Anyone know anything about disc brakes?

Ive heard/read a lot about lever throw on Shimano drop bar discs but have never worked on them myself so I can but guess.

Seems like there's something wrong with the way Shimano have translated mtb levers into road ones.

I imagine the problem is at the lever as it's the bit that's different. Ergo, new calipers aren't going to solve your issues.

I know you say mechanicals can >>>>>>> but have you tried a bb7?

I've bought some pretty old and some pretty new (but not brand new) Hopes and none of them have been amazing.

I've also bought a variety of ages of used Shimano brakes and found them better.

new calipers aren't going to solve your issues.

Not that issue, but they might help and might make less noise.

I know you say mechanicals can >>>>>>> but have you tried a bb7?

Not sure. I've tried cable discs but generally shit ones. It's not that I don't believe they work, it's that I don't want cables on my bike now that I don't have to. No more fucking barrel adjusters, no cable breakages, not rusty inners, worn outers.

Buying used hyrdaulics is a total crap shoot.

People who have Hope brakes tend to use their bikes. They are rider's brakes.

Shimano...not so much, although of course there are exceptions to the rule.

Anyway, ergo, buy used brakes, if you buy Hope they are more likely to be fucked simply because they have been ridden in to the ground. Shimano...not so much, but you might get unlucky.

If I sold you my Tech Evo / X2s you'd be blown away. I'm not going to though because the are incredible. They make the MT6s/Guides/SLX/Spyres we have look like the toys they are.

"Lever stroke (assuming the brake is properly bled) is a function of the ratio between master cylinder (brake lever) and slave cylinder (caliper) volume. A small master:large slave ratio means that a relatively small amount of fluid is displaced from the master cylinder, so there's a smaller movement at the slave cylinder = longer lever stroke but excellent modulation. A large master:small slave ratio gives high fluid displacement, for a sharp response but at the expense of controllability.

The only way you could attempt to shorten the lever stroke in these brakes it to highly pressurise the system. Close the bleed port at the lever and forcefully inject fluid at the caliper. The inward pressure will force the pistons out a little bit closer to the rotor."

buy Hope they are more likely to be fucked simply because they are bought by idiots because of their pretty colours

ftfy

If the noise is from pad rub, which you're getting because you've pumped the piston out to try and correct the lever throw issue then new calipers will do bugger all.

I can see your point re cables but just seems like you're trading one set of (relatively easily fixed) problems for another which are not so easily fixed.

I want to be one of those idiots.

https://www.youtube.com/watch?v=ntG50eXbBtc

The only way you could attempt to shorten the lever stroke in these brakes it to highly pressurise the system. Close the bleed port at the lever and forcefully inject fluid at the caliper. The inward pressure will force the pistons out a little bit closer to the rotor."

You can't pressurize the system. You can

• get all the air out
  
• use a smaller bleed block
  
  

Which has the same effect as pushing in more fluid with the normal sized bleed block.

Noise from pad rub, noise from grit on the disc/pads, noise from pads or spring rattling in the calipers, noise from levers rattling, noise from me yelling at the all the fucking noise.

use a smaller bleed block

This was the solution I was going for. I even found a guy selling custom printed bleed blocks that were, say, 1% smaller than stock Shimano ones for just this problem.

If people are making custom parts for an issue, you can be pretty sure it's not a mechanic's problem.

http://road.cc/content/forum/177528-shimano-r785-discs-lots-travel

http://forums.roadbikereview.com/components-wrenching/shimano-r785-disc-levers-have-excessive-free-stroke-343759.html

Re master:slave ratio chat, so the issues are maybe because Shimano had prioritised modulation over power?

A 4 pot slave would be larger and exacerbate your problem then no?

Here are those custom printed bleed blocks. 1mm and 0.5mm thinner than Shimano standard. Cool huh?! (not you Shimano, you can sit in the corner and think about how you're going to get me my new DA disc setup)

https://www.shapeways.com/product/NN5BKSGNJ/bleed-block-1mm?li=shareProduct
https://www.shapeways.com/product/A9DAXVXWP/bleed-block-5mm?li=shareProduct

Buying used hyrdaulics is a total crap shoot.

Does this apply to just the caliper, or the whole system?

asking for a friend

A 4 pot slave would be larger and exacerbate your problem then no

Presume they've adjust it to work similar to stock but I have no idea what to expect. Discs are still pretty new to me. If I had the Shimano bleed kit I'd have fixed this problem months ago I'm just lazy.

4 fucking pistons hahaha. only hope would do such a thing. cool though. stopeeees for days

Does this apply to just the caliper, or the whole system?

Every. Single. Part.

A 4 pot slave would be larger and exacerbate your problem then no?

How I understand that RX4 thingy is that the four pots have the same surface area as the two in the original Shimano caliper.

The reason why they've gone 4 smaller pots vs. 2 large ones is so you can run a large pad and keep the caliper low profile. The larger pad - and additional stiffness of the low profile one piece caliper body - gives you the extra bite.

This look kosher for my brakes?

http://www.ebay.co.uk/itm/Shimano-Brake-Bleed-Kit-for-ROAD-Di2-ST-R785-RS685-funnel-100ml-oil-spanner-/182417342626?hash=item2a78ebc0a2:g:WRYAAOSw9NxTuInP

sorry, I thought planet x had them for £95, but it seems not any more

Are you able to elaborate? I can see why buying a used pad or used cabling is a bad idea - but the caliper alone? What is the rationale there?

Moving parts, wear out. Seals get damaged.

seals die

fair enough - I picked up a single caliper for £12 so I guess if it is fucked then no big deal