The sae specs for automotive tire beads, rim and tire, are different from the sae specs for motorcycle tire beads. Simply put, a car tire doesn't seat it's bead correctly onto a motorcycle rim.

This does not mean failure must result. I have not actually heard of it happening. Just that the two pieces do not actually fit together correctly.

I'm not certain this drawing is in fact correct with regards to the sae specs, but it does look about correct.



Again, do not misunderstand me. I am not anti- car tire for motorcycles. Just pointing out that while the beads seem to work just fine, the interface is not "correct".

 

Thank you, that was what I was referring to in my comments about bead mis-match.

I read the same article somewhere recently but couldn't find it in my browser history.

 

Good posts!

 

Perhaps I misspoke on my terminology. Your videos demonstrate exactly what I was talking about. In a lean, the car tire rotates on the outside edge of the tread and is no longer flat as it is when going straight. It is riding on the outside edge of the tread, in a manner that it would never do if mounted in a car.

In your own videos, the contact patch of the CT is 1/3 to 1/2 in a turn compared to going straight. A MT has the same contact patch at any lean angle because it is curved rather than flat.

 

Your correct, a CT AND MC tire have the same contact in a curve. But the CT has 2-3 times as much contact in the straights. Therefore better traction and braking.

 

Question that comes to mind...what is to prevent some enterprising individual from designing and marketing motorcycle wheels with bead seats made specifically for car tire applications? Seems like there is an opportunity here, unless there is some DOT regulation or other red tape, liability issues, etc. preventing such an endeavour. Wonder if it has been done. Theres enough CNC machinery and talent out there to get this done. Group buy? Heck, I'd get in on that!
Excuse me if this has been discussed, but I seldom frequent this thread as it seems like too many pages of dead horse beating. But I do like the prospect of getting better traction, better stopping power and more mileage out of our touring bike rear tires. Money saved could pay for a new wheel soon enough.

Edit: Really just thinking out loud here. I've thought of this as well as a few other design changes, such as an interchangable cushdrive pulley to easily change final drives, as well as an adjustable length swingarm to add to the versatility and ease of belt usage. I'm always thinking these bikes can be improved on, quite easily.

 

Wow, real live data, thoughtfully presented. That is the first time I have ever seen such a thing. My hat is off to you.

That said, as you said it does not mean the CT will fail and no one has ever heard of it happening so I will continue to enjoy the benefits of the darkside.

Once again, very good post.

 

Foxtrapper, many thanks for the diagram. Pushing forward the boundaries of understanding!

 

Rider Magazine did a story on this topic a few months back... Google: "Tales From the Dark Side: Putting Car Tires on Motorcycles"

Seems well thought out

 

But that seems backwards to me. I believe that is one of the design tenants of a rounded MT, so that the contact patch remains relatively the same at any lean angle. If anything, I would think that you would want MORE traction in a curve not suddenly less. Seems you'd have to keep very mindful that this awesome traction you have going straight is going to be much less in the curve.

Isn't this a bit disconcerting, especially in the wet?