Peter W wrote: Disc brakes use STEEL rotors but with special modern pad material which modulates, and works predictably in all conditions. For what reason wouldn't a steel rim, which is a very large diameter rotor, work with the same callipers and pads in the same manner?
We know that modern rim brakes pressing on alloy rims can work well, though not with the same modulation and light hand force as hydro discs, but I fail to see how a steel rim with hydro calliper and pads wouldn't outlast an alloy rim, especially in winter conditions, by a large margin.
when disc brakes are completely, properly, wet the brakes do not work at all well on first application. I decided to abandon the use of disc brakes whilst commuting for this reason; there are better brakes for that purpose, which reliably give less than half the stopping distance when it is tipping down with rain. BTW this issue causes fewer problems when MTBing or leisure cycling simply because unplanned braking in very wet conditions is less likely.
Rubber brake blocks are flexible and that allows small variations in rim width to be tolerated. You need this because
a) it is impossible to make steel rims that are perfectly uniform in width (at a reasonable cost/weight) and
b) rims get knocked about.
If you used a rigid (disc brake) pad compound you would soon come unstuck; the brakes would no longer tolerate tiny variations in width, the brake still wouldn't work when soaking wet, and the (abrasive) pads would wear the rims out.
Steel rims are both thin-walled and rather heavy. It is also difficult to make them with sensible beads etc so that high pressure modern tyres can be fitted to them.
However the basic premise that rim brakes could be greatly improved is one I agree with. There are any number of hard-facing technologies and pad compounds that could be used.
My year plus old Roubaix road bike has hydro disc brakes and they have faultless and superb. Neither do they shriek or squeal, they just satisfyingly shhhs on application. Should they fail (piston trouble or salt corrosion problems) after say two years, I'd simply buy new ones, ready bled to just bolt on for way less price than having to buy two new wheels.....
The discs will probably be worn out (there is very little wear permitted in current shimano road discs BTW), the wheels may break anyway (because they are built light, what with the bike being fitted with heavy brakes and all) and if you are not putting new rims on your wheels then you won't be working on your own bike either, so the bill should include
brake calipers, brake pads + STIs
gear cables
bar tape
discs
hose clips etc
labour
I think that lot will come to at least double your 'about £160' estimate, nearer three times if you pay anywhere near rrp on the parts. Note also that the brakes may start to drive you nuts before they actually fail; just today I heard a TdF rider's bike make some foul noises which I am pretty sure came from the disc brakes....
You can buy workable training wheels (for rim brakes) for about a hundred quid a pair (leave aside that rims are less than this BTW) and at some small fraction of the total cost you can have a bike that is lighter and arguably more pleasant to ride (the rest the time) if it is fitted with rim brakes. Oh, and spare wheels will fit easily, IME, in stark contrast to spare wheels with brake discs on.
To hear some folk carry on about it you would think that disc brakes represent some kind of nirvana for road bikes, a panacea for all ills.... The truth is not at all like that, they are arguably just as much a curate's egg as rim brakes are, just in different ways.
cheers