At 06:05 PM 6/17/04 -0500, TJ Tryon, Jr. wrote:
>Anyone have any issues with tubes in tubeless tires (heat or
>cupping)? Any good methods to seal up spoked wheels to be able to run
>tubeless?
>....
I nearly missed this one, as a change of subject on the fly.
I have two concerns for using tubes in tubless tires. The first is that
tubes increase rolling resistance and heating in a few different ways.
If the tube sticks to the inside of the tire, then it effectively increases
the thickness of the tire carcass, which makes it a little stiffer. This
can cause a harsher ride. It also leads to heat buildup in the carcass
because of increased flexing of all of the rubber parts combined, and
because the overall thickness of the rubber is greater, which makes for a
longer thermal path for heat dissipation. If the tube can move or squirm a
little in contact with the inside of the tire, then the friction from this
motion will also generate more heat. All of the heat being generated
eventually has to find its way to the outside, including the heat from the
tube, which will have a longer escape path than anything else. This is why
the tire must run a little hotter when using a tube.
By the physical laws of energy conservation, the excess heat is being
generated by consuming mechanical energy. This means the tire will have a
higher rolling resistance, and you will be losing a little on fuel mileage.
An even greater concern may be the internal surface texture of the tubless
tire. Tube type tires should be very nearly perfectly smooth on the inside
where they contact the tube. Tubless tires commonly have a grid of molding
ridges on the inside, looking like a rectangular pattern of very narrow but
slightly raised ridges. It doesn't take much of an obstruction inside of a
tire to destroy a tube. In some cases just leaving a paper sticker inside
of the tire can be enough to cut through a tube in a few hundred miles of
normal travel. A sticker with a small wrinkle is almost guaranteed to ruin
a tube. I suspect that the molding grid pattern inside of a tubless type
tire can equally do nasty things to a tube.
Check this:
http://mgaguru.com/ak/pic1/1-12.htm
http://mgaguru.com/ak/pic1/1-13.htm
http://mgaguru.com/ak/pic1/1-14.htm
These new tires and tubes only made it about 200 miles from north Texas
before the first tube gave out in Oklahoma. It was most likely caused by a
crease in an oversize tube, but there were also paper stickers with
wrinkles found still attached inside of the new wire wheels. This was
followed by an order for a next day air shipment to Casper, Wyoming, for
new tubes and some wheel taping kits.
A problem with many classic cars is that they may not be driven much. If
it takes you a few years to acrue 500 miles on your car, then you may not
immediately associate a cut tube with the internal surface texture of the
tubless tire. Also a few years later may be rather out of bounds timewise
for acting on a warrantee problem with the shop that installed your tires.
Given any choice at all, I would never use tubes in tubless tires. For
wire wheels I would go to great pains if necessary to seal the spoke holes
to allow running tubeless.
$.03,
Barney Gaylord
1958 MGA with an attitude
http://MGAguru.com
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