Why are bike companies telling consumers that disk brakes are maintenance free?

ugo.santalucia

meanredspider wrote:

Carbonator wrote:

Stoping a spinning wheel at the hub requires more force than at the rim.
Its as simple as that, and discs only work if hydro.

Loving all the pseudo science and engineering in this thread.

Well... let's assume it takes one turn of the wheel to stop the bike in both cases, it takes more but it doesn't matter.
One turn of the rim is roughly 190 cm, one turn of a 140 mm rotor is roughly 44 cm. The force required to produce the same amount of friction in the two cases is very different.

Which probably explains why a pair of Spyre calipers retails at 150 quid, whereas a pair of 5800 calipers is 50 quid...

fat daddy

ugo.santalucia wrote:

Well... let's assume it takes one turn of the wheel to stop the bike in both cases, it takes more but it doesn't matter.
One turn of the rim is roughly 190 cm, one turn of a 140 mm rotor is roughly 44 cm. The force required to produce the same amount of friction in the two cases is very different.

does it matter that the rim is moving considerably further than the rotor ? and therefore the surface moving past the pad is going quicker ?

ugo.santalucia

fat daddy wrote:

ugo.santalucia wrote:

Well... let's assume it takes one turn of the wheel to stop the bike in both cases, it takes more but it doesn't matter.
One turn of the rim is roughly 190 cm, one turn of a 140 mm rotor is roughly 44 cm. The force required to produce the same amount of friction in the two cases is very different.

does it matter that the rim is moving considerably further than the rotor ? and therefore the surface moving past the pad is going quicker ?

Ha... good point... I guess it does matter... :roll:

Then there is no reason for the TRP to cots 3-4 times more than the 5800

fat daddy

ugo.santalucia wrote:

Ha... good point... I guess it does matter... :roll:

Then there is no reason for the TRP to cots 3-4 times more than the 5800

well I am glad you knew, because I tried googling it and still couldnt figure it out. .... Ultimately though despite what everything says on paper ... the whole lot comes down to what you prefer so arguing about it really is the new definition of retarded !

I like Hydraulics on stuff where I ride through mud
rims on my light road bikes
Mechanical on my cheaparsed SS cx, as it sees mud but I don't want to pay for hydro brakes

ugo.santalucia

fat daddy wrote:

ugo.santalucia wrote:

Ha... good point... I guess it does matter... :roll:

Then there is no reason for the TRP to cots 3-4 times more than the 5800

well I am glad you knew, because I tried googling it and still couldnt figure it out. .... Ultimately though despite what everything says on paper ... the whole lot comes down to what you prefer so arguing about it really is the new definition of retarded !

I like Hydraulics on stuff where I ride through mud
rims on my light road bikes
Mechanical on my cheaparsed SS cx, as it sees mud but I don't want to pay for hydro brakes

I always found bikes with a disc fork a bit uninspiring and dull to ride, especially so going uphill and even more so going up long Alpine climbs. Interestingly, talking to a large shop owner in Italy he had the same exact feedback, except he has ridden a lot more and a lot better bikes... they sell Trek and Cannondale among others.

meanredspider

ugo.santalucia wrote:

meanredspider wrote:

Carbonator wrote:

Stoping a spinning wheel at the hub requires more force than at the rim.
Its as simple as that, and discs only work if hydro.

Loving all the pseudo science and engineering in this thread.

Well... let's assume it takes one turn of the wheel to stop the bike in both cases, it takes more but it doesn't matter.
One turn of the rim is roughly 190 cm, one turn of a 140 mm rotor is roughly 44 cm. The force required to produce the same amount of friction in the two cases is very different.

I can see why your chosen career wasn't engineering.

Rim brakes are just everso slightly more sophisticated than using the soles of your shoes to stop. They are just an endless compromise. Can you tune the diameter of the wheel? Or have a larger wheel front to back? That'll be a no. Can you economically choose to make the braking surface any material you want without altering the prime function of the wheel? That'll be another no. Can you make the friction material anything you pretty well like? Well, you could but who knows how long the wheels would last. So another no. Can you fit any tyre cross-section you like? Yet another no. Can you keep your braking surface away from contaminants? Um, no. Can you design your caliper around ultimate stiffness? No. Can you manage heat generation independently from the tyre? No. These are just the starters.

In time bike frames will be designed to use the tech properly but the world of road biking is just stupidly conservative

ugo.santalucia

meanredspider wrote:

ugo.santalucia wrote:

meanredspider wrote:

Carbonator wrote:

Stoping a spinning wheel at the hub requires more force than at the rim.
Its as simple as that, and discs only work if hydro.

Loving all the pseudo science and engineering in this thread.

Well... let's assume it takes one turn of the wheel to stop the bike in both cases, it takes more but it doesn't matter.
One turn of the rim is roughly 190 cm, one turn of a 140 mm rotor is roughly 44 cm. The force required to produce the same amount of friction in the two cases is very different.

I can see why your chosen career wasn't engineering.

Rim brakes are just everso slightly more sophisticated than using the soles of your shoes to stop. They are just an endless compromise. Can you tune the diameter of the wheel? Or have a larger wheel front to back? That'll be a no. Can you economically choose to make the braking surface any material you want without altering the prime function of the wheel? That'll be another no. Can you make the friction material anything you pretty well like? Well, you could but who knows how long the wheels would last. So another no. Can you fit any tyre cross-section you like? Yet another no. Can you keep your braking surface away from contaminants? Um, no. Can you design your caliper around ultimate stiffness? No. Can you manage heat generation independently from the tyre? No. These are just the starters.

In time bike frames will be designed to use the tech properly but the world of road biking is just stupidly conservative

Yeah, I forgot that angular velocity is not the same as linear innit?

When I switched to discs everything did seem to make sense just as you said. Then my requirements for clearance shrunk to a 28, which fits nicely under a caliper... heat management has never been an issue with rim brakes, whereas I once smoked the pads of my HyRD.
Wheels size is academic, with very exceptions (Open UP), you won't be able to find a tyre size different from 700 c that fits frames on the market.

meanredspider

The point is that the force you need to apply to the braking surface using the friction material is a direct function of the coefficient of friction and the diameter of the braking surface.

With a disc brake, you can play endless tunes on those two parameters: bigger disc or higher coefficient of friction between your two surfaces (which you choose). With rim brakes, you've already removed one parameter: the diameter. And, because your wheel material is pretty limited, about the only tune you get to play is on the rubber block. Probably why a pair of rubber blocks can be £30. Oh, and then you add water, dirt and grit.

The other system that you have is that which applies force. Rim brake has elasticity built into it everywhere - cables, calipers, rubber blocks, wheel rim. Hydro discs have that elasticity (sponginess, in car terms) minimised throughout the system. It makes discs far more predictable and repeatable.

ugo.santalucia

meanredspider wrote:

The point is that the force you need to apply to the braking surface using the friction material is a direct function of the coefficient of friction and the diameter of the braking surface.

With a disc brake, you can play endless tunes on those two parameters: bigger disc or higher coefficient of friction between your two surfaces (which you choose). With rim brakes, you've already removed one parameter: the diameter. And, because your wheel material is pretty limited, about the only tune you get to play is on the rubber block. Probably why a pair of rubber blocks can be £30. Oh, and then you add water, dirt and grit.

The other system that you have is that which applies force. Rim brake has elasticity built into it everywhere - cables, calipers, rubber blocks, wheel rim. Hydro discs have that elasticity (sponginess, in car terms) minimised throughout the system. It makes discs far more predictable and repeatable.

Again, it's all academic, most likely nobody really needs a superior performance, when it relies on the grip of a few millimeters of rubber on the tarmac. It would be interesting to see if PROs on closed roads can descend faster with disc brakes, I suspect there won't be any difference, it's probably still down to cornering technique and balls.

I recall descending the Aubisque and the Tourmalet on the wet... what troubled me were not the brakes, but the cold... never been so bloody cold! I was glad a friend punctured so we could warm up our hands pumping the tyre up

I understand the need to innovate, but I think they should focus on making these bikes competitive on price, weight and ride quality

meanredspider

There's a massive amount of grip that can come from that rubber at the front if the load is applied correctly (i.e. progressively).

Agree, that long descents can get very cold. It didn't matter what brakes the lady who crashed on AD6 had - she couldn't feel her fingers.

Yup - at the cheap end of things, bikes should be simple as possible. I love my Paddy Wagon because it just feels so good to ride.

earth

ZMC888 wrote:

I've been working on my own disk brakes for over ten years, first on motorcycles and then on mountain bikes.

Recently I have gotten into hardcore angry flame wars with new hydraulic disk brake adopters with new disk road, CX and gravel bikes. They seem utterly certain that their bikes are maintenance free, seemingly they have been told this by whoever, but in my experience this just isn't true.

Firstly bicycle brakes don't get as hot as car or motorcycle brakes so you'll need to remove the caliper to clean inside occasionally. Also you'll need to partially eject the pistons to give them a proper clean and stop them from sticking now and again.

Secondly the pads are prone to glazing especially if they are not bedded in well. Pads are also prone to contamination any oil can ruin them. After removing pads you need to align them properly align them to the disk. Simply holding the brake and tightening the bolts rarely works well you'll need a proper alignment tool.

When installing new pads you'll need to force the pistons back into the caliper body with a soft plastic tire removal tool.

Then we have bleeding. Over a year or two your brake fluid or oil if you are using Shimano will get old and discoloured and you'll need to bleed the system and replace the fluid.

Also you may need to true the rotors and clean them with isopropyl alcohol.

Yes disk brakes are low maintenance and work amazingly well in the wet, in fact I'd recommend them for nearly everything unless you are into having an ultralight climbing type bike. But I have no I idea where this zero maintenance sunshine and rainbows bs comes from. Like anything there is a cost in new tools and spares and a certain amount of time in a learning curve if you want to do your own servicing.

Couldn't agree more. Pad wear alone is at least double that of rim brakes. I had mechnical discs on a CX bike and they were full time maintenance. Now I have a MTB for the odd occasion that has hydraulic disks. The rear caliper is dragging on the rotor like a vice and I thought hydraulics were suppose to self-align.

meanredspider

earth wrote:

Couldn't agree more. Pad wear alone is at least double that of rim brakes. I had mechnical discs on a CX bike and they were full time maintenance. Now I have a MTB for the odd occasion that has hydraulic disks. The rear caliper is dragging on the rotor like a vice and I thought hydraulics were suppose to self-align.

The caliper needs to be aligned at least to the disc - the calipers can't defy the laws of physics. But, provided this is done properly once, there's no reason it should need to be done again unless it gets a bash hard enough to misalign it.

People seem so easily bamboozled by discs.

ugo.santalucia

meanredspider wrote:

earth wrote:

Couldn't agree more. Pad wear alone is at least double that of rim brakes. I had mechnical discs on a CX bike and they were full time maintenance. Now I have a MTB for the odd occasion that has hydraulic disks. The rear caliper is dragging on the rotor like a vice and I thought hydraulics were suppose to self-align.

The caliper needs to be aligned at least to the disc - the calipers can't defy the laws of physics. But, provided this is done properly once, there's no reason it should need to be done again unless it gets a bash hard enough to misalign it.

People seem so easily bamboozled by discs.

I had post mounts on two frames... they were never perfectly flat, as I tightned the caliper bolts, whilst squeezing the brake, the caliper moved from the ideal alignment... always!!! So frustrating... :evil:

meanredspider

ugo.santalucia wrote:

meanredspider wrote:

earth wrote:

Couldn't agree more. Pad wear alone is at least double that of rim brakes. I had mechnical discs on a CX bike and they were full time maintenance. Now I have a MTB for the odd occasion that has hydraulic disks. The rear caliper is dragging on the rotor like a vice and I thought hydraulics were suppose to self-align.

The caliper needs to be aligned at least to the disc - the calipers can't defy the laws of physics. But, provided this is done properly once, there's no reason it should need to be done again unless it gets a bash hard enough to misalign it.

People seem so easily bamboozled by discs.

I had post mounts on two frames... they were never perfectly flat, as I tightned the caliper bolts, whilst squeezing the brake, the caliper moved from the ideal alignment... always!!! So frustrating... :evil:

Gentle, progressive, torque, in turn on both screws. In an ideal world, there'd be no adjustment.

ugo.santalucia

meanredspider wrote:

Gentle, progressive, torque, in turn on both screws. In an ideal world, there'd be no adjustment.

Yes, yes, but no, it slides, because one of the mounts is not perfectly flat.... it gets better if I add washers, but then I lose about 1mm of contact pads/rotor

apreading

ugo.santalucia wrote:

I had post mounts on two frames... they were never perfectly flat, as I tightned the caliper bolts, whilst squeezing the brake, the caliper moved from the ideal alignment... always!!! So frustrating... :evil:

I agree with you there. As I said above, you need to predict the amount of rotation from tightening and start the manouevre that much out of line in the opposite direction so that the rotation brings it in to line. It becomes easy once you get the hang of it.

ugo.santalucia

apreading wrote:

ugo.santalucia wrote:

I had post mounts on two frames... they were never perfectly flat, as I tightned the caliper bolts, whilst squeezing the brake, the caliper moved from the ideal alignment... always!!! So frustrating... :evil:

I agree with you there. As I said above, you need to predict the amount of rotation from tightening and start the manouevre that much out of line in the opposite direction so that the rotation brings it in to line. It becomes easy once you get the hang of it.

If it's not sitting happy on the mounts, it will move once you brake, so all pointless... pad wear always inconsistent

meanredspider

ugo.santalucia wrote:

meanredspider wrote:

Gentle, progressive, torque, in turn on both screws. In an ideal world, there'd be no adjustment.

Yes, yes, but no, it slides, because one of the mounts is not perfectly flat.... it gets better if I add washers, but then I lose about 1mm of contact pads/rotor

Take a file to the top of the mount, then. It isn't rocket science. If necessary, take 1mm off the post and use the washer.

ugo.santalucia

meanredspider wrote:

ugo.santalucia wrote:

meanredspider wrote:

Gentle, progressive, torque, in turn on both screws. In an ideal world, there'd be no adjustment.

Yes, yes, but no, it slides, because one of the mounts is not perfectly flat.... it gets better if I add washers, but then I lose about 1mm of contact pads/rotor

Take a file to the top of the mount, then. It isn't rocket science. If necessary, take 1mm off the post and use the washer.

With a file I would make it even less level than it is... I did this instead. I wanted a bike for long distance cycling and went for rim brakes this time... it's awesome

apreading

ugo.santalucia wrote:

apreading wrote:

ugo.santalucia wrote:

I had post mounts on two frames... they were never perfectly flat, as I tightned the caliper bolts, whilst squeezing the brake, the caliper moved from the ideal alignment... always!!! So frustrating... :evil:

I agree with you there. As I said above, you need to predict the amount of rotation from tightening and start the manouevre that much out of line in the opposite direction so that the rotation brings it in to line. It becomes easy once you get the hang of it.

If it's not sitting happy on the mounts, it will move once you brake, so all pointless... pad wear always inconsistent

But you said that you had perfect alignment but it was tightening the bolts that pulled it out. If tightening the bolt pulls it 1 degree clockwise out of line then start with it 1 degree anticlockwise from perfect alignment - the rotation will then pull it perfectly into line. And it will then stay perfectly in line. Once the bolts are tightened, it will not move again.

earth

meanredspider wrote:

ugo.santalucia wrote:

meanredspider wrote:

Carbonator wrote:

Stoping a spinning wheel at the hub requires more force than at the rim.
Its as simple as that, and discs only work if hydro.

Loving all the pseudo science and engineering in this thread.

Well... let's assume it takes one turn of the wheel to stop the bike in both cases, it takes more but it doesn't matter.
One turn of the rim is roughly 190 cm, one turn of a 140 mm rotor is roughly 44 cm. The force required to produce the same amount of friction in the two cases is very different.

I can see why your chosen career wasn't engineering.

Rim brakes are just everso slightly more sophisticated than using the soles of your shoes to stop. They are just an endless compromise. Can you tune the diameter of the wheel? Or have a larger wheel front to back? That'll be a no. Can you economically choose to make the braking surface any material you want without altering the prime function of the wheel? That'll be another no. Can you make the friction material anything you pretty well like? Well, you could but who knows how long the wheels would last. So another no. Can you fit any tyre cross-section you like? Yet another no. Can you keep your braking surface away from contaminants? Um, no. Can you design your caliper around ultimate stiffness? No. Can you manage heat generation independently from the tyre? No. These are just the starters.

In time bike frames will be designed to use the tech properly but the world of road biking is just stupidly conservative

These are all very impressive points, a fine argument. So why is it that disc brakes are so shit and rim brakes just work?

cooldad

You need proper hairy manly legs for discs to work. Smooth silky legs work with rim jobs.

meanredspider

earth wrote:

These are all very impressive points, a fine argument. So why is it that disc brakes are so shoot and rim brakes just work?

Much to my mum's chagrin, when I was a kid my rim brakes were "shoot" and I relied on the soles of my shoes...

The reason why people have trouble with disc brakes is because people simply don't know how to set them up. I've always maintained that, if you aren't mechanically competent (and, unfortunately, that applies to some LBS bike mechs) discs aren't for you. I'm sure it'll get better as designers realise that road bike riders aren't too handy with an Allen key and they make disc calipers more "user-proof". In the meantime, these people should stick to rim brakes (I've resisted a Darwin comment )

meanredspider

cooldad wrote:

You need proper hairy manly legs for discs to work. Smooth silky legs work with rim jobs.

I'm obviously the exception that proves the rule. I have localised alopecia on my legs - which, embarrassingly, looks like I've shaved them.

ugo.santalucia

meanredspider wrote:

The reason why people have trouble with disc brakes is because people simply don't know how to set them up. I've always maintained that, if you aren't mechanically competent (and, unfortunately, that applies to some LBS bike mechs) discs aren't for you. I'm sure it'll get better as designers realise that road bike riders aren't too handy with an Allen key and they make disc calipers more "user-proof". In the meantime, these people should stick to rim brakes (I've resisted a Darwin comment )

If you want to defend a point, this is the worst way of doing it. There are many very competent people, including shop mechanics, who struggle to get perfect alignment, consistent pad wear and occasionally even a decent brake action.

If you are the only one who seems to have no issues with them (except you do, for instance when they are faulty during your Alpe Dusez thing)... well, then it just proves that they are not foolproof and hence not worth bothering with.

I am in two minds... I like them in one way, I hate them in another way... at the moment the latter feeling is stronger. The sheer simplicity and foolproof ness of a rim caliper is a very attractive proposition... not to speak about the much lower cost of non disc framesets and components, like for like

A tapered carbon disc fork is how much? And how much is a non disc one? When I broke my disc fork I was not happy, I can tell you that

earth

meanredspider wrote:

earth wrote:

These are all very impressive points, a fine argument. So why is it that disc brakes are so shoot and rim brakes just work?

Much to my mum's chagrin, when I was a kid my rim brakes were "shoot" and I relied on the soles of my shoes...

The reason why people have trouble with disc brakes is because people simply don't know how to set them up. I've always maintained that, if you aren't mechanically competent (and, unfortunately, that applies to some LBS bike mechs) discs aren't for you. I'm sure it'll get better as designers realise that road bike riders aren't too handy with an Allen key and they make disc calipers more "user-proof". In the meantime, these people should stick to rim brakes (I've resisted a Darwin comment )

I count myself as fairly mechanically competent. I managed to get about as much out of BB5 mechanical disc brakes as I think they had to offer. The MTB with hydraulic discs is a newcomer to the stable and it came with a vice gripping the rear rotor. I have had a quick attempt at aligning the caliper by loosening the bolts then tightening while applying the brake but this yielded no improvement, probably for the reason ugo mentions. I will have to go through the full procedure this weekend following apreading's technique. If it works and they stay working for a reasonable amount of time then I might change my view. But I still maintain that rim brakes are far less hassle. It appears discs are binary. I'm told they work fantastically but if not set up properly performance is abysmal. It's easy to get rim brakes working to maximum performance.

meanredspider

ugo.santalucia wrote:

meanredspider wrote:

The reason why people have trouble with disc brakes is because people simply don't know how to set them up. I've always maintained that, if you aren't mechanically competent (and, unfortunately, that applies to some LBS bike mechs) discs aren't for you. I'm sure it'll get better as designers realise that road bike riders aren't too handy with an Allen key and they make disc calipers more "user-proof". In the meantime, these people should stick to rim brakes (I've resisted a Darwin comment )

If you want to defend a point, this is the worst way of doing it. There are many very competent people, including shop mechanics, who struggle to get perfect alignment, consistent pad wear and occasionally even a decent brake action.

If you are the only one who seems to have no issues with them (except you do, for instance when they are faulty during your Alpe Dusez thing)... well, then it just proves that they are not foolproof and hence not worth bothering with.

I am in two minds... I like them in one way, I hate them in another way... at the moment the latter feeling is stronger. The sheer simplicity and foolproof ness of a rim caliper is a very attractive proposition... not to speak about the much lower cost of non disc framesets and components, like for like

They're incredibly simple in principle though. But I have to recognize that in this plug-and-play world, they need more subtlety than people are used to. Setting up a disc caliper is no more difficult than setting the gap on a set of points. Trouble is, no-one does that these days. And being a bike mechanic is probably one of the simplest jobs with "mechanic' in the title that there is.

Yes, I had a problem with my HyRd - it was a design fault from TRP and replaced. But, even with that issue, I managed the 6 descents of the Alpe that I needed in a lot of diverse traffic at a good pace. I just managed my way around it.

ugo.santalucia

meanredspider wrote:

And being a bike mechanic is probably one of the simplest jobs with "mechanic' in the title that there is.

Have you decided this is a crusade to see how many people you can p-i-s-s off today?

meanredspider wrote:

Yes, I had a problem with my HyRd - it was a design fault from TRP and replaced. But, even with that issue, I managed the 6 descents of the Alpe that I needed in a lot of diverse traffic at a good pace. I just managed my way around it.

Except I had a 2.0 version HyRD, as confirmed by them and yet it had exactly the same problem... it could have killed me... it didn't because the Gent-Wevelgem is not that hilly, but running out of a front brake all of a sudden was not nice :?

mamil314

ugo.santalucia wrote:

meanredspider wrote:

The reason why people have trouble with disc brakes is because people simply don't know how to set them up. I've always maintained that, if you aren't mechanically competent (and, unfortunately, that applies to some LBS bike mechs) discs aren't for you. I'm sure it'll get better as designers realise that road bike riders aren't too handy with an Allen key and they make disc calipers more "user-proof". In the meantime, these people should stick to rim brakes (I've resisted a Darwin comment )

If you want to defend a point, this is the worst way of doing it. There are many very competent people, including shop mechanics, who struggle to get perfect alignment, consistent pad wear and occasionally even a decent brake action.

If you are the only one who seems to have no issues with them (except you do, for instance when they are faulty during your Alpe Dusez thing)... well, then it just proves that they are not foolproof and hence not worth bothering with.

I am in two minds... I like them in one way, I hate them in another way... at the moment the latter feeling is stronger. The sheer simplicity and foolproof ness of a rim caliper is a very attractive proposition... not to speak about the much lower cost of non disc framesets and components, like for like

A tapered carbon disc fork is how much? And how much is a non disc one? When I broke my disc fork I was not happy, I can tell you that

you seem to have missed the point of his post - there are people out there to whom the disc brakes are sheer simplicity and foolproofness. No need to be afraid of not being PC, it's in the name.
There's plenty of anecdotal horror stories regarding rim brakes, too, and price difference is a different topic.

ugo.santalucia

mamil314 wrote:

you seem to have missed the point of his post - there are people out there to whom the disc brakes are sheer simplicity and foolproofness.

Not many though...