Put bluntly, I don't believe it. I'd like to see some proof that this happened even one time. Warranty rumors are always rampant, but reality is quite a different thing. You'll get the same tripe about oil, filters, you name it. One thing is for sure, it keeps a lot of people coming back to the dealership for replacement parts. And for that, the rumors work like a charm.
Of course your Kenda rear tire wears out in the middle. It is simple physics. The OEM tire is 2 ply sidewall and 2 ply tread. On a tire this wide you have quite a tread span with not enough support. 2 plies are not strong enough to overcome both tire pressure and centrifugal force at speed. The center of the tire bulges out and you get center tire wear. You also have to realize that the wear area is all that is touching the pavement at freeway speeds.
The car tires I've been running (since my 1st Kenda wore out in the middle) have the same 2 ply sidewall, but 4 plies in the tread area. This is a picture of my Toyo Proxes that I then replaced with a Falken tire. As you can see, at 18K+ it is worn out but it has a nice, even wear pattern. Which means I had the entire tire tread in contact with the pavement at freeway speeds with 30-32 PSI.
I was concerened about weight also. But I should not have been. This Toyo weighed less brand new than my Kenda did when it was worn out!
So why does a better tire cost less? Because volume always costs less. The Kenda is only used by one vehicle in the entire world, a few thousand Spyders. This is Extremely small volume. How much competition is there? Really zero as there isn't anyone else making a similar, 2 ply tread tire.
How many Toyo, Falken, Michelin tires are sold each year? A few hundred million! How much competition is there? A lot! So these companies are continually upgrading and improving their tires while at the same time keeping prices as low as they can to compete.
So, this Toyo tire cost less, lasted longer, gave me a better traction footprint at speed, weighed less and had better wet/dry traction than the Kenda. And people still ask me why I'm running a car tire on my Spyder. The answer is, the stock tire
is a car tire. I just put a
BETTER car tire on for less money. I just cannot fathom what people see as the downside to this.... :dontknow:
I realize that many dealers will not mount a non-Kenda tire and you can't blame them. If I were a dealer I wouldn't do it either. And if you call a tire shop and tell them you want a motorcycle tire mounted they will say no. But it isn't a motorcycle tire. It's a car tire on a car rim. They may not be able to balance it because it won't mount to their balance machine. But there are ways around this as well. The real kicker is for those who cannot dismount and mount their rear wheel. Then you have to take it to the dealer and you're usually then stuck with a Kenda.
I suppose it sounds like I'm trying to tell everyone to put a car tire on their Spyder, which really is not what I am trying to accomplish here. I just think the facts need to be laid out on the table in every choice situation so that people can make an informed decision without all the erroneous flack that seems to accompany these things.
The Kenda is a decent tire and was specifically designed for the Spyder. Just like the seat, the exhaust, the shocks, the sway bar, the headlights, and everything else that some of us decide to upgrade.
pps: This is what 21K looked like for us 
