A caliper set sells for under $30 here.

https://cimg5.ibsrv.net/gimg/bikefor...67bd424662.jpg
USD1=IDR15500

I, myself, me personally would replace them preemptively.

(above) Oh, the Zooms are cable-actuated hydraulic. I can see the relationship between the cable and hydraulic cylinder; Weird, but if my memory is correct(?), I thought the early All-Packa I saw locally, had the piston right at the end of the cable and inline with it, but I could be wrong.

Regarding Shimano, I guess most bike makers get their Shimano parts directly, instead of through a distributor(?), as I would think that Bike Friday could use the same sources as local bike shops, who use equal or less volume of parts than BF.

Indeed. In an earlier discussion, our Belgian friend argued convincingly that mech/hydro hybrid brakes are neither fish not fowl, possessing the drawbacks of both. In fact, his explanation was a response to a question of yours.

My experience with the Zoom HB100 XTech hybrid disc brakes squeezing 160m disks:

Credit card touring, descending the 15%+ grades of the hilltop pueblos blancos in Andalucia, Spain, descending mountain passes featured in the Vuelta España, and descending and riding through gravel and dirt/mud farm roads. Brakes worked fine, never failed, but by the end of the trip they required increased lever pressure. In comparison, the other bike we had used v-brakes and had consistent initial bite and stopping power the whole trip.

Mountain biking near home. After replacing pads, initial bite and stopping power returned. No worries descending.

Loaded touring of GAP/C&O Trails (Pittsburgh, PA to Washington, DC). The trails themselves are relatively flat, but there are steep grades when you leave the trail. In often wet and muddy conditions, braking was strong and consistent.

Loaded touring of the Finger Lakes region of New York. Hilly region, with long and steep descents (1+ mile, 15%+ grade). On pavement and gravel, the brakes worked great, with good initial bite and good stopping power.

For comparison, I recently did some mountain biking around Lake Tahoe, Nevada, with a rental full suspension mountain bike with 2-piston SRAM hydraulic brakes squeezing much larger than 160mm calipers. Braking was powerful - easy to lock of the front or rear at will - and easy to modulate. It's now the bar by which I evaluate braking performance.

So the HB100s have not worked as well as the 2-piston SRAM hydraulic system, but they have worked well and have not failed. I would be curious how they'd perform with larger disks. Random YouTube videos aside (N=2), I'd consider buying them.

We are currently testing bikes and components for a planned big trip in the next several years which would eventually take us to some pretty remote places, and where long-term maintenance and availability of spares is a consideration. While I'm familiar with hydraulic disk brake maintenance on cars and motorcycles (maintaining your own brakes and then depending upon them at the end of a 125mph straight leading to a 2nd gear right-hander is a good life lesson), I'm a little concerned about field repairability. On the other hand, motorcycles have been traveling around the world for years with hydraulic brakes, so it may not be as big an issue as some may think. That said, motorcycles aren't folded up and stuffed into the back of pickup trucks and luggage compartments, so the hydraulic lines aren't subject to the same risks as a bicycle.

Full mechanical have roadside repair appeal, so they are still being considered. And with my HB100 experience, so do hybrid disk brakes. The next couple years will be testing out different options before making our final gear choices.

Huh, I don't remember that, but I'm sure you're right.

I do recall myself arguing that combined rear derailleur and IGH systems fall into that reasoning, advocating to go all-in with one or the other.

The issue with those Zoom brakes is not that they don't bite, but rather that they may be prone to failure. The other issue, of course, at least for me is why BF dares to spec these brakes on a $2,700 bike and why people don't seem to care. It's an example of that insidious bias on this channel. The more expensive the bike, the less critical folks are off it, with the converse being equally true. A sad corollary to the earlier channel theorem is that the same part on a cheap and on an expensive bike is more favorably appraised on the latter.
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When I first saw cable-actuated hydraulic, my immediate thought was best aspects of both, reliable and easy to swap cable in the boonies (BFs tend to do a lot of touring), no need for hydraulic fluid to refill, but force and modulation advantage of hydraulics. But not if they leak. My guess is BF may not have been aware of that, you wouldn't think they would source a known unreliable part.

For hydraulic, the first thing to look at is the type of oil they use.

If they use DOT (like SRAM, Hope...) it requires regular replacement, SRAM says at least once a year, more in case of intensive use.

Mineral oil like used by Shimano, Magura... doesn't require that regular replacement.

I do not know what type of oil Zoom is using?

The second issue is how to do the oil replacement and bleeding, how easy it is. And this depend of the brand and also type of brake because brands are continuously trying to find easier way to do that.

About the drawbacks of hybrid, actually they combine one weak point of mechanical, i.e. like mechanical they are very sensitive to the quality of the cable+housing and the way these cable+housing run on the bike frame and they have the potential maintenance issue of hydraulic, i.e. maybe DOT oil and maybe difficulties to change oil and do bleeding.

But hybrid have the advantage of automatic compensation of brake pad wear same as full hydraulic.

About my experience with hydraulic disc brakes, I had very bad experience with AVID/SRAM (Avid Code, Code R, SRAM Guide) and very good experience with Shimano (cheap Deore, XT 2 and 4 piston) and Magura (old Gustav, recent MT5 and MT4) recent Magura are the easiest to maintain with easiest brake pad replacement, never tried Hope because they use DOT.

About the use of the cheap Zoom brakes by Bike Friday even for the high end components packages, I have no idea, I don't think its a question of saving money, the only thing I have heard is that they have difficulties to source reliably Shimano components.
What I see is that for any reason, Bike Friday doesn't mount full hydraulic on their folding bikes (even not on their cargo and tandem bikes) and this means that they cannot use the biggest brands since these do not have hybrid, the most known one are from TRP and Juin Tech.

47-406, perhaps 50mm wide too, is a good compromise between asphalt and "gravel". 451? No.

https://cimg4.ibsrv.net/gimg/bikefor...afd8591c49.jpg
On the more hard packed and smooth end of the spectrum encountered
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I strongly disagree with that statement: I modified my Birdy (shown in the „Birdy Thread“) to excel in that exact situation. Mounting a flexible handle in the front and old inliner wheels on the rear rack it can be pulled or pushed precisely, no finesse required ;-)
The stock birdy with the lowrider front rack and its smaller wheels mounted on the rear rack used as a handle could also be pulled easily and precisely.

That said, and while I love it for urban transportation, I still think the Birdy is no substitute for a true „gravel“ type bike. It is not nearly as capable in that role as the Cannondale Slate I also own.

Wait, doesn't the fact that you had to modify your Birdy support my point? 🤔

I'd love to try a Birdy someday. Cool looking bikes. Do they have a gravel version?

A few images of actual gravelin', on a bi-fold, rather than theorizing about it...

https://cimg8.ibsrv.net/gimg/bikefor...7fef4bece4.jpg

https://cimg9.ibsrv.net/gimg/bikefor...7d9130180f.jpg

https://cimg0.ibsrv.net/gimg/bikefor...52563574f2.jpg

https://cimg1.ibsrv.net/gimg/bikefor...cfa32a5ff7.jpg

https://cimg2.ibsrv.net/gimg/bikefor...68a0c23f8c.jpg

I did not phrase it clearly: The Birdy as made by the manufacturer was already fine in that regard. I just made it even better.

There is no gravel version of the Birdy that I know of. A shame, really. I’d love to see something like the G-Line. While it is in its 3rd generation and is a great design apparently there has been no further development of the Birdy for several years. Unlike Brompton where the folding bike is the company the Birdy is a keepsake / side show for Riese & Müller: They concentrate on ebikes these days.
One of the founders recently started another company where an electric cargo bike with a built-in reclining chair / bed and a tent construction overhead apparently becomes the perfect glamping vehicle …

Pacific Cycles announced a gen 4 Birdy and a P45-30 special edition for 2025

Its clearly based on the P40 special edition frame that failed to become a gen 4 Birdy.

Some more information about the gen 4:

https://cimg9.ibsrv.net/gimg/bikefor...8721a89d01.jpg
https://cimg0.ibsrv.net/gimg/bikefor...c81721d61f.jpg
https://cimg1.ibsrv.net/gimg/bikefor...ebb4cc6d41.jpg
https://cimg2.ibsrv.net/gimg/bikefor...e9aed03485.jpg
https://cimg3.ibsrv.net/gimg/bikefor...17346996ae.jpg
https://cimg4.ibsrv.net/gimg/bikefor...5ad83d7a58.jpg

Cool! Makes sense that you would know about it before I do ;-)

The debate is of the same vib as what you get on the "gravel" specific subforum; a lot of it is down to what people consider gravel and from what I read in many places, it goes from fine hard pack smooth dusty paths to XC muddy trails that make "belgian CX" courses looking like a nice holiday...

Ultimately, with small wheel, it is doable but not as comfortable, in summer in dry conditions, you can ride pretty much any path on 20" wheels with 35mm tyres and rim brakes (like they do in CX).
the bigger cushiony bit with 50mm tyres, is more of a comfort thing and endurance. I can do winter muddy rocky gravel ride on a CX bike for 1-2hrs at most and then it is tiring. with a set of 50 ot 52mm tyres, I can do 4hrs before I get to state I get after 1hr of CX racing.

Brakes Rim/mech disc/hydrau disc/ mech Ac hydrau disc, it is a very long subject...
**the only advantage of Rim is the weight but everything else is rubbish (rim wear, mud clogging), it is something of its time and yes, I mostly ride a rim brake bike because the bike is cheap to run and maintain - perfect for winter training.
**mech disc, it is OK but they are not all equal; cost wise, I think the TRP spyre calipers are the only good large distribution product; it just need good pads. Yes there are things like paul brake caliper but you don't find them everywhere.
**Hydrau disc, shimano is the best ratio perf/maintenance/cost . Sram is OK but DOT which is not an issue (you get in any car); it just means that it needs servicing again, not an issue however, the bleeding procedure is rubbish as more complicated (similar to race car) and requires special equipment (I let my LBS do it because 5 service is the cost of the bleeding kit).
**mechAc Hydrau disc, juin tech get good review. I use TRPs as they very good in perf, the use Shimano pattern pads and they clamp well. the only issue is the bulkiness, they are huge and difficult to mount because the casting housing interferes with standards driving tools (Allen key, torx key, wrench driver etc.) and requires a cut down (5mm long) allen key... the weight can make the alignment a little tricky too. But, it is all HOME DIY with a little bite of care and time.


Note, I have been toying with the idea of racing my mini velo on 47-406 tyre in a local CX race just for fun and scrapped the idea because 20" wheels in ruts and potholes is not great; yes it is more fun when training but when racing, it is a little to much to handle.

Wider tires, 50 to 62mm wide, on ETRTO406 wheels allow to ride on softer surfaces like more muddy and more sandy.

Now, its true that gravel, that was originally a less extreme, more comfortable cyclocross bike with also wider tires than allowed in cyclocross competitions, is now used for a lot of very different bikes and actually doesn't mean a lot anymore.

That's an interesting point because some people will prefer narrow knobby tyres in deep mud or sand and ride the ruts like they do in cyclocross or some people will ride the soft on big/fat tyre like beach racer in NL riding 55-622 or 60-622 slicks :foo::lol:

personnally, my favorite gravel tyre is a XC tyre conti race king in 50-584 (since 2020)because they roll so well and if the terrain is getting looser, I put a cross king on the front ( better steering grip and little rolling penalty)
If MTB muddy, 52-584 mezcal rear and barzo front.... they don't roll on tarmac but grip very well on trails

Pretty high 32GI low. Under 300% gear range? 😳

"Asiatic" cable hydraulic? 🤣

A bit schizophrenic, neither fish nor fowl with, on one hand, drop bars and narrow tires, and, on the other, 355/406 rather than 451, and with efficiency zapping double suspension. Good job! 👏🏼

Does it too require replacement of key parts at €200 every two years lest the warranty be voided? 🤔

What's the price for this piece of work?🤔🤔

But the burning question is: Does it retain the "weird geometry" of previous Birdy due to their excessively long chain-stay length?🤔🤔🤔

That gear inch range is pretty typical of folders, and the high is adequate, but I agree a lower low would be better for most; they may be assuming athletic standing climbs all the time, I can only wish.

A rear suspension that bobs while pedaling will definitely suck power. I don't think that applies to their front suspension. But a suspension that can suck up small bumps (like in my city, tree root bulges on cycle paths) would mean faster travel, just like cushier tires, although suspension is notably heavier. Then it become intermeshed with tire choices; cushy + rigid, skinny + suspension, cushy + suspension... I think bump size and surface come into play. But Birdy's brand identity is built on front and rear suspension, so I don't fault them with staying with that, and otherwise trying to make it as racy as possible.

Chainstays don't look particularly long, but I'm just rough eyeballing.

Reach looks generous. Handlebar height looks too low and sporty for me, but clearly that is aimed at the sporty rider.

Required replacement of structural parts every couple of years... yeah that is a valid criticism IMO if they are still doing that. Just no reason for that, especially with a new design introduction that could correct that. Ultra-lightweight race bikes don't have that requirement.

...

(above) You're right, on a big-buck folder, I do expect 400% gear range, or at the very least, ability to get there easy. I recommended to the Origami Bull seller on here, that since it comes with an FD bracket, he should offer it with 2X, because it would offer much greater value to the buyer than it would cost for it to come factory that way. 1X is a great option these days as you've proven, but 20" makers seem to limit themselves to 34T RDs, but that may change.

I normally have high standards for value in what I buy, but that can be hard if *no one* offers what I want at reasonable cost. Dahon has had the offerings at times, but charged ridiculous multiples in price for discs and 2X (Formula 18) which added, what, at most USD$200 to the bike cost? That bike had stellar reviews, but didn't sell due to the price, like 3X that of a Mariner, IIRC.

Twice wrong:
- the chainstay of the Birdy 3 is 42.5cm this chainstay length fits perfectly with the wheelbase of 102cm.
- For the pedaling cadence while climbing, look at the way modern road champion like Chris Froome pedal: a (very) high pedaling cadence and they remain as much as possible seating on the saddle). Pedaling at a high cadence with a relatively low torque produces the same power as pedaling at low cadence with a high torque and protects the knees.

How come I don't see washboard roads in your gravel road photos? Am I just not picking up on it? Gravel roads here and the rest of the South (USA) invariable become washboards. They fix them, but they rapidly go back to being washboards.

In my mind, gravel exists between these two ends:

The route that you'd rather not do on skinny, high-pressure tires
The route where a mountain bike would feel slow and inefficient

That includes everything from crushed gravel to doubletrack and includes washboard