A customer from Nara Prefecture came in
asking me to install Challenge cyclocross tubeless tires.
Not shown in the photo above,
but they wanted me to install "Saikain" (bead tape) on a wheel with a DT XR331 rim,
and "Grifo" (tire) on the front wheel with an Iron Cross rim and rear wheel with a Crest rim shown in the photo above.
The bead diameter on this Challenge tire is remarkably small—
to the point where you'd wonder if the dimensions were wrong.
Originally, Challenge clincher tires are what you'd call "open tubulars"—
an intermediate product from tubular tire manufacturing
with the bead attached without stitching.
Other tires with similar specs include Vittoria Corsa variants
and Veloflex clincher tires.
In their standalone state, these tires don't have
the curvature they'll have when mounted on a rim,
instead looking flat like kombu seaweed.
The photo above shows the tubeless tire with air in it,
but when deflated, the tire tread
looks completely flat.
The all-black model might not flatten out as noticeably
since it has rubber on the sidewalls, which reduces flexibility.
These tires are abnormally difficult to install,
but the pattern is: narrower rim width makes it harder,
deeper central rim depression makes it harder,
taller rim bead hooks make it harder.
All four wheels brought in were ones I'd built,
and the first XR331 gave me considerable trouble,
but once I got the technique down, the second one installed without taking much time.
I can't entirely rule out individual tire variation, though.
It's almost never the case that I need two tire levers to install a tire.
Next I tackled the Iron Cross front wheel,
but my wrist tendons started acting up,
so I asked to keep the Stans front and rear rims as a deposit job.
The Iron Cross gave me the most trouble,
but the final Crest seated relatively easily.
This isn't due to tire variation—
I can say with certainty it's due to rim dimensions.
With these Challenge tires—both Saikain and Grifo—
the bead seating under pressure wasn't ideal.
In the photo above, you can see the black bead line
below the amber-colored tire sidewall,
and the tire is fully seated,
but in this section it hasn't seated.
In another spot, I placed a reference tape
at the apparent boundary between rim and tire.
When the tire seats from there, it looks like this
The tire's specified maximum pressure is 2.5 bar,
so ideally I want to get it to seat by then.
By the way, the Iron Cross is a cyclocross rim
with a specified maximum pressure of 3.1 bar,
so it's basically unusable for disc road bikes.
For lifting the tire bead, I use Maruni bead wax (ビードワックス) rather than soapy water,
but to begin with, Maruni bead wax has the purpose
of smoothing tire installation
in addition to assisting with bead lift.
With this Iron Cross, it was the first time
I used bead wax as an aid for tire installation itself.
The height of the "bead seated" indicator band on the Challenge tire
varies somewhat randomly depending on position,
but when I measured with calipers the distance from the lowest point of the black band
to the step in tire tread after bead seating,
it was, as you'd expect, the same.
While I'm on the subject of calipers,
the Stans Crest rim brought in this time
is from before the current offset-rim Crest MK4 model—
it's earlier than the Crest MK3.
So while it's just called "Crest," internally it's not the second generation MK2 or anything—
the progression is original Crest → MK3 → MK4.
The internal widths of these rims are: original at 21.0mm,
MK3 at 23.0mm, and MK4 at 25.0mm—
getting progressively wider.
There's also a Crest S1 rim, but
it has the same dimensions as the Crest MK3
and is about 70g heavier—
it's the budget-friendly model.
With the original Crest's 21mm internal width,
if you install an IRC Sirac CX Tubeless 32C,
at around 1.8 bar on a new tire
the tire sidewall width becomes about 33.4mm—
exceeding 33mm, which would violate rules in some race categories.
Even with this original Crest + Grifo 33C combination,
it measured about 34.5mm.
I've told the customer about this,
and apparently there's no issue with their category.
Incidentally, the Iron Cross has a 20mm internal width,
but even with an IRC Sirac CX Tubeless 32C installed,
the tire width doesn't exceed 33C (at least not on new tires).
Stans' MTB rims have bead hooks with remarkably short
internal protrusions—almost hookless rims even before the hookless craze—
and since the rim barely constrains tire shape,
tires tend to run wider relative to internal width.
So there's more difference between the Crest (MTB) at 21mm
and the Iron Cross (cyclocross) at 20mm
than the numbers alone suggest.
Let me wrap up the title.
When the customer brought the wheels in,
they gave me persimmons.
I mentioned I'd write: "The neighbor prefecture customer is the one who always gives persimmons,"
when I handed over the Stans front and rear rims,
and they said, "I brought them again today,"
and gave me more persimmons (plus rice too).
asking me to install Challenge cyclocross tubeless tires.
Not shown in the photo above,
but they wanted me to install "Saikain" (bead tape) on a wheel with a DT XR331 rim,
and "Grifo" (tire) on the front wheel with an Iron Cross rim and rear wheel with a Crest rim shown in the photo above.
The bead diameter on this Challenge tire is remarkably small—
to the point where you'd wonder if the dimensions were wrong.
Originally, Challenge clincher tires are what you'd call "open tubulars"—
an intermediate product from tubular tire manufacturing
with the bead attached without stitching.
Other tires with similar specs include Vittoria Corsa variants
and Veloflex clincher tires.
In their standalone state, these tires don't have
the curvature they'll have when mounted on a rim,
instead looking flat like kombu seaweed.
The photo above shows the tubeless tire with air in it,
but when deflated, the tire tread
looks completely flat.
The all-black model might not flatten out as noticeably
since it has rubber on the sidewalls, which reduces flexibility.
These tires are abnormally difficult to install,
but the pattern is: narrower rim width makes it harder,
deeper central rim depression makes it harder,
taller rim bead hooks make it harder.
All four wheels brought in were ones I'd built,
and the first XR331 gave me considerable trouble,
but once I got the technique down, the second one installed without taking much time.
I can't entirely rule out individual tire variation, though.
It's almost never the case that I need two tire levers to install a tire.
Next I tackled the Iron Cross front wheel,
but my wrist tendons started acting up,
so I asked to keep the Stans front and rear rims as a deposit job.
The Iron Cross gave me the most trouble,
but the final Crest seated relatively easily.
This isn't due to tire variation—
I can say with certainty it's due to rim dimensions.
With these Challenge tires—both Saikain and Grifo—
the bead seating under pressure wasn't ideal.
In the photo above, you can see the black bead line
below the amber-colored tire sidewall,
and the tire is fully seated,
but in this section it hasn't seated.
In another spot, I placed a reference tape
at the apparent boundary between rim and tire.
When the tire seats from there, it looks like this
The tire's specified maximum pressure is 2.5 bar,
so ideally I want to get it to seat by then.
By the way, the Iron Cross is a cyclocross rim
with a specified maximum pressure of 3.1 bar,
so it's basically unusable for disc road bikes.
For lifting the tire bead, I use Maruni bead wax (ビードワックス) rather than soapy water,
but to begin with, Maruni bead wax has the purpose
of smoothing tire installation
in addition to assisting with bead lift.
With this Iron Cross, it was the first time
I used bead wax as an aid for tire installation itself.
The height of the "bead seated" indicator band on the Challenge tire
varies somewhat randomly depending on position,
but when I measured with calipers the distance from the lowest point of the black band
to the step in tire tread after bead seating,
it was, as you'd expect, the same.
While I'm on the subject of calipers,
the Stans Crest rim brought in this time
is from before the current offset-rim Crest MK4 model—
it's earlier than the Crest MK3.
So while it's just called "Crest," internally it's not the second generation MK2 or anything—
the progression is original Crest → MK3 → MK4.
The internal widths of these rims are: original at 21.0mm,
MK3 at 23.0mm, and MK4 at 25.0mm—
getting progressively wider.
There's also a Crest S1 rim, but
it has the same dimensions as the Crest MK3
and is about 70g heavier—
it's the budget-friendly model.
With the original Crest's 21mm internal width,
if you install an IRC Sirac CX Tubeless 32C,
at around 1.8 bar on a new tire
the tire sidewall width becomes about 33.4mm—
exceeding 33mm, which would violate rules in some race categories.
Even with this original Crest + Grifo 33C combination,
it measured about 34.5mm.
I've told the customer about this,
and apparently there's no issue with their category.
Incidentally, the Iron Cross has a 20mm internal width,
but even with an IRC Sirac CX Tubeless 32C installed,
the tire width doesn't exceed 33C (at least not on new tires).
Stans' MTB rims have bead hooks with remarkably short
internal protrusions—almost hookless rims even before the hookless craze—
and since the rim barely constrains tire shape,
tires tend to run wider relative to internal width.
So there's more difference between the Crest (MTB) at 21mm
and the Iron Cross (cyclocross) at 20mm
than the numbers alone suggest.
Let me wrap up the title.
When the customer brought the wheels in,
they gave me persimmons.
I mentioned I'd write: "The neighbor prefecture customer is the one who always gives persimmons,"
when I handed over the Stans front and rear rims,
and they said, "I brought them again today,"
and gave me more persimmons (plus rice too).