Hi there. I wanted to gauge the opinion of this group on the safety of a wheel build I'm about to embark on. I'm a fairly accomplished wheel builder (over 300 wheels), but I haven't ran into this situation before.

I'm looking to build up a set of disc brake wheels (with disc brake hubs), but the rim I intend to use was designed for rim brakes. The hub drillings match the rim drillings - 24 hole. This is a carbon tubular rim and a centerlock, straightpull hub.

Other than having a visible brake track as an aesthetic drag, is there any design reason why this combination wouldn't work? Are disc brake rims designed to be any beefier than their rim brake counterparts? All else being similar that is. Will the forces of disc brakes be too much for the rim to handle?

For context, these wheels will be meant for cyclocross racing. I weigh 145 pounds. Thank you for your thoughts.

On Monday, June 13, 2022 at 5:03:42 PM UTC-7, Alexander Stephens wrote:
> Hi there. I wanted to gauge the opinion of this group on the safety of a wheel build I'm about to embark on. I'm a fairly accomplished wheel builder (over 300 wheels), but I haven't ran into this situation before.
>
> I'm looking to build up a set of disc brake wheels (with disc brake hubs), but the rim I intend to use was designed for rim brakes. The hub drillings match the rim drillings - 24 hole. This is a carbon tubular rim and a centerlock, straightpull hub.
>
> Other than having a visible brake track as an aesthetic drag, is there any design reason why this combination wouldn't work? Are disc brake rims designed to be any beefier than their rim brake counterparts? All else being similar that is. Will the forces of disc brakes be too much for the rim to handle?
>
> For context, these wheels will be meant for cyclocross racing. I weigh 145 pounds. Thank you for your thoughts.
Disk brake hubs are designed quite different. It isn't clear to me how you intend to attach a disk to a rim brake hub for first.

Also the spokes are significantly larger in diameter since they have to carry all of the load through the spokes which rim brake hubs are not designed for. Also because of the disk attachment, disk hubs are offset usually so that the left side is a straight or nearly straight pull and the right side have a normal offset from the hub center.

I would not recommend building a disk wheel on anything other than a disk hub and with the proper spokes and the MUCH higher tension they require.

On Monday, June 13, 2022 at 7:22:36 PM UTC-5, cycl...@gmail.com wrote:
> On Monday, June 13, 2022 at 5:03:42 PM UTC-7, Alexander Stephens wrote:
> > Hi there. I wanted to gauge the opinion of this group on the safety of a wheel build I'm about to embark on. I'm a fairly accomplished wheel builder (over 300 wheels), but I haven't ran into this situation before.
> >
> > I'm looking to build up a set of disc brake wheels (with disc brake hubs), but the rim I intend to use was designed for rim brakes. The hub drillings match the rim drillings - 24 hole. This is a carbon tubular rim and a centerlock, straightpull hub.
> >
> > Other than having a visible brake track as an aesthetic drag, is there any design reason why this combination wouldn't work? Are disc brake rims designed to be any beefier than their rim brake counterparts? All else being similar that is. Will the forces of disc brakes be too much for the rim to handle?
> >
> > For context, these wheels will be meant for cyclocross racing. I weigh 145 pounds. Thank you for your thoughts.
> Disk brake hubs are designed quite different. It isn't clear to me how you intend to attach a disk to a rim brake hub for first.
>
> Also the spokes are significantly larger in diameter since they have to carry all of the load through the spokes which rim brake hubs are not designed for. Also because of the disk attachment, disk hubs are offset usually so that the left side is a straight or nearly straight pull and the right side have a normal offset from the hub center.
>
> I would not recommend building a disk wheel on anything other than a disk hub and with the proper spokes and the MUCH higher tension they require.

Wow!!!!!!!!
How can Tommy misread a post so badly? Tommy's incompetence never ceases to amaze me.

On 6/13/2022 7:03 PM, Alexander Stephens wrote:
> Hi there. I wanted to gauge the opinion of this group on the safety of a wheel build I'm about to embark on. I'm a fairly accomplished wheel builder (over 300 wheels), but I haven't ran into this situation before.
>
> I'm looking to build up a set of disc brake wheels (with disc brake hubs), but the rim I intend to use was designed for rim brakes. The hub drillings match the rim drillings - 24 hole. This is a carbon tubular rim and a centerlock, straightpull hub.
>
> Other than having a visible brake track as an aesthetic drag, is there any design reason why this combination wouldn't work? Are disc brake rims designed to be any beefier than their rim brake counterparts? All else being similar that is. Will the forces of disc brakes be too much for the rim to handle?
>
> For context, these wheels will be meant for cyclocross racing. I weigh 145 pounds. Thank you for your thoughts.
>

Assuming the rim is otherwise suitable (do you commonly ride
similar weight 24h rims for cross?) the brake track or lack
thereof doesn't matter.

--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971

On 6/13/2022 7:22 PM, Tom Kunich wrote:
> On Monday, June 13, 2022 at 5:03:42 PM UTC-7, Alexander Stephens wrote:
>> Hi there. I wanted to gauge the opinion of this group on the safety of a wheel build I'm about to embark on. I'm a fairly accomplished wheel builder (over 300 wheels), but I haven't ran into this situation before.
>>
>> I'm looking to build up a set of disc brake wheels (with disc brake hubs), but the rim I intend to use was designed for rim brakes. The hub drillings match the rim drillings - 24 hole. This is a carbon tubular rim and a centerlock, straightpull hub.
>>
>> Other than having a visible brake track as an aesthetic drag, is there any design reason why this combination wouldn't work? Are disc brake rims designed to be any beefier than their rim brake counterparts? All else being similar that is. Will the forces of disc brakes be too much for the rim to handle?
>>
>> For context, these wheels will be meant for cyclocross racing. I weigh 145 pounds. Thank you for your thoughts.
> Disk brake hubs are designed quite different. It isn't clear to me how you intend to attach a disk to a rim brake hub for first.
>
> Also the spokes are significantly larger in diameter since they have to carry all of the load through the spokes which rim brake hubs are not designed for. Also because of the disk attachment, disk hubs are offset usually so that the left side is a straight or nearly straight pull and the right side have a normal offset from the hub center.
>
> I would not recommend building a disk wheel on anything other than a disk hub and with the proper spokes and the MUCH higher tension they require.
>

OP says he's using a rim with brake track on a disc hub. No
reason not to as long as the rim is otherwise suitable.

Disc hubs are drilled for 2.0mm spokes same as road hubs.
And track hubs. And MTB hubs.

Spoke tension is specified by the rim manufacturer, not the
hub vendor.

--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971

On Monday, June 13, 2022 at 5:50:19 PM UTC-7, AMuzi wrote:
> On 6/13/2022 7:03 PM, Alexander Stephens wrote:
> > Hi there. I wanted to gauge the opinion of this group on the safety of a wheel build I'm about to embark on. I'm a fairly accomplished wheel builder (over 300 wheels), but I haven't ran into this situation before.
> >
> > I'm looking to build up a set of disc brake wheels (with disc brake hubs), but the rim I intend to use was designed for rim brakes. The hub drillings match the rim drillings - 24 hole. This is a carbon tubular rim and a centerlock, straightpull hub.
> >
> > Other than having a visible brake track as an aesthetic drag, is there any design reason why this combination wouldn't work? Are disc brake rims designed to be any beefier than their rim brake counterparts? All else being similar that is. Will the forces of disc brakes be too much for the rim to handle?
> >
> > For context, these wheels will be meant for cyclocross racing. I weigh 145 pounds. Thank you for your thoughts.
> >
> Assuming the rim is otherwise suitable (do you commonly ride
> similar weight 24h rims for cross?) the brake track or lack
> thereof doesn't matter.

I misinterpreted the use of a centerlock disk hub. But that still doesn't cover the bases of the strongly offset spoke holes in disk hubs vs. rim brake hubs. I imagine that since Alexander is hardly likely to be a Tom Boonen it would probably survive. But the incorrect offset spoke holes still can cause premature failure.

On Monday, June 13, 2022 at 5:55:35 PM UTC-7, AMuzi wrote:
> On 6/13/2022 7:22 PM, Tom Kunich wrote:
> > On Monday, June 13, 2022 at 5:03:42 PM UTC-7, Alexander Stephens wrote:
> >> Hi there. I wanted to gauge the opinion of this group on the safety of a wheel build I'm about to embark on. I'm a fairly accomplished wheel builder (over 300 wheels), but I haven't ran into this situation before.
> >>
> >> I'm looking to build up a set of disc brake wheels (with disc brake hubs), but the rim I intend to use was designed for rim brakes. The hub drillings match the rim drillings - 24 hole. This is a carbon tubular rim and a centerlock, straightpull hub.
> >>
> >> Other than having a visible brake track as an aesthetic drag, is there any design reason why this combination wouldn't work? Are disc brake rims designed to be any beefier than their rim brake counterparts? All else being similar that is. Will the forces of disc brakes be too much for the rim to handle?
> >>
> >> For context, these wheels will be meant for cyclocross racing. I weigh 145 pounds. Thank you for your thoughts.
> > Disk brake hubs are designed quite different. It isn't clear to me how you intend to attach a disk to a rim brake hub for first.
> >
> > Also the spokes are significantly larger in diameter since they have to carry all of the load through the spokes which rim brake hubs are not designed for. Also because of the disk attachment, disk hubs are offset usually so that the left side is a straight or nearly straight pull and the right side have a normal offset from the hub center.
> >
> > I would not recommend building a disk wheel on anything other than a disk hub and with the proper spokes and the MUCH higher tension they require.
> >
> OP says he's using a rim with brake track on a disc hub. No
> reason not to as long as the rim is otherwise suitable.
>
> Disc hubs are drilled for 2.0mm spokes same as road hubs.
> And track hubs. And MTB hubs.
>
> Spoke tension is specified by the rim manufacturer, not the
> hub vendor.

I built a set of disk wheels for my Felt CX and they had the centerlock outside of the place where you could also use a bolt-on disk. Since that was the first time I had built a set of disk wheels I didn't think about it. But the rims were vertically positioned on the left (disk) side and quite widely spaced on the right. But now looking at the ready built disk wheels it appears quite strange.

On 6/13/2022 8:04 PM, Tom Kunich wrote:
> On Monday, June 13, 2022 at 5:50:19 PM UTC-7, AMuzi wrote:
>> On 6/13/2022 7:03 PM, Alexander Stephens wrote:
>>> Hi there. I wanted to gauge the opinion of this group on the safety of a wheel build I'm about to embark on. I'm a fairly accomplished wheel builder (over 300 wheels), but I haven't ran into this situation before.
>>>
>>> I'm looking to build up a set of disc brake wheels (with disc brake hubs), but the rim I intend to use was designed for rim brakes. The hub drillings match the rim drillings - 24 hole. This is a carbon tubular rim and a centerlock, straightpull hub.
>>>
>>> Other than having a visible brake track as an aesthetic drag, is there any design reason why this combination wouldn't work? Are disc brake rims designed to be any beefier than their rim brake counterparts? All else being similar that is. Will the forces of disc brakes be too much for the rim to handle?
>>>
>>> For context, these wheels will be meant for cyclocross racing. I weigh 145 pounds. Thank you for your thoughts.
>>>
>> Assuming the rim is otherwise suitable (do you commonly ride
>> similar weight 24h rims for cross?) the brake track or lack
>> thereof doesn't matter.
>
> I misinterpreted the use of a centerlock disk hub. But that still doesn't cover the bases of the strongly offset spoke holes in disk hubs vs. rim brake hubs. I imagine that since Alexander is hardly likely to be a Tom Boonen it would probably survive. But the incorrect offset spoke holes still can cause premature failure.
>

What does that mean?

--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971

On 6/13/2022 8:23 PM, Tom Kunich wrote:
> On Monday, June 13, 2022 at 5:55:35 PM UTC-7, AMuzi wrote:
>> On 6/13/2022 7:22 PM, Tom Kunich wrote:
>>> On Monday, June 13, 2022 at 5:03:42 PM UTC-7, Alexander Stephens wrote:
>>>> Hi there. I wanted to gauge the opinion of this group on the safety of a wheel build I'm about to embark on. I'm a fairly accomplished wheel builder (over 300 wheels), but I haven't ran into this situation before.
>>>>
>>>> I'm looking to build up a set of disc brake wheels (with disc brake hubs), but the rim I intend to use was designed for rim brakes. The hub drillings match the rim drillings - 24 hole. This is a carbon tubular rim and a centerlock, straightpull hub.
>>>>
>>>> Other than having a visible brake track as an aesthetic drag, is there any design reason why this combination wouldn't work? Are disc brake rims designed to be any beefier than their rim brake counterparts? All else being similar that is. Will the forces of disc brakes be too much for the rim to handle?
>>>>
>>>> For context, these wheels will be meant for cyclocross racing. I weigh 145 pounds. Thank you for your thoughts.
>>> Disk brake hubs are designed quite different. It isn't clear to me how you intend to attach a disk to a rim brake hub for first.
>>>
>>> Also the spokes are significantly larger in diameter since they have to carry all of the load through the spokes which rim brake hubs are not designed for. Also because of the disk attachment, disk hubs are offset usually so that the left side is a straight or nearly straight pull and the right side have a normal offset from the hub center.
>>>
>>> I would not recommend building a disk wheel on anything other than a disk hub and with the proper spokes and the MUCH higher tension they require.
>>>
>> OP says he's using a rim with brake track on a disc hub. No
>> reason not to as long as the rim is otherwise suitable.
>>
>> Disc hubs are drilled for 2.0mm spokes same as road hubs.
>> And track hubs. And MTB hubs.
>>
>> Spoke tension is specified by the rim manufacturer, not the
>> hub vendor.
>
> I built a set of disk wheels for my Felt CX and they had the centerlock outside of the place where you could also use a bolt-on disk. Since that was the first time I had built a set of disk wheels I didn't think about it. But the rims were vertically positioned on the left (disk) side and quite widely spaced on the right. But now looking at the ready built disk wheels it appears quite strange.
>

Rim centers over the locknuts.
Nothing else is relevant.

--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971

On Mon, 13 Jun 2022 20:27:00 -0500, AMuzi <am@yellowjersey.org> wrote:

>On 6/13/2022 8:04 PM, Tom Kunich wrote:
>> On Monday, June 13, 2022 at 5:50:19 PM UTC-7, AMuzi wrote:
>>> On 6/13/2022 7:03 PM, Alexander Stephens wrote:
>>>> Hi there. I wanted to gauge the opinion of this group on the safety of a wheel build I'm about to embark on. I'm a fairly accomplished wheel builder (over 300 wheels), but I haven't ran into this situation before.
>>>>
>>>> I'm looking to build up a set of disc brake wheels (with disc brake hubs), but the rim I intend to use was designed for rim brakes. The hub drillings match the rim drillings - 24 hole. This is a carbon tubular rim and a centerlock, straightpull hub.
>>>>
>>>> Other than having a visible brake track as an aesthetic drag, is there any design reason why this combination wouldn't work? Are disc brake rims designed to be any beefier than their rim brake counterparts? All else being similar that is. Will the forces of disc brakes be too much for the rim to handle?
>>>>
>>>> For context, these wheels will be meant for cyclocross racing. I weigh 145 pounds. Thank you for your thoughts.
>>>>
>>> Assuming the rim is otherwise suitable (do you commonly ride
>>> similar weight 24h rims for cross?) the brake track or lack
>>> thereof doesn't matter.
>>
>> I misinterpreted the use of a centerlock disk hub. But that still doesn't cover the bases of the strongly offset spoke holes in disk hubs vs. rim brake hubs. I imagine that since Alexander is hardly likely to be a Tom Boonen it would probably survive. But the incorrect offset spoke holes still can cause premature failure.
>>
>
>What does that mean?

Not to get involved in wheel building although I have built a few, but
with a disc brake where the braking force is applied to the spokes
close to the hub, have you seen any evidence of increased spoke
braking or deformation as a result? Or are disc brake wheels made with
stronger spokes?
--
Cheers,

John B.

On Monday, June 13, 2022 at 6:39:55 PM UTC-7, John B. wrote:
> On Mon, 13 Jun 2022 20:27:00 -0500, AMuzi <a...@yellowjersey.org> wrote:
>
> >On 6/13/2022 8:04 PM, Tom Kunich wrote:
> >> On Monday, June 13, 2022 at 5:50:19 PM UTC-7, AMuzi wrote:
> >>> On 6/13/2022 7:03 PM, Alexander Stephens wrote:
> >>>> Hi there. I wanted to gauge the opinion of this group on the safety of a wheel build I'm about to embark on. I'm a fairly accomplished wheel builder (over 300 wheels), but I haven't ran into this situation before.
> >>>>
> >>>> I'm looking to build up a set of disc brake wheels (with disc brake hubs), but the rim I intend to use was designed for rim brakes. The hub drillings match the rim drillings - 24 hole. This is a carbon tubular rim and a centerlock, straightpull hub.
> >>>>
> >>>> Other than having a visible brake track as an aesthetic drag, is there any design reason why this combination wouldn't work? Are disc brake rims designed to be any beefier than their rim brake counterparts? All else being similar that is. Will the forces of disc brakes be too much for the rim to handle?
> >>>>
> >>>> For context, these wheels will be meant for cyclocross racing. I weigh 145 pounds. Thank you for your thoughts.
> >>>>
> >>> Assuming the rim is otherwise suitable (do you commonly ride
> >>> similar weight 24h rims for cross?) the brake track or lack
> >>> thereof doesn't matter.
> >>
> >> I misinterpreted the use of a centerlock disk hub. But that still doesn't cover the bases of the strongly offset spoke holes in disk hubs vs. rim brake hubs. I imagine that since Alexander is hardly likely to be a Tom Boonen it would probably survive. But the incorrect offset spoke holes still can cause premature failure.
> >>
> >
> >What does that mean?
> Not to get involved in wheel building although I have built a few, but
> with a disc brake where the braking force is applied to the spokes
> close to the hub, have you seen any evidence of increased spoke
> braking or deformation as a result? Or are disc brake wheels made with
> stronger spokes?
> --
> Cheers,
>
> John B.

To clarify: my question was about the integrity of a rim designed for rim brakes when used in a disc brake application. My apologies for complicating it as a word problem.

I’m in a fortunate position where these materials have fallen into my lap: I have the rims, I have the hubs, I have the bike. I know for a fact that these hubs and rims can be successfully built into a set of wheels; I checked all of that before. The spoke offset and spoke gauge difference arguments are not real. I can elaborate more on that if necessary, but it isn’t the topic of discussion at the moment. I'm wondering about the safety and durability of this build (two separate things).

I understand wheel building and design very well. Where I want to further my knowledge here is in rim design. I’ve read and been told that disc brake forces on a wheel are very different than rim brake forces on a wheel. Under that assumption, I have the following question:

Can a rim brake rim withstand disc brake forces?

AMuzi has addressed this question. Thank you for that. To answer your question, I have ridden 20/24 hole rim brake wheels in the past under the same cyclocross conditions with no problems.

John B - Disc brake wheels are usually made with the same spokes you’d find in rim brake wheels. I haven’t personally seen greater fatigue spoke breaks in disc brake wheels, but that is a good thing to consider. I would be interested if anyone had ran into that issue with lower spoke count disc brake wheels. 24 hole is pretty much the lowest count you can go on a disc brake wheel.

On Tuesday, June 14, 2022 at 2:03:42 AM UTC+2, Alexander Stephens wrote:
> Hi there. I wanted to gauge the opinion of this group on the safety of a wheel build I'm about to embark on. I'm a fairly accomplished wheel builder (over 300 wheels), but I haven't ran into this situation before.
>
> I'm looking to build up a set of disc brake wheels (with disc brake hubs), but the rim I intend to use was designed for rim brakes. The hub drillings match the rim drillings - 24 hole. This is a carbon tubular rim and a centerlock, straightpull hub.
>
> Other than having a visible brake track as an aesthetic drag, is there any design reason why this combination wouldn't work? Are disc brake rims designed to be any beefier than their rim brake counterparts? All else being similar that is. Will the forces of disc brakes be too much for the rim to handle?
>
> For context, these wheels will be meant for cyclocross racing. I weigh 145 pounds. Thank you for your thoughts.

A rim for rim brakes are most of the times heavier than their disk brake counterparts. To me this means that they are at least not weaker which make sense since their should be material to wear off. I have a front wheel with a centerlock dynohub build in a rim for rim brakes. I can use this wheel on all my bikes (rim or disk brake) if I need a dyno light on any of those bikes.

Lou

On 6/13/2022 8:39 PM, John B. wrote:
> On Mon, 13 Jun 2022 20:27:00 -0500, AMuzi <am@yellowjersey.org> wrote:
>
>> On 6/13/2022 8:04 PM, Tom Kunich wrote:
>>> On Monday, June 13, 2022 at 5:50:19 PM UTC-7, AMuzi wrote:
>>>> On 6/13/2022 7:03 PM, Alexander Stephens wrote:
>>>>> Hi there. I wanted to gauge the opinion of this group on the safety of a wheel build I'm about to embark on. I'm a fairly accomplished wheel builder (over 300 wheels), but I haven't ran into this situation before.
>>>>>
>>>>> I'm looking to build up a set of disc brake wheels (with disc brake hubs), but the rim I intend to use was designed for rim brakes. The hub drillings match the rim drillings - 24 hole. This is a carbon tubular rim and a centerlock, straightpull hub.
>>>>>
>>>>> Other than having a visible brake track as an aesthetic drag, is there any design reason why this combination wouldn't work? Are disc brake rims designed to be any beefier than their rim brake counterparts? All else being similar that is. Will the forces of disc brakes be too much for the rim to handle?
>>>>>
>>>>> For context, these wheels will be meant for cyclocross racing. I weigh 145 pounds. Thank you for your thoughts.
>>>>>
>>>> Assuming the rim is otherwise suitable (do you commonly ride
>>>> similar weight 24h rims for cross?) the brake track or lack
>>>> thereof doesn't matter.
>>>
>>> I misinterpreted the use of a centerlock disk hub. But that still doesn't cover the bases of the strongly offset spoke holes in disk hubs vs. rim brake hubs. I imagine that since Alexander is hardly likely to be a Tom Boonen it would probably survive. But the incorrect offset spoke holes still can cause premature failure.
>>>
>>
>> What does that mean?
>
> Not to get involved in wheel building although I have built a few, but
> with a disc brake where the braking force is applied to the spokes
> close to the hub, have you seen any evidence of increased spoke
> braking or deformation as a result? Or are disc brake wheels made with
> stronger spokes?
>

No and no.
We have not seen spoke failure from braking torque and disc
wheels use the same spokes and flange dimensions as any
other hub.

--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971

On 6/14/2022 12:33 AM, Alexander Stephens wrote:
>
> I understand wheel building and design very well. Where I want to further my knowledge here is in rim design. I’ve read and been told that disc brake forces on a wheel are very different than rim brake forces on a wheel. Under that assumption, I have the following question:
>
> Can a rim brake rim withstand disc brake forces?
>
> AMuzi has addressed this question. Thank you for that.

I'm among those who think you'll have no problem.

We could think about the problem in more detail, as a physics problem.
The brake torque is transferred to the rim by the spokes. I'd assume
that the brake torque results in an increase in spoke tension in the
spokes pointing (circumferentially) one way, and a decrease in tension
in the opposing spokes. Those tension changes (especially the increase)
would be shared by half the wheel's spokes.

We could take a crack at calculating that change in tension, although at
first glance it looks like some not-fun trigonometry would be involved.
(The closer to tangential the spokes are relative to the hub, the
smaller the change in tension. The spoke-to-hub angle depends on hub
radius, wheel radius and most importantly spoke pattern.)

The problem, if any, would be a fatigue problem at the spoke bed. I say
that because we already know hard disc brake stops don't rip spokes out
of rims. The more frequent truly hard stops (say, approaching 0.7g) the
shorter the fatigue life of the rim's spoke bed. And for almost all
riders, near-maximum stops are tremendously rare.

Unless the spoke bed is super thin, I'd guess there would be near zero
chance of a problem. If one did appear, it would show up as cracks in
the spoke bed and resulting loosening of spokes. I'd think that would
give plenty of warning before any disaster.

--
- Frank Krygowski

On 6/14/2022 12:04 PM, Frank Krygowski wrote:
> On 6/14/2022 12:33 AM, Alexander Stephens wrote:
>>
>> I understand wheel building and design very well. Where I
>> want to further my knowledge here is in rim design. I’ve
>> read and been told that disc brake forces on a wheel are
>> very different than rim brake forces on a wheel. Under
>> that assumption, I have the following question:
>>
>> Can a rim brake rim withstand disc brake forces?
>>
>> AMuzi has addressed this question. Thank you for that.
>
> I'm among those who think you'll have no problem.
>
> We could think about the problem in more detail, as a
> physics problem. The brake torque is transferred to the rim
> by the spokes. I'd assume that the brake torque results in
> an increase in spoke tension in the spokes pointing
> (circumferentially) one way, and a decrease in tension in
> the opposing spokes. Those tension changes (especially the
> increase) would be shared by half the wheel's spokes.
>
> We could take a crack at calculating that change in tension,
> although at first glance it looks like some not-fun
> trigonometry would be involved. (The closer to tangential
> the spokes are relative to the hub, the smaller the change
> in tension. The spoke-to-hub angle depends on hub radius,
> wheel radius and most importantly spoke pattern.)
>
> The problem, if any, would be a fatigue problem at the spoke
> bed. I say that because we already know hard disc brake
> stops don't rip spokes out of rims. The more frequent truly
> hard stops (say, approaching 0.7g) the shorter the fatigue
> life of the rim's spoke bed. And for almost all riders,
> near-maximum stops are tremendously rare.
>
> Unless the spoke bed is super thin, I'd guess there would be
> near zero chance of a problem. If one did appear, it would
> show up as cracks in the spoke bed and resulting loosening
> of spokes. I'd think that would give plenty of warning
> before any disaster.
>
>

Right, for a wheel, braking is the exact mirror of
acceleration. A big guy standing in a low gear can make
significant torque on the drive spokes (the other set, which
isn't loaded by a hub/disc brake) and higher peak loads
than braking. If your wheel's strong enough for the climb
it's strong enough for the descent.

--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971

On Monday, June 13, 2022 at 8:03:42 PM UTC-4, Alexander Stephens wrote:
> Hi there. I wanted to gauge the opinion of this group on the safety of a wheel build I'm about to embark on. I'm a fairly accomplished wheel builder (over 300 wheels), but I haven't ran into this situation before.
>
> I'm looking to build up a set of disc brake wheels (with disc brake hubs), but the rim I intend to use was designed for rim brakes. The hub drillings match the rim drillings - 24 hole. This is a carbon tubular rim and a centerlock, straightpull hub.
>
> Other than having a visible brake track as an aesthetic drag, is there any design reason why this combination wouldn't work? Are disc brake rims designed to be any beefier than their rim brake counterparts? All else being similar that is. Will the forces of disc brakes be too much for the rim to handle?
>
> For context, these wheels will be meant for cyclocross racing. I weigh 145 pounds. Thank you for your thoughts.

Another +1 to the opinion that you'll have no issues as long as the build is good quality - coming from another 145# CX/road/MTB racer :)