Why no disc breaks on road bikes?

[MacB]

That does assume that the volte face required by the UCI to allow discs on roadies doesn't follow a similar one on bike weight minima!


Not a factor for the pros, as they're given the kit. Given that, will it filter into the consumer "race" bike?

That's a fair assessment, I think. It makes sense for cross, and I imagine this will be the route into the commuter & tourer market (tourers already use a lot of nominally Cyclocross equipment).

Fair question and I really can't see any sudden changes and maybe not even much in the way of gradual ones. Globalti mentioned something I hadn't taken into account. The 'Big Tart' rarely rides his road bike in the wet but I get the impression he's not alone in that. So the rim wear factor is greatly reduced and discs become even less attractive to a roadie.

I have a clear bias as I ride for utility or social reasons and racing, or ultralightweight, is unlikely to ever feature in my plans. I also have two handbuilt wheelsets where the rims cost me £40 each on bikes I ride in all conditions. I can put together a solid roadbike with disc brakes that weighs about 22lbs, for me that would be a very light bike.

But I'm also not keen on progress, though it will happen, to get hydraulics working with road setups. I'm quite happy checking brakes, rim or disc, and adjusting as necessary via cable tension/limiting screws. The faff of bleeding etc doesn't appeal, but I accept that I may just be old fashioned in this respect.

 

[snailracer]

MacB estimated a 700g weight penalty. Well, in the context of road bike frames that weigh 1-1.5kg, that's huge.

There is also the safety aspect of close group riding with two hot bacon slicers, in addition to the chainsaw.

 

[2Loose]

No it wouldn't - in poor conditions it would be even easier to lock the wheels up. FFS I can lock my wheels up on a wet road using old-school cantis - let along dual pivots.
Certainly you wouldn't be wearing out the rims, and the other advantage would be no heat induced blow-outs from riding the brakes on long descents.

One of the better aspects of disks, particularly hydraulics, is much better modulation.

There is such a direct correlation between lever movement and braking effect that it is easy to brake at or under the limit of the tyres grip. When I brake on my rim braked bike, sure it is easy to lock the wheel up, but the control before you get to that point is nowhere near as precise OR consistent as on my disk braked bike.

 

[MacB]

MacB estimated a 700g weight penalty. Well, in the context of road bike frames that weigh 1-1.5kg, that's huge.

There is also the safety aspect of close group riding with two hot bacon slicers, in addition to the chainsaw.

Fair comment for racing, as mentioned my bias is towards the sort of riding I do and expect to do in the future. Chaingangs don't enter in to it so no safety issues here. To be honest, though I now prefer riding with drop bars, I doubt that I will ever own a bike that a serious racer would see as a performance machine.

700g is only a significant weight from the race perspective for the rest it's inconsequential.

 

[zigzag]

For me the logical thing on a touring or audax bike would be dual pivot front, and cable operated disc on the rear.

In fact if my "TraumenFahrad" project ever approaches reality I shall be disccusing rear disc options with frame builders.

hmm.. i would do the other way around - disk in the front, v-brake/calipers in the back. i only use front brake on my bikes as it is stronger and stops the bike in a shorter distance if needed. so rear rims on my bikes are even untouched by brakepads - i would use them only in an emergency or on loose surface. but then again i only ride on tarmac so rear brake is just for a backup. rear disk brake usually gets in a way for rack/mudguard installation.

i have front disk brake on my hybrid commuter and i especially like the cleanliness of the bike - no grey gunk on the wheels after wet rides (i store my bike on the carpet). the efficiency is similar to good quality rim brakes. small weight penalty of disks doesn't matter in my case as the whole bike is heavy anyway.

 

[PpPete]

I think the modulation & the lack of rim heating is why I might want disks on the back. For me the rear brake is all about speed control in traffic or downhill, not about stopping or being a "back-up" to the front brake.

Dual pivot on the front... because they are fine for stopping, and I don't want to have a beefier fork to take the loads of a disc..... until that Canyon twin-rotor idea becomes common place maybe.

 

[HJ]

Disc brakes for road bikes are slowly coming in, but most roadies are ultra conservative and new ideas frighten them...

 

[nosherduke996]

Disc brakes for road bikes are slowly coming in, but most roadies are ultra conservative and new ideas frighten them...

You don,t need brakes on a road bike, do ya!

 

[Spokesmann]

I don't there is really any need for normal road cycling. I can stop my ancient Carlton with equally ancient Weinman brakes from 20mph+ with only one finger. They are easily powerful enough to lock wheels, even in the wet. What more do you want?

I agree, even my 1960s GB 66s do a goo job with the right blocks...

 

[steve52]

i see an opening for the use of more carbom mmmmmmmmmm slurp and then pretty orange disks glowing in the dusk decents mmmm im a dreamer i know

 

[gaz]

Unfortunately though, they haven't yet managed to get hydraulic braking systems onto road bikes

linky

 

[the_mikey]

I've had bad experiences with disc brakes on trail/mtbs often with them rubbing and creating noise, effectively using energy even when you're not braking, which is something I definately don't want to experience on a road bike. This also creates problems if you're trying to source replacement wheelsets, you'll have to take account of not only chainset and fork separation, you have to worry about discs too. Oh and those with fixed and freewheel options will need an extra disc... I suppose it'll be good for local bike shops !

 

[Andrew_P]

Same here, my current bike has Avid BB5 disc brakes, and setting them up and adjusting seems to be constant aggro, either I have poor braking and no rubbing or good braking and irritating rubbing. I long to go back to blocks and rim. Its on my list of prerequistes for my next bike. My kid has A GT Zum2 with Discs and Hydraulics without rubbing so it could just be the BB5

 

[BigSteev]

One of the better aspects of disks, particularly hydraulics, is much better modulation.

There is such a direct correlation between lever movement and braking effect that it is easy to brake at or under the limit of the tyres grip. When I brake on my rim braked bike, sure it is easy to lock the wheel up, but the control before you get to that point is nowhere near as precise OR consistent as on my disk braked bike.

I'd love to have whoever sets your brakes up to have a look at mine then! My experience of discs is that braking is all or nothing, there's no 'feel' to them at all. (Juicy 5s). If I could have had 'V' brakes on it I would but it seems that these days, once you go above a certain price point (and it's not that high end) that isn't an option.
As for race bikes, I think it'd be a more major issue for the mechanics than the riders. Much quicker to change a cable than to bleed a brake and when you've got 6-12 bikes to do every night, they won't be looking forward to a further reduction of sleeping opportunities.

 

[jack the lad]

Hydraulic bicycle disc brakes don't need bleeding unless you break into the pipes. They come sealed, ready bled and are 'fit and forget'. The Shimano XT discs on my new On-one have enough power and enough grip on hybrid road tyres to pull a stoppie at will but enough control not to do it accidentally! It is such a pleasure just to let it go on a steep downhill knowing that you can get it back under control instantly. Braking performance isn't affected by weather conditions or buckled rims. If you are spending a fair bit on a tourer or hybrid, good disc brakes are a no-brainer but cheap cable discs are rubbish and should be avoided at any price. More weight, less control and less ultimate power even than cheap rim brakes. They need constant adjustment and it is impossible to get any braking power without putting up with rubbing on warped discs.

I would guess that once the rules allow disc brakes to be fitted to racing bikes there would soon be development of ultralightweight drop bar compatible systems and then you would see even further development in frame, fork, wheel and tyre design to make the most of potential advantages that might not be obvious from a straight replacement for rim brakes without changing anything else.