Today it's wheels again (story abridged). Well, not exactly.
The last Saturday of the month is our regular day off,
but for the past several months I've been coming into the shop anyway to build wheels.
This month I managed to actually get a day off, so
I came in and built a set of personal wheels.
I picked up some DT XR331 rims. They're MTB rims, but
DT categorizes their MTB rims by discipline with a two-letter prefix on the model name:
XR Cross Country
XM All Mountain
EX Enduro
FR Freeride
BG Big Ride (Fat bike)
The XR331 is notably the narrowest within the XR lineup.
By internal/external width (mm):
XR331 is 20/23.5, XR361 is 22.5/26,
XR391 is 25/29,
so the 29" XR331 can be used as a cyclocross rim.
The profile is triangular, like Stans IronCross.
IronCross rim width is 20/23.2, so
the width and profile are essentially identical.
Now that IronCross has been discontinued, I've recently realized
this rim is incredibly useful as a post-IronCross alternative.
The reason I didn't notice this sooner is that
the previous DT distributor didn't stock it.
Unlike the RR411db, this is not an offset rim.
In terms of wheel-building logic, RR411db is superior—
with a spoke dish comparable to a disc hub, I'd call it good enough to build
semi-comp laced without re-tensioning—
but here's point #1 on why this rim earns the "post-IronCross" title:
rim weight lightness.
The 29" version is spec'd at 380g, but
the four rims I received this time weighed 373, 373, 381, and 382g respectively.
IronCross specifies a maximum spoke tension of 930N, but
XR331 goes up to 1200N, perhaps due to the PHR washer.
The recommended tire pressure varies by DT's rim internal width and tire width.
With XR331 at 20mm internal width,
DT charts show compatible tire widths of 28–62C:
28C gets 7.8 bar, 62C gets 2.9 bar.
For the 32C you'd probably run for cyclocross, it's 6.8 bar.
The ERD (effective rim diameter with washer) is listed as 606mm,
but this is DT's usual nonsense. Let's measure it ourselves.
My understanding of ERD differs drastically from industry standard,
so maybe DT's definition is actually the common one... no, that's not it.
The ENVE rim I built yesterday had ERD differing by only 0.3mm between spec and measurement,
so I used the spec for that wheel.
And Mavic's published ERD values match my measurements pretty closely.
DT is definitely the odd one out here.
I use ERD radius for spoke length calculations, and
303mm is, well, that's basically
the sort of ultra-low-profile tubular rim figure you'd see on an Ambrosio Nemesis
or Mavic GEL280 in the old days.
So here's point #2 on why this rim qualifies as post-IronCross:
its rim diameter is so close to IronCross
that (assuming your IronCross wheel isn't built with wildly wrong spoke length)
you can swap rims. That's a lifesaver.
XR331 comes in 28H and 32H, and I stocked up on the 28H.
Funny—every time I write this stuff here, the distributor's inventory seems to disappear.
Actually the distributor seems to have good rim stock, so I couldn't corner the market.
Speaking of which, those 14g 12mm silver aluminum nipples I bought out ages ago are still on backorder.
Yeah, that was a jerk move on my part.
Built the rear wheel.
There's a screwdriver in the valve hole—reason coming up.
DT 350 hub, 28H, semi-comp laced radial 4-cross with re-tensioning, gold aluminum nipples.
A disc-specific rim with a non-disc hub—
how's the braking supposed to work?—you might ask,
but for my own use there's no problem.
Built the partner's front wheel too.
DT RR411 rim.
The RR411 with brake zone (rim brake version) comes in both offset and non-offset,
but this is obviously non-offset.
The disc brake version RR411db is offset-rim only on the front wheel too,
so there's no non-offset option for that version.
Black hub, 20H,
Sapim Aero Star Bright II spokes, outpoke radial laced,
with nipples in purple, green, red order starting from the valve hole—
20H doesn't divide evenly by three, so I did 7-6-7 each color.
With two nipple colors, the wheel appears two-tone when spinning;
with three colors it obviously looks three-color (duh),
but this particular arrangement sometimes makes it look like there are even more.
If you're concerned about complementary color relationships, you might want to insert
a light blue between the purple and green and do five each of three colors instead.
About that screwdriver in the valve hole—
As I've mentioned before, DT rims have
stickers positioned 180° apart on one side, directly above and opposite the valve hole,
but on the other side they're rotated 90°.
On offset rims used as rear wheels, viewed from the right (freehub) side,
the valve hole position gets no sticker.
When building front and rear wheels with disc hubs and RR411db rims,
the offset direction flips between front and rear, meaning
the sticker/valve hole relationship necessarily reverses between wheels.
But when building with RR411 non-offset front and RR411 offset rear,
you need the front rim's no-sticker valve position on the right side,
otherwise the front and rear wheels' valve-to-sticker relationships won't match.
So today, even though both wheels use non-offset rims,
I oriented them so that both have "no sticker at valve hole, on the right side."
The washers that came with today's rims were
the new type with directional dots, so
I aggressively burned through the old-type stock, and it's nicely depleted now.
I'm using Stans tubeless rim tape.
The rear wheel will run with a tube in WO (clincher) format.
The XR331 has huge holes on the outer edge,
whereas the RR411 doesn't (just slightly larger than the valve bore),
but either way I've used a soldering iron to heat-weld the valve hole down to just barely fit the valve stem.
Stans rim tape comes in width options of 21, 25, 27, 30, 33, and 36mm,
but at our shop we mainly use the two narrower sizes: 21mm and 25mm (shown above).
The jump from 21mm to 25mm felt oddly large to me.
If 21mm stepped up to 24mm instead,
the whole lineup would be in 3mm increments, and
I've noticed even Stans' own rims sometimes look like they'd be better served by
something around 23mm, so
we keep DT's 23mm in stock too.
Stans tape seems to conform better to rim shape under inflation pressure,
and since DT rim tape doesn't melt holes when you heat it with a soldering iron,
our shop mostly defaults to Stans tape.
The last Saturday of the month is our regular day off,
but for the past several months I've been coming into the shop anyway to build wheels.
This month I managed to actually get a day off, so
I came in and built a set of personal wheels.
I picked up some DT XR331 rims. They're MTB rims, but
DT categorizes their MTB rims by discipline with a two-letter prefix on the model name:
XR Cross Country
XM All Mountain
EX Enduro
FR Freeride
BG Big Ride (Fat bike)
The XR331 is notably the narrowest within the XR lineup.
By internal/external width (mm):
XR331 is 20/23.5, XR361 is 22.5/26,
XR391 is 25/29,
so the 29" XR331 can be used as a cyclocross rim.
The profile is triangular, like Stans IronCross.
IronCross rim width is 20/23.2, so
the width and profile are essentially identical.
Now that IronCross has been discontinued, I've recently realized
this rim is incredibly useful as a post-IronCross alternative.
The reason I didn't notice this sooner is that
the previous DT distributor didn't stock it.
Unlike the RR411db, this is not an offset rim.
In terms of wheel-building logic, RR411db is superior—
with a spoke dish comparable to a disc hub, I'd call it good enough to build
semi-comp laced without re-tensioning—
but here's point #1 on why this rim earns the "post-IronCross" title:
rim weight lightness.
The 29" version is spec'd at 380g, but
the four rims I received this time weighed 373, 373, 381, and 382g respectively.
IronCross specifies a maximum spoke tension of 930N, but
XR331 goes up to 1200N, perhaps due to the PHR washer.
The recommended tire pressure varies by DT's rim internal width and tire width.
With XR331 at 20mm internal width,
DT charts show compatible tire widths of 28–62C:
28C gets 7.8 bar, 62C gets 2.9 bar.
For the 32C you'd probably run for cyclocross, it's 6.8 bar.
The ERD (effective rim diameter with washer) is listed as 606mm,
but this is DT's usual nonsense. Let's measure it ourselves.
My understanding of ERD differs drastically from industry standard,
so maybe DT's definition is actually the common one... no, that's not it.
The ENVE rim I built yesterday had ERD differing by only 0.3mm between spec and measurement,
so I used the spec for that wheel.
And Mavic's published ERD values match my measurements pretty closely.
DT is definitely the odd one out here.
I use ERD radius for spoke length calculations, and
303mm is, well, that's basically
the sort of ultra-low-profile tubular rim figure you'd see on an Ambrosio Nemesis
or Mavic GEL280 in the old days.
So here's point #2 on why this rim qualifies as post-IronCross:
its rim diameter is so close to IronCross
that (assuming your IronCross wheel isn't built with wildly wrong spoke length)
you can swap rims. That's a lifesaver.
XR331 comes in 28H and 32H, and I stocked up on the 28H.
Funny—every time I write this stuff here, the distributor's inventory seems to disappear.
Speaking of which, those 14g 12mm silver aluminum nipples I bought out ages ago are still on backorder.
Yeah, that was a jerk move on my part.
Built the rear wheel.
There's a screwdriver in the valve hole—reason coming up.
DT 350 hub, 28H, semi-comp laced radial 4-cross with re-tensioning, gold aluminum nipples.
A disc-specific rim with a non-disc hub—
how's the braking supposed to work?—you might ask,
but for my own use there's no problem.
Built the partner's front wheel too.
DT RR411 rim.
The RR411 with brake zone (rim brake version) comes in both offset and non-offset,
but this is obviously non-offset.
The disc brake version RR411db is offset-rim only on the front wheel too,
so there's no non-offset option for that version.
Black hub, 20H,
Sapim Aero Star Bright II spokes, outpoke radial laced,
with nipples in purple, green, red order starting from the valve hole—
20H doesn't divide evenly by three, so I did 7-6-7 each color.
With two nipple colors, the wheel appears two-tone when spinning;
with three colors it obviously looks three-color (duh),
but this particular arrangement sometimes makes it look like there are even more.
If you're concerned about complementary color relationships, you might want to insert
a light blue between the purple and green and do five each of three colors instead.
About that screwdriver in the valve hole—
As I've mentioned before, DT rims have
stickers positioned 180° apart on one side, directly above and opposite the valve hole,
but on the other side they're rotated 90°.
On offset rims used as rear wheels, viewed from the right (freehub) side,
the valve hole position gets no sticker.
When building front and rear wheels with disc hubs and RR411db rims,
the offset direction flips between front and rear, meaning
the sticker/valve hole relationship necessarily reverses between wheels.
But when building with RR411 non-offset front and RR411 offset rear,
you need the front rim's no-sticker valve position on the right side,
otherwise the front and rear wheels' valve-to-sticker relationships won't match.
So today, even though both wheels use non-offset rims,
I oriented them so that both have "no sticker at valve hole, on the right side."
The washers that came with today's rims were
the new type with directional dots, so
I aggressively burned through the old-type stock, and it's nicely depleted now.
I'm using Stans tubeless rim tape.
The rear wheel will run with a tube in WO (clincher) format.
The XR331 has huge holes on the outer edge,
whereas the RR411 doesn't (just slightly larger than the valve bore),
but either way I've used a soldering iron to heat-weld the valve hole down to just barely fit the valve stem.
Stans rim tape comes in width options of 21, 25, 27, 30, 33, and 36mm,
but at our shop we mainly use the two narrower sizes: 21mm and 25mm (shown above).
The jump from 21mm to 25mm felt oddly large to me.
If 21mm stepped up to 24mm instead,
the whole lineup would be in 3mm increments, and
I've noticed even Stans' own rims sometimes look like they'd be better served by
something around 23mm, so
we keep DT's 23mm in stock too.
Stans tape seems to conform better to rim shape under inflation pressure,
and since DT rim tape doesn't melt holes when you heat it with a soldering iron,
our shop mostly defaults to Stans tape.