Shinko 777 My tire is separating!

[SpencerPJ]

5 hours ago, Squidley said:

from I believe Dennis Kirk, I would have to try and research that out. I had my local Yamaha dealer install and balance it. So unfortunately it appears that I have to do a lot of legwork and time to get it to the point where they will look at it and determine if it's a warranty issue. I'm not sure I'm going to waste my time to do this on a $100 tire. I believe that I'm just going to try a different brand, perhaps something that I haven't tried before like a Pirelli. If i do decide to spend the time jumping through the hoops, I'll let y'all know what becomes of it.

Figures they would say that, but I kinda understand.  Something I've learned, I have a local cycle shop that mounts my tires, but I also order through them.  They easily match online prices, and they cut me a break on mounting because I bought through them.  I like better to do this, as I tell them do NOT mount a tire over a year old on it, plus now with your circumstance, warranty work would play out easier.  Just a thought, again happy you caught it. 

[saddlebum]

19 hours ago, Squidley said:

I live outside of Houston Texas and I ride all year long.

I have been noticing the cupping and could feel it buzzing in the handlebars. It just happened that the bad spot was right in plain view at the perfect angle for it to really catch my eye yesterday morning after I got off the bike.

 

 

Now I'm going to fill y'all in on something here, I run darkside as I have a 15" Nexen car tire on the back of my RSV. I've been running it for about 2 years. Now I know some of you are shaking your heads as you would never think of doing it, and that's cool, I just wanted to run one for myself for an extended period as a lot of my riding these days is 1 up and on the freeway. I'm fairly confident that running the car tire on the back should not have made any difference on this tire. I still get into the twisties, and even though my chicken strips aren't to the complete edge of the tire, I still ride it how I want to. The only thing I wonder about is the Shinko on the front is a bias tire and the back is a radial, I've heard about not mixing the 2, but not sure what the "side effects" are with running it this way. 

The reason radials and bias are not to be mixed and this applies to all vehicles with the exception of tandem axle highway tractors. bias and radials flex differently. A bias has a stiffer side wall which A) allows for  little to no side to side flexing or side to side rolling action ( B) The foot print which contacts the road is smaller than that of a radilal. (C)  the tread on a bias due to the stiffer side wall has  a tendency to cup in the middle of the foot print reducing even more the amount of rubber contacting the road.  As well because of the stiffer side wall this cupping action increases and decreases as the down ward pressure on the tire while moving down the road increase and decreases all of which results in more tread squirm in the contact patch increasing tread temperatures.

A radial on the other hand flexes more in the side wall Which A) allows for more side to side roll and B) creates a larger foot print and (C) because of the more flexible side wall and stiffer tread on the radial there is no cupping in the middle of the footprint allowing for more road contact with less squirm in the contact area and therefore better heat handling of the tire. Many will remember When radials first came out the two most immediate and  notable features of the radial was longer tread life and better traction, this was due to the differences noted above.

So now you come to to the mixing issue. Because of the difference in the way the two tires flex and the radical difference in the amount of rubber contacting the road When this tires were mixed on a four wheel vehicle, Handling became an issue even to the point of being dangerous because while going into the curve when the radial was maintaining a flat contact patch on the road and flexing in side wall due to the g forces the bias was trying to maintain those same  forces at the contact patch creating more heat and this force increased since due to the radials ability to absorb most of it bias was forced int dealing with more than if all four tires were bias and due to the difference in one set of tires handling those g forces one way the other handling it another way you ended up with handling issues. The only vehicle that was not effected by this to noticable extend was a tandem axle highway tractor and is why it is legal to have radials on the steer axle while running bias on the eight drive wheels.

So now getting back to your bike, here I am making an educated assumption based on my years as a Mechanic and dealing with all kinds of tire issues. My thoughts are that based on the above information and the fact that the scrub pattern on the tire in the second picture appears to be more porous than normal, I am thinking that that tire was running higher than intended tread temperatures for a bis tire  due to the mixing of construction types resulting in the tread separation. When we have had an abnormal run of issues on tires in the truck fleets we would set this tires aside and either have a tire rep come out or send the lot to the manufacture to be analyzed as to why a particular issue suddenly started to occur. It may not be a bad idea to see if you can send that tire in so the can determine the cause of the issue. Just don't mention the mixing of tires, let them figure out why it happened If you offer any theory or darkside info on your part they will just jump to conclusions instead of actually looking into the root cause.   

Edited July 27, 2021 by saddlebum

[saddlebum]

17 hours ago, SpencerPJ said:

On auto tires, Firestone claims that is normal and acceptable. I agree with you, just sharing my experience with car tires.  Firestone says sidewall cracks are a problem, but the rubber between the treads is very thin and does not impact the treads stuck to the belts.  

Generally on vehicles other than motorcycles we are only concerned with the cracks, in the groves between the lugs, if we can pry the crack open enough to see the cords. If we are unable to see any cord material we let it go. Now on a motorcycle I am not sure I would leave it go to that point but at the same time If they are only fine hair line cracks with little or no depth I would not be to concerned yet. As stated by Firestone about the rubber between the treads being very thin and does not impact the treads stuck to the belts, is true up to a point. But once the crack penetrates  to the cord you  now have a point were water can get to the cords. If steel cords they begin to rust and eventually fail and you get a bulge in your tire or you start to work towards a tread separation. Even a partial puncture were the foreign object only  penetrates to the cord you also run the risk of moisture penetration we usually seal those holes after removing the object provide no serious damage has begun. Another example of foreign penetration is what is referred to as a stone bore. This were a stone or small pebble gets lodged in the tread or sipping and over time bores its way into the the casing and eventually allow for moisture to attack the cord material in the tire resulting in tread failure of some sort. 

TIP: every once in a while go around your tires and pick out any stones etc.   Truckers are so aware of this that very often while we are working on their trucks you will see them go over their tires while they are waiting with a small screwdriver picking out any and all pebbles lodged in the tires. For them its  not just a safety issue but at $500 or more per tire it becomes a cost factor as well.

Edited July 27, 2021 by saddlebum

[videoarizona]

Good information! Learning experience for sure. Hopefully Squidley, you will follow through with the tire and let Shinko deal with it... If only to find out "why".

I was one of the first on this forum to run Shinko tires on my scoot. I was quite impressed with them and have had no issues at all on both bikes. Of course, knowing the technology got it's start in Yokohama racing, I knew they would be good tires if Shinko kept the quality up. 

Crossing fingers that they have...do... And continue to do so..

D

[Leland]

After Mr. Squid's Shinko experience, I decided to check mine.  I have the Shinko 777HD, 130/90B-16 Front and 150/90B-15 Rear.  The front tire is rated for a maximum air pressure of 49#.  I started out running about 45#, but found it squirrely at highway speeds.  Kept reducing the pressure and finally decided that the Yamaha factory spec of 36# did produce the best results.  However, I have already decided to go back to the stock 150/80-16 size, as others have stated more stable operation at speed.  I only have 4,655 miles on these tires.  No trip over 200 miles, never pulled the trailer with these, only one-up and the majority of my riding is in the mountain twisties - not interstate droning.  The front tire has a good 3/32nd of tread left.  BUT!  The rear tire is down to the wear bars.  Worst life of any tire that I have ever run.  They are rated at max pressure of 42#, I have been running 40#.  I had previously gotten about 8K max out of the stock Bridgestone, Dunlop E3s and Michelin II (130 front in the II).  These Shinko's are also the first time that my front tire isn't at least as worn down as the rear.  Given my rear tire experience, the handling of the 130 front tire and Squidley's stock front size experience, No more Stinkos for me.    

[RDawson]

4 hours ago, Leland said:

These Shinko's are also the first time that my front tire isn't at least as worn down as the rear.

No matter what brand I ran I always wore out two rears to one front until I went darkside. Now it’s almost two fronts to one rear. 

[Leland]

I know that you are in the majority with your statement, but that is typically not my experience. My fronts are usually just as worn as my rears. I only got 10K out of one set of E3's but Gawd were they noisy.  I also never achieve the gas mileage that others get. I'm doing good if I can get 35 mpg. But, I always consider myself fortunate because I don't have the whine.