sjanzeir

Hello everyone,

So, as I had mentioned earlier in a couple of other threads, I've been having issues with the BB5-based, single-action mechanical disk brakes on my Dahon Hemingway - namely, they don't work for s**t. Like, at all.

And the nastiness isn't just with the calipers or the undersized pads themselves, but how the front caliper is hung onto to the bike. Take a look at this:



This is the factory rear caliper.



And this is the factory rear rotor.

Now, if you look closely at the rotor's braking surface, you can tell by the wear pattern that the pads are in full contact with the braking surfaces. No issues there, apparently.

Now, look at the front factory caliper - particularly, how it's bolted to the adapter:



Now look at the rotor's braking surface:



As you can see, there's a clear overhang issue here. The way the caliper and adapter are arranged with the fork, the pads are not making full use of the rotor's available real estate. I tried a couple of ways to solve this problem, either by bolting the caliper directly to the adapter sans the cone washers and tried flipping the adapter around. In both cases, the caliper body would come into contact with the fork, not only becoming impossible to align, but also becoming impossible to bolt down all the way. And in both cases, the caliper still didn't sit where the pads would be in full contact the entire width of the rotor's braking surfaces.

That's when I fully realized that I had to make a decision: either spend money upgrading what's essentially a reasonably nice bike, or just sell the darn thing and be done with it. But I wouldn't want to live with the guilt of someone else getting hurt - or worse - because of the poor factory brakes. That, and the fact that I just like this bike too much. And it became even nicer after the Litepro seat post upgrade that made the thing handle like a dream, so, there's that.

There had been a couple of discussion earlier about retaining the mechanical setup and swapping out the nasty calipers for a pair of TRP Spykes. I cannot tell you how many times I came close to clicking that Buy Now button. But I'd always quickly back down and think to myself, "this can't be all there is to it this is just too easy. there has to be something better!"

So, I started doing my homework. I read technical articles, went through forum threads, and delved into the the science behind resin vs. sintered, the merits and shortcomings of cable-actuated" hybrid" hydraulic systems, and how to navigate Shimano's annoyingly opaque, labyrinthine website. I even learned of - and about - the fabulous things that are Shigura conversions! And at the end of it all, I realized that genuinely good, reasonably priced, brand-name hydraulic disk brakes are what I ought to be looking at.

In the middle of all this, I realized that, for about the price of a single TRP Spyke caliper (around $80, depending on where you look,) I could have me a whole Shimano BL-MT401/BH90/BR-MT420 unit from the very same vendor, all pre-assembled, pre-bled, and ready to ride! That, as they say, was the end of that.

The set I ordered came with a 1000mm hydraulic line for the front brake - which turned out to be just the right length - and a 1,700mm line for the rear. My concern here was that the hose for the rear brake might be a tad too short; I measured the old cable housing at 1,800mm or so, so I assumed that I was going to need a hose at least that long. Just in case, I ordered everything I might need to replace the original hose with a longer one: 2,000mm BH90 hose; home-use hose cutter; Shimano fittings, mineral oil, and a bleed kit. I even ordered some hardware for a possible Shigura conversion in the future! As it turned out, the 1,700mm hose was a tad too long, messing up the neat arrangement of the brake lines and the shifter cable. And that's okay, really; I could always rearrange all three lines as neatly as I want them to be, so I'm not too worried about that.

Now, bolting my newly acquired brakes onto the existing IS/PM adapters revealed more fitment and alignment issues. Up front, with the cheap factory IS/PM adapter, the caliper sat even farther out than the original, with the long, narrow D03S pads covering even less of the rotor's braking surfaces. On its own, a Hayes adapter I had ordered around the same time in anticipation of just this kind of issue, though far better made and finished than the factory one, wasn't of much help in that department. The solution I came up with was to order me a 170mm Avid HS1 rotor, which turned out to be more or less a perfect fit...






... Except for one more, slight issue: Once everything was in place, the tips of the rotor ever so slightly rubbed against the inside of the Shimano caliper:



A 1.5mm washer took care of that while still maintaining the pads in perfect alignment with the rotor:



Not surprisingly, I ran into a similar issue out back. Just like with the front, a 165mm Avid MTB rotor came to the rescue:





One final - and very minor - issue I'm experiencing right now is that the right (rear) brake lever has to travel noticeably longer than the left one before the pads "bite." At least for now, I'm chalking that up to the longer hose showing more stretch under hydraulic pressure, but I've got a couple of 165mm Grimeca rotors lying around that are 2mm thick (as opposed to the Avid's 1.84mm)that may or may not reduce clearance between the pads and the braking surfaces, but I haven't yet put that theory to the test.

So, after is said and done - after all the expenses, the shipping costs, the shipping delays, the aggravation of figuring out what works best and what doesn't work at all, of dealing with vendors who, though they speak the same language as you, don't really speak your language - how did this thing turn out?

For starters: it's awesome! Right before I swung a leg over the saddle of my newly refitted bike, I figured I'd be doing an endo the very first time I used my new front brake. But no, as soon as I got to the other end of the street and pulled the levers for the first time to start bedding the pads in, it was as though I had been born with this. Right from the get-go, modulation was practically second nature - a complete no-brainer.

And then there's the power. Oh, the power! In place of the white-knuckled desperation of trying - hoping, begging - to stop the bike with the earlier BB5s, there's now immediate, progressive, endless braking power! Now I can actually use the brakes to handle the bike instead of struggling to bring it to a stop. Now, rather than having felt like an overpriced big box BSO, it feels like a real quality bike that I can actually take place with absolute confidence!

Finally, credit is where credit is due. I must thank everyone who gave me advice and pointers. As always, you've been great.

Andrew R Stewart 

Sorry if you commented of this question, I kind of lost the flow during trying to keep track of all your efforts.

In the beginning I wonder if you tried to remove the convex "washer" between the adaptor and the caliper. The amount of pad displacement on the rotor's sides looks to be close to the washer's thickness, I have seen more than one caliper mounting that used these ball and socket washers as only spacers, lacking the other half of the pair that make it a ball and socket.

I would also add that "BB5 based" doesn't mean much but that another company "borrowed" the general appearance of another's caliper. Not the dimensional specs or all the design elements. If this caliper is not made by Avid then it's like saying a Kia is Mercades based because they share the same roofline and 4 wheels. So is this an Avid caliper? Andy

sjanzeir

Andrew R Stewart
Perhaps the picture of the front caliper and rotor does not fully convey the issue, but the amount of unused surface area is significantly greater than the thickness of the ball-and-socket washers. I did write somewhere in the middle of my admittedly TL;DR post that I tried doing away with the convex washers and mounting the caliper directly to the adapter. I also wrote that that brought the caliper in contact with the fork, making it impossible to secure to the adapter, not to mention getting it aligned.

And when I wrote "BB5-based" I meant that the calipers that Dahon chose to specify for this bike use Avid's BB5 pad design standard. Apparently, BB5 pads are some of the most popular ones in the world. With the possible exception of Swisssstop, every aftermarket manufacturer, from Galfer to Jagwire to about a zillion Chinese brands that I couldn't even pronounce, have "BB5" pads in their product lines (most of them don't even bother to mention "Avid.")

You ask if my original calipers had been made by Avid, and I couldn't tell you if they were. I could not find the actual brand or manufacturer's name anywhere on my bike's calipers - just a couple of mold numbers and a lot of casting parting lines. For all I know, Dahon probably couldn't source any quality calipers from any of the name-brand manufacturers in the middle of the universal COVID parts shortage, so they went with whatever they could get their hands on at the time.

Or maybe they were just penny-pinching, having struck some kind of deal for $2.99 apiece or something. In any case, all I know is that there wasn't much I could do to achieve any meaningful improvement in the performance of the my original brakes. I guess an upgrade was very much in order.

Andrew R Stewart 

I have no issues with wanting better performance. I just like to understand what's going on before I spend $ to avoid fixing the problem. Without the parts in hand all I can do is mentions possibilities. Glad it seems that you are happy now. Andy