The whole speeding thing

Frascp · June 2007

Nevermind hitting a person. You're far more likely to hit a car pulling out of a drive or junction. Do you not wince when you see those motorbike safety adverts? Even if you come out of it OK your bike would be a mess. I'm sure cyclecraft says the stopping distance for a bike doing 20mph is 60 metres. Ayeeesh!

maybrick · June 2007

<blockquote id="quote">quote:<hr height="1" noshade id="quote">drossall

Hitchin, Herts
United Kingdom
2298 Posts
Posted - 11/06/2007 : 23:15:32

maybrick - There's a big clue in the table in the HC, which doesn't have a row for cyclists - although it does mistakenly say that the limits apply to all traffic, when it means all motor traffic. Just shows that not even the HC is always reliable.

However, the introduction to that table also references the RTRA sections 81, 86 and 89.

The RTRA quite clearly says "motor vehicles". You can't apply a law that says "motor vehicles" to vehicles without motors.

Of course, other posters are quite correct. If the risks of a stretch of road are such that cars should not exceed 30mph, it's hard to see how cyclists could do 45mph without being open to a charge of reckless or furious cycling
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most of my cycling is furious.
i'm known for it you know.

_______________

i'm not bound by your earthling rules.

dondare · June 2007

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by drossall

maybrick - There's a big clue in the table in the HC, which doesn't have a row for cyclists - although it does mistakenly say that the limits apply to all traffic, when it means all motor traffic. Just shows that not even the HC is always reliable.

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Too bloody right it's not reliable. What this shows is that the DSA don't regard cyclists as traffic.

This sig is under construction.

Roastie · June 2007

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Fras

I'm sure cyclecraft says the stopping distance for a bike doing 20mph is 60 metres. Ayeeesh!
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But then again Cyclecraft advocates minimal use of the brakes, advising that cyclists coast to a stop without brakes.[:0]

Roastie · June 2007

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by dondare

Too bloody right it's not reliable. What this shows is that the DSA don't regard cyclists as traffic.
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And in this comment, the crux of the Equal Treatment thing.

Unknown · June 2007

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Fras

I'm sure cyclecraft says the stopping distance for a bike doing 20mph is 60 metres. Ayeeesh!
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That can't be right, do you mean 6 metres?

dondare · June 2007

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Fras

Nevermind hitting a person. You're far more likely to hit a car pulling out of a drive or junction. Do you not wince when you see those motorbike safety adverts? Even if you come out of it OK your bike would be a mess. I'm sure cyclecraft says the stopping distance for a bike doing 20mph is 60 metres. Ayeeesh!
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I do mind hitting people.

This sig is under construction.

rgisme · June 2007

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Ashaman

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Fras

I'm sure cyclecraft says the stopping distance for a bike doing 20mph is 60 metres. Ayeeesh!
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That can't be right, do you mean 6 metres?
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It can certainly be done in 6 metres if you go over the bars [B)]

speshcp · June 2007

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Ashaman

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Fras

I'm sure cyclecraft says the stopping distance for a bike doing 20mph is 60 metres. Ayeeesh!
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That can't be right, do you mean 6 metres?
<hr height="1" noshade id="quote"></blockquote id="quote">According to Cyclecraft, the stopping distance for an alert rider on a dry, level road is 17 metres from 20 mph. For a tired rider on a wet road, the distance increases to around 40 metres.

http://i143.photobucket.com/albums/r137 ... l/scan.jpg

What's significant is the first sentence after the table:

"If you need to brake at all quickly, you will need to apply both brakes."

This implies that the Cyclecraft stopping distances are based on the application of just one set of brakes - probably the front (see below).

I plugged the Cyclecraft numbers into a spreadsheet and factored in a typical reaction time of 0.67 seconds (worked out from speed and thinking distance in the Highway Code) in order to calculate the deceleration required to acheive the overall stopping distances quoted.

From 20mph, you would need to decelerate at around -0.37g relative to the direction of travel.

Some research by a chap called John Forester suggests that the maximum deceleration possible with the front brake before you are spat over the handlebars is around -0.67 g, although a typical cyclist will be doing well to produce -0.5g. Using just the rear brake, maximum deceleration is around -0.25g before rear wheel skids.

Decelerating to a dead stop from 20mph at -0.5g gives an overall stopping distance of 14 metres, and if you really grab a handful of brakes, you could stop from 20 mph in just over 12 metres.

<hr noshade size="1">"Two things are infinite: the universe and human stupidity; and I'm not sure about the universe." (Albert Einstein)

speshcp · June 2007

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by rgisme

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Ashaman

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Fras

I'm sure cyclecraft says the stopping distance for a bike doing 20mph is 60 metres. Ayeeesh!
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That can't be right, do you mean 6 metres?
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It can certainly be done in 6 metres if you go over the bars [B)]
<hr height="1" noshade id="quote"></blockquote id="quote">Ye cannae change the laws o' physics, cap'n! [:D]

<hr noshade size="1">"Two things are infinite: the universe and human stupidity; and I'm not sure about the universe." (Albert Einstein)

Archcp · June 2007

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by spesh

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Ashaman

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Fras

I'm sure cyclecraft says the stopping distance for a bike doing 20mph is 60 metres. Ayeeesh!
<hr height="1" noshade id="quote"></blockquote id="quote">

That can't be right, do you mean 6 metres?
<hr height="1" noshade id="quote"></blockquote id="quote">According to Cyclecraft, the stopping distance for an alert rider on a dry, level road is 17 metres from 20 mph. For a tired rider on a wet road, the distance increases to around 40 metres.

http://i143.photobucket.com/albums/r137 ... l/scan.jpg

What's significant is the first sentence after the table:

"If you need to brake at all quickly, you will need to apply both brakes."

This implies that the Cyclecraft stopping distances are based on the application of just one set of brakes - probably the front (see below).

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Um, sorry, I don't see the logic of that. Why should it imply the table is based on one set of brakes. In fact it implies it's based on both, doesn't it, since the advice is given...

If it said "Here are the distances butyou should use both sets...", then you'd have a point...

Frankly, I think riding anywhere at 45mph on two wheels is mad, but I'm not one for speed, even if I was capable of it. I think it would be a common courtesy to stick to the speed limit, even if it didn't legally apply to a cyclist.

If I had a baby elephant, it could help me clean the car. If I had a car.

Greenbank · June 2007

The more front brake you use the less effective the back brake becomes as there is less weight on the rear wheel.

If you take this to the extreme in a well executed emergency stop (i.e. as close to the skid threshold as you can) they'll be almost no weight on the rear wheel (it may even be off the ground) meaning the back brake is contributing no additional braking force (whether it's applied or not).

The wetter the roads the less front brake can be applied before skidding and if wet enough you might get to a point that the rear brake can provide additional braking, but it has to be quite wet for this to happen.

Sheldon has a good page on this if you want to read more:-

http://www.sheldonbrown.com/brakturn.html

--
If I had a baby elephant signature, I'd use that.

Archcp · June 2007

No, no, I see the logic of using both brakes, I meant I don't see how spesh came to the conclusion: "This implies that the Cyclecraft stopping distances are based on the application of just one set of brakes - probably the front (see below)" from the excerpt he posted...

If I had a baby elephant, it could help me clean the car. If I had a car.

walkercp · June 2007

If, like some, commuting is your training for this weekend's race then yeah I race too and from work. No point if your a flat bar or MTB though

Rhino's are the new Elephant

Roastie · June 2007

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by walker

If, like some, commuting is your training for this weekend's race then yeah I race too and from work. No point if your a flat bar or MTB though

Rhino's are the new Elephant
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Why not, surely your legs don't care what sort of bike you're on?

Graham O · June 2007

I seem to remember from a few years ago that "riding furiously" was repealed as being too vague. It was originally brought in to punish cyclists who upset horses, if I remember correctly.

rgisme · June 2007

Some people probably vaguely think that it was. Since the main form of transport at the time was the horse, however, when this was introduced, I think it more likely the offence was introduced to stop people riding horses 'furiously' at inappropriate times or places. In fact I seem to remember reading somewhere an account of horse-drawn cab drivers being penalised for it when I was trying to find out more about it some time ago.

rgisme · June 2007

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by spesh

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by rgisme

It can certainly be done in 6 metres if you go over the bars [B)]
<hr height="1" noshade id="quote"></blockquote id="quote">Ye cannae change the laws o' physics, cap'n! [:D]
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The laws of physics threw me right over bars in a spectacular somersault and roll that had me come to rest on standing my feet, looking through the nearside window of the taxi who'd turned right across my path little more than a taxi-length before I hit the brakes. The bike came to rest about three metres further back.

I don't know why JF thinks a typical cyclist would 'do well to produce -0.5g', if -0.67g is required for a circus-act excursion over the bars. I found it easy enough!

Greenbank · June 2007

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Roastie

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by walker

If, like some, commuting is your training for this weekend's race then yeah I race too and from work. No point if your a flat bar or MTB though

Rhino's are the new Elephant
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Why not, surely your legs don't care what sort of bike you're on?
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I bet there are some good standard amateur racers who probably commute in on rusty heaps of rubbish because they don't feel happy locking up their carbon pride-and-joy on the street all day. There are certainly a few of them that go past me (and almost every other cyclist on my commute) most days.

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If I had a baby elephant signature, I'd use that.

The whole speeding thing

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