Road Bikes - Why no hydraulics?

[GrasB]

I am certainly not disputing the better control and modulation with disk brakes, this, along with instant braking rather than having to clean off the rims all help with reduced braking distances. No disputing that at all, in fact I stated that. I only referred to total braking power causing skids more easily on narrow tyres.

When calipers do bite, they can deliver enough power to lock the wheels and skid. I believe the same bike with fatter tyres will take more braking force before skidding on the same surface , that is all.

This of course is offset by the better modulation so can be controlled more easily with disks, but that wasn't my point. I have owned more than one disk braked bike, so I do appreciate that disks are the better solution.

It doesn't quite work like that. I was far more likely to lock up or flip my self over the 'bars of my road bike than my hybrid because the harder I have to apply the brakes the less control I have over them.

GrasB, you drive fast cars on a track right? Simple question: Would they drive\accelerate\stop as well with skinny tyres?

Well you asked for it so don't blame me!... firstly that may be a simple question but the answer is certainly not simple. The short answer is: Yes, no, maybe & wrong metric!

The long answer is: Put 250/515R13 slicks on a 'cento Sporting or old mini 1250GT/Cooper you'll never get enough energy into the tyres when hammer it around a track, net result is that a 160/515R13 slick will deliver substantially higher grip levels. Not only that but the lighter tyres (& wheels) will mean that you've got less flywheel effect in the wheel which means you'll accelerate & brake even faster. When I was racing my Cinq I was just about getting to the point where the 180/515R13 was faster than the 160/515R13, it was lighter than stock but had over twice the power & three times the torque.

When you get to treaded tyres it gets even more complicated, I ran a particular tyre with a 205/45R13 profile because that tyre offered the same surface contact area as their 185/50R13 but with much better water dispersion. Also getting the tyres up to temp was much easier on the 205s, because the blocks were further apart it allowed the blocks to move more & thus get temps into the tyre to get everything working properly. Moving onto road legal tyres best tyres were 195/40R14 sports contacts, they were better than the 195/45R13 or 175/50R13 sports contacts because they were a different softer(?) compound but of the R13 options the 175/50 was better for cold & wet weather grip but the 195/45s were better options when hot/dry conditions prevailed.

The same thing applies to the Exige, the rear drive wheels can go fairly wide (255s can be had) however for the front tyres going much over 205 wide causes problems with grip even with significant amounts of downforce.

 

[Cubist]

A F1 tyre runs at amazingly low pressure, something like 5psi IIRC. I would have thought this was to maximize the contact patch area.

If so, that'll be at cold. Once warmed the same amount of air in a F1 tyre will give considerably higher temperatures and therefore higher pressures than 5psi.

 

[snailracer]

If so, that'll be at cold. Once warmed the same amount of air in a F1 tyre will give considerably higher temperatures and therefore higher pressures than 5psi.

IF the tyre was inflated to 5psi at ambient 25C, and it's working temperature went up to 150C, the pressure would still only be 7psi.

 

[snailracer]

... I was far more likely to lock up or flip my self over the 'bars of my road bike than my hybrid because the harder I have to apply the brakes the less control I have over them...

I can believe that, but how much of that is due to the shorter wheelbase and more forward weight distribution of the road bike?

 

[GrasB]

I can believe that, but how much of that is due to the shorter wheelbase and more forward weight distribution of the road bike?

The hybrid has a 17mm longer wheelbase, it's a smaller frame, however the hybrid had 39mm longer chain stays so pushed my weight further forward than the road bike does. Also under very hard braking I can push my weight further back on the road bike.

 

[Sir Humphrey Appleby]

Don't some countries run downhill road races? I'd be surprised if they didn't have disk brakes to make them stop a bit quicker for those pesky hairpin bends.

 

[gaz]

Don't some countries run downhill road races? I'd be surprised if they didn't have disk brakes to make them stop a bit quicker for those pesky hairpin bends.

I guess you are surprised then. road race bikes don't have disc brakes.

 

[andrew_s]

I was just wondering...
Also, has there ever been any hydraulic derailleurs (front & rear mech's) developed; if so, why aren't they used? If not, why not? Wouldn't this completely remove missed gears/wrongly indexed gears?

Surely they don't weigh that much heavier?

Here you are - hydraulic derailleurs. The reason they aren't used much is probably the €1600 per set price tag.

As for brakes, bring them on. If someone will sell me drop bar hydraulic disk brakes and levers at a price comparable to good flat bar brakes, I'll buy some straight away.

 

[mattsccm]

Running discs on 25mm tyres I have yet to see a problem. Modern dual pivots are powerful enough to put you on your ear in the wet so to suggest that only discs do is daft.

Early on some one wondered what tubs would be like. As tubs saty on better than wired ons I reckon they would cope well and indeed as a small but possible flaw of tubs, ie glue over heating, would be removed i would say discs would be nice.

Hydraulics are not needed for gears as electric is lighter as as accurate or better. Despite a post above the very best rim brakes are lighter than the very best discs. A good reason why pro's don't use them.
Its abit like lots of things in cycling. You could say that discs on the road are a solution to a non existant problem but we said that about clipless pedal, suspension and a host of other things. Where discs have it for me is in wet weather and crappy roads. ie most of my riding.

Then again I also ride my fixed with only a front brake which got a hammering some where recently.

 

[GrasB]

Running discs on 25mm tyres I have yet to see a problem. Modern dual pivots are powerful enough to put you on your ear in the wet so to suggest that only discs do is daft.

Early on some one wondered what tubs would be like. As tubs saty on better than wired ons I reckon they would cope well and indeed as a small but possible flaw of tubs, ie glue over heating, would be removed i would say discs would be nice.

I have the parts for combining tubs & discs on my fixie . It's just getting round to having the wheel built up that's my problem.

 

[oldroadman]

No reason not to play around with disc brakes on road bikes for general use, but not for race use. The current crop of rim brakes are powerful, DO work in the wet, and decent rims are hard coated with a braking surface, so wear is no more an issue than with metal rims.
BUT, if they were allowed, the problem would be that some riders would, and some would not, convert. Then you get the pronlem of over-powerful brakes within a group, and watch the crash rate soar (the first people to get them would probably be the 4th cats, who generally have the poorest skills and most expensive kit anyway, and that's bad enough as it is!). There is nonsense talked about descending (TdF is only one example, plenty of good races go down 80-100kph descents). You simply come to a terminal speed at some point, when you can't pedal any faster or the wind resistance is too great. Braking before corner is the skill, and leaving it any later because of discs still won't help in the wet - the limiting factor is the surface adhesion. In the dry, lean angles can't go much more anyway.
In conclusion, like certain other bits of kit beloved of equipment fetishists, a great marketing thing but not really much help in competition.

 

[chris grace]

First post on this forum so go easy.

How on earth did we manage before disc brakes were invented?Did we just keep going 'til we rolled to a stop or did we jump off at the last minute before we crashed?

 

[Piemaster]

Thick soled shoes?

 

[chris grace]

Thick soled shoes?

Yep,I remember that too

 

[Davidc]

An interesting thread.

I ride a tourer, which isn't fast but is certainly a road bike, in that that's where it's designed to be ridden.

The brakes (cantilever) work reasonably well, but as has been noted need a full revolution in the wet before they give real braking power, moe if they're alsso muddy. Disc brakes would solve this.

This bike hasn't gone through any yet, but its predecessor went through rims for too quickly, about 15,000 miles was typical. The cause was always the same - wear by the brakes. With discs the disc itself may wear, but is replaceable independently of the wheel.

I have had problems with heating. No bursts but tyres and tubes damaged and needing replacing, and blocks damaged by the heat.

Discs would solve most of the issues with rim brakes, as they have for off-road. Adding hydraulics to discs increases complexity, and I'd have to learn to set them up, but I've ridden a bike with this and I'd love to have that level and smoothness of control when out on the road.

The small weight penalty would be a pricce worth paying.

BUT before I'd be happy with a hydraulic disc equipped bike I'd want to know that the frame and forks had been designed for them and well tested. I'd take some convincing that retrofitting to kit designed for rim brakes was safe.

The difference between rim and disc is less than we saw when alloy rims replaced steel. Alloy rims with modern brakes and blocks work very well. Discs would simply work better.

Can't see it happening until UCI change their rules though. I'm sure it will come one day.