my logic with cable disc brakes and why they don't work well on drop bar levers, am i right?

[jonnyboy666]

@d8mok "many hours" is far from ideal, any brake should be set up in at most 20 minute's from fitting, cable-ing or bleeding, frankly if it takes someone that long to get a useable brake that doesn't rub, has reasonable safe stopping power and remains consistent for an acceptable period of time without further adjustment then it shouldn't be on the market.

 

[d8mok]

@d8mok "many hours" is far from ideal, any brake should be set up in at most 20 minute's from fitting, cable-ing or bleeding, frankly if it takes someone that long to get a useable brake that doesn't rub, has reasonable safe stopping power and remains consistent for an acceptable period of time without further adjustment then it shouldn't be on the market.

Whilst I agree in principle. Planet X bikes are such good value that something has to give


I’d argue that at this price point they’ve done a good job. Few hours to get them working and not touched again in 2 winters.

Admittedly I could have changed them ebut the whole idea of that bike was to be almost disposable when it dies so worth putting the time into if they end up working.

Remember I just an idiot in a garage with some Allen keys and not an engineer / bike mechanic / wheel builder so likely takes me longer too.

I’ve spent longer messing about with damn leaking GRX caliper seals , then a faulty RX4 caliper on my enigma.

 

[jonnyboy666]

@d8mok fair points in regards to not being trained etc, but a cable brake should be minutes to set up, no pistons to leak, it's clamp the cable and adjust the pads etc, from there they should be working, and for the most part that is not the end of it.

 

[wynne]

@d8mok i completely endorse your point about not cleaning too much. I reckon most people are too free and easy with cleaning products that build up and end up glazing brake pads.

I have TRP spyres and their tektro equivalent on all my bikes, including my best road bike, my crosser and my winter mudguarded tourer - all operated by sram force levers. Never once have i felt they didn't offer my 80kg enough stopping power - including a few 3 peaks cx races. Maybe it's the variability in mechanical/user competence, set up permutations, pre/misconceptions etc that make people dislike them rather than the fact that they can be made to feel and work superbly when you know their quirks and you can fine tune your set up.

 

[Woz]

There are a couple of things to understand: the first is the cable pull effect. The work done is the same but you can either get there by:
1) Lots of pull, low force
2) Short pull lots of force.
This is all about cable tension (less is good, less squish of outers, less lost to friction) vs. enough travel at the brake end to close the pads and have something left over. The critical thing is that the force necessary at the caliper needs to suit that available down the cable.

Least pull was needed by calipers and wide pull cantis, especially if the straddle cable was kept short.
Low-pro cantis needed a bit more pull (DiaCompe made a special road lever, the 287)
V's need lots of pull (DiaCompe again helped with the 287V along with Tektro / Cane Creek)

Long pull levers (like V's) will not give enough cable force at the brake end, will feel very firm but that's because they can't apply enough force to do anything useful.
Short pull levers give lots of force at the brake, but may lose over the cable run. They can feel squishy as the high cable tension means they can squeeze hard on everything down the line - but they often run out of travel.

Shimano has been fiddling round with pull ratios for its road calipers, which means later ones need longer pull. This is for 10-11-12 speed, so beware, the levers have subtle differences. These may not work as a result with Avid BB5/7 road brakes.

Good post. Somewhere, and being a bit sad, I've measured the pivot cable point and lever pivot point of several levers, canti, v-brake, drop-bar.

Can confirm it's something that's been messed around with and I'll get the numbers up later. I can confirm that across brands and generations actual MTB V-brake pivot cable point to arm pivot point was surprisingly consistant.

For rim brakes, there's also the question about pad thickness and squish which was also modified over time.

I'm of the view most road rim brake stuff was always a bit pants. Following with interest this thread, and it's shocking there are still issues and some very different opinions. Personally, I dumped Avid BB7 off because I was never happy with them. Got some TRP Spykes and Spyre new in a box and I'm still nervous and bracing myself to be disappointed when I get round to trying them.

 

[Guinessisgoodforyou]

Shimano altered the pivot point in the GRX lever to improve mechanical advantage at the lever, if memory serves. Way past my pay grade. I just don't like disc brakes after owning three disc equipped bikes. Don't shoot me it's only my opinion.

 

[M_Chavez]

AAARGH!!!
How did I miss this thread?!? I'm the runner-up for the lifetime "biggest road disk hater" award

Short answer: ditch the pizza cutters, get yourself some real brakes.

Long answer: the road disk brakes have driven me to the insanity of retro-modding a 1950s French randonneuse just so that I can have rim brakes on a steel "gravel" bike frame.

Thought #1: I've run cheapo cable-operated MTB brakes with various V-brake levers without any serious issues whatsoever for years. You do get disk rub, and you do need to spend an hour or two setting them up, but even as I type this, my Mrs is cycling on her hybrid with a 20-year old Hayes MX1 caliper that's still working well despite two decades of abuse. [Update: she's back home safe and sound without any brake failures]. They work with cheap cables, cheap pads and noname levers. They work.

Thought #2: I've tried BB7 road, BB7 MTB, Spyre road, Spyre MTB and a fistful of cheap Chinese hydro-cable hybrid jobbies. Tried them with Micronew levers. Tried them with Campies. Tried old school non-aero dia-compes. Tried the Tektro "long-pull" jobbies that are close to unusable. Tried them on 3 different framesets. Tried different pads.

The brakes never worked well.

After long hours of fannying with the set-up I did manage to get barely acceptable results from BB7 Road+Micronews... But this only lasted for a few months until the pads were worn. And I couldn't make them work with new pads, despite hours of tweaking.
Similarly, I've managed to get a semi-acceptable response from Spyre Road + Micronews. This lasted for several months until I suffered a catastrophic brake failure during an emergency stop . Out of the blue the pads just wouldn't bite at all. Never managed to set up the brakes to work well after that.

 

[M_Chavez]

Thought #3: The bike industry answers to your question (Why aren't my cable-operated road disk brakes working) are:
- Your cable housings compress too much, Have you tried zero compression housings at £60 a pop?
- Your cables are not good enough, but we can sell you new cables for just £30 for the set.
- Your pads are not good enough. Have you tried *insert fancy name* pads at £60 a pop?
- Your disk brake mounts are not perfectly aligned to the disks. Would you like us to ream them flat at £60 a pop?
- You can't possibly expect good results with those £25 rotors! Here's a good set that will work at £45 each.

I think this answers the question why nobody cares about designing cable-operated disk brakes that actually work. Why kill a cash cow? The MTB crowd has long switched to hydraulics; the really cool roadies are switching to hydraulics at £600 for a set of brakes & brifters. The rest of the schmucks would just have to pay the same £600 for their outdated cable disk brakes + all the wonderful bells & whistles that will never work anyway.

Also, I believe that there is a variance in the amount of cable pull from road lever to road lever, which might explain why disks sometimes work for some people. And you get very different leverage between braking on the hoods and in the drops, as you're pushing different parts of the lever... But somehow, my caliper 105 shimmies work like a dream in different set-ups.

 

[M_Chavez]

Rant almost over.

There is, of course, thought #4: Why, for the love of Reynolds-531db-riding-God do we need disk brakes on road bikes? You don't constantly get sand or mud building up on the rims, rendering them useless and grinding them away, like you get with MTBs. With a caliper brake you get so much stopping power, that the rear locks up all the time anyway, and the front can lock up or send you over the bars too if that's what you desire . The stopping power on a road bike and a gravel is limited by the tyres, not the pads. Also, caliper brakes are lighter, more reliable and easier to repair with your teeth and your nails on the side of the road when you're 50 miles away from home. Their set-up is at least logical, if not easy. They worked very well for decades.
I can't see any reasons apart from pure unbridled greed for the bike industry to ever make a road frame with disk mounts.

 

[legrandefromage]

My neighbour has bought a his n hers 2024 Specialised E5 Allez Disc road bikes

8spd |Claris and...

Cable

disc

brakes

I was asked to sort the shifting as the husband wasnt happy (the wife having ridden hers more, it was fine). On the test ride, the frame was quite nice and the shifting was fine but the brakes were like glass, they did not stop well at all. Even the bedded in bike wasnt any better

Yet the old Avid BB7 on a carboot find Boardman has been fine with a basic Avid v-brake lever