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Display Mesage #101900


Transitioning to the Dark Side - a Detailed Log
Written by daviddockstader on 4/2/2011 at 08:07 pm

We are not talking about the same thing. My statement was only about lean,
nothing else. I carefully specified that my statement applied to a given rider
position. Once the rider position is determined the motorcycle and rider can be
treated as if their entire mass were concentrated at the center of mass of the
system. If one imagines a line between the tire contact patches and then a line
perpendicular to this line through the center of mass, the only forces relevant
to lean are those acting on the center of mass that are perpendicular to this
line. All forces on the bike can be broken into forces perpendicular or parallel
to this line. Those parallel are balanced by the suspension, but those
perpendicular to the line must add to zero for the bike to be balanced. At this
point there are only two forces to consider: gravity and centripital.
Distribution of gravity forces are determined by the lean angle and the
centripital force is determined by the speed and radius of the curve. It is not
that tire forces are unimportant in cornering. They are obviously what makes the
bike turn, but for a given speed and a given radius for a given bike and rider,
those forces are fixed and any tire that makes the corner has to create those
forces. Force = mass X acceleration. For a given acceleration the required
force is what it is and changing tires won't change the equations.

Handling is another whole ball of wax. If your tires are distorting in an
unstable fashion and jumping around, then the driver has to go through all kinds
of contortions to compensate. Anyone who has hit a corner with a soft tire has
experienced this. As the tire jumps around both the lean angle and radius of the
turn jump around and the rider goes crazy. However, I don't think you can judge
any of this in a single still frame, other than to say that the rider looks
relaxed and riding in jeans and a T-shirt he looks pretty confident.

--- In ipcrc@yahoogroups.com, "literidr" <literidr@...> wrote:
>
> Sorry,
>
> The shape of the tire is a major factor in the ability of the tire to
negotiate a turn. When you are turning, the inside radius of the tire in
contact with the road is shorter than the outside radius of the tire, allowing
your tire to contribute to the steering ability of your bike. You can enhance
your bike's ability to steer by shifting your weight in the saddle, even
dragging a knee if you're that confident, but you have to start with the ability
of your tires to negotiate a curve and that means the shape of the tire.
Obviously, the rider in that picture was able to work with the bike to get
around the curves but as the pictures clearly showed as I looked at bikes before
him and after him (which would have limited how fast he was able to ride) he was
working harder to get the bike to do what he wanted. I've put over 200K on my
PC's now and I've been through the Dragon enough and seen pictures of me riding
through the dragon enough to know how it should handle and look. Your friend
was clearly having to work harder to get the same job done.
>
> John Handford, literidr@...
> Taylors, SC
> '90 PC "Spirit"
>
>
> --- In ipcrc@yahoogroups.com, "David" <david.dockstader@> wrote:
> >
> > I have to disagree. The lean angle for a give bike and rider position is
just a function of speed and radius of the turn. He was going fast! Anybody else
going that fast would also lean that far.
> >
> > --- In ipcrc@yahoogroups.com, "literidr" <literidr@> wrote:
> > >
> > > That photo in the Dragon is scariest of all. When you see how far over
that bike had to lean to make that curve compared to all the other bikes, you'll
realize that curves are not what those darkside tires are good at.
> > >
> > > John Handford, literidr@
> > > Taylors, SC
> > > 90 PC "Spirit"
> > >
> >
>

Message Thread for message #101900

timdearborn
3/18/2011, 02:07 am
Transitioning to the Dark Side - a Detailed Log
Purpose: I put a car tire on my back wheel 2 days ago. I hope to provide a detailed post of the experience, good and bad, in order to provide as much information as possible for those considering a similar move. Disclaimer: Riding a motor

    pgboyd
    3/18/2011, 11:35 am
    Transitioning to the Dark Side - a Detailed Log
    I plan on changing tires this weekend on Obsession, although sticking with Dunlops. As part of my science experiment I will be trying to mount my tires myself using only my Cycle Pump from BestRest and their Bead Setter gizmo:

    eleveldb
    3/18/2011, 03:40 pm
    Transitioning to the Dark Side - a Detailed Log
    I was the one who made the "knife edge" analogy soon after putting on the same tire you did. Maybe I've just gotten used to it but I don't have that sensation any more. I have had a few instances of the bike slipping a skooch on rainy

      timdearborn
      3/18/2011, 05:31 pm
      Transitioning to the Dark Side - a Detailed Log
      Bart, Thanks for the report on the Battleax. I will be looking to replace my front tire toward the end of the season and was thinking about trying one. Also appreciate the notes on your experience on cornering. The biggest concern about da

    ramauder
    3/26/2011, 12:57 pm
    Transitioning to the Dark Side - a Detailed Log
    I had the BF Goodrich mounted last week, but I have not had a chance to try it out yet since my bike is still apart while doing other maintenance/modifications. I ordered the tire from Walmart using the free ship-to-store option. Total was $9

    shotcoy
    3/27/2011, 12:29 am
    Transitioning to the Dark Side - a Detailed Log
    Tim: Thanks for the detailed report and looking forward to ongoing reports. There is little I can add, but mount the tire in warm conditions(and/or warm the tire), clean/polish the rim prior to mounting, and carefully apply your chosen tire l

    daddy_fry
    3/27/2011, 03:09 am
    Transitioning to the Dark Side - a Detailed Log
    --- In ipcrc@yahoogroups.com, "TimD" <tim@...> wrote: > > Purpose: I put a car tire on my bac

      g4321m
      3/27/2011, 03:53 pm
      Transitioning to the Dark Side - a Detailed Log
      My first impression of mounting a car tire was "why", are they crazy? But it sounds like your reason is that it offers much higher mileage than motorcycle tire do. I have always felt that motorcycle tires wear out much too soon also,

        gibinmich
        3/27/2011, 04:03 pm
        Transitioning to the Dark Side - a Detailed Log
        Can you get tires with red lines. That would be sweet! --- In ipcrc@yahoogroups.com, "Glenn" <g4321m@...>

          daddy_fry
          3/30/2011, 01:31 am
          Transitioning to the Dark Side - a Detailed Log
          > > > > Any photos of the tire mounted? > > > > thanks, > > Glenn > > You missed the great photos by KILLBOY down at the Dragon? He captured our Ohio brother's leans thru the curves that

            literidr
            3/30/2011, 04:17 pm
            Transitioning to the Dark Side - a Detailed Log
            That photo in the Dragon is scariest of all. When you see how far over that bike had to lean to make that curve compared to all the other bikes, you'll realize that curves are not what those darkside tires are good at. John Handford,

              daviddockstader
              3/31/2011, 09:45 pm
              Transitioning to the Dark Side - a Detailed Log
              I have to disagree. The lean angle for a give bike and rider position is just a function of speed and radius of the turn. He was going fast! Anybody else going that fast would also lean that far. --- In

                jim.strtr
                4/1/2011, 12:40 am
                Transitioning to the Dark Side - a Detailed Log
                Ah contrare! I am a former (very old) road racer. To lean the bike over less, all you have to do is get your butt off the seat and slide it to the inside and put all your weight on the inside foot peg. Once you do that the bike will lift up a

                  jprelock
                  4/1/2011, 12:58 am
                  Transitioning to the Dark Side - a Detailed Log
                  Well, David did say for a given rider position, but I was sort of thinking the same thing, how do you know exactly who is hanging off how far if it's only subtle? And the technique you describe works as well if you put weight on the outside p

                    jim.strtr
                    4/1/2011, 02:50 am
                    Transitioning to the Dark Side - a Detailed Log
                    Call me old fashioned, but I can't even fathom pressing down hard on the outside peg. That just sounds totally wobbly to me. But then I never was a fantastic road racer. Once I fell down a couple of times I had a vision that told me "thi

                      jprelock
                      4/1/2011, 05:30 am
                      Transitioning to the Dark Side - a Detailed Log
                      It's kind of interesting actually. Pressing down hard on the inside peg allows the bike to turn in very quickly, almost wobbly, because all your inputs are going in the same direction. Pressing down on the outside peg creates an isometric mov

                literidr
                4/1/2011, 04:43 pm
                Transitioning to the Dark Side - a Detailed Log
                Sorry, The shape of the tire is a major factor in the ability of the tire to negotiate a turn. When you are turning, the inside radius of the tire in contact with the road is shorter than the outside radius of the tire, allowing your tire

                  daviddockstader
                  4/2/2011, 08:07 pm
                  Transitioning to the Dark Side - a Detailed Log
                  We are not talking about the same thing. My statement was only about lean, nothing else. I carefully specified that my statement applied to a given rider position. Once the rider position is determined the motorcycle and rider can be treated

            shotcoy
            3/30/2011, 11:47 pm
            Transitioning to the Dark Side - a Detailed Log
            Photos available... click on "photos" on this page. Then go to " PC800 Darksider"...several pics. Dave --- In