What is an appropriate stopping time and distance?

[slimyxylofone]

So slimy, have you taken my advice and measured out the distance and tried stopping? As you should be able to see from the above posts and links, 8 secs is a long time and 51mts is not short either.
What are you doing with this information?

Well most of the above information shows that my stopping time and distance (which was timed in my head and paced out) is roughly average, not overly slow. That said, even if it is average, that means I have plenty of room for improvement.

As to whether I have actually done anything since my original post, no I haven't. I haven't even been on my bike. I'm in the middle of Uni exams which take precedence at this point.

I am planning to continue practicing with more accurate measurements this time (get someone to time me from them putting up a flag or something similar to include my reaction time; and try to get a hold of a walking tape measure).

Have you actually measured your stopping times, or were you just going off gut instincts that the times were slow? Maybe you can't stop as fast as you think?

I'll make an utmost attempt to post in this thread when I am able to get back on and go for another practice run. Two weeks and counting before I get to ride up to Auckland, pleanty of road for practice between Dunedin and Auckland!

[Macktheknife]

Slimy, PM sent in response to your questions. Good luck with your exams.

[Mental Trousers]

The only legal requirement for stopping distance I can find is:

Section 2.3 sub-section 6: (b) is capable of stopping it within a distance of 7 m from a speed of 30 km/h

Can anyone who knows a little physics extrapolate that out to 100 km/h and that will give a maximum distance you should be stopping within.

[Ixion]

Back in the day, 30 yards from 30mph was reckoned the standard for good brakes.Memory (fickle, but) insists that Vincents could stop from 30mph in 22 yards.

[spudchucka]

The only legal requirement for stopping distance I can find is:

Section 2.3 sub-section 6: (b) is capable of stopping it within a distance of 7 m from a speed of 30 km/h

Can anyone who knows a little physics extrapolate that out to 100 km/h and that will give a maximum distance you should be stopping within.

Could have a go at it but I don't have a scientific calculator at home. I'll try to remember to take this to work tonight and I'll post the results tomorrow.

[XP@]

Could have a go at it but I don't have a scientific calculator at home. I'll try to remember to take this to work tonight and I'll post the results tomorrow.

try Start -> Programs -> Accessories -> Calculator
then in the view menu select Scientific

[eliot-ness]

Back in the day, 30 yards from 30mph was reckoned the standard for good brakes.Memory (fickle, but) insists that Vincents could stop from 30mph in 22 yards.

I think you'll find that was feet, not yards. (see earlier post) although the Vincent figure would be a bit optimistic.

[Ixion]

Sorry. Yes, 30 foot it should be . Got carried away with all the switching of yards to metres. And lowish twenty something feet for the Vincent. It was very very good. Had twin front drums, never saw that again until the first Suzuki GT750. Vincents were only SLS though.

Part of the reason was the friction material. Bikes in those days weren't expected to be required to stop repeatedly from high speed, and there was less racing on the roads. So they used a softer material for the linings which gave better stopping at low speeds, at the expense of fade at high speeds.

[Ixion]

Yep. Found it. Vincent was 22.5 FEET from 30 mph (50kph). Copy of "The Motorcycle" road test here http://www.vincent-hrd.co.uk/story.html

Front brake only was 31 foot

22.5 foot is 6.75 metres
31 foot is a bit over 9 mtrs

Haven't come far in 60 years , have we?

[spudchucka]

try Start -> Programs -> Accessories -> Calculator
then in the view menu select Scientific

It doesn't have the functions I want. I've been too busy the last few nights, hopefully I'll get to look at it tonight.

[spudchucka]

Assuming that the vehicle, (a car) was under emergency braking and was fully locked up, to stop in 7 metres from a speed of 30kph the drag factor of the road would have to be only 0.5.

This is very low, most NZ roads are around 0.6 -0.65, some are as high as 0.7.

So a vehicle travelling at 100kph on the same surface, (drag factor of 0.5) would require 78.61 metres to stop under full lock up.

[Ixion]

I happened to be at werk this afternoon, with von Klunken and an empty car park. Large .

So I tried the experiment, Back up, accelerated to 50kph and hit the brakes hard - not quite hard enough to kick in the ABS but hard enough that one at least of the tyres was singing. Stopped and went back and measured the distance (started braking as I passed a mark)

Only paced out but I know pretty near exactly a one imperial yard pace Result was between 9 and 10 yards, about 8 to 9 metres.

Repeated , about a foot longer. Repeated again, this time hard enough for the ABS to engage, a couple of foot less . I imagine that in a real emergency adrenalin would knock a few foot off. I was probably releasing a foot or two earlier than necessary, even with ABS it is possible to lock a wheel and I didn't fancy a low speed spill.

So, the old 30 foot at 30 mph is pretty well right, and some of the figures discussed seem excessive.

EDIT. I think drums will always give better low speed braking distances than disks, it's a matter of the friction surface area. So we probably won't see figures to match the BMW or Vincent ones, but distances from higher speeds would be a different matter - at low speed the drum brake doesn't have time to get overly hot as it does from a high speed stop.

[Roj]

Some very interesting stuff in the various links posted, a lot of variation is possible, but the estimate of 50 or so metres from 100 kph from start of braking to complete stop is not unreasonable,

The "2 second rule" gives about 1 car length per 10kph, a car lenth being approx 4-4.5 metres, so at 100 kph you may be less than 50 metres from the vehicle in front, assuming that the vehicle in front starts stopping suddenly, taking 1.5 seconds to react would loose about 40 metres of distance, meaning the vehicle in front may be close to stopping, doesn't leave much room for error.

While watching the vehicle in front is very important, watching what is further ahead is just as important, its all about identifying hazards as quickly as possible, and always consider if you have to stop, the possibility of have to go beside the leading vehicle to give yourself more space, or in other words, "plan ahead and have an escape route"