As the subject line says, I'm seeking a 700c rim that is suitable> for both disc brakes and rim brakes.>
To clarify: I'm building up a cyclocross bike, and wish to have> a disc brake at the front, and normal canti's at the rear.
Any rim suitable for rim brakes is suitable for disc brakes, but the converse is not true. If you wish to have matching rims, then your front wheel will have a redundant brake surface. It's of no consequence.
One thing that does matter is the spoking pattern. Front wheels work fine (in most cases) with cool radial spoking, but that won't last long with any hub brake. Torque transference.
On Mon, 07 Mar 2005 17:42:05 +0000, Vic <victor_papanekOBFUSCATION@hotmail.com> may have said:
Hello all.>
As the subject line says, I'm seeking a 700c rim that is suitable>for both disc brakes and rim brakes.>
To clarify: I'm building up a cyclocross bike, and wish to have>a disc brake at the front, and normal canti's at the rear.
All rim-brake rims are disc-compatible.
All disc-brake hubs are rim-brake compatible.
What you want, then, is to use rim-brake rims with a disc-brake front hub. That's easy.
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Qui Si Parla Campagnolo 8 March 2005 17:48:28 [ permanent link ]
Vic wrote:> Hello all.>
As the subject line says, I'm seeking a 700c rim that is suitable> for both disc brakes and rim brakes.>
To clarify: I'm building up a cyclocross bike, and wish to have> a disc brake at the front, and normal canti's at the rear.>
plover3141592654@bobgoon.co.uk
Any rim that is canti compatible is of course 'disc compatible', since you don't use the rim to brake. There are no 700c rims that are disc only rims, that is w/o braking surfaces.
Any rim that is canti compatible is of course 'disc compatible', since > you don't use the rim to brake. There are no 700c rims that are disc > only rims, that is w/o braking surfaces.
I have an Alex TD17 right next to me that is disc only.
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On 8 Mar 2005 17:25:50 -0800, "JeffWills" <jwills@pacifier.com> may have said:
S R Sharp wrote:>> Qui Si Parla Campagnolo wrote:>> >
Any rim that is canti compatible is of course 'disc compatible',>since>> > you don't use the rim to brake. There are no 700c rims that are>disc>> > only rims, that is w/o braking surfaces.>>
I have an Alex TD17 right next to me that is disc only.>>
I knew there had to be *one* 700c disc-specific renegade out there somewhere. Of course, the chances of coming across one of those are pretty slim.
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I would think that those wouldn't be too useful on a roadie that needs 700c, though.
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I have an Alex TD17 right next to me that is disc only.> >
Thanks, didn't know that BUT disc only rims make no sense to me.
Whether> they be MTB or 700c. Whether or not you use the braking surface, having> one on a rim doesn't 'hurt' it.
Well, yes and no. A rim with a superfluous machined "braking" surface is would be weaker than an unmachined rim. However, I prefer unmachined rims for caliper brake applications anyway.
I have an Alex TD17 right next to me that is disc only.>> >
Thanks, didn't know that BUT disc only rims make no sense to me.>Whether>> they be MTB or 700c. Whether or not you use the braking surface,>having>> one on a rim doesn't 'hurt' it.>
Well, yes and no. A rim with a superfluous machined "braking" surface>is would be weaker than an unmachined rim. However, I prefer unmachined>rims for caliper brake applications anyway.
You'd be right if you said "a rim of equal weight with a superfluous machined..." All other things being equal, adding a mm or two of thickness to the sidewalls only makes a rim stronger, after all.
On Tue, 08 Mar 2005 19:43:41 -0600, Werehatrack>><rault00@earthWEEDSlink.net> wrote:>>>I knew there had to be *one* 700c disc-specific renegade out there>>>somewhere. Of course, the chances of coming across one of those are>>>pretty slim.
Mark Hickey wrote:> "JeffWills" <jwills@pacifier.com> wrote:>
You'd be right if you said "a rim of equal weight with a superfluous> machined..." All other things being equal, adding a mm or two of> thickness to the sidewalls only makes a rim stronger, after all.>
Yeah, but... the machined rims I've seen are not machined *flat*. The machining leaves a series of concentric rings, which would tend to be stress risers, I think. Given machined and non-machined rims of *equal weight*, I'd think the non-machined rim would be stronger.
Probably not much difference in reality, but what the heck...
Mark Hickey wrote:>> "JeffWills" <jwills@pacifier.com> wrote:>>
You'd be right if you said "a rim of equal weight with a superfluous>> machined..." All other things being equal, adding a mm or two of>> thickness to the sidewalls only makes a rim stronger, after all.>
Yeah, but... the machined rims I've seen are not machined *flat*. The>machining leaves a series of concentric rings, which would tend to be>stress risers, I think. Given machined and non-machined rims of *equal>weight*, I'd think the non-machined rim would be stronger.
Absolutely, the machined rims are "partially worn out" when you get 'em. Since they have to make the walls extra thick to handle the variation, you end up with either a rim with too much material in some places and/or not enough in others (compared to a non-machined rim).
I wouldn't worry too much about the concentric rings, since by the time the sidewalls are worn enough for sidewall strength to be an issue, they're long gone anyway. I think it's a fashion thing, myself.
Probably not much difference in reality, but what the heck...
That's probably the thing to take away from this discussion.
Qui Si Parla Campagnolo 10 March 2005 18:10:09 [ permanent link ]
Mark Hickey wrote:> "JeffWills" <jwills@pacifier.com> wrote:>
Qui Si Parla Campagnolo wrote:>>
I have an Alex TD17 right next to me that is disc only.>>>>
Thanks, didn't know that BUT disc only rims make no sense to me.>>
Whether>>
they be MTB or 700c. Whether or not you use the braking surface,>>
having>>
one on a rim doesn't 'hurt' it.>>
Well, yes and no. A rim with a superfluous machined "braking" surface>>is would be weaker than an unmachined rim. However, I prefer unmachined>>rims for caliper brake applications anyway.>
You'd be right if you said "a rim of equal weight with a superfluous> machined..." All other things being equal, adding a mm or two of> thickness to the sidewalls only makes a rim stronger, after all.>
I guess all above shows my disdain for disc brakes on bicycles in general. Discs are great for some applications, like downhill, cross, tandems. But to apply them to road bikes is just plain silly. I got a kick out of a recent ad for a disc conversion kit that claimed the disc caliper is more 'aero' since the air from the front wheel is 'disturbed' by the front brake rim caliper..
On Thu, 10 Mar 2005 07:10:09 -0700, Qui Si Parla Campagnolo <peter@vecchios.com> may have said:
I got a >kick out of a recent ad for a disc conversion kit that claimed the disc >caliper is more 'aero' since the air from the front wheel is 'disturbed' >by the front brake rim caliper..
Yeah, like the disc caliper doesn't have a profile. Uh-huh. Sure.
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On Thu, 10 Mar 2005 11:50:37 -0600, dianne_1234 <dianne_1234@NOSPAMyahoo.com> quoted another source thusly:
"... Additionally, the space at the>fork crown above the tire has been maximized to help air flow through>rather than damming it up."
So, for a different reason, they've finally added enough room to allow a broader range of tires to be used.
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On Thu, 10 Mar 2005 07:10:09 -0700, Qui Si Parla Campagnolo> <peter@vecchios.com> wrote:>
Discs are great for some applications, like downhill, cross, > >tandems. >
I'm thinking of discs on our tandem but have read bad things about> fork fatigue and heat build up.
Fork fatigue? Have you read or seen any case where a fork broke due to repeated disc brake usage, as I haven't (and not referring to aftermarket disc mounts on thin forks).
Heat build up is said to potentially> cause brake fade, warped rotors and sometimes melted plastic parts on> the caliper. Any advice for me?
Heat build up on rim brakes on tandems can also cause brake fade and blown tyres. There is no perfect brake. What plastic bits on which disc calipers are you referring to?
But to apply them to road bikes is just plain silly. >
I'm beginning to think the rim is the best "disc" for tandem brakes,> but I'd love to be assured otherwise...
Try it, rather than relying on postulations, theories, tales and spooky stories. It's easy to get forks with both disc and caliper mounts these days; test both.
On Thu, 10 Mar 2005 20:39:21 GMT, Jose Rizal <_@_._> wrote:
dianne_1234:>
I'm thinking of discs on our tandem but have read bad things about>> fork fatigue and heat build up. >
Fork fatigue? Have you read or seen any case where a fork broke due to>repeated disc brake usage, as I haven't
Forgot where, but out there on the 'net somewhere are, as you say, "spooky" tandem fork failure reports, and in this newsgroup Jobst warns against simply adding disc mounts to existing forks, even on single bikes. It makes sense to me, and since failure on a tandem makes me especially nervous, I want to feel sure before we plunge in.
(and not referring to aftermarket disc mounts on thin forks).
Can you name some aftermarket tandem road forks that come with disc brake mounts? I haven't been able to find any. Cannondale sells one, but only attached to their bike.
Heat build up on rim brakes on tandems can also cause brake fade and>blown tyres. There is no perfect brake.
Right, rim heat build up is one reason many tandem teams use a drum brake in addition to rim brakes. So far our experience with Bontrager Tandem wheels and no drag brake is zero blow-offs (touch wood!). There is some talk on the tandem list of deeper rims cooling better, but I'm not sure that's why we haven't had problems.
What plastic bits on which disc calipers are you referring to?
Try it, rather than relying on postulations, theories, tales and spooky>stories.
I'm leaning towards trying discs. We're adventurous, but not foolhardy!
It's easy to get forks with both disc and caliper mounts these>days; test both.
We have great experience with caliper brakes on our old tandem, so that leaves discs.
What tandem disc brake forks do you recommend, and where can I buy them? Also, what test procedure would you suggest? How will we know if the set up is safe?
On Thu, 10 Mar 2005 07:10:09 -0700, Qui Si Parla Campagnolo><peter@vecchios.com> may have said:>
I got a >>kick out of a recent ad for a disc conversion kit that claimed the disc >>caliper is more 'aero' since the air from the front wheel is 'disturbed' >>by the front brake rim caliper..>
Yeah, like the disc caliper doesn't have a profile. Uh-huh. Sure.
I think it would be more believable to claim the front caliper acts like a fairing around the highest-drag portion of the wheel (the upper spokes coming "over the top"). Still bugle oil, but hey... you can almost imagine it being marginally true (unlike the "invisible-to-the-wind disc brake system").
On Thu, 10 Mar 2005 20:39:21 GMT, Jose Rizal <_@_._> wrote:>
dianne_1234:>>
I'm thinking of discs on our tandem but have read bad things about>>> fork fatigue and heat build up. >>
Fork fatigue? Have you read or seen any case where a fork broke due to>>repeated disc brake usage, as I haven't >
Forgot where, but out there on the 'net somewhere are, as you say,>"spooky" tandem fork failure reports, and in this newsgroup Jobst>warns against simply adding disc mounts to existing forks, even on>single bikes. It makes sense to me, and since failure on a tandem>makes me especially nervous, I want to feel sure before we plunge in.
The best anecdotal evidence of the need for a beefier fork is to look at the difference between the 'cross forks built for cantis and for discs. The Winwood (for example) disc fork has MUCH thicker legs.
(and not referring to aftermarket disc mounts on thin forks).>
Can you name some aftermarket tandem road forks that come with disc>brake mounts? I haven't been able to find any. Cannondale sells one,>but only attached to their bike.
I haven't seen one. I'm sold on the fact that a caliper brake is a better solution than cantis for a tandem that won't ever have 28mm+ tires or fenders. The difference in braking ability between my old Santana with cantis and my new caliper-equipped twofer is amazing.
Heat build up on rim brakes on tandems can also cause brake fade and>>blown tyres. There is no perfect brake. >
Right, rim heat build up is one reason many tandem teams use a drum>brake in addition to rim brakes. So far our experience with Bontrager>Tandem wheels and no drag brake is zero blow-offs (touch wood!). There>is some talk on the tandem list of deeper rims cooling better, but I'm>not sure that's why we haven't had problems.
I've also never had a problem - I suppose it's got a lot to do with where you ride and how you descend. I like to "let the bike roll" and don't really drag the brakes much on most descents. When I do, I'll tend to build up speed between switchbacks (where aero drag is a significant slowing force), and brake hard into the corner, and let it roll coming out the other side.
I'm leaning towards trying discs. We're adventurous, but not>foolhardy!
You could always do what motorcycle manufacturers do and mount TWO discs on the front wheel, one on the back (or better yet, two on each). That way, each would only have to deal with the same heat loading as a half-bike (well, plus a little more due to the aerodynamic advantage).
It's easy to get forks with both disc and caliper mounts these>>days; test both.>
We have great experience with caliper brakes on our old tandem, so>that leaves discs. >
What tandem disc brake forks do you recommend, and where can I buy>them? Also, what test procedure would you suggest? How will we know if>the set up is safe?
They're probably out there, but I haven't seen 'em.
On Thu, 10 Mar 2005 20:39:21 GMT, Jose Rizal <_@_._> wrote:>
Fork fatigue? Have you read or seen any case where a fork broke due to> >repeated disc brake usage, as I haven't >
Forgot where, but out there on the 'net somewhere are, as you say,> "spooky" tandem fork failure reports, and in this newsgroup Jobst> warns against simply adding disc mounts to existing forks, even on> single bikes. It makes sense to me, and since failure on a tandem> makes me especially nervous, I want to feel sure before we plunge in.
This is what I was not referring to. Adding disc mounts to cantilever-only-designed forks is not a good idea.
Can you name some aftermarket tandem road forks that come with disc> brake mounts? I haven't been able to find any. Cannondale sells one,> but only attached to their bike.
Co-motion manufactures tandems and custom tandem forks. It might be able to make you one to your liking (but I wouldn't go for a carbon fibre fork, disc or not).
TET Cycles and Wily Cycles both can make you custom forks with disc and canti mounts; get in touch with both and ask if they can make one for a tandem (ie something beefier than cyclocross dimensions).
Spectrum Cycles make their own tandem forks; ask if they can make you one with both brake mounting options.
Yes, but re-read the characteristic of the downhill road they use for the tests (Mountain Ave. in CA):
"Rim brakes and most disc brakes will fail at or before the second stop. (Rim brakes don't actually fail, but the tire leaves the rim)."
If you're going to subject your brakes to the loads specified in the tests, then you might be best off using drums, or just stop occassionally to let the brakes cool down (whichever type you choose).
I'm leaning towards trying discs. We're adventurous, but not> foolhardy!
You don't have to be.
What tandem disc brake forks do you recommend, and where can I buy> them?
I can't recommend any specific tandem forks since I don't ride a tandem. I can only suggest you make contact with the people above, and make sure that they are aware of the greater loads placed on tandem forks (and hence can manufacture a strong enough disc+canti fork for you).
Also, what test procedure would you suggest? How will we know if> the set up is safe?
Testing by yourself may not be as practical as I made it seem. You might ask around tandem clubs for people who have done testing for you by their experience. It may also pay you to ask Chalo Colina what forks he uses.
A good feature with disc rigid forks is forward-facing dropouts. Non-tapered tubes may likely be stronger than tapered ones. Also good is if the manufacturer guarantees safe tandem use for the forks; Co-motion and Spectrum seem to do this, and so do the tandem suspension fork manufacturers mentioned above.
David Damerell 11 March 2005 19:47:17 [ permanent link ]
begin quoting dianne_1234 <dianne_1234@NOSPAMyahoo.com>:><peter@vecchios.com> wrote:>>Discs are great for some applications, like downhill, cross, >>tandems. >I'm thinking of discs on our tandem but have read bad things about>fork fatigue and heat build up. Heat build up is said to potentially>cause brake fade, warped rotors and sometimes melted plastic parts on>the caliper. Any advice for me?
Same as we said last time. You want a brake with a huge heatsink in, and neither disc nor rim will do; that implies a drum brake, and that precludes a rear disc. -- David Damerell <damerell@chiark.greenend.org.uk> flcl? Today is Friday, March.
begin quoting dianne_1234 <dianne_1234@NOSPAMyahoo.com>:>
<peter@vecchios.com> wrote:>>
Discs are great for some applications, like downhill, cross, >>>tandems. >>
I'm thinking of discs on our tandem but have read bad things about>>fork fatigue and heat build up. Heat build up is said to potentially>>cause brake fade, warped rotors and sometimes melted plastic parts on>>the caliper. Any advice for me?>
Same as we said last time. You want a brake with a huge heatsink in, and> neither disc nor rim will do; that implies a drum brake, and that> precludes a rear disc.
What about an aluminium alloy disc wheel? 0.6 square meters of surface area to dissipate heat! ;)
What about an aluminium alloy disc wheel? 0.6 square meters of
surface> area to dissipate heat! ;)>
Oddly enough, I've seen such a beast. Back in the '80's Sugino made disc wheels from carbon fiber and from aluminum. In order to keep weight manageable, the aluminum one had a honeycomb core- and it was still rather heavy: 1600 grams, I think.
The weak point was the connection between the hub and the disk. I saw more than one where the center had been ripped out in an attempt to remove the freewheel.
They were sew-up tire only- maybe it was an attempt to prevent melting of glue!
(Sorry, Tom- I don't think they were ever made in 16" or 20" sizes.)
