[Hanno Spoelstra]

Originally posted by Mike Timoshyk
Thanks for the advice Hanno, yes I will be careful.

Mike, while sipping on your wine make sure to read Richard Notton's experience fitting Simex ST24 Trak Grip tyres to CMP rims back in May 1999. Eight years later we have learned it is not the bead angle, but the larger rim diameter which makes fitting US tires to British rims difficult, but the process he describes should give you an idea of what you could be about to undertake:

I've posted this info piecemeal to interested individuals previously but
this is just the forum now to spread it further, it wont be short,
please bear with me.

(...)

British v Canadian rims and fitting.
Its a bit incredible that we went to war with two identically defined
tyre sizes that are actually different, all is not lost. The difference
as far as I can determine is the tyre bead angle, everything except the
Canadian is a 5º bead (to the horizontal or axle line), the Canadian
tyres are 0º, theoretically this makes the Brit ones easier to get off
as they become sloppy on the rims with the smallest movement away from
the rim edge.

We have heard the tales of rim machining to ease the current types onto
Canadian rims and people shaving off the inner lip of the bead with a
utility knife, but its not really needed, the bead on modern tyres seems
to be quite flexible enough to fit but it is a struggle. Here's how we
have done it several times over on a F15 with various current
manufacture 9.00x16's, let me stress its our way and I am not advocating
or recommending the method which has its dangers if extreme care is not
taken as I hope will be patently obvious.

Once on, the 5º bead angle tyres WILL need a hydraulic truck sized, four
arm bead pusher-offer of substantial grunt to remove them again, you
will never get them off at home.

You need an extra pair of understanding, strong, competent hands, don't
for one moment think wife/girlfriend/lad next door can lend a hand when
needed.

Clean, shot-blasted, painted rims are an essential starting point, just
getting the tube and flap in a new tyre is difficult, the beads are
always sprung together, whichever way you seem to fit these the flap
hole, valve, or both, always seem to be pointing the wrong way no matter
how hard you try to deduce where they are going to end up, the flap
often gets slightly too far round and needs taking out to stop it
pulling the valve sideways.

You need a lot of rubber lubricant - washing-up liquid contains salt and
will rust the rim, Vaseline/petroleum jelly rots rubber, we have used
Hellerine - a commercial rubber lubricant used in the electronic
industry for fitting rubber sleeves on wiring, its made by Hellerman;
this stuff is thicker than 90EP and twice as slippery. You will find a
air impact wrench almost vital for spinning the split rim nuts on and
off unless you happen to be Mr Universe. You will get very hot, very
angry and totally filthy.

Get the tube in and give it a little air, valve core removed, to open
the beads and see where the valve settles, get plenty of lube up the
inside of the bead for at least an inch, struggle with the flap and get
it all in then add a puff of air again and see all is sensibly lined up,
it probably wont be too well.

Really, really lube the bead; really lube the whole of both the inner
rim faces that form the well right out to and up the rim edge. Lots.

Put a long brass extention on the valve, it will disappear if you don't,
place the tyre on the inside rim as square as possible, it will only
just sit on it, put the outside rim on and start the two long rim studs,
pull them down enough to start all the rim nuts by nearly half depth.
Don't over-do it you WILL pinch the flap and tube somewhere.

Put a _little_ puff of air in, just enough to make the tube take shape,
and with a mirror and a bit of flat wood inspect between the rims and
encourage the flap, by pushing with the wood, to centralise itself and
go up into the tyre a bit, but don't over-do it as the flap will pop out
elsewhere.

This bit is POTENTIALLY LETHAL and intrinsically UNSAFE - BE WARNED.

Ensure you're happy that the two long studs have a sensible amount of
thread engaged and all the rest have at least two or three turns on
them, all should be just bearing on their seats. With the valve core
still out to allow instant deflation, GINGERLY, inflate in short bursts
until you see the beads start to move up and out along the rim, it takes
a moment, give it time and NO MORE THAN 10 -15 psi, as soon as this
happens remove the inflator immediately.

The rims will likely now fall together when it deflates which is a good
sign, to be certain, lever them apart and inspect with the mirror to see
the flap is now properly up in the tyre and will not get trapped
anywhere. Torque the split rim nuts down fully and inflate, the beads
will pop out fully onto the rim edges at about 20 - 25 psi, remove the
extention piece and fit the core, bring the tyre up to about 50 psi and
check the side wall concentricity rings, a few hearty thumps with a
hide-faced mallet usually corrects any slight anomalies.

If you can't immediately visualise what I've described and how to
achieve it, then I make the only recommendation herein, which is that
you should NOT be doing this at all.

Richard
(Southampton UK)

Source: http://groups.yahoo.com/group/CMP/message/70 (yes, I'm a search guru )