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[Brompton] Brazing disk mount or v-brakes studs?

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[Brompton] Brazing disk mount or v-brakes studs?

Old 02-12-21, 06:01 AM
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[Brompton] Brazing disk mount or v-brakes studs?

Hello,

I have a question for people who have a good knowledge of building their own frames: Do you think brazing a disk mount or v-brake studs (+ adding a brake booster) on a Brompton fork — front, at least — would be a good idea, or could it snap/twist while braking?

Not sure if Brompton uses chromoly steel or hi-ten steel.

I'd rather a disk brake, but a Magura rim brake might already be nice — although I was told they aren't stronger than the current, dual-pivot Brompton caliper brake, but they might require less force to operate, especially when riding downhill.

I know an experienced bike builder who could try, but I'd like your opinion before bothering him.

Thank you.

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Old 02-12-21, 08:18 AM
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Why not just buy a fork already made for such?
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Old 02-12-21, 09:33 AM
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I'd be reluctant to add a disk brake mount to a fork that wasn't designed to handle disk brake loads. Perhaps there is a Bromton-compatible fork with such mounts already in place?
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Old 02-12-21, 09:50 AM
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JohnDThompson 's reluctance reminded me that since disc brakes were introduced, it's been decided that quick release skewers are so great an idea with discs. Supposedly the braking force puts more strain on the axle in a direction that makes it want to "be free". So that is another point for getting a fork for disc with a through hub axle.

Of course if you know you'll never ever have to stop quick, you are good. Sort of like those folks that ride with their helmet hanging on their bars. They have them handy to put on when they decide to wreck I suppose. <grin>

Though there are plenty of bikes with QR's and discs. But I think they are mainly old bikes. Maybe not.
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Old 02-12-21, 10:16 AM
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QR skewers can handle the brake reaction forces if common sense and a little drop out thought is applied. Common sense in keeping the skewer tight, and the exposed cam types don't provide the clamping pressures that an enclosed cam type can. Drop out thought in changing the drop out slot orientation so on a fork the slot points more forward and less down, This way the axle has a slot side to push against instead of the open slot. Andy
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Old 02-12-21, 10:17 AM
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Should have added that through axles are more about rotor/pad rub then axle retention. Andy
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Old 02-12-21, 10:37 AM
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Originally Posted by Iride01 View Post
Why not just buy a fork already made for such?
Thanks. Because they're a lot more expensive, and make for a wider folded bike (100mm vs. 74mm).

Besides, the disk is located on the left per usual… which isn't a good option for a Brompton because of the way it folds.

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Old 02-12-21, 10:49 AM
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Yeah, I'm really not capable of comprehending that tangle in the picture. I'm a road bike guy only. I can't imagine any reason to fold a bike up like that! <grin>

I just have to resort to "different strokes for different folks" when I see such.
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Old 02-12-21, 12:09 PM
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If you are needing better braking, you could swap to better pads from SwissStop or KoolStop and use Jagwire Elite Link Housing or potentially other high quality compressionless housing and polished stainless steel cables (that aren't coated) and since the money is on the table swap to Cane Creek eeBrakes which will give you pretty damn fine braking without altering the frame and causing other issues.

If you want to step it up even more a nice set of Paul Canti Levers would probably improve the lever feel at least a little with the bearings in the pivots and a nice feel on the levers. A Brompton is a classy folder and deserves some classy parts.
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Old 02-12-21, 01:53 PM
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Considering all the posts I have seen over the years about:
  • don't add disk to forks that are not designed for it
  • Bent my disk
  • having problems with pads not clearing disk after taking wheel of
  • etc
It really seems this is not a good idea, especially with a folder where when folded the clearances are tight, chances of ongoing problems/complications are high
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Old 02-12-21, 04:31 PM
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Thanks for the infos.

I just happened on this page about a recently (2019) modified Brompton with v-brakes, belt drive, and a Nexus gear hub:
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Old 02-13-21, 02:02 PM
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Just curious, why so unhappy with the rim brakes? Or at least that is why I perceive you ask about disc or v-brake.

While the old single pivot rim brakes never gave a great feeling of stopping power compared to other types of brakes, they generally are always good enough to stop in time.

Also, I find that my Shimano 105 5800 double pivot brakes stop my old Paramount much better than any rim brake I've ever had. And even slightly quicker than the Shimano Tiagra 4700 double pivot brakes that are on my son's Emonda. Although I'm surprised myself at that last difference. However the 105's do look beefier than the Tiagra's.

So if stopping power is the issue, maybe it can be more easily and simply solved by a better model rim brake.
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Old 02-13-21, 09:22 PM
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One aspect of folders, or other small wheel bikes, is the rim brake loss of leverage as the rim gets smaller in diameter. On the other hand hub brakes pick up leverage with smaller rims. Andy
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Old 02-14-21, 06:11 AM
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Originally Posted by Iride01 View Post
Just curious, why so unhappy with the rim brakes? Or at least that is why I perceive you ask about disc or v-brake..
I have to pull stronger than the hydraulic disk brakes on my big bike, especially going downhill, and the rims wear too fast, especially when I ride off-road (crap getting under the brake pads).

CaneCreek does offer better brake calipers, but they might be a more expensive option that just brazing an adapter (caliper + lever).

https://www.bike24.com/p2315396.html
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Old 02-14-21, 03:00 PM
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What about mounting brakes for the electric Brompton? E-bikes usually need stronger brakes.
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Old 02-15-21, 05:28 AM
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Another factor for disc brakes, other than packaging them so there is no contact when the bike is folded, is that the smaller the wheel gets, the closer to the ground the disc is. Come off a curb at an angle or kiss a rock while off road, and your disc becomes a fender.

I run classic side pull callipers on my classic folders on steel rims, and no they are not going to stop me like a train but they do require little maintenance. My point is that the harder you push your equipment, the heavier and more complex it becomes, and the quicker everything will wear.

If your rims are wearing quickly your choices may be:
- create a heavier replacement
- create a lighter more complex replacement that will need more servicing
- change riding style
- change machine
- treat rims as a consumable
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Old 02-15-21, 06:06 AM
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Originally Posted by Winfried View Post
Because they... make for a wider folded bike (100mm vs. 74mm).
I'd be surprised if you could find a 74mm hub with disc attachments; the flanges would be very close together, and the wheel would need considerable "dish". A wheel built with such a hub would be weaker and more susceptible to damage.
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Old 02-15-21, 06:11 AM
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[QUOTE=Winfried;21923301]...the rims wear too fast, especially when I ride off-road (crap getting under the brake pads)./QUOTE]
I solved this problem by changing the rear brake from a direct-pull to a roller brake (a sort of drum brake). Shimano has a modular roller brake that is compatible with some Nexus and Alfine hubs. You might be able to find a different rear wheel with a drum brake if your current hub can't accept a brake module.
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Old 02-15-21, 06:15 AM
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Originally Posted by Iride01 View Post
Yeah, I'm really not capable of comprehending that tangle in the picture. I'm a road bike guy only.
Here's an example: in my area the local rail service doesn't allow bikes on trains during rush hour. However, a folded bike in a bag is considered "luggage", and allowed at any time.
I'd love to commute on my road bike, but the folder is the only option since the total round-trip is too long (100 miles)!
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Old 02-15-21, 06:29 AM
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Originally Posted by 2_i View Post
What about mounting brakes for the electric Brompton? E-bikes usually need stronger brakes.
I read the brakes are the same, although the bike is heavier (→ braking isn't too good in the rain).

Originally Posted by sweeks View Post
I'd be surprised if you could find a 74mm hub with disc attachments; the flanges would be very close together, and the wheel would need considerable "dish". A wheel built with such a hub would be weaker and more susceptible to damage.
What about those?
https://www.aliexpress.com/item/1005001397867505.html

Dahon and other Asian brands do sell folders with disk brakes on 74mm forks (like Brompton).

Originally Posted by sweeks View Post
I solved this problem by changing the rear brake from a direct-pull to a roller brake (a sort of drum brake).
It won't work on a Brompton. Greenspeed in Australia had to saw off part of the Sturmey-Arche hub to fit it into a Brompton:
https://www.atob.org.uk/brompton-hub-brake/
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Old 02-15-21, 07:47 PM
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Originally Posted by Winfried View Post
Well, I *am* surprised, but I am pleased to stand corrected.
I do, however, wonder about the lateral stability of a wheel with flanges so close together.
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Old 02-16-21, 04:52 PM
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Originally Posted by Winfried View Post
I have to pull stronger than the hydraulic disk brakes on my big bike, especially going downhill, and the rims wear too fast, especially when I ride off-road (crap getting under the brake pads).

CaneCreek does offer better brake calipers, but they might be a more expensive option that just brazing an adapter (caliper + lever).

https://www.bike24.com/p2315396.html
completely off topic, but I would love to see a pic of off road riding........I have never envisioned an off road folder
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Old 02-16-21, 06:17 PM
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Anything besides asphalt, nothing the Brompton was meant for, so I can't complain.

I doesn't take long for rims to look like this:

Last edited by Winfried; 02-16-21 at 06:22 PM.
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Old 02-17-21, 01:47 AM
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Originally Posted by squirtdad View Post
completely off topic, but I would love to see a pic of off road riding........I have never envisioned an off road folder
As requested, although nothing so flash as a Brompton...


In a forest somewhere.

After offroading in the snow
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Old 02-17-21, 02:07 AM
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Originally Posted by Winfried View Post
Anything besides asphalt, nothing the Brompton was meant for, so I can't complain.

I doesn't take long for rims to look like this:
Hmm, that is bad, and I sometimes wonder if the wear rate is worse when the rim is smaller. Assuming that the aluminium wears at a fixed rate, and the bike comes to a stop in the same road distance whatever the size of wheels, then because a smaller wheel has a shorter rim length it should have a shorter life.

Even with 24" wheels I notice quite rapid wear, so as a result my aluminium rims live on a hook in my garage and I run with squealing steel rims instead. I usually keep a number of wheels in stock, and in your situation I would give serious consideration to buying several sets of rims and weaving fresh rims onto my spare wheels ready to swop over when the current set looks worn. A local bike shop shouldn't charge much to put your replacement rims on your wheels.
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