Mr. Dazzle wrote: ↑Tue Sep 20, 2022 6:15 pm
I theory like, drums are better than discs.
When cold. And new. And correctly set up
Plus they weigh a fucking tonne.
Have you been drinking?
Isn't he right - in theory? The interface area between drum and brake material is (should be) greater I would have thought - giving greater friction.
In theory, he may be. In practice, he's been drinking...
If drum brakes are so superior, why aren't they in widespread use at all levels of automotive and motorsport endeavour? They're not - they're crap (relatively speaking). They overheat when pushed even mildly and were old tech well before the 1980s.
If you rank them in order of "how much they brake vs how much actuation you need to apply" it goes twin leading shoe, leading/trailing, twin trailing (has anyone ever made those? Car with TLS driving backwards I guess ) then discs.
That assumes perfect conditions.
The major advantages of discs are cooling, consistency and, the real doozy, self adjustability. If you could get your drums to always be perfectly set they'd be stellar, but you can't. The moment you use them and they wear a bit and get hotter they go out of whack. That's the real benefit of discs and why they're so universal.
Last edited by Mr. Dazzle on Tue Sep 20, 2022 9:53 pm, edited 1 time in total.
KungFooBob wrote: ↑Tue Sep 20, 2022 9:52 pm
Some cars use combined rear drums/discs, with the drum part for the handbrake.
The main reason for that is cause as the brakes cool down they shrink. In discs that means the disc shrinks away from the pad, releasing the brake. The opposite occurs in drums. So if you have drum hand brakes you don't need some second mechanism to take up the slack when the brakes cool.
Isn't he right - in theory? The interface area between drum and brake material is (should be) greater I would have thought - giving greater friction.
In theory, he may be. In practice, he's been drinking...
If drum brakes are so superior, why aren't they in widespread use at all levels of automotive and motorsport endeavour? They're not - they're crap (relatively speaking). They overheat when pushed even mildly and were old tech well before the 1980s.
Theory and practice don't always go hand in hand. In practice they aren't superior. (Shouldn't fade in the wet though )
Doubt is not a pleasant condition.
But certainty is an absurd one.
Voltaire
Drum (internally expanding) are inferior to disc ( externally expanding) in situations requiring heavy braking from high speed or repeated use...which is why they were developed for air craft and subsequently high performance vehicles. Drum have more feel and less rolling resistance....when set up correctly.
And aye, there's the rub.......
Le_Fromage_Grande wrote: ↑Wed Sep 21, 2022 7:45 am
Drum brakes are better than discs on off road bikes, they give loads more feel and they don't suddenly lock, admittably they're useless when wet.
So that'll be why virtually every current manufacturer of enduro/MX bikes use disc brakes, then? These days you can get equivalent feel to drums from discs and they are way lighter and far less susceptible to fade.
I was actually thinking this morning that band brakes offer even more power than drums They're even worse than drums in terms of heat, dirt, adjustment etc though.
Le_Fromage_Grande wrote: ↑Wed Sep 21, 2022 7:45 am
Drum brakes are better than discs on off road bikes, they give loads more feel and they don't suddenly lock, admittably they're useless when wet.
So that'll be why virtually every current manufacturer of enduro/MX bikes use disc brakes, then? These days you can get equivalent feel to drums from discs and they are way lighter and far less susceptible to fade.
You can't get the same feel from a disc that you do from a drum, you just get used to riding with discs off road, but they have improved massively to when they were first fitted to MX bikes in about 1984, my 1986 KTM 250 had discs that were pretty much on or off in sand.
Le_Fromage_Grande wrote: ↑Wed Sep 21, 2022 7:45 am
Drum brakes are better than discs on off road bikes, they give loads more feel and they don't suddenly lock, admittably they're useless when wet.
So that'll be why virtually every current manufacturer of enduro/MX bikes use disc brakes, then? These days you can get equivalent feel to drums from discs and they are way lighter and far less susceptible to fade.
You can't get the same feel from a disc that you do from a drum,
I'd have to disagree with that. With modern radial calipers and master cylinders, I'd say you have as much power and feel as you could possibly want. The setup on my Duke 690 R is truly phenomenal and is light years better than any drum setup I've used.
Le_Fromage_Grande wrote: ↑Wed Sep 21, 2022 2:56 pm
you just get used to riding with discs off road, but they have improved massively to when they were first fitted to MX bikes in about 1984, my 1986 KTM 250 had discs that were pretty much on or off in sand.
I'd suggest that quoting experiences from 40 years ago isn't really relevant to today. Yes, disc brakes were pretty dire when they first came to market in the late 60s/70s but continuous development has long since ironed out early problems. Comparing the disc brakes on my LC to those on the KTM shows just how far we've progressed.
I think rear brakes on a lot of bikes have become less effective since the advent of rear discs. It's hard to get any kind of feel the drums used to have. Probably deliberate from the manufacturers to protect us from ourselves. Front brakes are awesome now.
mangocrazy wrote: ↑Wed Sep 21, 2022 3:17 pm
I'd suggest that quoting experiences from 40 years ago isn't really relevant to today. Yes, disc brakes were pretty dire when they first came to market in the late 60s/70s but continuous development has long since ironed out early problems. Comparing the disc brakes on my LC to those on the KTM shows just how far we've progressed.
I have ridden modern dirt bikes, it was an example that disc on dirt bikes are better now than they were in the 80s, but I still don't think they have the feel of a good, well adjusted drum.
Last time I rode the old girl was in Sept/Oct*, can't remember exactly. I did the 100 mile round trip to work without incident. Since then the bike was been in my garage. Other family and home matters have meant I've not had a great deal of time to work on it.
But spring is dangerously close to being sprung and I've brewed up a list of things to do with the Bonnie. I'm also flogging the 5TA** to my wife's Uncle (BiL of the Bonnie's former owner) which will make the garage a bit roomier.
So the list of things to do on the Bonnie is:
Fix the centre stand. Makes many of the subsequent jobs much easier. This is actually the one with the most head scratching. The stand is just bent out of shape and I don't have a big bench/vice to hold it in. I used to have access at work, but not any more.
Change engine and gearbox oil
Change front fork oil / rebuild front forks. They've got a slight "clunk" so probably the latter. Needs new gaitors too.
Valve clearances, plug gaps etc.
Change front brake shoes, generally clean up and reset. Might as well get a new front brake cable too, I've been pretty impressed with the Venhill PTFE/Stainless ones I've fitted elsewhere on the bike so I'll go for that. Added bonus in that they don't need lubing.
Maybe get the 'bacon slicer' back on the front brake/wheel.
Get the clocks rebuilt. They're the original '69 Smiths gauges, so I want to keep 'em. They're basically random number generators at the moment though. They'll need new drive cables too.
See if I can do anything about the top end oil leaks. Ha! As if!
Replace all the fairing screws/bolts so a) they're all present and b) they all match.
New tyres, maybe new wheels. The Dunlop TT100s on there have very few miles on but are probs 10 years old. I looked at getting the wheels refurbed but all indications are it's not worth it, brand new wheels make more sense.
Bank account might get a spanking
*Married life eh?
** Not actually a 5TA. It's a 3TA which the police modified with a 500cc engine, my FiL bought as an ex-copper bike. It has 100SS branding on it too. Proper bitsa.
) then discs.
)
Brown seat.
