting it. I've gone for a couple of spirited drives, and at times my car now scares me. In high speed sweepers, or during quick transition, or even uneven pavement during a maneuver, the rear of the car seems to be in disagreement with the front; likewise side-to-side. Meaning that it feels like the vertical axis has become jelly. It's very difficult for me to describe with my limited performance/suspsension vocabulary.

Here's why I'm confused: I never experienced this behavior on the previous tires. I experienced the typical rear sideways flutter. For example going in a straight line over frost heaves on the interstate. But not this behavior. So it's logical to believe it's the tires. But why? What about the tires is causing this behavior? It doesn't feel like a soft sidewall; the tires don't feel like they're rolling laterally. It feels like really bouncy shocks, but with each corner attempting to operate counter to any other.

I've got some coupe springs/shocks that came off an 04. I was told they had a little more than 20k miles on them. I put them on before I reached 10k, and I now have almost 30k miles. So let's assume the shocks have at least 40k miles on them. It is possible it's the shocks? All of them, or only the rears? Is it possible that this condition was there before, but the stiffer summer rubber just now made it more visible? I also just put on stillen sways a couple of months ago(med/med).

So, what's the verdict? Do the tires just suck that bad? Is it my shocks? Or is it a combination of the tires, shocks, and sways?

 

What pressure are you running?

Have you tried bumping it a few pounds either up or down?

 

I started out at roughly 38psi hot. My other kumhos were crap under 40psi(and that contributed to the wear). I ran them like that for about a week and a half. A couple of days ago I upped them to 42 hot all around. I've not been able to really push the car yet, but the one time I went through a quick corner with uneven pavement the car behaved like it did with the lower pressure.

 

I'd have to say it's most likely related to the sway bars. What are you're settings? The coupe springs, at least with my G, site about .9" lower in the rear than the stock Sport springs. Factor in your use of Stillen sways and you've significantly decreased the rear roll center. The reason you probably didn't feel these sensations with the other tires is because the all-season sidewalls were probably a bit softer and would absorb some of the movement. Also, stiffer sway bars can increase suspension bind and bounce on undulating roads especially if the car is stock.

Interestingly, I'm experiencing the disconnected feel you're describing with my new Avon M550. However, mine car's new trait doesn't sound as severe as yours. Mine is more of a twitchiness. I think the issue is related to:

1) My drop. I have 350z springs in the front and coupe springs in the rear. This drop has lowered the roll center by a crack over 1". With the new suspension geometry, there is a little more play in the suspension during turn-in which can lead to a disconnected feel.

2) The new tires, though still all season, have significantly stiffer sidewalls and a lot more traction than those POS EL42s. Also, the new tires have a .8" wider contact patch even though the tire size is the same. The stiffer sidewalls and added traction greatly increase chassis reponse.

3) The new tires have a lot more tread than my EL42s with 41K miles. The additional tread adds more tire squirm and reduces response. The transition from squirm to bite can be a bit adrupt.

After some experimenting, I took the rear pressure from 34psi to 31psi. This seemed to help quite a bit. So now I'm running 34psi front and 31psi rear. For your car, you might was to consider adjusting psi and taking the sway bar settings down to softest settings both front and rear.

 

damn i just ordered a set of the spt's for my wheels 245/35/20...hope they are gonna be okay...

 

try measuring your tire pressures when cold. I know one of my first checks at a gas station showed 42 psi hot, but 36 cold when i checked later. Less variation in measurement if you measure it cold.

 

FYI for those buying non stock size tires - TireRack made it very clear that we needed to run the 245/40/18 Kuhmos that we bought at 36 psi (cold) at minimum. I think this was more related to the size than anything else but likely affected by the difference in the rigidity of the sidewalls.

I would also like to note that Trey and I have had very different experiences and opinions of the all-season tires. Now that I think about it, I wonder whether or not our different experiences are affected by something going on with Trey's car.

 

so how are the Kumho ECSTA SPT tires doing now?

 

I've determined that the "squishiness" is not the tires. I have a hunch that the combination of the stiffer tires and sways were making the inadequacies of the chassis more apparent(basically what dave said). I don't know this for a fact; but I'm pretty sure as I've put more time on the tires.

The tires seem to be wearing well; I don't have enough mileage on them to predict how long they'll last. They're a bit stiffer than the all seasons, but still plenty comfortable. They're a bit louder than the all seasons, but not by much. After the tires have broken in, lateral traction is *much* better than the all seasons. And running >40psi hot has helped the sidewalls a lot; I don't feel any roll in my "aggressive" daily driving. I'll get a better idea of roll tendencies when I autocross these suckers.

Straight line traction is better, but it's not a huge improvement. I can still chirp 2nd, 3rd, AND 4th. Last week, I was even chirping 3rd regularly with two passengers and the A/C on, short-shifting at 5500.

 

The real test is at the 8,000 mile point. This is where many tires give up since this is the limit tires are tested to comply with Federal standards.

They drive them to this mileage then extrapolate from the wear up to this point..........manufacturers have learned to cheat with different compunds in outer and inner layers..........weak low cost cord materials [stretch and explode] like rubber bands after this point.......but there are millions of them.

Michelins claim to fame is they use expensive [a few dollars more at most]materials which prolong this destruction to the 15-20,000 mile point.

 

Hmmm I wonder if it is possible the different compounds are not consistent within the same model of tires. Can the factories change or mix up the compound blends on the same models of tire?

There seems to be huge variations with G owners in some of the OE tires life- ones like the Pilot Sports on my coupe. Some have claimed 30K+ miles and others like me have the rears done in 13K miles and the fronts may make it to 16k miles.

 

The unknown factors [besides driver friskiness] are the EXACT alignment numbers and the composition of the roads driven. Roads are designed to eat tires and save the roads.......tires are easier to change than roads to resurface.

Concrete vs asphalt [course drainage vs smooth slick wet].

Over the years on the same OLD Q45 with same tires [160 treadwear Michelins] and brake pads we use to see variations in tire life 12,000-28,000 miles and pads of 15,000-45,000 miles.

Men vs Women; Kids vs adults; Interstate Commuters vs real estate agents.

If you add in regional variances like HOT ARIZONA vs North Dakota it will be even wider.