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Old 02-09-12, 09:50 PM   #1
mtalinm
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weld disc tab on fork, or use jubilee clip to mount drum brake?

I have a folding bike (Xootr Swift) and want to put a weather-agnostic brake on the front.

my original plan was to try a disc brake, which I understand requires a tab on the front fork. no one seems to sell a fork for this bike with a tab, but I suppose I could have one welded on (it is a steel fork). Should that make me nervous, or is that a reasonable approach? (of course I would need to get a wheel built)

someone suggested going the drum route instead, mounting it using a jubilee clip on the fork which would not require welding. sounds easy but also sounds less secure. also, how is the performance say of a Sturmey-Archer 90mm X-RD? I have shimano IM-50 drum brakes on my Trek Soho, but they suck rocks so I am skeptical.

of course I could just leave the V-brakes on there, but they don't work so well in the rain and snow
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Old 02-10-12, 12:05 AM   #2
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Anyone recall seeing a photo online of a fork that had been retrofitted with disk tabs? It bent just above the upper tab where the fork wasnt designed to take the stress...
Just can't remember where I saw that one, otherwise I'd post it for dramatic effect.


Get kool stop salmon pads for your existing v-brakes.



P.S. i just looked up what 'jubilee clip' means; No, I would not trust a 'hose clamp' to hold anything structural -ie a drum brake reaction arm.

Last edited by xenologer; 02-10-12 at 12:10 AM.
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Old 02-10-12, 12:32 AM   #3
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yikes, maybe welding is a bad idea. the jubilee clip sounded weird to me though someone swore by it.

I already have koolstop salmons on all my bikes, so maybe that's the best I can do unless I have someone build a custom fork...?

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Originally Posted by xenologer View Post
Anyone recall seeing a photo online of a fork that had been retrofitted with disk tabs? It bent just above the upper tab where the fork wasnt designed to take the stress...
Just can't remember where I saw that one, otherwise I'd post it for dramatic effect.


Get kool stop salmon pads for your existing v-brakes.



P.S. i just looked up what 'jubilee clip' means; No, I would not trust a 'hose clamp' to hold anything structural -ie a drum brake reaction arm.
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Old 02-10-12, 12:40 AM   #4
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hose clamps are super strong for their intended purpose, which is to keep tube shaped things together.

I am not too familiar with front drum brake hubs, but from the looks of it, there's nothing special about the forks used, other than the fact they are metal and the action arm is attached with a hose clamp, just like the ones used on rear drum brake hubs.

even going by sturmey archer tech docs, the brake arm for drum brakes only require 2Nm of torq to be held on. This is in comparison to 22Nm of torq for the axle nuts.
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Old 02-10-12, 12:54 AM   #5
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#1, the frame tube needs be chosen to anticipate the disc tab..
And that is extra important for forks..

on my drum brake hub, they come with a frame band clip., rear has 1 bolt for itself
and a second one for the brake arm . my front has a slot for the arm in the band .
arm slides in when you put the wheel back in again .
neither require a welding job.
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Old 02-10-12, 10:30 AM   #6
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AEO/fietsbob, with 12k posts apiece I should probably take your word(s) for it. I looked at my /Soho again this morning and while it does have a tab to hold the brake in place maybe a clip would indeed do the trick. this would be GREAT news if so.

here is the drum hub I am thinking about: http://harriscyclery.net/product/stu...ub-36h-813.htm
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Old 02-10-12, 10:32 AM   #7
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Quote:
Originally Posted by mtalinm View Post
someone suggested going the drum route instead, mounting it using a jubilee clip on the fork which would not require welding. sounds easy but also sounds less secure. also, how is the performance say of a Sturmey-Archer 90mm X-RD?

The 70mm Sturmey-Archer drums are reasonable on 700c or 26" wheels. Seeing as the stopping power of any kind of hub brake increases as the wheel diameter decreases, on a 20" or 16" folding bike wheel, a 70mm one will be more than adequate for your stopping power, never mind the 90mm one.

By the way, the X-RD is a 70mm rear drum brake hub, the 90mm front drum is an XL-FD (XL indicates 90mm drum, F indicates front). As I said, I'd suggest the 70mm X-FD, as the larger drum would probably be overkill on a small wheel .

You don't need to kludge anything with a jubilee clip, the drum hubs come with a special clip which is designed to allow easy removal of the wheel, but still be secure.

Edit, you must have posted while I was typing, that hub in your link is the one I was suggesting.
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Old 02-10-12, 10:38 AM   #8
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there are a few different fork mounting bands to match the diameter of your fork, Measure..
At the place on the fork blade, 6" up from the axle.

I've run the UK made version of that hub for 25+ years..
26" wheel, now studded tire fitted..

Last edited by fietsbob; 02-10-12 at 10:43 AM.
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Old 02-10-12, 11:19 AM   #9
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P-clamp works fine. Here's mine still going strong after 25+ years, hauling two kids around in a trailer, etc:



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Old 02-10-12, 11:34 AM   #10
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well, this is sounding like a plan now. I'm a fattie so can use all the stopping power I can get! so i may stick with the 90mm brake. great to hear that the mounting clip is included - sure sounds easier than removing the fork and welding a disc tab.

thanks all!
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Old 02-10-12, 04:27 PM   #11
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I'm a fattie so can use all the stopping power I can get! so i may stick with the 90mm brake.
I still think it's overkill. A 20" wheel (which is what the Xootr seems to have from the picture in your signature link) has an outside diameter of maybe 450mm, while my 700c had one of around 650mm. That's a bit more than two-thirds the diameter, so a bit less than three halves the braking power, or say 140% of what I used to get, for a given amount of force pulling the cable. Seeing as I was mostly braking from the hoods of an old set of non-aero drop bar brake levers, you'll also be pulling the cable harder than me, assuming you still have the flat bars from the picture and some reasonable levers (with pivots in a more sensible place for the position they're being used from). You'll probably be able to get twice the stopping power as I did from a given amount of hand force, and my brakes were reasonable in the first place.

I use the past tense to describe my wheel because I bent it, and the bike now has a 26" one. Hooray for not having rim brakes!

Last edited by Airburst; 02-10-12 at 04:28 PM. Reason: typo
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Old 02-10-12, 04:50 PM   #12
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Does it make a difference that they are sti levers?
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Old 02-10-12, 05:11 PM   #13
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Quote:
Originally Posted by xenologer View Post
Anyone recall seeing a photo online of a fork that had been retrofitted with disk tabs? It bent just above the upper tab where the fork wasnt designed to take the stress...
I remember seeing that on the Rodriguez Bikes web page in the FAQ about disc brakes
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Old 02-10-12, 05:11 PM   #14
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Quote:
does it make a difference that they are sti levers?
Aero road levers are rather high leverage,
little "work" (cable pulled) moved for a long swing of the effort arm
may bottom out before the brake does enough.

But , there is an Inline Travel Agent, [made for cable disc brakes]
just needs to be anchored somewhere , like to a braze on.


I'm using old cable out the top Campag brake levers on mine ..

Last edited by fietsbob; 02-10-12 at 05:17 PM.
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Old 02-12-12, 03:28 AM   #15
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Does it make a difference that they are sti levers?
Drop handlebar ones, or flats? That bike in your signature looks like the Xootr Swift in the link, and seems to have drop handlebars, so if it's the one you mean, you're fine.

If it was flat handlebar sti shifters, they all have V-brake levers in them these days as far as I know, so it would be an issue.
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Old 02-12-12, 08:51 AM   #16
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well, this is sounding like a plan now. I'm a fattie so can use all the stopping power I can get! so i may stick with the 90mm brake....
I have a 90mm dyno/drum hub, it's great. I had a 70mm dyno/drum but just had to try out the XL when it finally came out, glad I did. 90mm has braking power close to a disc, a bargain when the cost of a dyno is factored in.
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Old 02-12-12, 12:03 PM   #17
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drops, yes
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Old 02-13-12, 11:41 AM   #18
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To be honest the main reason I'm only using a 70mm drum is that I got it cheaply on eBay, if I was buying new I might well get the 90mm one for the front, seeing as it doesn't cost that much more and there's no real reason not to, apart from the weight. Don't let me put you off by being a cheapskate.
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Old 02-13-12, 12:03 PM   #19
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+1 70mm Sturmey Archer X-FD drum hub.

+1 Clip that comes with the S/A hub/wheel will work and is fine.

Your STI brake levers should work fine -- same pull on a drum as for "road" caliper brakes.

Here's a wheel I built on a 20" folder:



PS: if you replace your headset star nut and top cap with a BMX-style "brake cable through the headset" type (Answer makes one model), and route brake cable appropriately, it looks real clean...
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Old 02-15-12, 11:24 PM   #20
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thanks all for the great suggestions. I placed an order at Harris Cyclery for a 20" wheel with the 70mm S/A drum hub (they just shook their head at me when I said I might like the 90mm). skipped the dynohub b/c I am so in love with my MagicShine

Once this is installed I think I am going to have the perfect commuter...
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Old 02-16-12, 02:28 AM   #21
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I've got a pair of wheels built around old Sachs drum brake hubs. Installation manual says to use long-pull levers, but braking power felt a bit marginal. Switched to short-pull. Front is OK. Lock-up is possible, but requires a determined effort. Rear still kinda marginal, as the adjustment window between lock-up before bottoming out and no drag at coasting is really narrow.
The hubs came from a donor bike, so the reaction arm bracket(a wraparound strip with a sleeve in it) wouldn't fit. Cut a collar out of 1/2" aluminium plate, filed it down to something (almost) seat clamp looking, but with a sleeve in it. Stuck it on a 26" MTB steel fork and haven't had any issues with that part.
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