Continental brakes - Wrong way round

For discussions about bikes and equipment.
Brucey
Posts: 42858
Joined: 4 Jan 2012, 6:25pm

Re: Continental brakes - Wrong way round

Postby Brucey » 5 Oct 2018, 8:14pm

Mick F wrote:30mph.
Squeeze the front brake as hard as you can without touching the rear brake.

What happens?
You slow down, but you don't do a header...


if that is the case then you just don't have exceptionally powerful brakes.

I quite like some brakes that (often) work like this (for example SA 70mm drums) because you can pull instantly as hard as you like on the brake lever without fear of doing a header. But if you try that with a lot of modern disc brake systems (and some DPs come to that) you will simply launch yourself into oblivion.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

User avatar
Mick F
Spambuster
Posts: 50934
Joined: 7 Jan 2007, 11:24am
Location: Tamar Valley, Cornwall

Re: Continental brakes - Wrong way round

Postby Mick F » 5 Oct 2018, 8:22pm

Mercian:

Campagnolo Athena calipers and pads with Campagnolo cables, combined with Campagnolo Chorus brake levers operating on 700c Ambrosio Excellence rims.

Have I got it wrong?
Mick F. Cornwall

Brucey
Posts: 42858
Joined: 4 Jan 2012, 6:25pm

Re: Continental brakes - Wrong way round

Postby Brucey » 5 Oct 2018, 8:38pm

for some reason you clearly are not able to generate enough force at the caliper to produce either of the two outcomes I mentioned previously. There are numerous possible reasons for this including

- you are not pulling hard enough
- the cables are robbing you of force (eg because they are not lubricated properly)
- the brake blocks are the sort that melt too easily when braking from high speed (which makes the coefficient of friction fall off or self-limit)

BTW this is maybe just as well; I don't recommend repeatedly doing stoppies (or near stoppies) on lightweight steel frames; they tend to break.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

User avatar
Mick F
Spambuster
Posts: 50934
Joined: 7 Jan 2007, 11:24am
Location: Tamar Valley, Cornwall

Re: Continental brakes - Wrong way round

Postby Mick F » 5 Oct 2018, 8:46pm

Wrong in all that.
Mick F. Cornwall

Brucey
Posts: 42858
Joined: 4 Jan 2012, 6:25pm

Re: Continental brakes - Wrong way round

Postby Brucey » 5 Oct 2018, 9:07pm

Mick F wrote:Wrong in all that.


not at all.

A suggestion; get a bike (eg a cheap used MTB with powerful disc brakes) and you (or a proxy who is younger and more rubbery) have a mess about (on soft ground, wearing protective clothing as necessary). You will soon realise that you are mistaken. It is just (fairly simple) physics.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

User avatar
The utility cyclist
Posts: 3607
Joined: 22 Aug 2016, 12:28pm
Location: The first garden city

Re: Continental brakes - Wrong way round

Postby The utility cyclist » 5 Oct 2018, 9:27pm

gxaustin wrote:
I don't know about the 1950s but by the late 70s plenty of kids could do what would later be termed as an 'endo' either by design or by misfortune.


Put on brakes, move centre of gravity forward off saddle, when front wheel stops the rear of the bike lifts. Put foot down quick. Actually that's maybe where the fear of going over the handlebars comes from?
Put on brakes, remain seated, bike stops under control.
Stand over bike while stopped, apply front brake hard, push handlebars away - rear of bike lifts. That's how I change gear when I stop in the wrong ratio.
Simple physic
s

It's not simple physics for a child or even inexperienced adults, when you have professional riders still locking their wheels up due to panic braking then trying to apply physics to kids just cycling is somewhat futile.

cycle tramp
Posts: 1041
Joined: 5 Aug 2009, 7:22pm

Re: Continental brakes - Wrong way round

Postby cycle tramp » 5 Oct 2018, 10:04pm

Mick F wrote:30mph.
Squeeze the front brake as hard as you can without touching the rear brake.

What happens?
You slow down, but you don't do a header.
You will slow down more if you use both brakes.


Actually I did... and I was only going 12 miles an hour, too. The bike itself used some long arm linear pull brakes, with 4 fingered flat levers (originally for cantilever brakes) new sticky pads and about 2 mm clearance between the brake pads and front rim
...So when I applied the front brake in haste, the front wheel stopped and sadly the forward motion of the bike continued... because the front wheel had stopped the forward motion then travelled in an arc using the front wheel's contact with the road as a pivot and I became airborne.. for a second or so anyway.... needless to say I have developed a dislike for any brake that does offer it's user a feel of modulation...

User avatar
Mick F
Spambuster
Posts: 50934
Joined: 7 Jan 2007, 11:24am
Location: Tamar Valley, Cornwall

Re: Continental brakes - Wrong way round

Postby Mick F » 6 Oct 2018, 8:45am

Brucey wrote:
Mick F wrote:Wrong in all that.


not at all.

A suggestion; get a bike (eg a cheap used MTB with powerful disc brakes) and you (or a proxy who is younger and more rubbery) have a mess about (on soft ground, wearing protective clothing as necessary). You will soon realise that you are mistaken. It is just (fairly simple) physics.
I don't disagree in the slightest!
Instant header I would think! :lol:


I'm taking about MY bike and how it handles and brakes, not ALL bikes.
Mick F. Cornwall

Brucey
Posts: 42858
Joined: 4 Jan 2012, 6:25pm

Re: Continental brakes - Wrong way round

Postby Brucey » 6 Oct 2018, 10:56am

Mick F wrote:
Brucey wrote:
Mick F wrote:Wrong in all that.


not at all.

A suggestion; get a bike (eg a cheap used MTB with powerful disc brakes) and you (or a proxy who is younger and more rubbery) have a mess about (on soft ground, wearing protective clothing as necessary). You will soon realise that you are mistaken. It is just (fairly simple) physics.
I don't disagree in the slightest!
Instant header I would think! :lol:


I'm taking about MY bike and how it handles and brakes, not ALL bikes.


well

a) your bike is not somehow immune to the laws of physics and
b) your earlier statements and previous refutals clearly are not in reference to 'your bike only' else you wouldn't have made them in the way you did.....?

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

pwa
Posts: 13860
Joined: 2 Oct 2011, 8:55pm

Re: Continental brakes - Wrong way round

Postby pwa » 6 Oct 2018, 11:12am

A couple of decades ago I was regularly going to the Alps on cycling holidays and I had a couple of inner tube explosions due to overheated rims. So I did some reading to find out what I was doing wrong. It turned out that I was making the mistake, on long fast descents, of retarding the speed more or less constantly, feathering the brakes. That is a recipe for very hot rims and disaster. What I should have been doing, and have done ever since, is have spells with no braking, letting the speed rise, and doing all the braking really hard at the last possible moment. That heats the rims less than constant feathering.

But if you are braking hard you need to know the most effective way to do it. And the technique I picked up was this. Apply both brakes at once, not too firmly, then as the deceleration puts more force down through the front tyre, increase front wheel braking. All this transition in a couple of seconds. Obviously you also want your body weight low down and you bum far back, and doing whatever leaning you need for the corner. And it works. I'm not saying we should all be doing this to the extreme on average UK roads, but it illustrates how once deceleration is under way it is the front wheel that can handle most braking, with the rear just helping.

User avatar
Mick F
Spambuster
Posts: 50934
Joined: 7 Jan 2007, 11:24am
Location: Tamar Valley, Cornwall

Re: Continental brakes - Wrong way round

Postby Mick F » 6 Oct 2018, 11:17am

Sorry if I was misconstrued.
I say that if your COG is far enough back, you won't do a header in an emergency stop situation.
No doubt you can do it on purpose, but not accidentally.

Note.
COG far enough back.

I very much doubt I could have done one on the Raleigh Chopper even if I wanted to. Wheelies were always a big problem though!
Mick F. Cornwall

pwa
Posts: 13860
Joined: 2 Oct 2011, 8:55pm

Re: Continental brakes - Wrong way round

Postby pwa » 6 Oct 2018, 11:26am

Tandems make it simpler. You will never get the rear wheel to lift on one. But you can easily slide the rear wheel and flat spot a tyre if you persist.

User avatar
Mick F
Spambuster
Posts: 50934
Joined: 7 Jan 2007, 11:24am
Location: Tamar Valley, Cornwall

Re: Continental brakes - Wrong way round

Postby Mick F » 6 Oct 2018, 12:13pm

Exactly!
COG far enough back.
Mick F. Cornwall

User avatar
Chris Jeggo
Posts: 203
Joined: 3 Jul 2010, 9:44am
Location: Woking

Re: Continental brakes - Wrong way round

Postby Chris Jeggo » 6 Oct 2018, 4:00pm

If your COG is height H above a level road and horizontal distance D behind the front tyre point of contact, then excessive braking will send you over the handlebar if the coefficient of friction is greater than D/H and cause a skid otherwise.

Brucey
Posts: 42858
Joined: 4 Jan 2012, 6:25pm

Re: Continental brakes - Wrong way round

Postby Brucey » 6 Oct 2018, 4:22pm

Chris Jeggo wrote:If your COG is height H above a level road and horizontal distance D behind the front tyre point of contact, then excessive braking will send you over the handlebar if the coefficient of friction is greater than D/H and cause a skid otherwise.


exactly!

pwa wrote:A couple of decades ago I was regularly going to the Alps on cycling holidays and I had a couple of inner tube explosions due to overheated rims. So I did some reading to find out what I was doing wrong. It turned out that I was making the mistake, on long fast descents, of retarding the speed more or less constantly, feathering the brakes. That is a recipe for very hot rims and disaster. What I should have been doing, and have done ever since, is have spells with no braking, letting the speed rise, and doing all the braking really hard at the last possible moment. That heats the rims less than constant feathering.

But if you are braking hard you need to know the most effective way to do it. And the technique I picked up was this. Apply both brakes at once, not too firmly, then as the deceleration puts more force down through the front tyre, increase front wheel braking. All this transition in a couple of seconds. Obviously you also want your body weight low down and you bum far back, and doing whatever leaning you need for the corner. And it works. I'm not saying we should all be doing this to the extreme on average UK roads, but it illustrates how once deceleration is under way it is the front wheel that can handle most braking, with the rear just helping.


exactly #2!

BTW 'hard braking' is often a lot harder than some folk imagine. If you are able to stop at about 1G (H = or < D and a suitably high coefficient of friction prevails ) then stopping distances can be thus (approximately) ;

at ~10mph you can stop in just over 0.5s and travel ~1.25m in the process
at ~20mph you can stop in just over 1s and travel ~5m in the process
at ~30mph you can stop in just over 1.5s and travel ~11.25m in the process

It will normally take over 0.5s for a rider to sense the braking effort and then adjust it, which is why achieving these stopping distances (or doing a controlled stoppie) is actually rather difficult; unless you are going quite fast the stop is short duration (or could be) and there just isn't time to react and modulate the brake effectively. Most folk don't brake hard enough to get near these stopping distances, or only manage to apply the brake hard enough to lift the rear wheel near the end of the stop.

Note that the most effective time (during a hard stop) to scrub off speed is initially, not latterly. If you manage to (say) scrub off 10% of your speed right away (at 1G), you are going 10% slower for the whole stop, whereas if you only manage 1G near the end of the stop, this has relatively little impact on your stopping distance.

Obviously there is reaction time to add on to the above distances; this can soon outweigh the actual stopping time/distance if you cannot react quickly enough, which is why anticipation is so important.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~