A while back I built a front wheel with DT XR331 rim and HB-RS770 hub,
and never actually used it. I've now rebuilt it from half-competition lacing to full CX-RAY lacing.
I had to replace the rim tape and sealant. Well, actually I had no choice but to.
↑Rotor side with 4-cross CX-RAY lacing
This is a photo sent to me by a customer.
It shows the hydraulic brake caliper of a SRAM Rival setup, and
the bolt head holding the banjo fitting at the end of the brake hose is making contact
with the final crossing area of the competition-laced spokes.
The front hub doesn't have any unusually extreme dimensions,
and 28-hole 4-cross lacing isn't some exceptional way to build a wheel,
but since the contact is actually happening, something needs to be done about it.
So I decided to change the spokes to CX-RAY.
I haven't seen results yet, but if this doesn't work,
I'll have to go with 6-cross CX-RAY lacing.
As a similar issue,
with half-competition rear wheels, the spokes sometimes make contact
with the rear derailleur pulley cage when in the lowest gear.
When building the wheel, if you tap the base of the non-rotor-side spokes
with a plastic hammer to nestle them flat against the hub flange,
it almost never happens. And in that case anyway,
derailleur adjustment and bent derailleur hanger are the bigger factors.
For this current issue, the largest factor outside of the wheel itself
is the use of a 140mm rotor
(with a 160mm rotor, the caliper position would be a bit more toward the outside of the wheel),
and the customer's bike is an older GIANT TCX model
that comes stock with a 140mm rotor.
It's not that GIANT is bad,
but when I checked the 2019 model,
the TCX SLR2 uses a GIANT-made CONDUCT cable-actuated hydraulic brake,
and both rotors are 140mm.
The next model up, the TCX Advanced, uses SRAM Apex brakes with 160mm rotors front and rear.
The model above that, the TCX Advanced Pro 2, uses SRAM Rival brakes with 140mm rotors front and rear.
And at the very top, the TCX Advanced Pro 1 has SRAM Force brakes
with a 160mm rotor in front and 140mm in the rear.
This is a bit of a tangent, but that CONDUCT brake mentioned above
came out around 2017.
Due to brake power ratio considerations, it's compatible with 9000-series Dura-Ace
and its related models (like 6800), but not with R9100 Dura-Ace or R8000 Altegra.
However, the drivetrain on the 2019 TCX SLR2 (especially the brake levers)
is SRAM Apex, and the power ratio difference between SRAM brakes is
far greater than the difference between 9000 and R9100,
so if 9000 is OK and R9100 is not, then SRAM should also be incompatible. Strange.
Anyway, with a 140mm front rotor and handbuilt wheels,
you need to consider spoke-to-caliper contact as well.
Learned something new.
On a separate note, something I've come to realize anew,
or maybe just been reminded of something I already knew.
The reason I used half-competition lacing is because the XR331 is a non-offset rim.
If the rim were an RR411db (offset rim),
I've found from experience that there'd be much less left-right tension difference,
so full CX-RAY would be fine.
The XR331 is a lighter rim,
and comparing a half-competition XR331 with a full CX-RAY RR411db,
the former actually ends up lighter overall.
A full CX-RAY XR331 would be optimized for lightness,
but in my opinion, without crossing spokes on the non-rotor side,
it feels a bit "hmm..." (though I do include them).
So I cleanly removed the competition-laced spokes on the rotor side and replaced them with CX-RAY.
Then I tried to center the wheel by only tightening the CX-RAY spokes on the rotor side...
Even after tensioning the rotor-side spokes to their maximum,
I couldn't get the wheel centered.
So I had to loosen the non-rotor-side CX-RAY spokes a bit
to achieve proper centering.
But really, this is obvious in hindsight.
I'm just experiencing the flip side of the fact that half-competition lacing allows slightly lower tension
compared to full CX-RAY.
This only happens when the high-tension side is tensioned right up to its limit.
If the pre-rebuild tension state had been loose,
changing from half-competition to full CX-RAY would've let me center it
with just tightening the rotor side.
One more thing worth noting:
Whether people are copying me or arrived at this independently, I don't know,
but I sometimes see half-competition rear wheels built by others
where the builder clearly doesn't fully understand this principle—
they just built it loosely with half-competition lacing.
With those rear wheels, this phenomenon doesn't occur.
and never actually used it. I've now rebuilt it from half-competition lacing to full CX-RAY lacing.
I had to replace the rim tape and sealant. Well, actually I had no choice but to.
↑Rotor side with 4-cross CX-RAY lacing
This is a photo sent to me by a customer.
It shows the hydraulic brake caliper of a SRAM Rival setup, and
the bolt head holding the banjo fitting at the end of the brake hose is making contact
with the final crossing area of the competition-laced spokes.
The front hub doesn't have any unusually extreme dimensions,
and 28-hole 4-cross lacing isn't some exceptional way to build a wheel,
but since the contact is actually happening, something needs to be done about it.
So I decided to change the spokes to CX-RAY.
I haven't seen results yet, but if this doesn't work,
I'll have to go with 6-cross CX-RAY lacing.
As a similar issue,
with half-competition rear wheels, the spokes sometimes make contact
with the rear derailleur pulley cage when in the lowest gear.
When building the wheel, if you tap the base of the non-rotor-side spokes
with a plastic hammer to nestle them flat against the hub flange,
it almost never happens. And in that case anyway,
derailleur adjustment and bent derailleur hanger are the bigger factors.
For this current issue, the largest factor outside of the wheel itself
is the use of a 140mm rotor
(with a 160mm rotor, the caliper position would be a bit more toward the outside of the wheel),
and the customer's bike is an older GIANT TCX model
that comes stock with a 140mm rotor.
It's not that GIANT is bad,
but when I checked the 2019 model,
the TCX SLR2 uses a GIANT-made CONDUCT cable-actuated hydraulic brake,
and both rotors are 140mm.
The next model up, the TCX Advanced, uses SRAM Apex brakes with 160mm rotors front and rear.
The model above that, the TCX Advanced Pro 2, uses SRAM Rival brakes with 140mm rotors front and rear.
And at the very top, the TCX Advanced Pro 1 has SRAM Force brakes
with a 160mm rotor in front and 140mm in the rear.
This is a bit of a tangent, but that CONDUCT brake mentioned above
came out around 2017.
Due to brake power ratio considerations, it's compatible with 9000-series Dura-Ace
and its related models (like 6800), but not with R9100 Dura-Ace or R8000 Altegra.
However, the drivetrain on the 2019 TCX SLR2 (especially the brake levers)
is SRAM Apex, and the power ratio difference between SRAM brakes is
far greater than the difference between 9000 and R9100,
so if 9000 is OK and R9100 is not, then SRAM should also be incompatible. Strange.
Anyway, with a 140mm front rotor and handbuilt wheels,
you need to consider spoke-to-caliper contact as well.
Learned something new.
On a separate note, something I've come to realize anew,
or maybe just been reminded of something I already knew.
The reason I used half-competition lacing is because the XR331 is a non-offset rim.
If the rim were an RR411db (offset rim),
I've found from experience that there'd be much less left-right tension difference,
so full CX-RAY would be fine.
The XR331 is a lighter rim,
and comparing a half-competition XR331 with a full CX-RAY RR411db,
the former actually ends up lighter overall.
A full CX-RAY XR331 would be optimized for lightness,
but in my opinion, without crossing spokes on the non-rotor side,
it feels a bit "hmm..." (though I do include them).
So I cleanly removed the competition-laced spokes on the rotor side and replaced them with CX-RAY.
Then I tried to center the wheel by only tightening the CX-RAY spokes on the rotor side...
Even after tensioning the rotor-side spokes to their maximum,
I couldn't get the wheel centered.
So I had to loosen the non-rotor-side CX-RAY spokes a bit
to achieve proper centering.
But really, this is obvious in hindsight.
I'm just experiencing the flip side of the fact that half-competition lacing allows slightly lower tension
compared to full CX-RAY.
This only happens when the high-tension side is tensioned right up to its limit.
If the pre-rebuild tension state had been loose,
changing from half-competition to full CX-RAY would've let me center it
with just tightening the rotor side.
One more thing worth noting:
Whether people are copying me or arrived at this independently, I don't know,
but I sometimes see half-competition rear wheels built by others
where the builder clearly doesn't fully understand this principle—
they just built it loosely with half-competition lacing.
With those rear wheels, this phenomenon doesn't occur.