Possible new bike, road bike and disks

jeremyrundle

I use my MTBs and my hybrid for all my needs, however this year I may build (get my shop to) another for road.

My question is....

Why do all road bikes use the type of brakes I had when I was in school, many, many years ago, as I see none with disks, or is it just me.

Thank you.

whyamihere

Pretty sure disc brakes aren't allowed in races run under UCI rules (which is good, the last thing you need after crashing in a pack is being sliced or branded by the rotor on someone's wheel), so there's no reason for manufacturers to make them. They have recently been made legal in UCI CX races, so there will be a lot more CX bikes with discs now.
There's plenty of hybrids or more relaxed road bikes with them anyway, just not race bikes.

Berk Bonebonce

The brakes you had fitted to your Raleigh Grifter or whatever would have been single pivot. The ones these days are dual pivot and more powerful.

Why do you not get disc brakes on road bikes? Too much weight. And they get in the way of fitting racks and mudguards.

ride_whenever

Pompetamine versa has hub gears, disc brakes and drop bars...

jeremyrundle

Thanks, so as I only ride for pleasure on the road, there is no reason not to fit disks :?:

Moodyman

Out and out road bikes are designed with speed and low weight in mind. Disc brakes are heavy and don't help with these aims.

Caliper or Canti brakes are plenty powerful enough for day to day road use. The only time discs come onto their own is wet weather commuting in hill areas and, despite Britain's reputation for being wet, you only get about a dozen wet commutes a year.

Not worth the constant hassle of the extra weight.

wgwarburton

jeremyrundle wrote:

Thanks, so as I only ride for pleasure on the road, there is no reason not to fit disks :?:

Rim brakes are simpler, I feel, and mudguards and racks useful.

I'm not yet convinced that discs offer sufficient net gain to be worthwhile. I'm probably just being a luddite, though, I should clearly be much more open to the massive advances of recent years- carbon frames, 10-speed transmissions, fancy new BB and headset designs that are so much better than the totally inadequate designs of yesteryear...

..or maybe not.

Cheers,
W.

whyamihere

Moodyman wrote:

Out and out road bikes are designed with speed and low weight in mind. Disc brakes are heavy and don't help with these aims.

That's not a huge issue any more, it's pretty trivial to build a bike which weighs less than the UCI's lower weight limit (6.8kg). Some pro teams have to add ballast to the bikes in order to make them weigh enough to be legal. The added weight of disc brakes will be relatively low down as well, helping keep the COG nice and low (good for handling). Shifting the braking to the hub would allow the use of lighter rims as well, which would make more of an effect (the rotating mass being further from the axis of rotation, blah blah blah, look it up).

Discs really shouldn't be used in road racing though, so while we're all riding around on road race bikes, we're not going to have them.

desweller

Orbea Diem Drop. Carbon fibre frame + fork, drop bars, mudguard and rack mounting points and disc brakes front and rear. The ultimate all-year-round SCR weapon.

Sadly I don't think Orbea still make it :-(.

EDIT: BR review

jeremyrundle

I fail to see the point of the weight of disks against the other type argument, that is irrelevant, when you consider the fact that one ham sandwich and a cup of coffee taken half way through the day addds more weight!

Perhaps you should use the loo before setting off :?

And there is no point in building a 10oz bike then carrying all you need for work in a rucksack weighing pounds.

What I am talking about is the benefits not weight related of one type over another, after all when you then add lights, helmet, bags, pump, bell etc, a few oz's on brakes is not a consideration for a commuter surely.

whyamihere

jeremyrundle wrote:

I fail to see the point of the weight of disks against the other type argument, that is irrelevant, when you consider the fact that one ham sandwich and a cup of coffee taken half way through the day addds more weight!

Perhaps you should use the loo before setting off :?

And there is no point in building a 10oz bike then carrying all you need for work in a rucksack weighing pounds.

What I am talking about is the benefits not weight related of one type over another, after all when you then add lights, helmet, bags, pump, bell etc, a few oz's on brakes is not a consideration for a commuter surely.

You're still thinking as a commuter. Road bikes aren't designed for commuters, commuters just use them. For bikes designed for commuters, look at hybrids or tourers, and you'll find all the compromises you want.

jeremyrundle

Berk Bonebonce wrote:

The brakes you had fitted to your Raleigh Grifter or whatever would have been single pivot. The ones these days are dual pivot and more powerful.

Why do you not get disc brakes on road bikes? Too much weight. And they get in the way of fitting racks and mudguards.

I'm honored that you think I may have ridden something like that (Googled it), no more like

http://cgi.ebay.co.uk/VINTAGE-1970S-PEU ... 20b6c3726e

nation

The weight issue is a bit of a red herring, I think. A fully bled Formula R1 disc brake (front including caliper, hose, lever and pads) is 160g

A Dura-ace caliper brake with pads(not counting lever, cable, etc) is 150-ish g

There's the weight of the rotor added to the wheel, but then you can use a lighter rim because it doesn't need a braking surface.

Personally I think that going from rim brakes to disc brakes is a massive gain in terms of control, they're much less fiddly to set up and maintain, and the power available is far more consistent. Rim brakes have been what's put me off road bikes for years, because they scare the bejesus out of me, but I quite fancy something like a Roadrat or one of the new CX bikes.[/i]

Berk Bonebonce

jeremyrundle wrote:

Thanks, so as I only ride for pleasure on the road, there is no reason not to fit disks :?:

Yup. Disk brakes great, until you want to fit full mudguards or carriers.

tgotb

Or until the disk gets dinged (which seems to happen to my GF's bike all the time). Yes, the rim could get dinged, but in practice they're so well supported by the spokes that it never seems to happen. The rims on her bike are a lot truer than the disks...

I rented an MTB with hydraulic disks in the Alps last year. Within a couple of miles I'd boiled the fluid and was left with a front brake which was permanently neither on nor off.

I'll vote for the KISS principle every time...

rolf_f

I cover a lot of road miles on my hydraulic disc fitted MTB. They are OK - they do stop nicely but then they squeak a lot (Avid Juicy 3). It's annoying. And then they rub so the wheel doesn't spin freely. Also annoying though good for the thighs. Also, they are no better at stopping a bike in the dry than calipers (different in the wet though I've not tried wet compound brakes on my road bikes yet).

I tend to favour the mtb when conditions are poorer - so, if I have the option (which I do), 95% of the time (ie when it isn't wet), I vastly prefer calipers.

If you do get hydraulic calipers, for heavens sake just leave them alone. Loads of people complain about them because they keep bleeding them and getting air in. I've had mine on for 2 and a half years and covered a good 5000 miles on the bike and not touched them. They are fine. Some numpties will start wittering on about needing to change the fluid regularly but this isn't a car and the fluid doesn't suddenly become hugely compressible. I will change the fluid when it isn't working anymore or when it really does need to be bled.

Incidentally, single pivot calipers are anything other than obsolete and ineffective. Have a look at what's on the back of a bike fitted with Campag Super Record (or any other Campag groupset) - a single pivot brake. Single pivot = finer control, dual pivot = greater stopping power - they are really the same thing; only the leverage differs. Different things for different purposes.

nation

You can fit carriers and guards to disc-braked bikes, either with spacers, using specifically disc-compatible parts, or with p-clips.

Also, Rolf: your Avids should have self-centring caliper mounts (or at least my old ones did, and my newer Elixirs do). Put the wheel on the bike, slacken the mount bolts by a turn or so, squeeze the lever, and re-tighten the bolts and the caliper whould be perfectly aligned.

rolf_f

nation wrote:

Also, Rolf: your Avids should have self-centring caliper mounts (or at least my old ones did, and my newer Elixirs do). Put the wheel on the bike, slacken the mount bolts by a turn or so, squeeze the lever, and re-tighten the bolts and the caliper whould be perfectly aligned.

I did actually work that one out - I'm dead clever me! Trouble is, the damn pads still stick. Sometimes they start to whistle - usually on long slow climbs and the only way to stop it is to briefly apply the brakes. I'd got them running sweetly, then I went away for a week - came back and they were all stuck again - even before getting on the bike!

I'm tempted to change them for Shimano brakes instead but the Avids do work and they are fine off road. Maybe I just need to bin the Superstar pads which are probably more accurately named Crapperstar. Two pads have completely fallen off the back plate!

jonny_trousers

Moodyman wrote:

despite Britain's reputation for being wet, you only get about a dozen wet commutes a year.

You reckon? I think I've used up all of mine this January alone then. Bring on the sun!

Funnily enough I passed by a guy with an interesting looking road bike with discs on the way in today, but I couldn't make out what it was.

I must admit, if I could have any one upgrade to my commuter it would be disc brakes. I find the rim brakes pretty damn woeful at this time of year. I too am tempted by a Cotic X.

The Rookie

I think the biggest issue with discs on a proper road bike is the increased aero drag, a traditional caliper style sits where you have 'bits' (like the fork crown) in the airflow anyway, a current disc sits out in the airflow, also roadracers rarely brake.

A Friend has Avid BB7 road discs on his drop barred tandem, reckons he gets much better braking than with calliper style brakes.

A Traditional caliper system is lighter than discs for sure, while the 'brakes' are of similar weight the lightest steel discs with bolts come out about 90g, you have the heavier hub (with the mounting flange as well) which adds about another 100g (I have 2 Mavic 117 rims, one on a M475 disc hub, one on a Parallax, the Parallax is 100g lighter) and that all more than offsets the reduced rim weight.

Simon

jeremyrundle

Then again surely disks don't wear out wheels as they do not touch the rims, expensive when you pay hundreds for wheels.

rolf_f

The Beginner wrote:

A Friend has Avid BB7 road discs on his drop barred tandem, reckons he gets much better braking than with calliper style brakes.

Tandem is a bit unusual but I bet plenty of people 'reckon' their disc brakes are much better than calipers but how many have actually tested the theory? I have. censored all difference (in the dry) - might post the results of my tests tonight if I remember. Pad material was more of an issue than brake type.

whyamihere

Rolf F wrote:

The Beginner wrote:

A Friend has Avid BB7 road discs on his drop barred tandem, reckons he gets much better braking than with calliper style brakes.

Tandem is a bit unusual but I bet plenty of people 'reckon' their disc brakes are much better than calipers but how many have actually tested the theory? I have. censored all difference (in the dry) - might post the results of my tests tonight if I remember. Pad material was more of an issue than brake type.

I've tested it too. In terms of absolute stopping distance in the dry, there is no difference, the limiting factor is tyre grip. There is a definite, measurable difference in wet conditions though, though this is almost entirely resolved using good pads like Salmons. On a woollier, more personal note, disc brakes 'feel' more controllable, with better modulation, which is why I much prefer them for mountain biking, when often a controlled slowing is preferable to a quick stop.

iPete

I've not ridden a disc roadie but I'm pretty sure these comparisons are unfair.

Try the test again whilst riding on the hoods, not the drops. Throw in some water and stopping on the hoods, even with wet weather pads, is sometimes a very scary experience. With the dics on my mtb I can stop in the wet on the spot using my little finger.

ride_whenever

Disc brakes are considerably better than even dual pivots, purely because you don't get rim wear.

The power available is probably too much for the grip on a road bike, however with really tiny rotors, (say 100mm) you could have lots of control and more than adequate power.

They are considerably more reliable than calipers and the pads last a hell of a lot longer (especially if you run soft pads to save your rims)

I'm seriously considering building up a crazy cx/29r hybrid with drops and hydraulic brakes and possibly a hub gear, running the brakes as cable actuated hydraulics (kinda like an interrupter) which should be quite an interesting plan.

As for fluid boil, it's a hugely irrelevant problem, on dyno runs some setups with smallish rotors get to over 500 degrees before boiling, if you're needing to brake that much then you'll have already blown your tyres off with the increased heat.

whyamihere

iPete wrote:

I've not ridden a disc roadie but I'm pretty sure these comparisons are unfair.

Try the test again whilst riding on the hoods, not the drops. Throw in some water and stopping on the hoods, even with wet weather pads, is sometimes a very scary experience. With the dics on my mtb I can stop in the wet on the spot using my little finger.

My tests were all done on the same flat barred bike, in order to eliminate any other variables.

whyamihere

ride_whenever wrote:

I'm seriously considering building up a crazy cx/29r hybrid with drops and hydraulic brakes and possibly a hub gear, running the brakes as cable actuated hydraulics (kinda like an interrupter) which should be quite an interesting plan.

I was planning to do that at some point too, as well as gutting an Ergoshifter and replacing the shifter rings etc with custom ones to control a hub gear. Just haven't found the time...

nicklouse

whyamihere wrote:

On a woollier, more personal note, disc brakes 'feel' more controllable, with better modulation, which is why I much prefer them for mountain biking, when often a controlled slowing is preferable to a quick stop.

not that woolly as we know the bigger the disc the more the power but the less the modulation.

and modulation is the bit that gives the feeling of control.

iPete

whyamihere wrote:

iPete wrote:

I've not ridden a disc roadie but I'm pretty sure these comparisons are unfair.

Try the test again whilst riding on the hoods, not the drops. Throw in some water and stopping on the hoods, even with wet weather pads, is sometimes a very scary experience. With the dics on my mtb I can stop in the wet on the spot using my little finger.

My tests were all done on the same flat barred bike, in order to eliminate any other variables.

In that case the difference is probably negligible, if you have to brake suddenly on the hoods in the wet, you have no chance as you can't get the leverage, where I'm fairly sure discs would bite much easier.

whyamihere

iPete wrote:

whyamihere wrote:

iPete wrote:

I've not ridden a disc roadie but I'm pretty sure these comparisons are unfair.

Try the test again whilst riding on the hoods, not the drops. Throw in some water and stopping on the hoods, even with wet weather pads, is sometimes a very scary experience. With the dics on my mtb I can stop in the wet on the spot using my little finger.

My tests were all done on the same flat barred bike, in order to eliminate any other variables.

In that case the difference is probably negligible, if you have to brake suddenly on the hoods in the wet, you have no chance as you can't get the leverage, where I'm fairly sure discs would bite much easier.

Try better pads. I can just about get my rear wheel to lift braking in the wet from highish speeds on my road bike from the hoods.

Nick - By woolly I meant less directly measurable.

pdw

I've just bought a Kinesis Decade Tripster as the frame for my new commuter. This has disc brakes, and mudguard and rack mounts. The rear brake is on the chainstay rather than the seatstay, and the front mudguard eyelets are higher up the fork, allowing you to use all of them at the same time.

Discs do add a fair bit of weight. In addition to obvious extra weight of the calipers and discs, the hubs are also heavier (unless you spend a lot of money) and you need a cross-spoked front wheel.

I decided to do it, as rim brakes can be pretty unpleasant in the wet. In truly wet conditions it takes a couple of rotations of the wheel to clear off the water before they start to grip.