POLL: Disk brakes on road bikes?

MichaelW

Pro peloton are probably the last people who need disc brakes. Commuters, winter trainers, tourists all benefit from discs but pro racers ride nose to tail, any sudden braking results in a collision.
I think that introducing discs at an elite level and using trickledown to eventually provide them to normal users is the wrong method.
Road disc systems need to address rack and fender compatibility, they need to use narrow profile caliber units with cable angles optimised for chain stay mounting.

nwallace

springtide9 wrote:

Good point. We should all go back to drum brakes on our cars and HGVs. Imagine putting disc brakes on cars that can weigh in excess of 2 tonne and can travel in excess of 100mph :roll: Or maybe switch to cable disc brakes for cars?
Boiling hydraulic fluid must be a daily occurrence and I guess 100's of lives are lost every day due to hydraulic disc brakes on our roads.

unless you are driving a car with a 2 stroke engine, you will almost certainly have no freewheel device which allows engine braking to keep speed in check.
You don't get that braking on a geared bike.

I'm Running BB7s on one of my road bikes.
There is no bluing of the disc at all so I've not over heated that.
Pad wear is almost non-existant too.

Contrast with my MTBs where every wheel has a rotor with some level of bluing and I go through pads regularly, which either says I don't brake hard enough or don't have to brake hard enough for heat to be a problem on the road.

I think the fears of hot rotors in crashes on road bikes is going to prove largely unfounded.
There are already issues with overheating rims, although a 29" rotor will cool quicker than a 140mm one due to surface area, there are many things you can do with a disc to make it run cooler, things that performance Motorcycles and Cars have had for years. Those being Drilling and Venting.
Also on MTB disc rotors manufacturers are using "floating rotors" where the braking surface area is made of a different material from the support spider, which apparently also lets them run cooler.

Also if you have just slammed the anchors on, and put your braking surface up to 100c, and it's about to come in contact with your leg, does it really matter if it's a 29" braking surface or a 140mm one? It's still at 100c!

Oh and I've boiled brake fluid on an MTB before, it was a descent where there was more tech and angle than I had balls for.

MichaelW wrote:

Pro peloton are probably the last people who need disc brakes. Commuters, winter trainers, tourists all benefit from discs but pro racers ride nose to tail, any sudden braking results in a collision.
I think that introducing discs at an elite level and using trickledown to eventually provide them to normal users is the wrong method.
Road disc systems need to address rack and fender compatibility, they need to use narrow profile caliber units with cable angles optimised for chain stay mounting.

You know, with both cable and hydralic disc brakes, it's not just a case of on or off, you can brake very very lightly with them once you're used to them.

entershikari

I have to correct you on a few things:

Also on MTB disc rotors manufacturers are using "floating rotors" where the braking surface area is made of a different material from the support spider, which apparently also lets them run cooler.

Floating rotors do not make the rotors run cooler. They are designed so that the rotor sits or 'floats' on dowels which allow the disc to thermally expand without warping the disc. So a floating rotor allows it to run hotter, not cooler, without damage to the disc. The dowels also act as a thermal barrier between the disc and the hub which prevents premature bearing wear due to heat.

Also if you have just slammed the anchors on, and put your braking surface up to 100c, and it's about to come in contact with your leg, does it really matter if it's a 29" braking surface or a 140mm one? It's still at 100c!

This makes no sense to me at all, if you have a tiny brake surface (like say a 140mm disc) and a large one (say a 29" wheel) and you ask them both to convert the same amount of kinetic energy to heat (like braking from 30mph) then it's fairly clear that the disc is going to be A LOT hotter than the braking surface on the rim. Or have I just misunderstood what you were trying to say?

One thing that must be pointed out though is that a disc brake can take much higher temperatures than a rim brake since there is no issues with the heat going into the tire.

nwallace

Aye ok I miss-understood the purpose of Icetec rotors.

And you've spotted the flaw in the last one that I've heated both braking surfaces up to 100c, when the rim won't heat up that much under the same amount of braking (I was aware of that issue as I wrote it, but the point was more that a hot surface is a hot surface no matter what it is)

Don't know what sort of temperatures should be expected from rim brakes, although the bedding in instructions for Superstars pads is to brake hard without locking up and chuck water at the disc to see if the water boils. If it does then the pads have been up to temperature.

markos1963

I'm a fairly new convert to discs. My commuter/tourer has cable discs and for all round general riding especially in the wet I find them great. Plenty of feel and not too powerful that they will lock up(unlikely as the beast weighs 14kg!)
After a visit to the company that makes Factor bikes last week I'm also a convert to discs on race bikes. The installations they have made for their bikes and the Aton Martin ones show what can be done with the right engineering. They had managed to 'build in' to an STI the parts needed to run hydrolic discs, it's very expensive to do at their level but I'm sure the someone like Shimano must have done it by now. Weight wasn't a factor at all, in fact the bikes are well under UCI weight limits.
I was lucky enough to see their new 'entry level' bike I'm but honour bound not to give any details, all I can say is I think I have seen the future of cycling.

Nick Fitt

I think its a disastrous idea. The main issue for me is that it opens the 'bike' up to even more fringe development. This will mean we are all coerced into buying more expensive frames and wheels and brakes. And if the performance argument is true (Ive not seen a test between a dura ace and disc bike yet) riding in an amateur bunch will be scary as at the moment, most people stop at similar rates, add hi-po discs and its scary. Unless there is no 'real' difference in which case we are back to just buying more jingly janglies.

Personally, I find the cost of this sport high enough at the moment.

Mikey41

At this stage, discs are an expensive addition, but I feel it's a development that needs to happen as they really are much better than rim brakes, particularly in wet conditions. Give it a few years and they will be pretty much standard fit and much cheaper. Hydraulic ones will end up on the high end bikes only IMO.

The one thing I miss from my hybrid is the disc brakes, they are entry level (from 2008!) and cable actuated, but they are better than my Giants' rim brakes. When the rotor eventually wears out, it's about £30 or less to replace rather than £100 for a wheel, and pads cost no more than pads for rim brakes.