Checkswrecks said:
Found where I'd dumped the data and it's in Post # 75 of this very thread! You can go there to see the profiles of the respective wheel flanges and some data. As related by EricV, Tombstone, and others (includes me) handling is not an issue.
http://www.yamahasupertenere.com/index.php?topic=16401.75
The technical reason why car tires will work is that the bead dimensions of the wheels are only 5mm different. The 5mm missing from the MC rim is from a dimension which assures a car tire will not unseat the bead when pressure is lost. A LOT of testing is involved in getting products to meet NHTSA and international standards. This is not to say that a car tire WILL unseat on a MC with low pressure, just that there are no known test results which show how the missing 5mm will affect the bead's ability to either retain or prevent unseating.
So the two bottom lines that I see are:
(1) Using a CT involves an assumed risk, which everybody running CTs is already extremely aware of.
(2) If using a CT on a MC wheel, then do not to let the air pressure get low.
I've seen that before, from the engineer friend of mine that wrote it all up. {side note, he was running a CT on his Wing because of concerns over the load limits and heat. He later changed back to a moto tire when he stopped running two up loaded for rally riding and was just poking around more.}
What's not really discussed is that rubber molds to the shape of the rim and that the CT sits deeper on the bead area on a moto wheel. I have personally experienced a flat, (non-run flat), CT on the bike at various speeds a few times. You need to pay a bit more attention to the symptoms of low pressure/no pressure, but it becomes apparent as a weave. Not severe and there was no danger of the tire coming off the wheel in my personal experiences. Or any loss of control. I know of several others in the FJR Darksider group that have experienced flats and none felt things were scary, just slowed down, dealt with the flat or in one case, rode on the flat tire until they got home. That tire was toast, having inside side wall damage from the extended running w/o pressure.
My personal option in mounting a CT to a moto wheel, with the 205/50-17 size used on the FJR, is that it's simply not coming off unless you take it off. It's a good bit of effort to get it on in the first place, though seasoned tire changers argue it's no worse than heavy sidewall cruiser tires.
Worth mentioning here is the dynamic that occurs when you lean the bike with a CT mounted. At lower lean levels the tire deforms into an eliptical shape, with all of the tread staying on the ground. When you lean far enough over to exceed the ability of the carcass to deform, a couple of things happen simultaneously: The tire goes back to a round shape, the outside of the tread lifts up and this raises the back of the bike. This is important to understand because at this exact moment, you would expect to feel resistance to turn in. You don't, because as the bike rear lifts, that steepens the rake and quickens turn in, in actual effect, canceling out the increased resistance to turn in when the tire transitions from elliptical to round. None of this is felt by the rider. Just smooth turn in all the way over.
It's still possible to drag pegs, but most riders that go DS aren't riders that drag pegs to begin with. Nothing dramatic occurs when you ride the bike hard, aside from accelerated wear to the edge of the tread. More normal, or shall we say, less aggressive riding results in typically very even tread wear accros the tire. I was getting 40k from CTs running all season tires with tread wear ratings in the 400 range.
I look forward to seeing what kind of tread wear sallydog gets. Too bad there isn't a broader selection in this size. I have already investigated the possibility of running a 205/50-17 tire, but it's not possible to do this on a wheel wide enough for that tire and I personally am not comfortable running the tire on a narrower rim than it's rated for. This new tire is rated to fit the rim width of the Super Ten. Hope it wears well.