Disc brakes, hydraulic versus cable

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thelawnet
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Re: Disc brakes, hydraulic versus cable

Postby thelawnet » 15 Jun 2019, 11:22am

My main observation is that flat bar hydros are cheap, and anyone who claims a cost saving over v brakes is being excessively parsimonious.

OTOH the STI versions are a ripoff for now, but no doubt the price will continue to fall.

I rather fancy myself a pair of the new Shimano gravel STIs with the additional interrupter levers at top, as I find my Deore flat bar lever discs to be about 100x better at stopping from the tops compared to my 105 drops, but perhaps that is my setup as well....

jerg
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Re: Disc brakes, hydraulic versus cable

Postby jerg » 15 Jun 2019, 11:25am

Don't you run the risk of getting air into the system with hydraulic brakes if you have to up end the bike to remove a wheel? Thinking about if you have to fix a puncture when touring. Cable brakes would therefore be better in this situation.

reohn2
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Re: Disc brakes, hydraulic versus cable

Postby reohn2 » 15 Jun 2019, 11:32am

Cugel wrote:
You make several good arguments for cable-operated disc brakes. I found (from comparing similar in hydro and cable versions) that the hydro-operated disc brakes of good quality have a singular advantage: they can be operated with greater precision and with much less hand strength for long and/or steep downhills where there is a need for continuous or very frequent, sometimes hard, braking.

That may be a small matter for those not living or riding amongst the long and/or steep downhills. Whippersnappers with an immense and tenacious hand grip may also be fine with cable-operated brakes, even going down the 300M bendy-gravelly drop from the top o' Brechfa forest into Brechfa village! For olde gimmers and their slight ladywives the hydros are, I would say, a necessity if one is to avoid hand-twangle; or even a feeble under-brake causing a hedge-bite or worse.

On the other hand, I can get down that bendy steep road on a rim-brake bike albeit with utter concentration on picking the right line and leaning madly on the large, soft and sticky tyres (in the dry). Still, me poor little graspers are all a-tremble at the bottom (along with the rest of me). :-)

Cugel

I've never had that problem with either cable discs or rim brakes FTM,rim brakes much less so in the wet,perhaps I have a strong grip though my grip strength in recent years isn't what it was.
I do have large hands though and you know what they say about men with large hands..... .......they need large gloves.
Last edited by reohn2 on 15 Jun 2019, 5:58pm, edited 1 time in total.
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andrew_s
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Re: Disc brakes, hydraulic versus cable

Postby andrew_s » 15 Jun 2019, 11:48am

So you take the wheel out without turning the bike upside down - it's not difficult.

Turning the bike upside down is bad practice, and is forbidden by rule 49. You risk damage to the saddle, bar tape, any GPS or computer you forgot to take off the bars, emptying your bidons etc.

Brucey
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Re: Disc brakes, hydraulic versus cable

Postby Brucey » 15 Jun 2019, 11:53am

flat tyre wrote:Thanks for the replies. I feel as if I'm teetering on the edge of an abyss here as all my other four road bikes are rim brakes. I'm looking at a bike for long road rides in all weather (well, wet weather certainly). At present the only thing pushing me to jump into the disc brake abyss is the dreaded rim wear, I'm not bothered by braking performance, as I've managed perfectly with rim brakes for 55 years! At 8,000 miles a year I find I'm going through rims fairly frequently, particularly as I live in the south downs area with plenty of braking required and ideal rim grinding paste conditions.


when you say 'road bike' are you thinking of 'road racing' type bike or something more touring oriented? If the latter then another option is drum brakes; this works out better than you might expect (*) and the brakes have the longest service life of any brakes out there. Another option is to use rims with a hard coating. Ryde still offer some rims with CSS coating and Mavic offer some with 'exalith' treatment. Realistically such rims ought to do at least 20000 miles.

In any event there are other considerations if you jump ship and use a different type of brake; for one thing you won't have a spare set of wheels for the new bike unless you buy a second set. Another is what kind of hubs you use with disc brakes; through axles are now being specified (rather than conventional QRs) and new formats are emerging all the time for both this and the brakes themselves. For hubs there are several different OLNs and though axle 'standards', as well as several different disc mounting systems. Current road racing frames tend to have 'flat mounts' for calipers. These mounts can be converted to accept post-mount or ISO mount calipers, but 'flat mount' calipers can't (easily or at all) be fitted to frames with post-mounts or ISO mounts. Some hubs can be converted (using spacer kits) to allow them to be used in a different kind of frame, others can't. If you want 'conventional' hub internals (i.e.with conventional cup and cone bearings etc) then a frame that uses normal QR hubs is probabaly the best choice.

(*) Re drum brakes; its easy to dismiss these as being 'heavy' but if you equip a typical 1" steerer steel frameset with 70mm drum brakes it works out about the same weight as a current steel touring frameset equipped with 1-1/8" steerer and QR type hubs/disc brakes. It takes near-submersion to get drum brake internals wet, so they are nigh-on unaffected by the weather. [By contrast disc brakes can lack 'bite' when first applied in the wet (this varies with the pads used), but soon get some power back as the water comes off the disc; this means that for planned braking discs are fine but for unplanned braking in the wet, they only work well if the pads are carefully chosen.] As well as drum brake IGH hubs you can get drum brake hubs that at the rear accept either an 8/9/10/11s MTB cassette or that accept a screw-on freewheel. At the front you can have 70mm or 90mmm drum with or without a hub generator. Nearly all these hubs use cartridge bearings which are of a conventional type that are easy to change. The hubs are exceptionally smooth running and have been used in many record-breaking HPVs amongst other things.

There are some features about disc brakes which have not yet been mentioned much;

- the discs themselves get hot; this can mean you can burn yourself if you come into a contact with a hot disc (eg having dismounted at the foot of a descent)
- discs get contaminated; anything oily is pretty deadly; you need to be careful e.g. a good deal more scrupulous when applying chain lube
- discs get bent; if you knock a disc it can go out of true and rub
- discs can warp; some discs go out of true when they get hot for the first time
- disc brake mountings tend to get in the way of mounting luggage racks, mudguards etc. There are work-arounds for these things of course, which vary in elegance.
- disc pads vary in wear resistance; the hardest wearing pads are sintered ones, but they are somewhat noisy in use, and conduct heat into the caliper body rather better than most other pad types; this would increase the chances of a boil-up with hydraulic brakes. A day's muddy/wet riding can be enough to see off the least wear resistant pads.
- discs wear out; wear limits and costs vary so that six-bolt discs are probably least expensive to run and fancier discs (e.g. ICE-tech centrelocks) can be worn out inside two sets of pads and are expensive to replace.
- disc brakes are (or should be) heavier than rim brakes (at any given price point); there is hidden weight in the frameset to contend with as well as the more obvious issues
- using disc brakes imposes loads that are up to ~x5 higher than 'normal' (i.e. for rim brakes) on the hub bearings.
- disc brakes are kind of sharp-edged and in a spill, nasty gashes are possible.
- disc brakes normally use a stiffer fork than is necessary with rim brakes; this often translates to less comfort
- disc brake wheels are built differently to rim brake wheels; the front wheel is dished (and weaker than normal) and the spokes see greater loading too.

Few of the above issues are show stoppers but for some folk they might be. If you were thinking of changing to rim brakes from discs there would be a similar list of differences for rim brakes of course, but i'm assuming that you are already familiar with those things! For some uses the advantages outweigh the disadvantages for most folk so for example in MTBs you find mostly disc brakes not rim brakes; however for road use the argument seems much less compelling.

One of the things you will have to get your head around is the differences in brakes, bike to bike. It doesn't take long to recalibrate the brain so that in planned braking you use the brakes sensibly; however in unplanned braking instinct and habit takes over and if you have very much more powerful brakes on just one bike then an emergency stop on that machine might turn into 'a single vehicle accident'.

cheers
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mattsccm
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Re: Disc brakes, hydraulic versus cable

Postby mattsccm » 15 Jun 2019, 5:08pm

In my experience turning a bike upside down doesn't let air in. I guess maybe it could but never heard of it. However as mentioned an inverted in has drawbacks that make it a iffy idea anyway.

mattsccm
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Re: Disc brakes, hydraulic versus cable

Postby mattsccm » 15 Jun 2019, 5:11pm

Please show me 15 miles of down hill in the Uk that needs both brakes. What a wonderful ride. On or off road?

reohn2
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Re: Disc brakes, hydraulic versus cable

Postby reohn2 » 15 Jun 2019, 5:56pm

thelawnet wrote:My main observation is that flat bar hydros are cheap, and anyone who claims a cost saving over v brakes is being excessively parsimonious.

OTOH the STI versions are a ripoff for now, but no doubt the price will continue to fall.

I rather fancy myself a pair of the new Shimano gravel STIs with the additional interrupter levers at top, as I find my Deore flat bar lever discs to be about 100x better at stopping from the tops compared to my 105 drops, but perhaps that is my setup as well....

Cable cross top interrupter levers do IME provide as good if not better stopping power than dropbar levers.
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reohn2
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Re: Disc brakes, hydraulic versus cable

Postby reohn2 » 15 Jun 2019, 6:00pm

mattsccm wrote:Please show me 15 miles of down hill in the Uk that needs both brakes. What a wonderful ride. On or off road?

People do cycle elsewhere other than the UK these days :roll:
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reohn2
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Re: Disc brakes, hydraulic versus cable

Postby reohn2 » 15 Jun 2019, 6:03pm

jerg wrote:Don't you run the risk of getting air into the system with hydraulic brakes if you have to up end the bike to remove a wheel? Thinking about if you have to fix a puncture when touring. Cable brakes would therefore be better in this situation.

I've never had the need to turn a bike upside down when removing a wheel,so can't se that as a problem even if it's true that it would let air into a hydro system,which I'm not convinced it is.
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hondated
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Re: Disc brakes, hydraulic versus cable

Postby hondated » 15 Jun 2019, 6:33pm

Oh well thats the disc brake Gravel bike I had thought of buying out of the window then :wink: :lol:

rmurphy195
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Re: Disc brakes, hydraulic versus cable

Postby rmurphy195 » 15 Jun 2019, 8:35pm

flat tyre wrote:Thanks for the replies. I feel as if I'm teetering on the edge of an abyss here as all my other four road bikes are rim brakes. I'm looking at a bike for long road rides in all weather (well, wet weather certainly). At present the only thing pushing me to jump into the disc brake abyss is the dreaded rim wear, I'm not bothered by braking performance, as I've managed perfectly with rim brakes for 55 years! At 8,000 miles a year I find I'm going through rims fairly frequently, particularly as I live in the south downs area with plenty of braking required and ideal rim grinding paste conditions.


Precisley why I had my new tourer as the disc version, using cable discs - at the time I was using gritty canal towpaths and cycle trails which do give the rim brakes a hard time.. The performance is consistently better than the cantis on my old bike, and I find them easier to adjust and to replace the pads than the cantis. A side benefit is that they are less affected by rain/wet roads. (However you asked about hydro v cable, not discs v cantis!)

As I said before, the cable discs aren't as powerful as the hydros that I have tried(briefly), but the limiting factor for me is the tyres anyway. On my bike the rear disc mountings don't get in the way of the pannier rack - the Heritage (Disc) is using the rack from my old Galaxy (Rim), though the front mudguard stays on the left are a bit convoluted!

Interestingly my son at one time had hydraulic rim brakes, made by Magura I think. Boy do the rims wear quick with those!
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pjclinch
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Re: Disc brakes, hydraulic versus cable

Postby pjclinch » 15 Jun 2019, 9:07pm

rmurphy195 wrote:
Interestingly my son at one time had hydraulic rim brakes, made by Magura I think. Boy do the rims wear quick with those!


My recumbent tourer has them (HS-33s). Has had them a long time. I don't notice the rims wearing any quicker than when it had Vs. I do find the braking a lot more responsive and controllable, however, and spend a lot less time fettling brakes.
I'd sooner have HS33s than cable discs.

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Often seen riding a bike around Dundee...

Brucey
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Re: Disc brakes, hydraulic versus cable

Postby Brucey » 15 Jun 2019, 9:50pm

current Hydro disc systems have a bladder or a diaphragm in the reservoir which is meant to accommodate volume changes in the system as the pads wear. In theory if the system is correctly bled out there is no air anywhere in the system, so inverting the bike oughtn't cause any problems. However during the bleeding process there is no way of establishing for sure that

a) there is really no air in the system anywhere or even that
b) there is enough fluid in the system.

These faults will only manifest themselves in service or if you do some thorough checks;

1) if the brakes go spongy when the bike is inverted there is still air in the system; more bleeding required.
2) if the brake pistons are (with care) pumped onto a spacer (eg bleed block) which is only the same thickness as the disc plus the pad backings (about 5mm) the brake should remain firm. If it goes spongy then there simply isn't enough fluid in the system, and worse yet if the caliper pistons are draggy you might draw air into the system.

IME you can quite quickly get a system bled so that it seems to be working OK. However to be 100% free of air and with enough fluid to accommodate full pad wear is quite another matter; it can take a few goes and may cause some frustration before a good result is obtained. I believe that quite a lot of riders are blissfully riding around with (potentially dangerously) sub-standard brakes, which simply don't have enough fluid in them and/or still have air in the reservoir.

cheers
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jerg
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Re: Disc brakes, hydraulic versus cable

Postby jerg » 16 Jun 2019, 12:36pm

reohn2 wrote:
jerg wrote:Don't you run the risk of getting air into the system with hydraulic brakes if you have to up end the bike to remove a wheel? Thinking about if you have to fix a puncture when touring. Cable brakes would therefore be better in this situation.

I've never had the need to turn a bike upside down when removing a wheel,so can't se that as a problem even if it's true that it would let air into a hydro system,which I'm not convinced it is.


It might just have been coincidence but after having removed and refitted the wheels on my Longitude (by committing the cardinal sin of turning it upside down to do so :D ) I found that my brakes had become non-existent, requiring a thorough bleed to get them working again. I'd never had hydraulics on a push bike before so I was a bit surprised.

I've never removed a rear wheel without turning a bike upside down and have no idea how hard it is to do it any other way !