Road Bikes - Disc or Not

[Woody John]

Rim brakes all day. Work perfectly fine.

Disc brakes are just a means to sell new bikes.


Locked up using rim brakes yesterday in the wet. Was able to control it. The skinny tyres didn't allow much stopping.
No benefit of disc brakes in that situation. Fatter tyres the way to go if you are concerned about stopping in the wet; better than disc brakes.

[E65Ross]

TheInternet said:

E65Ross said:

I guess the discs may weigh 300g or so more, perhaps...but, even at a 55kg rider, I don't notice the difference between a 1/2 full and a full drinks bottle, so I doubt any others would really notice much difference.

Looking at a CAAD12 Ultegra, the rim brake version is 7.5kg and disc brake is 8.5kg. An irritating penalty IMO but others may feel it's worth it.

Clearly there are other differences on that bike as the Canyon Aeroad differences are nowhere near that.

[TheInternet]

E65Ross said:

Clearly there are other differences on that bike as the Canyon Aeroad differences are nowhere near that.

That's good to hear, I'll look at those instead. Although I wonder is the difference because the Cannondale disc or Canyon rim brake versions are porkier than they could be. Either way, 8.5kg struck me as a bit high for the CAAD12 disc.

[E65Ross]

Woody John said:

Rim brakes all day. Work perfectly fine.

Disc brakes are just a means to sell new bikes.


Locked up using rim brakes yesterday in the wet. Was able to control it. The skinny tyres didn't allow much stopping.
No benefit of disc brakes in that situation. Fatter tyres the way to go if you are concerned about stopping in the wet; better than disc brakes.

Rim brakes work "fine" if you mean a slight delay in stopping power in the wet, and awful performance on carbon rims. Drum brakes on road cars worked just fine, doesn't mean we should stick with it.

You may well have locked up the wheels yesterday, but you simply cannot deny that the time between application of lever pull to slowing down IS better with discs. It just is.

I can't actually fathom why people seem to dislike rim brakes so much. Other than a very mild weight penalty which no-one really notices (I'm a 54kg rider with 4.6W/kg FTP and I can't tell the difference between a full drinks bottle and a half full one, so kudos to you if you can).

What other disadvantages are there?

In the scheme of cost.... It's not much, plus not having to replace inner and outer cables means they're actually cheaper to maintain as you only bleed them every few years which costs peanuts. You also don't wear out rims which can be expensive if you want really nice wheels.

They can stop you faster, there's less delay in power and so in an emergency situation it can make a big difference.

They also require less maintenance overall, no inners and outers to replace, when cables stretch you need to adjust the barrel adjuster, if you have a single mount then getting the pads to align dead central isn't always the easiest.

Disadvantages? Can't think of any aside perhaps weight, but as said, even as a real lightweight rider I don't think it's an issue. Aerodynamics is much more important.

The people complaining about discs, one thing I can't understand is the following....

"they don't stop you any quicker" and the other argument often used "they dangerous in a group because riders with rim brakes may go in the back of you".

I don't understand that, as they seem to conflict.

I'm genuinely interested in what actual disadvantages people think they have.

It's nice knowing I'm not wearing the rim surfaces out on my Zipp wheels. Wasn't happy replacing my RS80s on my old bike at £325 after 5 years!

[Kawasicki]

Disc Disadvantages

Complexity.
A disc brake system is more complex than a cable operated rim brake. Clearances are much smaller, potential for dragging brakes way higher.

Cost.
They cost more.

Weight.
They weigh more. It is irrelevant whether you can feel it or not, you are slower uphill with discs.

Packaging.
They take up valuable space at the hub. This means that the dish of the spokes is less, wheel lateral stiffness is lower, steering and handling worse.

Force path through frame.
The force at the disc caliper generating the braking torque is higher and in a less efficient position, meaning the frame and fork needs to be stiffened in areas that potentially worsen ride.

[E65Ross]

Kawasicki said:

Disc Disadvantages

Complexity.
A disc brake system is more complex than a cable operated rim brake. Clearances are much smaller, potential for dragging brakes way higher.

Cost.
They cost more.

Weight.
They weigh more. It is irrelevant whether you can feel it or not, you are slower uphill with discs.

Packaging.
They take up valuable space at the hub. This means that the dish of the spokes is less, wheel lateral stiffness is lower, steering and handling worse.

Force path through frame.
The force at the disc caliper generating the braking torque is higher and in a less efficient position, meaning the frame and fork needs to be stiffened in areas that potentially worsen ride.

Complexity - yes, they're more complex, but it's not rocket science and really isn't an issue. I've done approx 5k miles on my current disc bike and needed no adjustment at all, so the complex one seems to require less maintenance than the more simple one.

Cost - I don't think they do cost more when one looks at the life cycle of a bike. Replacing cables (inner and outer) yearly can be £30+ if you can't do it yourself, or £20 if you get jagwire ones).... Over 7 years that's £140 minimum for the bleeding of the brakes 1 or 2x, maybe £40 total.... So extra £100 there alone.... Plus if, like me, you ride a lot and wear through a set of decent wheels then that completely blows the cost part aside.

Weight - does that mean I'm faster down the hills? Let's say average rider 70kgs, bike plus drinks another 10kg....the difference between 80 and 80.3kg is around 0.375%....(I checked Canyon.com....Aeroad 9.0 disc di2 is 300g heavier than rim brake version

Packaging and force path through the frame (since your arguments largely fall into the same category, no?) - I doubt there's any real difference in stiffness between a rim brake bike on QR skewers and one with discs and thru axles. It must be absolutely minuscule of there is.... Since the pad sits close to the rotor any flex would cause disc rubbing under load, and I've never experienced that under heavy sprinting.

So, all extremely minor points compared to the benefits of less maintenence (and cheaper maintenence), better stopping power and reliability, in the wet especially. It's also worth noting that for people with relatively small hands don't need such leverage as you require less force on the lever to get similar braking power.

Either way.... If your next new road bike is rim brakes, I doubt the one after will be.

Edited by E65Ross on Sunday 11th November 12:29

[frisbee]

Kawasicki said:

Disc Disadvantages

Complexity.
A disc brake system is more complex than a cable operated rim brake. Clearances are much smaller, potential for dragging brakes way higher.

Cost.
They cost more.

Weight.
They weigh more. It is irrelevant whether you can feel it or not, you are slower uphill with discs.

Packaging.
They take up valuable space at the hub. This means that the dish of the spokes is less, wheel lateral stiffness is lower, steering and handling worse.

Force path through frame.
The force at the disc caliper generating the braking torque is higher and in a less efficient position, meaning the frame and fork needs to be stiffened in areas that potentially worsen ride.

Advantages

Better modulation
More aerodynamic
Better tyre clearance
No rim wear
Self adjusting

[Kawasicki]

E65Ross said:

Complexity - yes, they're more complex, but it's not rocket science and really isn't an issue. I've done approx 5k miles on my current disc bike and needed no adjustment at all, so the complex one seems to require less maintenance than the more simple one.

Cost - I don't think they do cost more when one looks at the life cycle of a bike. Replacing cables (inner and outer) yearly can be £30+ if you can't do it yourself, or £20 if you get jagwire ones).... Over 7 years that's £140 minimum for the bleeding of the brakes 1 or 2x, maybe £40 total.... So extra £100 there alone.... Plus if, like me, you ride a lot and wear through a set of decent wheels then that completely blows the cost part aside.

Weight - does that mean I'm faster down the hills? Let's say average rider 70kgs, bike plus drinks another 10kg....the difference between 80 and 80.3kg is around 0.375%....(I checked Canyon.com....Aeroad 9.0 disc di2 is 300g heavier than rim brake version

Packaging and force path through the frame (since your arguments largely fall into the same category, no?) - I doubt there's any real difference in stiffness between a rim brake bike on QR skewers and one with discs and thru axles. It must be absolutely minuscule of there is.... Since the pad sits close to the rotor any flex would cause disc rubbing under load, and I've never experienced that under heavy sprinting.

So, all extremely minor points compared to the benefits of less maintenence (and cheaper maintenence), better stopping power and reliability, in the wet especially. It's also worth noting that for people with relatively small hands don't need such leverage as you require less force on the lever to get similar braking power.

Either way.... If your next new road bike is rim brakes, I doubt the one after will be.

Edited by E65Ross on Sunday 11th November 12:29

Complexity improves performance. There are downsides associated with it though, when it goes wrong it needs specialist knowledge and tools to repair. I also disagree that rim bikes are expensive to maintain, but I only change my brake cables once every 5 years or so (my reserve road bike has 19 year old, perfectly operating rim brakes...even the cables. I ride about 6-7k km per year. Rims last years too. I am a bit unusual, though...as I do spend 30 min a month keeping the friction surfaces clean though...which is also necessary with discs...to avoid slowly degrading stopping power and squealing.

The stiffness I was talking about mainly has to do with lateral rim stiffness due to less dishing of the spokes, front and rear. Thru axles won’t help, as the deflection occurs between hub and rim.

So, gotta go...my final statement is that I am not anti disc brakes. I have more bikes with discs than without. For how I ride I like the elegant simplicity of a rim brake. I have been trained as an engineer...one aspect of engineering is design efficiency. The elegance in a rim brake comes from the fact that the rim has multiple functions, it supports the tyre and it acts as a large diameter disc brake. The large diameter means the forces to generate braking torque are low and that the flow of forces through the wheel mean there is no braking torque acting on the hub. To cut a long story short...I like the elegance of rim brakes and the function, though worse for actual braking than discs, has already far surpassed my minimum requirements.

[keith2.2]

Yes and if you put a spout on a mug it could double up as a teapot - but that means it's not as good a mug as a mug and not as good a teapot as a teapot.

'Elegance' doesn't mean better - and they were designed like because of availability of tecnology and not the other way around.

Imagine a world where we all have discs.

"Hey hey come see my kickstarter - these ugly separate braking surfaces and tyre supporting rims - I've come up with a way to combine the two! It doesn't perform anything like as well for a myriad different reasons but JUST LOOK AT IT!'

[Kawasicki]

keith2.2 said:

Yes and if you put a spout on a mug it could double up as a teapot - but that means it's not as good a mug as a mug and not as good a teapot as a teapot.

'Elegance' doesn't mean better - and they were designed like because of availability of tecnology and not the other way around.

Imagine a world where we all have discs.

"Hey hey come see my kickstarter - these ugly separate braking surfaces and tyre supporting rims - I've come up with a way to combine the two! It doesn't perform anything like as well for a myriad different reasons but JUST LOOK AT IT!'

If I was going on a physically demanding expedition, I wouldn’t bring a teapot, a mug and a set of cutlery with me. I would bring a light mug and a spork. They wouldn’t function as well as a complete dining set, but for my needs the simple solution is the more elegant. So elegant solutions are better and you are wrong.

[whatleytom]

you've not ridden a road disc bike then?

[Kawasicki]

whatleytom said:

you've not ridden a road disc bike then?

Yes, I borrowed one, rode it 500m. Heard pads dragging at the rear. Fixed it by emptying some fluid from the overfilled system. Then rode it again, it was then excellent. My brother had been riding if for years in the previous condition, absolutely loving it, raving about the brakes. The bike was excellent for crappy, wet, muddy, rough roads...which was where I rode it.

I was super happy to get back on my own bike though, fitted with good rim brakes, and ride that on mainly dry, smooth, clean roads.

[E65Ross]

You can't try to use poor maintenance as a somewhat roundabout way of saying they're problematic. If done properly, discs require less maintenance than rims. As said, I noticed my front brake rubbing on my rim brake equipped bike due to increased internal cable friction, lubing it helped but not enough so I had to spend money getting new inner and outer cables.

There's nothing WRONG with the rim brakes on my other road bike, they're just nowhere near as confidence inspiring as the discs on my Canyon. Before going disc I didn't really think "these brakes need improving"....except once or twice in the wet on salty roads I guess, but since having discs, I shan't be going back. The same as many, many people it would seem.

[Kawasicki]

E65Ross said:

You can't try to use poor maintenance as a somewhat roundabout way of saying they're problematic. If done properly, discs require less maintenance than rims.

My brothers bike came like that from the shop. No maintenance had been carried out on the braking system.

Discs probably need less maintenance than rims, I agree, but when problems do occur they are more likely to be complicated.

[E65Ross]

Kawasicki said:

E65Ross said:

You can't try to use poor maintenance as a somewhat roundabout way of saying they're problematic. If done properly, discs require less maintenance than rims.

My brothers bike came like that from the shop. No maintenance had been carried out on the braking system.

Again, not a fault of discs, that's poor bike shop. A mate of mine had a bike which came from the shop with a loose seat post....that doesn't mean the seat post clamp on the bike was crap, the shop didn't tighten it adequately.

Are they more complex? Bleeding, is it more difficult than feeding wires through awkward internal frame channels? Changing pads is probably easier and no issues with alignment as they self adjust.....

[Kawasicki]

So Ross, can you list a few rim brake advantages/disk brake disadvantages?

[E65Ross]

Kawasicki said:

So Ross, can you list a few rim brake advantages/disk brake disadvantages?

Yes, but they are almost non-existent in my opinion.

If you're doing a hill climb or a mountain top finish, the discs would be a bit slower (not by much on any UK climbs, perhaps on some really long ones)

The initial outlay costs more, although the cost is coming down rapidly, and over the course of the lifetime of the bike, they'd be cheaper or certainly no significant difference. Especially if one uses expensive wheels. So this is an upside and a downside to rims (which wear your rims and require more maintenance)

Bleeding can require special tools, but it is done very infrequently and so once every 2-3 years you pay someone £20 to do it, if that....cheaper than replacing inner/outer cables)

I guess if there's debris or an alignment issue it's not as quick to sort roadside as just loosening the caliper, but in 10 months on my road bike and years on my MTBs I've not had any issues...? But the flip side is that rim brakes can be awkward to set to apply the forces 100% evenly on both sides.

Can't think of any others really? All pretty minor stuff IMO.

[frisbee]

clubsport said:

I understand the push from the bike industry towards discs, it will give some a reason to buy a new bike.

Having said that the latest Shimano groupsets Ultegra/DA/8000/9000, have the dual pivot calipers.
Several reviews suggest the brakes are the most significant update over the previous equivalent groupset.

On that basis, it appears the bike industry haven't given up on rim brake tech, just yet.

Dual pivot callipers have been around since the mid 90s. Do you mean direct mount?

[keith2.2]

Kawasicki said:

keith2.2 said:

Yes and if you put a spout on a mug it could double up as a teapot - but that means it's not as good a mug as a mug and not as good a teapot as a teapot.

'Elegance' doesn't mean better - and they were designed like because of availability of tecnology and not the other way around.

Imagine a world where we all have discs.

"Hey hey come see my kickstarter - these ugly separate braking surfaces and tyre supporting rims - I've come up with a way to combine the two! It doesn't perform anything like as well for a myriad different reasons but JUST LOOK AT IT!'

If I was going on a physically demanding expedition, I wouldn’t bring a teapot, a mug and a set of cutlery with me. I would bring a light mug and a spork. They wouldn’t function as well as a complete dining set, but for my needs the simple solution is the more elegant. So elegant solutions are better and you are wrong.

A more accurate version of your analagy would be that you're not going to take your hunting knife because your spork has a serrated bit on the edge.

But to each their own. I'll enjoy the effecacy of allowing things to be designed to do the absolute best job they can of the task they are required to do, and you can enjoy the elegant simplicity of flawed combined design - but there's nothing elegant about wearing out the bit that supports the tyre because you're also using it as a friction surface that can get hot enough to blow the inner tube. Been there, done that, survived the tank slapper.

My background is industiral design, believe me I understand entirely where you're coming from, but to my mind it's only 'better' if it does the same job without compromising on performance.

I also entirely accept that disc brakes on road bikes are overkill for probably a majority of users and I wouldn't want to retro fit them to a vintage bianchi - they're just not as pretty.

Edited by keith2.2 on Tuesday 13th November 05:39

[GOATever]

dantournay said:

Discs every time. Perform better, look better, easier to maintain and won't trash my carbon rims.
I'm looking at getting a TT bike for triathlon. Holding off for the next season or so until they become standard fit on something like a Scott Plasma, Canyon Speedmax or Argon 18 E119.

I'd never go back to rim brakes given the choice

I have to admit, the only time I’d purposely aim for a disc braked road bike, is if I had expensive Carbon rims, because rim brakes tend not to be quite as effective on Carbon tracks, as alloy tracks, and they tend to cost a lot more than alloy rims. I was looking at upgrading one of my bikes to a Giant Propel 0 SL, which only comes specced with discs.