Discs on a road bike - yes or no?

mattrixdesign2

Discs are good, I would take discs over rim brakes on a road bike despite any addtional weight gain. Discs on bike just make sense, like someone posted above, using a block against the rim of your wheel isn't exactly ideal, it wears the rim, add some water to the equation and it becomes even less effective. Setup correctly they can be maintenace free for a long period, and don't need to be released for chaning wheels.

I am sure with devlopment/demand/competition they would get nice and light, given there is basically a disc/pads/caliper, given a shrikage in size from the MTB types (i.e. road bikes not as heavy etc), a few bits of carbon, some drilling, and other jiggery pokery, and they will start to weigh as much as current setups.

When I am next in the market for a road bike, I would like to see some options for discs other than on Cross Bikes, even if its just have the mounts good and ready for an upgrade.

thescouselander

It makes no sense to me. Given the amount of fanaticism on weight in road biking I just cant see how it can work. The front wheel will have to be built up as strong as the rear to withstand the braking force applied to the hub so that means more spokes (and aero resistance) and more rotational mass for limited benefit.

meanredspider

I rode my Boardman CX today for the first time in some serious wet conditions. The disc brakes are great though I soon discovered their limitation - that of grip at the tyre. The 25c Gators I'm using currently on my commute aren't the grippiest tyre but it was really easy to lock the rear. That said, I'd prefer the power to lock the tyre than the set-up on my road bike (105 rim brakes) where I really struggle to do the same in the wet.

I don't understand the arguement about the strength of forks etc The fork needs to be able to withstand the grip generated by the tyre not the force generated by the brake (which should always be able to exceed the tyre's grip - ie lock up)

thescouselander

meanredspider wrote:

I rode my Boardman CX today for the first time in some serious wet conditions. The disc brakes are great though I soon discovered their limitation - that of grip at the tyre. The 25c Gators I'm using currently on my commute aren't the grippiest tyre but it was really easy to lock the rear. That said, I'd prefer the power to lock the tyre than the set-up on my road bike (105 rim brakes) where I really struggle to do the same in the wet.

I don't understand the arguement about the strength of forks etc The fork needs to be able to withstand the grip generated by the tyre not the force generated by the brake (which should always be able to exceed the tyre's grip - ie lock up)

The fork thing is about where the calliper is mounted. With disk brakes there is a serious bending moment near the bottom of the fork where the calliper is mounted because the force from braking the wheel is magnified due the distance from the hub to the outside of the tyre.

chrisw12

On the note about the rear locking up, perhaps there's a case for a disc on the front and normal brake on the rear. From a safety point of view this also could make sense as a front rim failure is a lot more critical than a rear failure. It would also mean that old bikes could be retro fitted with new forks, we wouldn't have to buy a new frame or rear wheel for that matter.

Also with regard to weight and rotational weight. If you were to use discs then the rim would not have to be overbuilt as is the case now, also carbon would become the rim material of choice without it's limitations.

MaxwellBygraves

thescouselander wrote:

It makes no sense to me. Given the amount of fanaticism on weight in road biking I just cant see how it can work. The front wheel will have to be built up as strong as the rear to withstand the braking force applied to the hub so that means more spokes (and aero resistance) and more rotational mass for limited benefit.

I'm not an engineer and you might be right - we might have to beef up carbon forks a little. I'm sure with some thought manufacturers could get weight of the discs themselves close to existing caliper systems.

And surely when building a wheel you would no longer require any breaking surface so this would allow some super light carbon wheels, or much lighter deep rim wheels.

saintdracula

thescouselander wrote:

It makes no sense to me. Given the amount of fanaticism on weight in road biking I just cant see how it can work. The front wheel will have to be built up as strong as the rear to withstand the braking force applied to the hub so that means more spokes (and aero resistance) and more rotational mass for limited benefit.

True, but it'll stll be really easy to get under the UCI limit!

maddog 2

It's inevitable. Discs are better in every way* to rim brakes, except a small weight penalty (which will get smaller and smaller).

* more control, better modulation, more feel, more power, more consistency especially on long descents and in the wet, longer lasting pads and rims!, plus I think they look better too.

Having just returned from the Pyrenees I can vouch for the need.....

squeeler

Cable discs on road bikes seem to be getting more popular but until the big three develop hydraulics to work with road groupsets they won't become mainstream. IMO the sooner the better, it's inevitable: they are just better, especially in the wet.

I've just come back from 2 weeks in the alps road and mtbing and one of the best things is not necessarily the power but the fact that over a long decent your hands don't cramp because it's so much easier to slow down.

I look forward to my next road bike having digital gear shifting and hydraulic brakes, I expect to have to wait 5+ years for this to be in my price range though!

prawny

chrisw12 wrote:

On the note about the rear locking up, perhaps there's a case for a disc on the front and normal brake on the rear. From a safety point of view this also could make sense as a front rim failure is a lot more critical than a rear failure. It would also mean that old bikes could be retro fitted with new forks, we wouldn't have to buy a new frame or rear wheel for that matter.

I was actually going to do this to my boardman for the commute, nothing stopping people doing this at all. Kona 700c disc forks are cheap enough.

It wasn't that long ago that mtbs had a disc on the front and a v brake on the rear.

meanredspider

chrisw12 wrote:

On the note about the rear locking up, perhaps there's a case for a disc on the front and normal brake on the rear. From a safety point of view this also could make sense as a front rim failure is a lot more critical than a rear failure. It would also mean that old bikes could be retro fitted with new forks, we wouldn't have to buy a new frame or rear wheel for that matter.

You've lost me on this. Rear locking is much safer than front locking - locking the front means a trip over the handlebars or a face-plant as you lose front grip. Locking the rear is benign. I've not understood the V-brakes on the rear and disc on the front on some MTBs - assumed it was to do space requirements. Most of the weight is on the rear of a bike so it can sustain more braking before grip is lost.

u05harrisb

yeh but most of your breaking power is from you front brake! if i could only have one brake id have a front, would like to see sombody do a real full pace alpine down hill with just a rear brake! i thin kteh whole disc front v back was because people could then just buy a new fork instead of new frame then retro fit in but kept the v on the back for ease.

dawebbo

I'm in the process of retro fitting my commuting bike with kona p2 forks and bb7 disks.

I've tried various canti and mini-v brakes and they've all been ok in the dry but rubbish in the wet.

On my racing bikes the stopping power is absolutely fine, but it can sometimes be a bit jerky, so I'd certainly consider disks if there was a viable top end solution (and uci legal).

cougie

I've only ever blown a front tyre thru overheating once - descending Alpe D'Huez after race day.

It was hot.

I used to run my tyres at max pressure. Far too high.

As there was so much traffic - there was a lot of braking.

I cant see those circumstances coming together ever again.

And its pretty easy to lock up a front wheel with decent brakes - I dont need to be able to do this.

What are wheel changes like with disk brakes ? Is there a standard disk that fits all brakes ? How would it work in a pro peleton with 12 different systems ? All compatible or not ?

MaxwellBygraves

I don't think it's so much to prevent blowing tyres. At least it isn't for me.

It's about better braking in the wet. Road bike brakes are okay in the dry. But when I was in Devon this summer (it was raining, of course) descending a 20% hill they were awful. I am a big guy so this might not be so much of a concern for skinnier folk.

mattv

As you brake, your weight is thrown forwards so you can make use of more braking force on the front tyre before it loses traction, hence disc on front only of some mtbs (as well as many cars). On a road bike, discs will give more braking power than the tyre can deal with and transmit to the tarmac. On my MTB I can lock up the rear tyre on road with one finger. Thats on a sticky 2.0 hardpack tyre.
To go for discs on a road bike would be unnecessary, add significant weight, and seriously limit the fork, wheel and spoke lacing choices.

jevanszx636

I am against it for road bikes. As a couple of people have said, if you can skid the tyre your brakes are powerful enough. As for the control and consistency, i've never had a problem riding with rim brakes, including descents of the Wrynose Pass in the wet, and long Alpine descents in France. And has anybody really proved that brake pads caused a rim failure for them? If so, shouldn't they have noticed that the rim was worn away?

I know I could learn, but my main reason is that I don't know how to fix disc brakes. People are talking about electronic shifters too, but I don't want to be in the position where everything on my bike has to be fixed at the bike shop. That's what happened to cars and it's crap and depressing. I'm happy with the technology we have - it seems more than enough to me.

cougie

Rim brakes may be slightly worse in the wet - but I cant really remember having any problems with them - and I've survived many a Welsh and Alpine wet descent.

I have had a rim blow on me - I guess it was worn out - but lots of rims now have wear indicators - so it makes it a bit easier to see.

andyp

I tried BB7s with Campag shifters on my cross bike and was very disappointed with the performance, despite investing in decent cables, discs and pads.

However, as soon as one of the big three do a hydraulic disc system that works with road shifters then I'll be buying them as I think the performance of discs far outweighs cantilevers or v-brakes in muddy, wet conditions.

IanLD

Have Formula RX discs on my hybrid and they are great, but I wouldn't have them on a road bike (use Campag Centaur on that).

Extra weight, ugly looks but most of all the delay in putting a wheel back in would mean it won't happen. It is a real pain when you are used to being able to bang a wheel in to have to align the disc with the calliper and pads before the wheel can be fully home in the dropouts.

Really annoys me compared with how simple it is to get the wheel home and then move the quick release button back to have brakes and wheel properly aligned again without rubbing. I've tried different methods, but do it too quickly and everything stops as the disc hits the pads rather than sliding between them.

In saying that, on a hybrid or MTB, I wouldn't want anything other than discs now (although I've had some amazing stoppies and left half the rear tyre behind a few times).

markos1963

I think it depends on the application, for ordinary road riding/commuting then discs can make sense but for racing I doubt that there would be enough benefits. After all not many races are decided on kamikazi braking manouvres. As others have pointed out your braking is limited by the grip of the tyre, I can lock up either of my wheels with rim brakes(105s) using sticky race tyres, would disc brakes inprove on this? Notice the move towards aero brakes as well( mounted within the front fork and under the chainstays) this is probably of more use to sports cyclists. One more thing, if you have a large collection of wheels they would all have to be set up with the same discs regardless of what use they were for so limiting your choice of kit.

Ber Nard

I think the major advantage would be consistency. Wet, dry, carbon or aluminium rim wouldn't make much of a difference.

The weight/power concerns wouldn't be an issue either. The brakes would have to be made specifically road bikes so they would only need to be small. Four inch or smaller discs, single piston callipers etc. The disc brakes currently available are overkill for road use.

One draw back would be the consequences of crashing and ripping out a brake line but that could happen MTBing and hasn't dampened their popularity.

Rob

chrisw12

meanredspider wrote:

chrisw12 wrote:

On the note about the rear locking up, perhaps there's a case for a disc on the front and normal brake on the rear. From a safety point of view this also could make sense as a front rim failure is a lot more critical than a rear failure. It would also mean that old bikes could be retro fitted with new forks, we wouldn't have to buy a new frame or rear wheel for that matter.

You've lost me on this. Rear locking is much safer than front locking - locking the front means a trip over the handlebars or a face-plant as you lose front grip. Locking the rear is benign. I've not understood the V-brakes on the rear and disc on the front on some MTBs - assumed it was to do space requirements. Most of the weight is on the rear of a bike so it can sustain more braking before grip is lost.

Sorry I wasn't clear. For me, the worst thing that can happen on a bike is a front wheel blow out and two of the ways that this can occur are by either rim damage or excessive heat on the front tyre. These two catastrophic situations can be avoided easily if we had disc brakes.

I appreciate that there are other ways of avoiding them and I appreciate that there are other causes of blowouts.

DubaiNeil

markos1963 wrote:

I think it depends on the application... but for racing I doubt that there would be enough benefits

I agree with the sentiment, however as (top end) racing is driven by sponsorship, and a large portion of that comes from bicycle manufacturers, who need to sell new bikes to justify their (marketing) investment in racing, then I feel that disk brakes (when/if UCI ratified) will be appear instantaneously on all "top end" bikes, and trickle down to lower levels in same way as MTB's did.

I do find that the "nay sayers" who believe that this will not happen as they are happy with what they have, have not used a good disk brake set up, to see how it feels.

Yes, I can lock my wheels with my calliper brakes, v-brakes, disk brakes etc on my various bikes. The biggest difference is that ONLY on the disk brakes do I have the modulation, feedback and control to CONFIDENTLY hold the tyre at "just before locking" which is where the maximum retardation occurs - especially on a (relatively) consistent surface such as tarmac.

Not sure about some of the comments as to wheel spokes being affected by the switch,as currently the brakes interact directly with the rims , which is connected to the hub by the spokes, with the spokes subsequently transferring the braking force from the rim to the hub and through to the frame. In a disk brake set up, the disk is directly connected to the hub, so therefore not having to transfer the braking force from the rim via the spokes, so (possibly) making it feasible to have both lighter rims and spokes.

I for one can't wait for di2 with hydraulic disks!

Neil

dbb

really interesting thread.
i recall when SIS gears were first introduced and all of the old timers said there was no benefit.
now i wouldn't be without my SIS (indexed) gears with the gear change moved from the down tube to the levers.

i can see discs the same.

the question i have for those who have used discs is; (genuine question as i have not used disc brakes)
why would you want hydraulic discs on a road bike?
doesn't this just introduce more complexity when it is not really required?
the benefit of discs is moving away from rim brakes.
so why not use cable discs?

rolf_f

I use my disc fitted MTB as a commuter in December to early Feb. Whilst the discs are fine off road, they drive me insane on road. They habitually stick ever so slightly and start to make a whining noise (usually on slow climbs) and the only way to stop it is to apply the brake (which on a climb is irritating!). That stops the noise but then it gradually starts again slowly increasing in volume!

Then there is the proper stickiness despite filing the pads to make them fit better and the occasional pad falling off the backing.

I think I'll have to replace the entire brake system on that bike and I'm sure other, non Avid brands are better but the sheer simplicity of caliper brakes easily wins for me on road. Many people don't ride in the wet anyway but, though I do (commuting every day whatever the weather), I just ride a little more defensively to account for the slightly reduced brake performance.

That said, if I was riding in London I suspect I'd be keener on disc brakes on my commuter.

And, re the previous poster, I have to admit I do like down tube shifters (non-indexed!). In fact, in flat country I think the advantages of downtube shifters almost outweigh their disadvantages!

gilesjuk

I've got two road frames that can take discs. Avid BB7 road brakes are great

anto164

Only thing i can think of..

What happens if there's a big bunch pile up? Surely having disc brakes means there are more chances of burns/sliced fingers?

Other than that, as long as they can sort the heat issue with hydraulic brakes with teeny tiny rotors over long descents, then i think they're a great idea.

manxshred

Everyone said that there would be mass mutilation of MTB riders due to disk brakes but as far as I can see everything has been fine.

Heat shouldn't be a problem even now. Downhill mtb use big rotors for better braking and cooling but that is a 35Lb+ bike with rider in full armour down a steep mountain side with more braking than you would be doing on a road bike.

MaxwellBygraves

Rolf F wrote:

I use my disc fitted MTB as a commuter in December to early Feb. Whilst the discs are fine off road, they drive me insane on road. They habitually stick ever so slightly and start to make a whining noise (usually on slow climbs) and the only way to stop it is to apply the brake (which on a climb is irritating!). That stops the noise but then it gradually starts again slowly increasing in volume!

Then there is the proper stickiness despite filing the pads to make them fit better and the occasional pad falling off the backing.

I think I'll have to replace the entire brake system on that bike and I'm sure other, non Avid brands are better but the sheer simplicity of caliper brakes easily wins for me on road. Many people don't ride in the wet anyway but, though I do (commuting every day whatever the weather), I just ride a little more defensively to account for the slightly reduced brake performance.

That said, if I was riding in London I suspect I'd be keener on disc brakes on my commuter.

And, re the previous poster, I have to admit I do like down tube shifters (non-indexed!). In fact, in flat country I think the advantages of downtube shifters almost outweigh their disadvantages!

But MTB discs are to be used off road. You may as well compare a cars disc brakes and say 'no they're too powerful for road bike use'.