Another wheel day (and so on). But first.
When installing a 700C wheel on a Cannondale Jekyll,
very wide tires can't be fitted (they interfere with the frame and fork),
so the customer's request was to build front and rear wheels with 650B rims.
The planned tire width is around 38-40C.
The rim for nomulab wheel No. 8,
the Tni AL22W has an internal width of 19mm and
can accommodate a 40C tire,
but it only comes in 700C size.
Tni makes an aluminum rim called ED30,
an MTB rim, but with an internal width of 30mm it's quite wide,
and the weight for a 650B rim is a nominal 497g—not exactly light.
The retail price with tax is 6,820 yen.
DT has rim models called GR531 and G540
as gravel-use rims. Just like the difference between road RR and R models,
when the second character is R, Squorx nipples and
PHR washers are used,
making it a single-sided eyeleted spec.
Japanese distributors only handle
the GR531 rim,
in 700C and 650B, 32H only, though
the manufacturer site lists 28H and 24H versions.
Like road rims, the number in the model name
is roughly the nominal weight,
but in this case it's the weight of the 700C rim:
535g.
For the 650B rim it's 500g.
The fact that only the 32H version is kept in stock
isn't a problem since this build is also 32H.
DT rims don't specify tire size or maximum pressure
based on "purpose"—whether for road or MTB.
It's determined purely by rim internal width.
The rear wheel rim on my everyday road bike is
the XR331, which is for MTB, but with a 20mm internal width it's as narrow
as a road rim, so it can fit 25C tires.
The specified maximum pressure isn't from the manufacturer's chart
but from a sticker on the rim itself:
8.5 bar for tubes, 7 bar for tubeless.
Numbers you'd never expect from an MTB rim.
Though it's been discontinued.
Listing DT's rim internal width/specified tire size ranges:
18-19.9mm / 23-60C
20-22.4mm / 28-62C
22.5-24.4mm / 35-68C
24.5-27.5mm / 40-76C
I interpret the XR331 rim's 20mm internal width as
19.9mm and run 25C tires,
or 23C if it's an IRC S-Lite.
The GR531 rim has a 24mm internal width so
it should be 35-68C,
but Japanese distributor docs list it as 32-60C.
Even the 650B rim is a nominal 500g—not light—and
the retail price per rim is 17,800 yen excluding tax / 19,580 yen including tax,
so your wallet loses weight a bit too aggressively.
I mentioned it as an option to the customer
but it was rejected.
DT's XC race rim series is the XR line,
and the wider all-mountain rims are the XM line.
The XR series includes XR331, XR361, and XR391,
which appear on the manufacturer site as of writing,
but Japanese distributors have discontinued XR331 and XR361.
Some Canyon small frame sizes use 650B instead of 700C,
and XR331 650B rim would be the perfect solution for a lightweight custom wheel,
but Japanese distributors don't stock it anymore. However, I know
somewhere that still sells it,
so I've told customers to bring the rim themselves
and built the wheel.
Currently the only available XR-series rim,
the XR391, has a 24mm internal width and
specified tire range of 40-76C.
This straddles the 24.4/24.5mm boundary, so
compared to the GR531 rim with 24mm internal width and
specified range 35-68C,
a 1mm rim width difference results in the tire range minimum being 5mm different.
Surely a 1mm difference wouldn't change the limit that much
(even if it says 40C minimum, you could probably fit 38C),
or so I thought.
Oh, the XR391 rim turned out to be useless anyway.
The XR391 rim comes in 700C (29-inch) and 650B (27.5-inch) versions,
but currently Japanese distributors only stock
the 700C version.
The narrowest XM-series rim, the XM421, does come in 650B
and has the same 25mm internal width as the XR391,
but both XR391 and XM421 are 19,900 yen excluding tax / 21,890 yen including tax,
so your wallet lightens again (and so on).
So it came down to Stans Crest MK4.
The 650B rim has a nominal weight of 374g,
and this actual measured weight is quite light for a rim,
and the retail price including tax is 17,000 yen—cheaper than DT.
By 1g, I used the lighter rim for the rear wheel.
The internal width is 25mm and the manufacturer's specified tire size is
gravel 40C to MTB 2.3-inch (roughly 58C).
It just barely matches the customer's planned minimum tire size,
but honestly, this was about the only 650B rim option
that wasn't unnecessarily heavy or unnecessarily expensive.
The Crest has gotten wider with each generation—
the previous version was 23mm, the one before that was 21mm.
The 21mm Crest could even be used for cyclocross depending on the tire.
There's an aluminum rim called Grail for road and gravel use,
the original Grail was 24.5mm tall / 20.3mm internal width with
specified tire size 25-40C,
and the next Grail MK3 was also
24.5mm tall / 20.3mm internal width,
same specified size,
but the MK3 also went out of manufacturer stock.
Actually I have the original Grail in stock,
but it's 28H so it won't work with this hub.
The carbon Grail CB7
is currently in use, but its rim height is only 19.3mm—quite flat—
and internal width is 21.6mm, wider than the aluminum rim of the same name,
yet the specified tire size remains 25-40C.
DT is more strict about that sort of thing.
So, another wheel day (and so on).
Built the rear wheel with Crest MK4 650B rim.
The hub is a DT Onyx 135mm width quick-release disc hub
built in half-comp 46 JIS lacing.
Truing will come later.
With a 6-bolt rotor mount, the non-drive side necessarily becomes
large-flange, but the drive side has a similar flange diameter to Shimano road hubs,
making it reverse hi-lo flange.
With 46 lacing, the drive side has noticeably shorter spoke length,
but when I checked what length would be needed for 66 lacing with this rim and hub,
I found that with a non-offset rim
both sides can be built with the same length (within 1mm difference).
But if you assume left-right same diameter, it doesn't always work out that way—
with 44 lacing the drive side comes out 1mm longer.
Also, with a very low-profile rim like Mavic's old GP4
or Araya's keirin racing rims at 32H,
the drive side would be 3mm longer.
Though I don't do it on rear wheels,
if you consider both sides radially laced, or
imagine a small-wheeled bike with an extremely small rim inner diameter,
you realize that for a given hub's dishing amount,
as long as you use the same lacing pattern on both sides, you can't create a hub
where spoke length comes out identical on both sides.
But with this hub, up to about a 50mm rim height from this Crest MK4,
as long as you do 66 lacing,
there's a range where one integer-mm spoke length can be shared left-right,
and aside from extremely unusual conditions,
it seems the hub dimensions were reverse-engineered so that
"(both sides) 6-lace so both sides end up the same length."
Also, since this rim is offset,
depending on the offset amount,
I applied a correction factor to shorten the non-drive side spokes
and lengthen the drive side spokes.
As a result, when finished, the spoke length on both sides
was right at the nipple end face,
but the rim-hole outer-side photos I sometimes post—
though they don't lie—
don't actually prove which side is which.
But this time the rim has witness marks from the
holes in the sticker placed opposite the valve hole location, so
↑Drive side
↑Non-drive side
I can prove it.
When installing a 700C wheel on a Cannondale Jekyll,
very wide tires can't be fitted (they interfere with the frame and fork),
so the customer's request was to build front and rear wheels with 650B rims.
The planned tire width is around 38-40C.
The rim for nomulab wheel No. 8,
the Tni AL22W has an internal width of 19mm and
can accommodate a 40C tire,
but it only comes in 700C size.
Tni makes an aluminum rim called ED30,
an MTB rim, but with an internal width of 30mm it's quite wide,
and the weight for a 650B rim is a nominal 497g—not exactly light.
The retail price with tax is 6,820 yen.
DT has rim models called GR531 and G540
as gravel-use rims. Just like the difference between road RR and R models,
when the second character is R, Squorx nipples and
PHR washers are used,
making it a single-sided eyeleted spec.
Japanese distributors only handle
the GR531 rim,
in 700C and 650B, 32H only, though
the manufacturer site lists 28H and 24H versions.
Like road rims, the number in the model name
is roughly the nominal weight,
but in this case it's the weight of the 700C rim:
535g.
For the 650B rim it's 500g.
The fact that only the 32H version is kept in stock
isn't a problem since this build is also 32H.
DT rims don't specify tire size or maximum pressure
based on "purpose"—whether for road or MTB.
It's determined purely by rim internal width.
The rear wheel rim on my everyday road bike is
the XR331, which is for MTB, but with a 20mm internal width it's as narrow
as a road rim, so it can fit 25C tires.
The specified maximum pressure isn't from the manufacturer's chart
but from a sticker on the rim itself:
8.5 bar for tubes, 7 bar for tubeless.
Numbers you'd never expect from an MTB rim.
Though it's been discontinued.
Listing DT's rim internal width/specified tire size ranges:
18-19.9mm / 23-60C
20-22.4mm / 28-62C
22.5-24.4mm / 35-68C
24.5-27.5mm / 40-76C
I interpret the XR331 rim's 20mm internal width as
19.9mm and run 25C tires,
or 23C if it's an IRC S-Lite.
The GR531 rim has a 24mm internal width so
it should be 35-68C,
but Japanese distributor docs list it as 32-60C.
Even the 650B rim is a nominal 500g—not light—and
the retail price per rim is 17,800 yen excluding tax / 19,580 yen including tax,
so your wallet loses weight a bit too aggressively.
I mentioned it as an option to the customer
but it was rejected.
DT's XC race rim series is the XR line,
and the wider all-mountain rims are the XM line.
The XR series includes XR331, XR361, and XR391,
which appear on the manufacturer site as of writing,
but Japanese distributors have discontinued XR331 and XR361.
Some Canyon small frame sizes use 650B instead of 700C,
and XR331 650B rim would be the perfect solution for a lightweight custom wheel,
but Japanese distributors don't stock it anymore. However, I know
somewhere that still sells it,
so I've told customers to bring the rim themselves
and built the wheel.
Currently the only available XR-series rim,
the XR391, has a 24mm internal width and
specified tire range of 40-76C.
This straddles the 24.4/24.5mm boundary, so
compared to the GR531 rim with 24mm internal width and
specified range 35-68C,
a 1mm rim width difference results in the tire range minimum being 5mm different.
Surely a 1mm difference wouldn't change the limit that much
(even if it says 40C minimum, you could probably fit 38C),
or so I thought.
Oh, the XR391 rim turned out to be useless anyway.
The XR391 rim comes in 700C (29-inch) and 650B (27.5-inch) versions,
but currently Japanese distributors only stock
the 700C version.
The narrowest XM-series rim, the XM421, does come in 650B
and has the same 25mm internal width as the XR391,
but both XR391 and XM421 are 19,900 yen excluding tax / 21,890 yen including tax,
so your wallet lightens again (and so on).
So it came down to Stans Crest MK4.
The 650B rim has a nominal weight of 374g,
and this actual measured weight is quite light for a rim,
and the retail price including tax is 17,000 yen—cheaper than DT.
By 1g, I used the lighter rim for the rear wheel.
The internal width is 25mm and the manufacturer's specified tire size is
gravel 40C to MTB 2.3-inch (roughly 58C).
It just barely matches the customer's planned minimum tire size,
but honestly, this was about the only 650B rim option
that wasn't unnecessarily heavy or unnecessarily expensive.
The Crest has gotten wider with each generation—
the previous version was 23mm, the one before that was 21mm.
The 21mm Crest could even be used for cyclocross depending on the tire.
There's an aluminum rim called Grail for road and gravel use,
the original Grail was 24.5mm tall / 20.3mm internal width with
specified tire size 25-40C,
and the next Grail MK3 was also
24.5mm tall / 20.3mm internal width,
same specified size,
but the MK3 also went out of manufacturer stock.
Actually I have the original Grail in stock,
but it's 28H so it won't work with this hub.
The carbon Grail CB7
is currently in use, but its rim height is only 19.3mm—quite flat—
and internal width is 21.6mm, wider than the aluminum rim of the same name,
yet the specified tire size remains 25-40C.
DT is more strict about that sort of thing.
So, another wheel day (and so on).
Built the rear wheel with Crest MK4 650B rim.
The hub is a DT Onyx 135mm width quick-release disc hub
built in half-comp 46 JIS lacing.
Truing will come later.
With a 6-bolt rotor mount, the non-drive side necessarily becomes
large-flange, but the drive side has a similar flange diameter to Shimano road hubs,
making it reverse hi-lo flange.
With 46 lacing, the drive side has noticeably shorter spoke length,
but when I checked what length would be needed for 66 lacing with this rim and hub,
I found that with a non-offset rim
both sides can be built with the same length (within 1mm difference).
But if you assume left-right same diameter, it doesn't always work out that way—
with 44 lacing the drive side comes out 1mm longer.
Also, with a very low-profile rim like Mavic's old GP4
or Araya's keirin racing rims at 32H,
the drive side would be 3mm longer.
Though I don't do it on rear wheels,
if you consider both sides radially laced, or
imagine a small-wheeled bike with an extremely small rim inner diameter,
you realize that for a given hub's dishing amount,
as long as you use the same lacing pattern on both sides, you can't create a hub
where spoke length comes out identical on both sides.
But with this hub, up to about a 50mm rim height from this Crest MK4,
as long as you do 66 lacing,
there's a range where one integer-mm spoke length can be shared left-right,
and aside from extremely unusual conditions,
it seems the hub dimensions were reverse-engineered so that
"(both sides) 6-lace so both sides end up the same length."
Also, since this rim is offset,
depending on the offset amount,
I applied a correction factor to shorten the non-drive side spokes
and lengthen the drive side spokes.
As a result, when finished, the spoke length on both sides
was right at the nipple end face,
but the rim-hole outer-side photos I sometimes post—
though they don't lie—
don't actually prove which side is which.
But this time the rim has witness marks from the
holes in the sticker placed opposite the valve hole location, so
↑Drive side
↑Non-drive side
I can prove it.