The Disc Brake Naughty Corner Thread

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Vorpal
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Re: The Disc Brake Naughty Corner Thread

Postby Vorpal » 20 Apr 2016, 8:25am

mattsccm wrote:Not in the slightest bit convinced that the current fallout is a big issue. Discs are not particularly sharp. I have QR's that are thinner at the end.
The chap that supposedly was injured recently was very unlucky as the combo of leg and where it was damaged made it obvious that he was riding the opposite direction to the other chap. It can happen but I bet more people have been chainringed or had a pedal in the belly.

I'm sure that you are right about more people being chain ringed, but anything like that is a hazard and can make accidents much worse. Discs *are* sharp, but even if you don't accept that they are sharp, they can still cause considerable damage just for being a metal edge. People aren't allowed to race, even in amateur races without plugs in their handlebar ends. That's because of the potential for damage in an accident.

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Paulatic
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Re: The Disc Brake Naughty Corner Thread

Postby Paulatic » 20 Apr 2016, 1:47pm

I see they've been banned from French Sportifs.
That'll hurt sales if it happens here too
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Mark1978
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Re: The Disc Brake Naughty Corner Thread

Postby Mark1978 » 20 Apr 2016, 3:06pm

Paulatic wrote:I see they've been banned from French Sportifs.
That'll hurt sales if it happens here too


It'll hurt sales even if it isn't the case. If the average MAMIL (like myself) has the thought in the back of their mind that there's even the slightest chance they might want to go do some crazy French sportive thingy, then getting that bike with disc brakes seems a less attractive option.

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Re: The Disc Brake Naughty Corner Thread

Postby Paulatic » 20 Apr 2016, 3:40pm

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Dave W
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Re: The Disc Brake Naughty Corner Thread

Postby Dave W » 20 Apr 2016, 8:39pm

Could be a derailleur - ban them!!

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Re: The Disc Brake Naughty Corner Thread

Postby vandjq » 20 Apr 2016, 8:49pm

This thread is 24 pages long, so I hope I'm not repeating another contribution:

John Allen thinks that:

'All in all, disc brakes are advantageous on bicycles which have front suspension and are ridden in mud and snow.' Here's the link to his article:

http://www.sheldonbrown.com/disc-brakes.html

I have been looking at Cube bikes, many of which come fully equipped for commuting, but all of them have disc brakes. So I may need to look elsewhere.

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Re: The Disc Brake Naughty Corner Thread

Postby reohn2 » 20 Apr 2016, 8:52pm

vandjq wrote:.....I have been looking at Cube bikes, many of which come fully equipped for commuting, but all of them have disc brakes. So I may need to look elsewhere.


Why?
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Re: The Disc Brake Naughty Corner Thread

Postby samsbike » 20 Apr 2016, 8:55pm

reohn2 wrote:
vandjq wrote:.....I have been looking at Cube bikes, many of which come fully equipped for commuting, but all of them have disc brakes. So I may need to look elsewhere.


Why?


Indeed why?

For rubbish weather they are great for stopping, in fact I worry about being hit in the back by other cyclists who don't have discs when it rains.

Tires and rims are cleaner in case you need to fix a puncture and rims take less of a beating for obvious reasons. For commuting I cannot see a downside especially with hydraulic discs. The only bit of hesitation, is that some disc calipers non-hydraulic take a lot of lever pull (hy-rd) which is a little disconcerting at times.

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Re: The Disc Brake Naughty Corner Thread

Postby vandjq » 20 Apr 2016, 9:07pm

Thanks for the prompt replies, guys: I guess you don't agree with John Allen:

'•A front disc brake stresses one blade of the front fork very heavily, requiring a stronger, heavier fork, resulting in a bumpier ride with a non-suspension fork, and if a fork isn't quite rigid enough, producing 'brake steer".
•A front disc brake caliper behind the fork blade generates a powerful force tending to loosen a quick release and pull the wheel out of the fork. Special hub and fork designs are needed to surmount this problem.
•Disc brakes are generally heavier than rim brakes.
•Disc brakes are more complicated, expensive and difficult to maintain than rim brakes or drum brakes.
•Some disc brakes are grabby. This problem is likely if dirt gets trapped between the calipers.
•Disc brakes require special fittings on the frame and fork, and special hubs.
•Disc brakes can interfere with baggage racks and fender stays.
•The disc is vulnerable and easily bent. Other hub brakes do not have this weakness.
•Hub flange spacing is often reduced, resulting in a weaker wheel.
•Adjustment may be difficult to avoid calipers' rubbing on the rotor when the brake is not in use.
•The disc gets extremely hot and can cause injury if touched, and melt nearby plastic or cloth items. Care must be taken to use the correct brake fluid with a hydraulically-actuated disc brake, so it does not boil, resulting in loss of braking'

I should stress that I've never ridden a bike with disc brakes and am simply weighing up the pros and cons
Last edited by vandjq on 20 Apr 2016, 9:50pm, edited 1 time in total.

Dave W
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Re: The Disc Brake Naughty Corner Thread

Postby Dave W » 20 Apr 2016, 9:40pm

Some of those points are out of date. Read about the Cannondale CAAD 12 disc - lighter than it's rim braked sister. Some bikes have through axles these days. Manufacturers would have thought about adapting frame and forks to take discs by now. Mountain bikes have used them for years so too rigid Tandems. My own tandem hasn't lost a wheel yet or stripped the spokes on one side or overheated or burnt anyone despite the obvious increase in the weight of two riders. Some callipers have both pads adjustable.Discs can be tweaked with a special tool should the run out of true. Racks are available to clear the calliper.

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Re: The Disc Brake Naughty Corner Thread

Postby Mattyfez » 20 Apr 2016, 9:58pm

Dave W wrote:Discs can be tweaked with a special tool should the run out of true. Racks are available to clear the calliper.

A hard flat surface and a hammer, plus some mole grips to fine tune them :D

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Re: The Disc Brake Naughty Corner Thread

Postby Brucey » 20 Apr 2016, 10:29pm

Dave W wrote:...Some of those points are out of date. Read about the Cannondale CAAD 12 disc - lighter than it's rim braked sister.....


"it's sister..." yeah, its ugly sister, deliberately made heavier because they want to shift bikes with disc brakes.... :roll:

Please don't confuse marketing with engineering.... :wink:

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Manc33
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Re: The Disc Brake Naughty Corner Thread

Postby Manc33 » 20 Apr 2016, 11:14pm

I'm really tight and I thought why have rim brakes if they will eventually wear the metal down on the rim, since I have a decent set of Mavic rims that although scraped away at by brake blocks from rainy rides in the past, actually still have 2mm of metal to the braking surface, so I laced them to some XT disc hubs and slapped some BB7's on. I can't say there's any advantage at all as far as the brakes, using them and the braking "power" go, but I know my Mavic's are now one of the few things on my bike I won't need to replace from wear.

I did have Dura Ace 7800 calipers on a road bike not long ago and I never thought I could miss a pair of brakes like I currently miss those. :cry: Still I won't go hydraulic on the disc brakes, no thanks. I'd rather have less powerful brakes since they are at least adequate.
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Re: The Disc Brake Naughty Corner Thread

Postby reohn2 » 20 Apr 2016, 11:15pm

vandjq wrote:Thanks for the prompt replies, guys: I guess you don't agree with John Allen:

'•A front disc brake stresses one blade of the front fork very heavily, requiring a stronger, heavier fork, resulting in a bumpier ride with a non-suspension fork,

Taken care of easily with a larger section tyre,if you're worried about extra weight buy Vittoria Voyager Hypers or Randoneur Pro tyres
and if a fork isn't quite rigid enough, producing 'brake steer".

If it is a disc specific fork it won't.

•A front disc brake caliper behind the fork blade generates a powerful force tending to loosen a quick release and pull the wheel out of the fork. Special hub and fork designs are needed to surmount this problem.

What manufacturer in their right mind would fit a disc brake to a non disc spec fork? :?
BTW I have Halo Hexlock skewers fitted to all five disc bikes,mainly so the wheels don't go walkies when I'm in a cafe.I don't need qr skewers as I'm not racing so don't need a quick wheel change,so I've no worries there. :)

•Disc brakes are generally heavier than rim brakes.

Agreed but their advantages far out weight their sight weight penalty

•Disc brakes are more complicated, expensive and difficult to maintain than rim brakes or drum brakes.

I can't speak for hydraulic discs,but the Avid BB7's provide far better braking in all conditions than any other type of brake I've used,and are an absolute doddle set up and maintain which is minimal, and by far easier and less trouble than rim brakes.
I can't speak for drums as the only drum brake I'm familiar with are Arai drag brakes on tandems which give no problems.

•Some disc brakes are grabby. This problem is likely if dirt gets trapped between the calipers.

I've been using cable discs for over 8 years and have never experienced that phenomena,in fact it's the first time I've ever heard of it :? .
•Disc brakes require special fittings on the frame and fork, and special hubs.

Agreed but where's the problem with that?
Once the bike is built that problem ceases to be any kind of a problem.
•Disc brakes can interfere with baggage racks and fender stays.

All my bikes with discs have mudguards and I can honestly say the interference is minimal, mudguard stays are easily and simply adjusted to fit,and once fitted need no further maintenance or concern any more than m/guards fitted to rim brake bikes .
Racks can be adapted simply with a bit of bending and a spacer or two,or a disc specific rack bought to fit straight on.
•The disc is vulnerable and easily bent. Other hub brakes do not have this weakness.

Disc rotors can be bent,but I've yet to manage to bend one.
I've had one or two out of true,which was easily trued up with an adjustable spanner clamped on the spoke(s)of the rotor,it took me about <5 minutes to fix.
•Hub flange spacing is often reduced, resulting in a weaker wheel.

Left side front wheel is slightly dished but nowhere near as much as a dished rear wheel on the driveside.If you ride Campag the rear driveside dish is about as bad as you can get,more so with 11sp+ wheels and far,far worse than a front disc wheel.
The rear non driveside,is unaffected by disc brakes.
•Adjustment may be difficult to avoid calipers' rubbing on the rotor when the brake is not in use.

Only true if the rotor is out of true,see above how to true up a rotor.
•The disc gets extremely hot and can cause injury if touched, and melt nearby plastic or cloth items.

I find the best thing is not to touch a rotor directly after a long descent when the brake's been used a lot.I've monitored this and found the 203mm discs on our tandem(with approx 190kgs of bike two people and two rear panniers)after some serious braking on a 2 mile long North Wales descent,which made the rotor a rather attractive straw colour,took less than minute for me to be able to touch without harm.
No plastic parts have yet melted on any of my disc brakes.
I don't go near my disc brakes with any kind of cloth and only use a little nail varnish remover on a square of kitchen roll,to clean the rotor and pads occasionally.
Care must be taken to use the correct brake fluid with a hydraulically-actuated disc brake, so it does not boil, resulting in loss of braking'

I don't use hydro's or feel I need them.
If I can lock up either wheel with two fingers on the brake lever I reckon that's enough brake power I'll ever need and the modultion of BB7's are great too :) .

I should stress that I've never ridden a bike with disc brakes and am simply weighing up the pros and cons

Been using them for over 8 years and upto last year was averaging 7 to 9k miles per annum,on tandems and solo bikes and an MTB.
The pros far outweigh the cons,especially in wet and or mucky conditions.They need minimal maintenance,pads far out last rim brake pads,and there's no rim wear.And unless riding in filthy and or wet off road conditions pad adjustment is also minimal.
What's not to like?
PS,should you overcome someone else's prejudice,make sure you buy the best calipers,I've had no problems with Avid BB7's :D
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Re: The Disc Brake Naughty Corner Thread

Postby jb » 20 Apr 2016, 11:15pm

One observation on modern hydraulic disk brakes on bicycles: if you don't mess with them they don't normally give any trouble for the lifetime of the product. Its only when people attempt to change the fluid that problems begin.

As I see it there is so little fluid in there to begin with that they have to be set up at the factory under very clean conditions with all air removed from the fluid that your normal garage DIY enthusiast cant hope to replicate. changing the pads is all one should ever do.
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J Bro