Bike porn

are you new here then?

(e.g. http://www.lfgss.com/post1487226-708.html)

i just read this. all of it. thats fifteen minutes of my life im not getting back...

buy mine then ;)

I'm a 54!

I love the amount of thought and engineering that has gone into these. They are highly engineered to be light, stiff and powerfull, and it is interesting to see how that has led to trade-offs in other areas.*

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I'm not digging into these because i don't like them, i do. I'm digging just because they fascinate me.

nice one, just goes to show how interesting brakes can be if you look hard enough.
I for one had never contemplated any of what you said about brakes before, so i learned some new things from what you said.
Thanks.

But the linkage is also at the root of several niggles:

Indeed. I want the lower half of this brake combined with a parallelogram linkage to drive it, à la Campag Delta. Inherently symmetrical, albeit doing nothing to address the problem of getting the rising rate at the right point in the travel.

Oh, and a Mavic SSC style leaf spring, much neater than that bit of bent wire.

As we should be getting master cylinders in STI/Doubletap levers in a year or two, an hydraulic actuator would be a step up from any kind of linkage, and we'll be right back to the late lamented Magura HS77

that look is fucking nice.
apart from the fucking knog!

I'm absolutely in love with 396s at the moment.
Saw a sprinter lass on a white one at the track the other day and in my uneducated naivety thought "if i could get an old one of them for the right price i'd base my bike for when the glasgow 'drome opens around it".
When I came home and googled it I was gutted.
Kinda like when you were in school and noticed a smoking hot lass, a couple years above you. You know, the right popular one that went out with someone from the football team or the school bully.
No matter how you might want/dream/try, you were never gonna get a ride.

Indeed. I want the lower half of this brake combined with a parallelogram linkage to drive it, à la Campag Delta. Inherently symmetrical, albeit doing nothing to address the problem of getting the rising rate at the right point in the travel.

Oh, and a Mavic SSC style leaf spring, much neater than that bit of bent wire.

As we should be getting master cylinders in STI/Doubletap levers in a year or two, an hydraulic actuator would be a step up from any kind of linkage, and we'll be right back to the late lamented Magura HS77

Why doesn't someone just make a cable actuated hydraulic brake, the resivoir / actuator could be really small and mounted on the brake. You could then use all brakes / shifter combinations. Wow design idea for the day - can I be bothered firing solidworks up???

Fuck.

A classic Jack Taylor track frame, with fillet brazed goodness and curvy seat tube, there's nothing more annoying holding one up knowing it's too small for you.

^Taylor frames have an Interesting history.

Why doesn't someone just make a cable actuated hydraulic brake?

Because you'd still have a cable, which is the one thing you're trying to eliminate for the sake of all-weather reliability. I reckon Shimano will be first with a fully hydraulic cyclo-cross disc set up, simply because they have the space to stuff a master cylinder into the body of a Di2 lever now that the shifter guts have been taken out. Rich kids and Shimano sponsored Pro CXers only, then, since that will be a big premium over the already eye-wateringly expensive Di2.

Fuck.

A classic Jack Taylor track frame, with fillet brazed goodness and curvy seat tube, there's nothing more annoying holding one up knowing it's too small for you.

Ed. how big is it?

Because you'd still have a cable, which is the one thing you're trying to eliminate for the sake of all-weather reliability. I reckon Shimano will be first with a fully hydraulic cyclo-cross disc set up, simply because they have the space to stuff a master cylinder into the body of a Di2 lever now that the shifter guts have been taken out. Rich kids and Shimano sponsored Pro CXers only, then, since that will be a big premium over the already eye-wateringly expensive Di2.

You are right, but your overplaying the "cables are unreliable" card. Infact a lot of guys with jumpbikes ride with cable / disks because you don't have to worry about ripping out / bending fittings. To me its more about getting brakes that stop more effectively in a compact unit, much the same size a normal brake, plus you can retrofit it to any bike.

Ed. how big is it?

Hasn't a clue, but it's defintely not 56-57cm judging the head tube height.

Hasn't a clue, but it's defintely not 56-57cm judging the head tube height.

Don't always presume it's traditional geometry. Some 58cm+ bikes have tiny headtubes, especially if they were TT or pursuit bikes

I know what you mean, I've google Jack Taylor Time Trial, and to my surprise, the very same frame popped up;

You are right, but your overplaying the "cables are unreliable" card. Infact a lot of guys with jumpbikes ride with cable / disks because you don't have to worry about ripping out / bending fittings.

That's a different issue to the normal reason for switching to hydraulics. Cables do indeed work fine when new, and are robust in crashes, but they also get worse quite quickly if used in all weathers without maintenance, and they stretch over time. It's horses for courses, innit?

I love the amount of thought and engineering that has gone into these. They are highly engineered to be light, stiff and powerfull, and it is interesting to see how that has led to trade-offs in other areas.

Stiffness demands the shortest possible lever arms, so: dual pivots down close to the pads and shorter than normal slots for the pad holders, with the rest of the adjustment achieved by an eccentric fixing bolt. Stiffness also demanded the depth and diameter of the main pivots.

Lightness machines away the material that is contributing least to stiffness, leaving a chunky ridged un-aero structure.

Power comes from the progressive advantage linkage - as more cable is pulled the leverage increases (and pad-motion reduces). This matches well the force profile needed to move the arms in initially against just the spring then also against the compressing pads. I don't know of any other brakes that do this as radically. The dual-pivot and cam mechanisms of other brakes increase the mechanical advantage more uniformly across the range of motion - something that could be done less compactly by just making the cable-arms longer.

But the linkage is also at the root of several niggles: you have to make sure the linkage is ramping up the leverage at the right point in the pad motion. The barrel-adjuster isn't in the right place in the mechanism to set this, so the brakes come with a variety of spacers to put between pads and the lever arms to adapt to different rim widths. That isn't a complete solution - as the pads wear down you'd have to change the spacers to keep the leverage profile the same.

The linkage combines with the dual pivots to create another niggle. The structure of two arms with fixed lower pivots and two upper pivots that are pushed apart is potentially unstable - if the upper pivots are closer than the lower pivots it will tend to flop sideways, one arm moving in and the other out. Springing the arms against each-other rather than the un-moving central parts exacerbates this, but it's putting the cable anchor on the lower pivot that guarentees the linkage would flop if not constrained.

So it is constrained, by a mini link - the little rod that runs from one arm of the main linkage to just in front of the central bridge bolt. This forces the arms to move symmetrically - consistant pad motion they call it.

Consistent pad motion sounds good, and inconsistant motion can be a real problem that frustrates setting up brake pads clear of the rim, but once the pads reach the rim what you really want is symmetrical force. If the rim is a little off-centre from the brakes, the diminutive mini-link will be struggling to make one pad push harder, trying uselessly to centre it. On other brakes it would be the springs that fight to centre an off rim, but springs are happy to loose and bend; the mini-link isn't. The brakes can be set up centred over incorrectly dished wheels, but that takes time and doesn't address poorly trued wheels.

The snap-in pad holders are a real innovation - it would be good to see other manufacturers licence them.

I'm not digging into these because i don't like them, i do. I'm digging just because they fascinate me.

excellent stuff!!!! lengthy, not quite as well written as a tester piece but passionate and commendably obsessive 9/10

do cables really stretch, or is it the outers that compress?

My own idea for the 'ultimate' rim brakes is to take the arms of the EE brakes from the main pivots down, build them into the forks and drive them with hydraulics. The only reason conventional brakes need so much brake-drop adjustment range is to accommodate forks with different tyre clearances. Build the brakes into the fork and you can probably get away with no drop adjustment at all, leaving little more than the pads in the air-stream. The pipes would run down inside the steerer, and i'd build a progressive advantage linkage into the levers, where it can be designed to recalibrate automatically if it gets too close to bottoming out. (A good reason not to build progressive advantage linkages into cable brake levers is that the high leverage bit would be quite harsh on the cables. I think hydraulics would tolerate this better.) You might need to stiffen the forks a bit, but that should be more efficient than providing an entirely separate structure. I'd worry a bit about how brake heat is handled.

The rear brakes would be built into the chain-stays, as they are already pretty chunky.

Why doesn't someone just make a cable actuated hydraulic brake...

What would be the advantage over a purely cable driven brake?

Nice strappies.

I'm pretty sure this is a repost by me, but it's worth it

[/little ghost child]

I fucking love the colour on the 3Rensho.

it is a nice colour. The owner doesn't appreciate it though looking at the colour of bar tape they have chosen!