Strange problem with 185/60/14 KUMHO solus HP 716

[Westerly]

Noticed that after about 8k miles with proper tire care that the edge blocks (inner and outer) of all tires have worn down to the sipe...Ok so people would think poor alignment, however upon closer inspection I noticed that the sipeing depth and channels next to the out side blocks are much shallower than the three inner sipe bands. What gives?

I bought these tires at SEARS...Very strange as I know that this tire has received good reviews from many people over the years . What do you think I should do about this

 

[CapriRacer]

First, a 185/60R14 is a pretty unusual size. Was this the original tire size? If not, what was it? Also, what's the year make and model of your car, and how many miles are on it. (yes, I know you have 8K on the tires, but how many are on the car?)

Are the tires the same as these?

http://www.discounttire.com/dtcs/tireProductBySize.go?tc=KUMHH6&cs=185&ar=60&rd=14


If not, what is different? (OK, maybe that's too complex a question.)

Which "sipe" is it that has worn? In particular, is it the one that is pretty close to a circumferential shallow groove?

OK, enough question for now.

I have a couple of theories, but the information I asked for will help sort out which one it is.

 

[eljefino]

I noticed with another kumho, 738 IIRC, a relatively cheap one.

There's a bar, like a treadwear indicator, but running around the circumference, in the outer tread blocks.

My theory is it stiffens the shoulders so the tread blocks don't squirm as much.

When the tire is half worn, it'll look "bald" there. Bet rain evacuation takes a nosedive too.

 

[rpn453]

Those ribs are common.

I avoid that design and buy tires with full depth tread on the shoulder blocks. I think those gaps should be left clear for water evacuation.

 

[wbwanzer]

That's my thinking exactly. Why would you close off the connection between the circunfrential groove and the lateral groove? I avoid those types of tires also.

 

[CapriRacer]

Originally Posted By: wbwanzer


That's my thinking exactly. Why would you close off the connection between the circunfrential groove and the lateral groove?......



Because it really stabilzes the tread shoulder. That means less noise - especially during handling manuevers - and better cornering feel, not to mention the cornering itself, and the wear.

Honestly, everyone points to the directionality of the tire and concludes that water evacuation is really important for hydroplaning resistance. The single most effective way to get hydroplaning resistance is to use circumferential grooves. The "V" shape only accounts for about a 5% improvement - something only a trained driver could take advantage of and then only when the circumstances were right.

But back to the original question:

Westerly, where are you?

 

[rpn453]

Originally Posted By: CapriRacer
Honestly, everyone points to the directionality of the tire and concludes that water evacuation is really important for hydroplaning resistance. The single most effective way to get hydroplaning resistance is to use circumferential grooves. The "V" shape only accounts for about a 5% improvement - something only a trained driver could take advantage of and then only when the circumstances were right.


I developed the assumption of water evacuation through the lateral channels of the outer tread blocks when I got a set of Cooper Cobras back in university. Since I was driving an old beater, I was still in the phase where it seemed like fun to hit every puddle as hard as I could in the spring, and those Cobras seemed very resistant to hydroplaning and would throw the water out to the side much farther than anything I'd ever driven. I just assumed that the deep channels had something to do with that. I guess not. I'm sure they contributed to how good those tires were on snow though.

But the 5% does seem noticeable to me. The Goodyear RS-A tires that my car came with were about 1/2" narrower in tread width than my current Michelin Pilot Sport A/S and had four circumferential grooves compared to only two on the Pilots, yet the Goodyears would hydroplane mildly over standing water on the highway while the Michelins do not. My friend had to borrow my car to get to work one rainy day a few months ago and when he got back he told me he was surprised at how my car was the only car or truck he's ever driven that didn't hydroplane at all.

Do you have any links to any tests or anything related to this subject?

 

[CapriRacer]

Originally Posted By: rpn453


..........

Do you have any links to any tests or anything related to this subject?



Funny you mention that. Just today I was doing some research and came across this paper on tread depth. (Sorry, but it's in 6 parts.)

I doubt if I can find the info about the 5% directionality thing. If I remember right, this was an report written for company distribution and was never published to the outside world.

Anyway here's what I found.

http://www.geocities.com/barrystiretech/blytheontreaddepth/blytheontreaddepth1.jpg

http://www.geocities.com/barrystiretech/blytheontreaddepth/blytheontreaddepth2.jpg

http://www.geocities.com/barrystiretech/blytheontreaddepth/blytheontreaddepth3.jpg

http://www.geocities.com/barrystiretech/blytheontreaddepth/blytheontreaddepth4.jpg

http://www.geocities.com/barrystiretech/blytheontreaddepth/blytheontreaddepth5.jpg

http://www.geocities.com/barrystiretech/blytheontreaddepth/blytheontreaddepth6.jpg

 

[PandaBear]

Originally Posted By: CapriRacer

http://www.geocities.com/barrystiretech/blytheontreaddepth/blytheontreaddepth4.jpg




Good article. It seems like putting the best tires on the front actually give you a slight oversteer rather than puttting in the rear and give you a lot of understeer. This on a RWD car, so FWD will be even more important to put the best tires on the front.

 

[CapriRacer]

PandaBear,

The comments in the paper were that there were a lot of folks have published statements advocating putting the best tires on the rear.

I think the data presented in the paper only says that you get oversteer and understeer with differences in tread depth. The amount of steering wheel angle change is not very large in either case (20 degress vs 10 degrees). Unfortunately, the issue of where the tires should go was more fully explored in another paper - which I don't have - but obviously the conclusion from that paper was that they should go on the rear.

 

[rpn453]

Originally Posted By: CapriRacer
Funny you mention that. Just today I was doing some research and came across this paper on tread depth. (Sorry, but it's in 6 parts.)

I doubt if I can find the info about the 5% directionality thing. If I remember right, this was an report written for company distribution and was never published to the outside world.


I've seen another article/study discussing how much wet performance falls off after 4/32". I think it was European, because they used millimeters as the unit of measurement for tread depth. A good argument for not taking your tires right down to the wear bars before replacing them.

I'm pretty sure I've read a tire rack article where they reversed the rotating direction of directional tires on a wet track and couldn't notice the difference. I don't doubt that directionality itself is a minor advantage. But I would like to see a test that compares the wet performance and hydroplane resistance of a tire with large, open lateral channels on the outer tread blocks compared to a tire where the tread blocks are closed up.

 

[rpn453]

Originally Posted By: PandaBear
Good article. It seems like putting the best tires on the front actually give you a slight oversteer rather than puttting in the rear and give you a lot of understeer. This on a RWD car, so FWD will be even more important to put the best tires on the front.


How did you come to that conclusion after reading the article?

"Some members of the scientific community have known for many years (at least from 1970) that the best rubber always should be on the rear wheels of passenger cars, to provide for stability under wet-road conditions. See, for example, reference (9). In 1982 the Tire Industry Safety Council stated "if selecting only a pair of replacement tires ... put the two new tires on the rear wheels for better handling" (10). More recently, the Tire Industry Associaton, in recommending that, when only two tires are replaced, the two new tires should be on the rear, included the phrase "...to prevent an oversteer condition or loss of vehicle stability..." (11). The Rubber Manufacturers Association recommends that "...newer tires should be installed on the rear axle unless the new replacement tires are of a lower speed rating..." (12). This caveat takes into account that the lower-speed rated tires will have lower critical characteristics than the higher-speed tires. The fundamental consideration is to have the tires with the best traction and lateral stiffness properties on the rear."

 

[Westerly]

Car is a 1996 VW Golf GL 2L engine.


As the subsequent posters have mentioned there is a stabilizer rib connecting the edge blocks together (it is not the wear bar either) recessed within the edge blocks .

so, 8k miles....
Tires have been perfectly cared for and their is no alignment problem, should SEARS cover these tires under the regualr tread wear warranty. It is astonishing to believe that this should wear down to a flat surface, due to water evacuation, correct?

 

[Westerly]

Good picture that is very close to the style of set up that my tires have (except the bar is longer) and indeed the edge blocks are just about completely worn down. Notice in your pic you CAN see the WEAR BAR further down from the support rib you point out. So it is clear that they are not one in the same.

 

[Westerly]

Home is Augusta Maine, although I am working in South Carolina right now.

So do you think that I should ignore the wear and just use them as is again the center three sipes have plenty of life left as you would expect.

 

[eljefino]

You mostly likley have to ride your tire until it's 2/32" to cash in on the treadwear warranty.

They could have stuck a harder compound under the soft outer, so your wear may not be linear.

They could just feel like being jerks, and want you to drive until you're almost unsafe, before giving you some prorated money off your next set.

 

[CapriRacer]

Originally Posted By: Westerly


........Tires have been perfectly cared for and their is no alignment problem, should SEARS cover these tires under the regualr tread wear warranty. It is astonishing to believe that this should wear down to a flat surface, due to water evacuation, correct?



a) There is still plenty of tread left, so the tires aren't worn out - which is where the tread wear warranty would kick in.
b) The issue is strictly about the way it looks - and after 8K miles, Sears probably isn't going to "see" this the same way you do. If there aren't any performance differences noted, then it's hard to imagine there could be a compelling argument that could be presented to Sears. Even if there were, it's been 8K miles, and unless the tires are falling apart, this isn't a "warranty" situation, and I think Sears would clearly understand that.

The groove that you mentioned that disappeared probably contributed so little to water evacuation, that even test equipment couldn't measure the difference. The tread wear probably contributed more to a loss of wet traction than that little groove. (I guess that means I disagree with eljefino - I don't think there is any performance issue!)

So if I were you, I'd just continue driving on them and just be aware that as the tire wear, the wet traction is going to decrease.

BTW, you should be aware that certain parts of the Carolinas use a lot of sand in their asphalt mix, and that makes tires more prone to wet traction problems - some more than others. In this situation, tread compound starts to play an increasingly larger role in wet traction - especially compared to hydroplaning resistance that is mostly a pattern issue. This is part of the problem in trying to compare tires - this type of situation will cause reversals in comparisons - and that's why folks should take Tire Rack's tests with a grain of salt.

Tire Rack doesn't use much water when they do wet traction testing, so it tends to emphasize tread compound. Add more water and the test results would change. Unfortunately, Tire Rack is taking an "Indiana" approach to this - "This is the way we've always done it, and we aren't going to change".

 

[Westerly]

Thanks for the very detailed explaination you posted .

I have to agree with you that the amount of water evacuation contributed to the tire from that outer edge sipe is minimal and I will simply keep driving on them without returning to Sears and inquiring about a warranty claim. It is completely true that the tread wear indicator easily visible through the inner three sipes and is far from being worn down to the bar. According to it there is plenty of tread life left.

Again I really appreciated the technical explaination in such a way that even a layman could comprehend it.