Specific heat absorption capacity of disc brakes

The TRP Spire disc is working well in every respect. Solid feeling smooth without vibration quiet make that dead quiet and with good modulation.
Currently waiting for a bottom bracket cable guide to get the rear roller brake operating. Ive been using front disk exclusively these last few days. At first tried the brake lever in roller brake mode for a day.
It was spongy and required too much force to stop. Impossible to lock up in error and had a very long braking distance. Rather dangerous
V-brake mode felt so much better having both a sharp pull when needed and nice modulation. I have not had a error lock up and dont think I will. The Organic pads are silent and smoother then smooth , I can see why they are suggested up front.
 
eCue said:
At first tried the brake lever in roller brake mode for a day.
It was spongy and required too much force to stop. Impossible to lock up in error and had a very long braking distance. Rather dangerous
V-brake mode felt so much better having both a sharp pull when needed and nice modulation.

My favorite levers to use with drums and roller brakes have been adjustable gain linear pull levers, like Avid Speed Dial or Dia-Compe PC-7 EXA. However, I feel that long blades are an advantage in this application, and linear pull levers generally have short blades.

So-called "compressionless" brake cable housing is really good at improving lever feel and brake response with drum or roller brakes. I didn't believe it until I tried it.
 
Chalo said:
So-called "compressionless" brake cable housing is really good at improving lever feel and brake response with drum or roller brakes.
Is that the kind with the full-housing-length "wires" paralleled around the circumference of the housing? (rather than the spiral-wrapped type)
 
amberwolf said:
Chalo said:
So-called "compressionless" brake cable housing is really good at improving lever feel and brake response with drum or roller brakes.
Is that the kind with the full-housing-length "wires" paralleled around the circumference of the housing? (rather than the spiral-wrapped type)

Yes, but it differs from index shift housing in that the parallel wires are contained in a snug Kevlar jacket to keep the housing from bursting under high compressive load. Here's the kind I use.

I had encountered long lay cable housing before that promised compatibility with both brakes and shifters; it was marketed by Odyssey. But that stuff definitely wasn't stiffer in compression than good quality Bowden cable housing.
 
I have the Jagwire housing on my cargo bike with BB7's, the stuff is worth the money, really stiffened up the braking response.
 
Prototyped a new fork today for a super- heavyweight pedicab. We opted for dual 203mm discs, which was the main reason we had to make our own fork.

rps20180207_173222.jpg

That's a 29x2.1" tire on a 42mm wide rim.
 
speedmd said:
Nice! Like the look of the rotors mounted backwards.

Yep. Good thing there are no calipers on it yet.

I'm on the lookout for reasonably priced 8" rotors with a non-directional pattern to prevent the inevitable reverse installation of the symmetrical wheel by end users. Any ideas?
 
Brakco? Closer to a bi directional design. Float points and outer slots not.
https://www.ebay.com/i/282773086090?chn=ps&var=582056669164
s-l1600.jpg
 
Origin looks to be fully symmetrical, but possibly some cbore at the mounting screws. Not sure outer slots on the lower cost option would be a issue. KCNC also with a nice lightweight design. https://www.ebay.com/itm/Origin-8-SpeedCheck-Two-Piece-Disc-Rotors-Brake-Part-Disc-Rotor-2p-6b-203mm-Bk/282510773960?epid=1649164921&hash=item41c6f44ec8:g:sKYAAOSwVqlaHClC
s-l1600.jpg

s-l500.jpg
 
Thanks for finding these.
 
Chalo said:
Thanks for finding these.

No problem. Like the idea of dual rotors, have been playing with the idea and glad you posted as we have many near moto requirements here that can test these lightweights out for suitability. Even if you need to get some outer rings water jet'd out a bit more heavy duty, the center hub may become a standard for most here on ES.
 
Lebowski said:
I agree with Chalo about rim brakes... I mean disc brakes are getting larger and larger diameter, only a few more years till the disks are as large as the rims.... at which point everyone will realise rim brakes are basically disc brakes with the biggest disk possible.

:shock: just went through the rim...
DSC02093-800x800.jpg
 
Lebowski said:
:shock: just went through the rim...

Ha ha, funny timing. I've done that a few times myself and witnessed it countless times on customer ebikes.
There's a reason for disk brakes. But the ultimate solution for ebikes, of course, is GOOD REGEN!!!!
 
I have good regen :mrgreen: just not on this bike.

This one is a non-ebike which I use 2-3 times a week to climb the local 350 m high hills. Then on the descent I am lightly on the brakes to keep speed around 40 kmh. I am happy that I didnt do a strong brake action, pushing through the rim locking the wheel. I think the wheel has around 20000 km on it...
 
Lebowski said:
Lebowski said:
I agree with Chalo about rim brakes... I mean disc brakes are getting larger and larger diameter, only a few more years till the disks are as large as the rims.... at which point everyone will realise rim brakes are basically disc brakes with the biggest disk possible.

:shock: just went through the rim...
DSC02093-800x800.jpg

When I lived in Seattle, it seemed like year-round commuters would grind through their rims every year or two. Here in Austin, it only rarely happens, mostly to MTBers who intentionally ride in mud. Seattle's dirt is more abrasive, and it's wet and gritty most of the time.

I can say that in more than 200,000 miles of cycling, mostly with rim brakes, I've never worn out a rim sidewall.
 
From a recent wheel that came in... he was a Canadian transplant and running high psi tires, which seems to be a commonality in the rim failures I've seen.

rimcrack.jpg
rimcrack2.jpg
 
I did that in the distant past, running 140psi in 700x28 tires.

I don't exceed pressure ratings anymore; I just use tires that are big enough for the job.
 
Odd folks think your rotors are mounted backwards. As a man who has overheated and wadded up a half dozen bicycle brake rotors into a hot mess of steel, I found mounting them they way you did so it pulls on the rotor spokes vs pushing on the rotor spokes enabled them to survive much longer at extreme temps.



Chalo said:
Prototyped a new fork today for a super- heavyweight pedicab. We opted for dual 203mm discs, which was the main reason we had to make our own fork.

rps20180207_173222.jpg

That's a 29x2.1" tire on a 42mm wide rim.
 
Iv'e also always thought rotors should be mounted that way as well. Seems like in the case of a catastrophic rotor failure you would want the "spokes to fold away to a smaller radius rather than growing to a larger radius and stabbing everything. I guess its probably silly to try and apply logic to such a chaotic event.
 
liveforphysics said:
Odd folks think your rotors are mounted backwards. As a man who has overheated and wadded up a half dozen bicycle brake rotors into a hot mess of steel, I found mounting them they way you did so it pulls on the rotor spokes vs pushing on the rotor spokes enabled them to survive much longer at extreme temps.

In the picture, they are backwards relative to their directional markings.

I think the idea is that leading spokes exert an expanding force on the outer ring of the rotor, which helps keep it straight by means of hoop tension. Trailing spokes contract against the outer ring, promoting buckling. I don't know how much of this is founded in test results.

The first disc brakes I owned in the early '90s were Mountain Cycle Pro-Stop 9" full floating cable-hydraulic brakes with hard anodized aluminum rotors. They were labeled specifically to have trailing spokes when mounted, contrary to common practice today.

I figure I'll mount them the way the manufacturer suggests, all the while wondering why more disc rotors don't use a non-directional pattern.
 
liveforphysics said:
Odd folks think your rotors are mounted backwards. As a man who has overheated and wadded up a half dozen bicycle brake rotors into a hot mess of steel, I found mounting them they way you did so it pulls on the rotor spokes vs pushing on the rotor spokes enabled them to survive much longer at extreme temps.
[/quote]

I have used them both ways for a bit also. Never had a fail. Then I started seeing photos of the fails.
AshimaFacePlant2.jpg
 
Wow. I'm not an engineer but as a machinist I dont like anything about that rotor design. In my experience with steel you typically want to avoid sharp corners and avoid thin sections that concentrate heat/stress. That rotor looks like the worst possible design for the heat and loads it would be under. Just eyballing it though.
 
Buckling the spokes from compression in a rotor happens way easier than pulling on them until tinsel strength failure.

You really want some offset in the spokes vs being radially arrayed, but just like in a bicycle wheel you want to be pulling on the spokes and with a hub exit offset.

Most bicycle brake rotors I've seen looked like they had artists make the designs to look flashy rather than doing a mechanical stress optimization.
 
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