Disc Brakes (are they any safer)

by Shep73   June 6, 2014  

Now on a mountain bike they are invaluable, i use one of the best on my MTB but today I realised that I think they could a waste of time on a road bike. attacking a descent on a road ride today and I'm doing 45mph, I see a car so I slow to 30 but I'm on it in no time, the next thing the car stops on the hill. Now admittedly I was getting close, so although she stopped it was more my fault than hers. But anyway I hit the brakes (Ultegra units) and I ain't stopping, all I'm doing is sliding along with the back end coming around on me. I manage to see a gap on her inside and just point for it.

I actually didn't stop until I was past her front door. So if my braking had got the better of my grip with rim brakes, what will disc brakes do. As an experienced Road/mountain biker (trail, XC and downhill), All I can see is less control in emergency situations. Also people wasting money on a new fad.

I think my mountain biking helped me but I did shit myself. It was more instinct than calm control.

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I use discs for commuting because I ride all year round and they don't suffer from the same loss of performance in the rain as rim brakes do. I need to be able to stop or scrub off speed quickly, reliably and predictably. Discs give me that in wet weather as well as dry.

I use rim brakes quite happily at the weekend because the emergency stop is less of a certainty. However, I need to be much more aware of how well each brake is functioning at any given moment and need to make sure that I ride and brake within a much smaller window of effective performance when it comes to avoiding hazards.

So... In answer to you question, yes discs are "safer". However, what's more important is your braking technique, skill in handling the bike at speed, observation and anticipation.

My eyes prefer Celeste, my bum prefers titanium.

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posted by Jack Osbourne snr [304 posts]
6th June 2014 - 21:30

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I have Ultegra rim brakes on my road bike and my husband has Tektro mech disc brakes on his commuter bike (Jamis Nova) and in heavy rain going downhill he has much better stopping power than I do. We were going downhill in the rain with a 5-7% grade only going 20-25 mph and I had front and rear brakes fully engaged and it took me 2-3 times the distance to slow than he could with just a few pumps of his disc brakes. When it's dry I can pretty much stop whenever I need to and there doesn't seem to much of a difference between us. Looking forward to getting a disc braked 'cross bike for the winter/wet months so I'm not limited to flatter rides this winter.

Melancholy is incompatible with bicycling. ~James E. Starrs

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posted by movingtarget [134 posts]
6th June 2014 - 22:21

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Yes they are.
You have proved yourself that its not the equipment that's dangerous but the rider.
You want your head testing to be riding on open roads with cars about at that speed. Just as a car driver would for driving faster than the road conditions allow. Its fair enough on closed roads but you have proved that the conditions were not acceptable as it went wrong. The brakes were not to know but you should have made that assessment.
Its not a personal attack, and I would defend your right to do so in the right circumstance, but the same applies when a car driver tail ends another in a traffic queue or can't stop at legal speeds when a deer walks out or maybe a dim-witted kid.
The brakes work, humans don't use them properly.
In most circumstances (exceptions are largely red herrings in most things in this world) disc brakes are more effective. What may not illustrate this is how or when they are used.
Disc brakes have few if any disadvantages. They do have some advantages. Power is the main one. I have very short fingers which means that basically its hard to get a decent pull on any brake. The fact that discs give more oomph makes up for my limited power. I do wonder if the deaths of those two women recently would have happened if they had been using discs? The inquest for the one in Devon??? suggested that she had "cyclists palsy". Daft term to describe either the numbness cyclists get in their hands or the aches that happen on long descents if you hold the brakes for a long time. The death in Winnats pass fits that general theory as well. Just wondering of course.
Nope. To say that disc brakes are dangerous is wrong. They just didn't work for you in that situation and can you prove that rim brakes would have done so?

posted by mattsccm [247 posts]
7th June 2014 - 8:32

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I'm not saying that the brakes themselves are any worse in terms of performance, my point is the tyres, road tyres don't have the grip that mtb tyres have or the squish. So if you do get in a situation of having to brake hard, you have more chance of sliding rather than slowing down. As for skill, I guess you didn't watch the Giro where riders had no time to react in a controlled environment on a closed road? you will skid no matter who you are on a road bike.

As for riding at speed on roads, I have always done so and this is the first time I have had to hit the brakes in this manner and I am more than well aware of whats going on around me as I stated. I started to react to her coming into view, I also stated I didn't have disc brakes, and as for the conditions? sunny, dry roads, the conditions were fine. Considering I ride with a lot of riders who go the same pace and none of us have died yet I would say it's no more dangerous than some idiot going up the inside of a lorry at 5mph.

posted by Shep73 [137 posts]
7th June 2014 - 10:00

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it's a bit of a straw man argument, really. you got yourself into a situation where no amount of braking would have allowed you to stop in time. that doesn't really have any bearing on whether discs are better than rim brakes.

disc brakes won't stop you any quicker on a dry road in fine conditions; we know that and i proved it to myself when i chucked two bikes down Mt Etna last year:

http://road.cc/content/blog/96531-shimano-road-discs-final-thoughts-now

they'll stop you a sight quicker in the pissing cold rain on wet rims though, especially if those rims are carbon. that's a stone cold fact as far as i'm concerned and i'd challenge anyone who's used shimano's new hydraulic discs to tell me otherwise. they'll not ruin those carbon rims on gritty winter rides either. and they'll stop your hands cramping up on tricky, dangerous descents.

we go over this a lot. the maximum braking force is a distant third behind two other factors: the ease of applying that power, and the consistency of that power in all conditions. that's what makes disc brakes better brakes.

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posted by Dave Atkinson [7317 posts]
7th June 2014 - 11:24

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Discs are generally better for all-round road riding, particularly winter training and commuting in the rain. They don't eat through rims like rim brakes, and they will stop much better in wet weather.

There are some caveats, though. What determines how fast you can stop is not the brake type, but the traction of your front tire, your total weight and your center of gravity. While disc brakes do help you reach your maximum stopping velocity quicker than rim brakes, the increased power, if you're not used to it, can cause you to unwittingly exceed your front tire's traction, at which point it skids and down you go.

Discs don't cool nearly as well as rims, so if you're on a long descent, say in the alps, discs are more susceptible to overheating and, consequently, fading. This can be very dangerous. That said, I'd prefer disc brakes to carbon clinchers; carbon builds and retains heat so it can lead to a tire blowing out. This will result in a dead cert crash.

Discs require a different frame design, with significantly stronger forks and stays. For steel bikes this isn't a big factor, but on carbon race machines (cyclocross mainly) I've heard lots of complaints about carbon disc frames feeling dull and wooden. Because of this I don't think discs will be a big factor in race bikes. Also, they're heavier and less aerodynamic than rim brakes. Sure, the difference is fractional, but when breaks are made and races are one by inches, it's hard to see why you'd choose discs.

posted by Gordy748 [83 posts]
7th June 2014 - 20:40

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Gordy748 wrote:
Discs are generally better for all-round road riding, particularly winter training and commuting in the rain. They don't eat through rims like rim brakes, and they will stop much better in wet weather.

There are some caveats, though. What determines how fast you can stop is not the brake type, but the traction of your front tire, your total weight and your center of gravity. While disc brakes do help you reach your maximum stopping velocity quicker than rim brakes, the increased power, if you're not used to it, can cause you to unwittingly exceed your front tire's traction, at which point it skids and down you go.

Discs don't cool nearly as well as rims, so if you're on a long descent, say in the alps, discs are more susceptible to overheating and, consequently, fading. This can be very dangerous. That said, I'd prefer disc brakes to carbon clinchers; carbon builds and retains heat so it can lead to a tire blowing out. This will result in a dead cert crash.

Discs require a different frame design, with significantly stronger forks and stays. For steel bikes this isn't a big factor, but on carbon race machines (cyclocross mainly) I've heard lots of complaints about carbon disc frames feeling dull and wooden. Because of this I don't think discs will be a big factor in race bikes. Also, they're heavier and less aerodynamic than rim brakes. Sure, the difference is fractional, but when breaks are made and races are one by inches, it's hard to see why you'd choose discs.

Good post, I have over heated my brakes on the mtb on descents. I now use Ice Techs which do help. But at least a mtb has better grip which is the biggest factor in stopping so in hard braking situations you will stop.

posted by Shep73 [137 posts]
7th June 2014 - 22:38

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And MTB tyre has better grip off road.
On road it doesn't grip better than a road tyre.

You're just blaming your brakes/tyres for what was getting yourself in a situation you very nearly couldn't get out of.
Ride more aware and with in your abilities/the conditions.

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posted by glynr36 [363 posts]
7th June 2014 - 22:54

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glynr36 wrote:
And MTB tyre has better grip off road.
On road it doesn't grip better than a road tyre.

You're just blaming your brakes/tyres for what was getting yourself in a situation you very nearly couldn't get out of.
Ride more aware and with in your abilities/the conditions.


That's utter rubbish, a mtb tyre will grip far more than any road tyre on the road. Mechanical grip comes from the squish of the tyre, which forces it into the surface. The tyre hooks up into the tarmacs uneven surface. A road tyre will not do this as efficiently due to width and tyre pressures.

I'm also not blaming my brakes, I'm just making an observation that powerful brakes are only as good as the rubber/tyre type that's underneath you. I'm also more than capable as a rider.

posted by Shep73 [137 posts]
8th June 2014 - 11:39

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if you are using the ultegra dual pivot brake with the standard shimano ultegra pad then you really wont get a great deal of early bite when you pull the brakes on, the compound is very hard and designed for longevity rather than good bite and lack of fade.
My preference is to swap the shoes and pads out for swissstop.
The black prince pads are great on carbon, i have them on duraace dual pivot brakes and they stop very quickly for carbon but although the best stopping combo for carbon rims they are the slowest.
Fastest stopping is BXP on alloy rims, i really mean they stop you so quick they are as quick as a disc. caveat is though that i have a specific regimen for cleaning the rims.
So here is my recipe for the best possible performance improvement anyone can do at home.

put rubber gloves on
take the wheels off the bike.
get a damp microfibre cloth and wipe around the outside of the tyre to clean it and check it for foreign objects.
then wipe any dust or dirt from the hubs and rims and spokes.
take another cloth and dry them.
get out a bottle of isopropyl alcohol and dampen the corner of a cloth
run the dampened corner around the braking surface, avoid the tyre. then wipe dry pressing hard to polish the rim.
repeat until all braking surfaces are cleaned, i.e. no further residue shown on cloth, so change cloth frequently.

next dampen cloth in alcohol and clean brake pad surface, dry off with cloth.
remount wheels into bike
check brake pad adjustment with a 5p piece and adjust as required.

this method takes about 8 or 9 minutes with practice and ensures your bike will have optimal rim braking setup with totally predictable performance on every ride.

so are disc brakes better, nah just different, the move for disc brakes on road bikes is all about over all wheel performance.

posted by steven miles [22 posts]
8th June 2014 - 15:57

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'But anyway I hit the brakes (Ultegra units) and I ain't stopping, all I'm doing is sliding along with the back end coming around on me'

You locked the back brake, hence the back wheel coming past you. You don't need more braking power, you need to modulate your braking better.

posted by Chris James [182 posts]
8th June 2014 - 17:41

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There's some massive logical flaws in this - through your own actions you got into a situation where no amount of braking power was going to stop you in time, you locked a wheel using Ultegra rim brakes and because of all that you've somehow leapt to the conclusion that disc brakes aren't needed?!

Quote:
a mtb tyre will grip far more than any road tyre on the road. Mechanical grip comes from the squish of the tyre, which forces it into the surface. The tyre hooks up into the tarmacs uneven surface. A road tyre will not do this as efficiently due to width and tyre pressures.

Yes and no. Rubber compound also plays a massive role in it. But the whole thing is an aside to the topic of conversation anyway...

In that situation you need to release the brake, allow the tyre to gain traction again, then re-apply, possibly with more weight over the back wheel. Having said that, it's an easy thing to describe from the comfort of an armchair, very different to when you're flying towards the back of a car!
Glad you survived it unscathed.

posted by crazy-legs [506 posts]
8th June 2014 - 22:01

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I am sure this is the same argument as banded about when discs first came into use on the MTB scene.

Yes there is a finite amount of tyre grip available, and yes, disc brakes are going to help you find that limit quicker, but its exactly the same off-road where there is rarely enough tyre traction to be able to apply the brakes full force.

Where discs come in handy is consistency and as mentioned, modulation. They will still require the rider to have a degree of competency.

It does raise the argument however, that potentially disc brakes are going to encourage more cavalier riding from roadies as they feel more confidence in their braking.

A few falls should right that one I'm guessing.

posted by Jimmy Ray Will [263 posts]
9th June 2014 - 13:07

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It's not so much about overall braking power as that's limited by tyre area but sustained ability to brake all the way down a lengthy descent. Blown tyres due to rims over heating is a proven problem on mountain stages. Blown rim walls due to wear on the braking surface is another problem for day in day out riders that is eliminated as well so discs help both the pro and the commuter.

posted by MKultra [212 posts]
9th June 2014 - 13:27

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Disc brakes in perfect condition may well give better braking power and modulation than rim brakes. They may well outperform rim brakes in the wet, also when in perfect condition. However keeping disc brakes in working order can be a non trivial activity.

Disc brake pads are more susceptible to contamination. If you get oil or similar on a disc pad, it's basically scrapped. Until you replace it, it is not giving you good braking performance. Cleaning and lubing your bike can get expensive if you are sloppy. Loss in power may not be complete and you may not notice a reduced power until you haul full on, and carry on. In the wet rim brakes can be the same, but you tend to notice it's raining (well I do) and in the wet I pre-brake regularly to dry the rims and pad surfaces. Which helps somewhat.

Hydraulic systems give superb response, while they are perfectly bled. After a time, hydraulic lines can become contaminated and need bleeding. The loss in braking power however is slow, and not obvious, until you haul full on.... and yep, carry on. If you ride aggressively you are obviously more likely to notice, but a commuter may not, if they are low on braking usage.

Then you need to bleed your hydraulic system. This requires a modicum of patience, and a friendly garage. Not to help with the bleed, to legally dispose of used Dot fluid. Putting it down the drain is illegal. It's also irritant and harmful, and you're pushing down on a loaded syringe against a back pressure. Anyone get safety glasses in their bleed kit? Or even gloves? Thought not.

Nor for that matter do you carry spare pads or a bleed kit, or even a spreader wedge. So if the brakes jam on, which they can do, you can't get them free without damaging the pads. Or if you're on a muddy cyclocross sportive, and get to the feed station with no braking left, you can't just tighten the cables, like rim brakes, you're waiting for the broomwagon. Because 30 miles of slurry have eaten your pads completely. If you think that's unrealistic then look at the number of pads MTB riders go through at enduro events. If discs go wrong in the wild, and they do, you are probably stuffed. Rim brakes, you stand a chance. It's unlikely you'll wear through new pads in a day, and adjusting them to get optimum performance is something I can do with 1 Allen key.

When I has a MTB the hydraulic discs failed over winter in extreme cold. They jammed on and died completely. They could not be resurrected. The combination of salt from the roads and the temperature differential between the cylinder and piston metals meant they jammed and welded in place in sub zero temperatures. Rim brakes... still working, but hard to avoid sliding I'll confess, till I got ice spikes.

SRAM recalled their road discs because 'extreme cold' (like an unusually warm UK winter) could cause units to leak fluid and fail completely with no warning due to poor design.

Last time someone recalled a rim brake for sudden failure?

Yes road discs are new, however MTB discs aren't and they are fit for trail use, but I would not say road discs are suitable for everyday usage yet. That will come in time, however I won't be looking to use them. Not because they are not better in perfect condition, but because I can keep rim brakes working optimally with a little low hazard tinkering now and then. And it's not like I ride many Alpine descents in Middlesex...

And for those who assert discs are low maintenance, and they never have any hassle. I hope you never have problems. But do go and look on the bikeradar MTB forum which last time I was on there was knee deep in 'my discs are not working' type posts and guides on getting them working again, which sometimes end in 'go buy a new ... '.

posted by robdaykin [160 posts]
9th June 2014 - 20:40

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Lets cut the cr@p. If you can lock the wheels easily with the brakes you have in wet or dry conditions they are man enough for the job and the rest is down to the skill of the rider and the friction between the tyres and the road. What I find, is that with rim brakes in the wet is that there is that horrible "oh f@ck" few moments if you need to stop in a hurry - which could mean the difference between a prang and walking away. I have a road bike with rim brakes and a full susser MTB with Hope Tech disc brakes which as far as I'm concerned are the best thing since sliced bread. What I really want is to fit my MTB brakes or similar on my road bike and as soon as it is possible I will. 20 years from now, cable brakes will only exist on cheap and nasty bikes from wherever they are making them and retro bikes. Lets not get into the risk compensation arguments blah blah blah, it's all about the brakes!

Come the revolution!

posted by BigglesMeister [16 posts]
9th June 2014 - 21:21

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Well, 'robdaykin' wins the award for most negative, doom-mongering pile of shite posted so far...

Quote:
Disc brake pads are more susceptible to contamination. If you get oil or similar on a disc pad, it's basically scrapped

So, same as a rim brake pad then.

Quote:
After a time, hydraulic lines can become contaminated and need bleeding.

Once every 2 years or so, half as frequently as I'd change brake cables (which also involves re-taping my bars, unlike a hydraulic bleed). And re the disposal thing - the quantities of oil are so tiny you can just soak it up in a rag and bin/burn it with virtually zero environmental issues.

Your comments about pad wear - same issue for rim and disc pads, I've eaten through both rim and disc pads in MTB events and disc pads are far easier to replace. One allen bolt, drop old pads out, new ones in, pop the wheel back, squeeze levers and the pads/pistons auto adjust.

Quote:
Rim brakes, you stand a chance

How?! Pads worn out/contaminated = no brakes whether it's discs or rims. And if I wear my pads out, squeeze the brakes and wreck a disc with metal on metal, I'm not bothered. If I wreck a rim by trying to apply worn out pads, that's catastrophic and can write a wheel off in seconds.

Quote:
SRAM recalled their road discs because 'extreme cold' (like an unusually warm UK winter) could cause units to leak fluid and fail completely with no warning due to poor design.

It was nothing to do with poor design, it was poor quality control of a single O-ring from another manufacturer completely (and even then they only ever discovered the issue at US cyclocross races in sub-zero temperatures, only a couple of units ever actually failed but on a safety critical part you've got no option but to do a full recall).

These arguments are exactly the same as when MTBs went from cantis to V's to discs - each time there were all sorts of comments predicting sudden death, failures and the usual rubbish of "you don't need that much power"...

/sigh

posted by crazy-legs [506 posts]
10th June 2014 - 19:59

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Shep73 wrote:

That's utter rubbish, a mtb tyre will grip far more than any road tyre on the road. Mechanical grip comes from the squish of the tyre, which forces it into the surface. The tyre hooks up into the tarmacs uneven surface. A road tyre will not do this as efficiently due to width and tyre pressures.

This depends very much on the tyre and surface. Total contact area determines grip. A supple road tyre, correctly inflated, does this very efficiently on a road. As such an expert MTB rider you'll be aware that there are different tyres for different surfaces. In my experience a heavily lugged MTB mud tyre certainly does not exceed the grip of a road tyre on a smooth road, while a slick MTB tyre may.

posted by johndonnelly [20 posts]
11th June 2014 - 10:39

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Interesting debate

The locking up of the wheel could be rider error or reflect the traction level and characteristics of the tyre. It shows the brakes are good enough, however

All I know is that this happened to me the other day on a descent so I have some sympathy with the OP's point of view. Athena brakes, 23/4 mm vittoria tubs. partly my fault, partly limitations of narrow road tyres I believe. I still think I'd have lost it with discs.

I wouldn't write off discs though, especially if they allow even better modulation and better wet weather performance

posted by 700c [556 posts]
11th June 2014 - 12:12

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robdaykin wrote:
Last time someone recalled a rim brake for sudden failure?

December.

http://road.cc/content/news/101264-trek-recalls-some-2013-madones

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posted by Dave Atkinson [7317 posts]
11th June 2014 - 12:16

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Some good posts on here.
In terms of disc brake reliability, mine (XT Ice Techs) have been fine for 2 years. The only problems I had using disc brakes was on my last set of Avids which were terrible in keeping any consistency. If the pads get any oil or road film on them, then just sand them down a bit and they are fine. The main issue is brake disc cleaner as that can make them squeal which is more annoyance than performance related, oh and the contact adjustment on Shimano's is bloody useless.

As someone else said I think people will fall fail of discs on road bikes. I remember all the crashes when Magura first brought out their hydraulic calliper brakes in the 90's.

posted by Shep73 [137 posts]
11th June 2014 - 14:34

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been riding a cx style disk braked bike for a couple of years and def' wouldn't consider going back to rim brakes - love the consistent braking in the wet, to be able to scrub speed accurately and with confidence on long descents

Got fed up with road riding on busy main roads near where I lived.
Built up a bike with 700c wheels that would ride tracks and steep hills (25%ish) and have drops so I could deal with headwinds, it had rim brakes - but I soon realised I was actually riding down road hills on this bike slower than I would on my MTB - reason was lack of confidence on twisty narrow lanes that I could brake when needed - disks fixed that

so depends what you do - if you ride predictable roads with reasonable sight lines and don't go out in the rain (much) then disks add complexity - so for many road cyclists simply no point - if you ride in the rain on narrow steep roads or push carbon rims to the limit on long downhill sections you probably need disks .....and the rest is marketing

posted by antigee [148 posts]
11th June 2014 - 15:04

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In response to Robdaykin above who I think may be suffering from a touch of the Luddites. Sick

If you accidentally contaminate your disc pads then a quick squirt of brake cleaner and a bit of hard braking will usually clear them. Learn to be less cack-handed. Big Grin

MTB riders go through a lot of pads on Enduro events because a) lots of extreme braking and b) they're using resin pads not sintered metal. So 30 miles of slurry will eat your pads. Nerd

Most modern hydraulics are self bleeding. Even if you have to leave the bike inverted for some time, a few hard squeezes on the brakes will bleed them. Safety glasses and gloves are PPE - you should have them already if you regularly work on your own bike. Nerd

If you buy your brake system new you will find in the kit two brake protectors. These are to protect your pads when the bike has the wheel removed. If you accidentally squeeze the brake with the wheel removed (maintenance or transport) you will find it next to impossible to separate the pads without damage. This protector can also be used to move the pistons back before pad replacement. An old tyre lever will do the job as well. Nerd

Disc brakes need care just like every other component on your bike. Wash your bike regularly, particularly in winter, and you won't have too many problems. Big Grin

My commuter which is used all year round is based on an MTB and has Shimano XTR hydraulic disc brakes, they have never let me down. And I don't have to do a lot of tinkering to maintain optimum performance. Devil
Because my road bike was sick I did the Etape Caledonia on it one year in a time of 5hrs 35min. Had absolutely no problem with overheating brakes or fading, in fact had a real feeling of confidence on the morning damp stretches. Cool

I truly believe that the teething problems of road-bike disc brakes will be sorted and that they will become the default braking system. Day Dreaming

posted by levermonkey [361 posts]
13th June 2014 - 17:47

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levermonkey wrote:
If you buy your brake system new you will find in the kit two brake protectors. If you accidentally squeeze the brake with the wheel removed (maintenance or transport) you will find it next to impossible to separate the pads without damage. This protector can also be used to move the pistons back before pad replacement. An old tyre lever will do the job as well.

Or Ikea plastic knife, the ones you buy for your children to use before they are grown up enough for real cutlery. Wish I could find useful things to do with all the other childrens' crap that they have now grown out of.

posted by surly_by_name [142 posts]
13th June 2014 - 18:27

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