Rim recommendations

fmackay said:

Hi,

I recently broke the dynamo bracket I had bodged together (forks being
too fat for the normal type), and while looking around for a replacement
noticed roller-brake compatible shimano dynohubs for only £45 on wiggle.
So now I find myself poised to build my first wheel. I had rather hoped
the new hub would have the same sized flanges as the old one so I could
reuse the existing spokes, but no such luck, and I reckon I may as well
save the old wheel as a spare/for summer use. So a new rim is called
for.

Do I need a disc-specific rim?

Disk specific rims do not have braking services for rim brakes. You can
use non-disc rims with hub brakes, but not disk rims with rim brakes.

...d

This is what I have at the moment, but

Quoted message said:

I'm sure people were building wheels with normal rims and roller/drum
brake hubs long before discs came along. Also are any types of spoke
unsuitable for this application? Finally, any recomendations for rims
(559 size, £20 or thereabouts). I am tempted by the Campag ones EBC has
(shiny!) but should probably really go for something in black to match
the rear.

cheers,

fin

In article <[email hidden]>

fmackay said:

Hi,

I recently broke the dynamo bracket I had bodged together (forks being
too fat for the normal type), and while looking around for a replacement
noticed roller-brake compatible shimano dynohubs for only £45 on wiggle..
So now I find myself poised to build my first wheel. I had rather hoped
the new hub would have the same sized flanges as the old one so I could
reuse the existing spokes, but no such luck,

Hub flange diameter can make a surprisingly small difference to spoke
length, depending on the lacing pattern. The more nearly the spoke is
tangential to the flange, the less difference flange diameter makes (so
obviously it makes a big difference with radial spoking). Spokes
tangential to the flange are also less stressed by hub brakes.

Quoted message said:

and I reckon I may as well
save the old wheel as a spare/for summer use. So a new rim is called
for.

Do I need a disc-specific rim? This is what I have at the moment, but
I'm sure people were building wheels with normal rims and roller/drum
brake hubs long before discs came along.

Disk specific rims are designed only to support the tyre, non-disk rims
also have to provide a braking surface so the sides will tend to be
flatter, deeper, and thicker.

Quoted message said:

Also are any types of spoke unsuitable for this application?

Apparently there was a quantity of DT Swiss spokes produced a while ago
that had longer than usual elbows - this causes a potential fatigue
weakness that is probably worse for hub brakes. Make sure the spoke by
the elbow is tight against the back of the flange when the head is
pushed against the front of the flange - you can put a small brass
washer under the head to remove any slack.

Quoted message said:

Finally, any recomendations for rims
(559 size, £20 or thereabouts). I am tempted by the Campag ones EBC has
(shiny!) but should probably really go for something in black to match
the rear.

Sorry, I'm out of touch with current products.

in message <[email hidden]>, fmackay

(') said:

Hi,

I recently broke the dynamo bracket I had bodged together (forks being
too fat for the normal type), and while looking around for a replacement
noticed roller-brake compatible shimano dynohubs for only £45 on wiggle.
So now I find myself poised to build my first wheel. I had rather hoped
the new hub would have the same sized flanges as the old one so I could
reuse the existing spokes, but no such luck, and I reckon I may as well
save the old wheel as a spare/for summer use. So a new rim is called
for.

Do I need a disc-specific rim?

You never /need/ a disk specific rim - it's perfectly OK to build a wheel
for disk or roller brakes with a standard rim. You cannot use a
disk-specific rim with rim brakes, because what makes it 'disk specific'
is that it has no brake tracks. On the other hand quality for quality a
disk specific rim should be cheaper, because it doesn't have the precision
machined brake track; and lighter, because it doesn't need extra wall
thickness for the brake track.

Quoted message said:

Finally, any recomendations for rims
(559 size, £20 or thereabouts). I am tempted by the Campag ones EBC has
(shiny!) but should probably really go for something in black to match
the rear.

Anything from Mavix or DT Swiss should be OK. Mavic XM321?

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

;; Good grief, I can remember when England won the Ashes.

Simon Brooke said:

in message <[email hidden]>, fmackay
([email hidden]'😉 wrote:

<building a wheel on a roller-brake hub>

Quoted message said:

Quoted message said:

Do I need a disc-specific rim?

You never /need/ a disk specific rim - it's perfectly OK to build a wheel
for disk or roller brakes with a standard rim. You cannot use a
disk-specific rim with rim brakes, because what makes it 'disk specific'
is that it has no brake tracks. On the other hand quality for quality a
disk specific rim should be cheaper, because it doesn't have the precision
machined brake track; and lighter, because it doesn't need extra wall
thickness for the brake track.

Sadly the first part of your theory does not seem borne out by the
prices charged for disc/non-disc versions of the same rim! But it does
seem I'd be better with a disc rim on weight grounds, eg xc717 is 25g
lighter in the disc version.

I asked really because of quotes like "designed to cope with the
different stresses imposed by locating the brake on the hub, not the
rim" (EBC, mavic EX325 disc) or "specifically designed to withstand the
increased stress caused by disc braking" (wiggle, xc717 disc). I
suspected this to be a load of marketing guff, but wanted to check.

cheers,

fin

fmackay said:

Hi,

I recently broke the dynamo bracket I had bodged together (forks being
too fat for the normal type), and while looking around for a replacement
noticed roller-brake compatible shimano dynohubs for only £45 on wiggle.
So now I find myself poised to build my first wheel. I had rather hoped
the new hub would have the same sized flanges as the old one so I could
reuse the existing spokes, but no such luck, and I reckon I may as well
save the old wheel as a spare/for summer use. So a new rim is called
for.

I built a wheel nearly a year ago with one of these hubs. I built it
with a rim suitable for rim brakes. In fact I only fitted a roller-brake
to the wheel a couple of weeks ago as I had to replace my suspension
forks, so bought a pair with disc-brake mounts for a IM75 brake.

Shimano also manufacture dynohubs with discbrake mounts. If you already
have a disc brake, it would probably be better to use one of these to
make swapping wheels easier. Roller brakes cost about 30-40 pounds, so
the additional cost of the hub would be offset against the cost of the
brake.

Quoted message said:

Do I need a disc-specific rim? This is what I have at the moment, but
I'm sure people were building wheels with normal rims and roller/drum
brake hubs long before discs came along. Also are any types of spoke
unsuitable for this application? Finally, any recomendations for rims
(559 size, £20 or thereabouts). I am tempted by the Campag ones EBC has
(shiny!) but should probably really go for something in black to match
the rear.

Use Swiss Dt spokes with a 3 cross pattern.

Martin.