Stumpy - I bow to your figures but I find you can outbrake pretty well anything I have driven or ridden on a bike and have measured ( very roughly) braking in shorter distances than a car on tarmac. - certainly beating 1g easily.
It is suprising how quickly a bike can stop.
cheers stumpy, i'll stick to nursing as that kinda maths on a friday morning makes my head hurt!
i've got a nearly new bike, brakes in good condition, pads bedded in, know how to use both the front and back brake effectively to stop with or without locking up and skidding depending on how childish i'm feeling... but i weigh about 14 1/2 stone (pure muscle of course 😆 ) and at 20mph if i had to brake suddenly i think i would've probably overshot the 5 meters with just reaction time alone!
if it helps i also have a heavy bike, tyres with big tread, 160mm rotor on the back and 185 on the front if anyone's feeling geeky enough to do more complicated equations.
TJ, i propose that you film yourself riding at 20mph then when someone shouts stop you have to stop within 5 meters, thats the only way i can see this being settled.
either that or we can admit it doesnt matter in the scheme of things and have a cuppa tea and relax, after all its friday 8)
toys19 - MemberAhh you forget about the effect of the mass on your momentum
No I am not. Of course more mass = more momentum
and how the brakes will have to work that much harder to bring the wheel to a stop? Assuming you are applying the same force at the lever the brakes will be less effective.
Of course the brakes will have to work harder thats my point - you can use more braking power- but you can apply them harder as you have more grip if you are heavier. You are assuming the same level of lever pressure - that would obviously mean longer stopping. I am saying you can use more lever pressure as you have more grip
Please =- read what I wrote
[b]On gravel[/b] is grip not the limiting factor to the deceleration you can achieve - there is plenty of power in the brakes?
If you are heavier do you have more grip? as the loading on the tyres is greater?
TJ although the science is correct (friction is proportional to the reaction force), it doesn't work like that in real life. I would be able to stop much quicker then you, for example.
I'm sorry, but you are wrong.
Real man - why not? why does the therory not apply in the real world?
You say you would be able to stop quicker than me? Why. I am 13 stone.
I am not saying you are wrong but I would like greater understanding of this and I can't see a flaw in my reasoning.
TJ - like I say I'm a bit bored and thought I'd do a rough calculation - it's probably a bit more complicated in real life!!
On the road you probably could stop in 5m, but on a gravelly trail - I'm not so sure. I always have to relate a distance to something for it to mean anything & apparently a SWB Transit is just under 5m long. I'm not sure I could stop off-road from 20mph in the length of a Transit van.
Technically his fault but she was being a total dick about it. WTFU!
I would have:
Bunny hopped her with massive awesomeness landed 180, flashed my six pack and asked her out for a drink.
He failed to do this so it's his fault for being a bit sh!t
Thanks
Cornelius Reginald Xavier III
he stayed very calm after having a bike thrown at his face.... he must be a psych nurse.
surely its a bit of an unwritten rule that if you have to stop on a trail you pull to the side and get your bike off the track? big overreaction from her... and you cant spell overreaction without ovaries, 'cos she's a woman.
hang on, shouldnt she be in a kitchen? 😆
[i]Of course the brakes will have to work harder thats my point - you can use more braking power- but you can apply them harder as you have more grip if you are heavier. [/i]
Ah so that's why those 4x4 stop so quickly on icy roads..
Well, it is his fault to be fair, but given her reaction, I would have told her to ** off. It was a pretty lame fall and anyone who can jump to their feet and launch a bike at you isn't hurt!
This is why I like a proII hub. People tend to hear them before you get close enough to shout trail.
Even though the whiny American psycho girl is more annoying than eczema, it's still the blokes fault - he just didn't leave enough room.
What if she'd fallen off? Or stopped because a baby Unicorn was frolicking on the trail in front of her, hmmn?
And why was he trying to pass her anyway? She had quite a nice bum, 'till he left tyre marks all over it.
This is why I like to ride little known natural singletrack either on my own or with folks whose capabilities I know and those who know my limitations.
I could imagine the wifie sueing the cameraman for whiplash injury and hissy fit trama compensation.
I liked the other video on the thread where someone did similar, and when he apologised, the girl he crashed into said, 'it's ok I was being a sloth'. 😀
Boo my work isnt letting me watch that. It does my swede in when people ride really close behind me though.
Deranged psycho harpies like her are the reason I have a little ping! bell on all my bikes, including mtbs. I've found it invaluable, from riding around London's mean streets and canal towpaths, to the middle of nowhere. Weighs nowt, and is a polite and friendly way to let others know you're there. Dunno if it would have been any use in this particular situation, but it's been useful for me many a time.
beaucoup lollage
bloke's "at fault" but the psycho harpy(TM) caused the crash and needs to ****in shut up whining
(did anyone watch past the broken leg bit? - I had to stop)
somewhere online there is a video of sharki riding into the back of me after I punctured and he realised a bit late except he is swearing about hitting his balls on the stem and I'm laughing at him.
maybe I should have thrown my bike at him.
You say you would be able to stop quicker than me? Why. I am 13 stone.I am not saying you are wrong but I would like greater understanding of this and I can't see a flaw in my reasoning.
I'm considerably lighter then you.
And anyway, you have a tandem (I would assume). Which stops quicker, you on a solo bike, or the tandem? Using your logic, they should both stop in the same distance.
but realman. A tandem has a much longer wheelbase than a regular bike so surely given sufficient rider skill and good tyre/brake setup the tandem will stop significantly quicker as the back end wont lift up so fast. I often find, when my brakes actually work, that this is the real limiting factor. Unless of course its shitty mud or ..gravel.
I just realised im agreeing wtih your realman. Reading ftw.
That's one angry woman, I get the impression she really didn't want to be there. Yeah rider behind maybe could have swerved but he didn't shit happens and no one was hurt but that reaction was way over the top. You have to remember there's other riders and they may be behind you.
Its easier to do an emergency stop on the tandem as the rear doesn't lift. On a solo to get the same deceleration you have to get your weight right back and low. You do have to be progressive with the front brake to load the tyre up tho or else it locks even on tarmac but load it up and the grip is amazing.
This is all assuming that there is plenty of brake force available. The tandem has sixpots on 203 discs.
So we agree momenteum is greater with more weight but grip is greater as well. therefore the braking distance should be the same for a light and heavy rider assuming that here is plenty of braking force available - ie you are not reaching the maximum capacity of the brakes.
Can someone explain why this is not right? Several people have said it don't work like that but I don't see why not.
*awaits enlightenment*
So we agree momenteum is greater with more weight but grip is greater as well. therefore the braking distance should be the same for a light and heavy rider
Lovely bit of pseudo-science there - isn't that assuming that the greater momentum is completely cancelled out by the increased grip? A fairly big assumption.
Can someone explain why this is not right? Several people have said it don't work like that but I don't see why not.
Might be something to do with the fact that (ignoring momentum and forces) you have to convert a lot of kinetic energy into a lot of heat energy as quickly as possible. And with a lighter person, there is just a lot less kinetic energy to deal with.
chakaping - Member
Oof, looks like she was in a bit of a grumpy mood anyway. Maybe she hates MTBing but her boyfriend makes her do it.
PMT maybe? Can't believe it hasn't been mentioned in the previous three pages.
In response to the OP's original question, I'd say it was a 70:30, he should have been able to react, but she stopped in such a stupid manner & place, almost makes you think she knew he was there!
Realman - "[u]assuming plenty of brake power[/u]" - which on gravel we have - you skid or go over the bars before you run out of brake power / get fade do you not? single stiop from realistic speeds.
Grum - I agree its an assumption but is it unrealistic - is friction not directly proportional to the weight per unit area?
I love STW - video of an idiot mashing into the back of another rider, the other rider completely overreacting and going psycho... and you're discussing physics. 😀
TJ you are forgetting that the friction between the brake pads and the rotor has nothing to do with the weight of the rider.
Why don't you just go out and test it if you really don't understand. Get a big heavy bag of bricks, try stopping with and without from the same speed.
S'funny how there're so many riders on here but, rather than quoting trail etiquette, comparisons to motorway driving have been drawn. What's that all about? Using your bike to clobber someone is way out of order.
Realman - I kno0w that - its not the limiting factor tho is it?
grip and going OTB are the limiting factors - or else the tandem would take twice as long to stop as a solo
Think about it.
Think about it.
😆
That's the funniest thing I've seen all week!
To be fair that was a super gnarrrrly tree root there
jam bo - Member
somewhere online there is a video of sharki riding into the back of me after I punctured and he realised a bit late except he is swearing about hitting his balls on the stem and I'm laughing at him.maybe I should have thrown my bike at him.
What i found was, using a compact camera with a wide angled lens, zipped tied to my lid, mean i needed to be very close to the rider in front, in this case 'pinch flat jambo', as well as not being able to see where the hell i was riding, i was blissfully unaware that he was clamping is saint brakes to come to a very abrupt halt. My delayed braking meant an even more abrupt coming to a halt using an embankment as an assist.
Much laugher and wincing meant any bike hurling or abuse never happened.
[url] http://www.youtube.com/user/sharki1971#p/u/11/nQhFeRYYL9Y [/url]
Surely when stopping on the road grip is also the limiting factor. A truck travelling at 70mph could easily lock its wheels, and a hatchback travelling at 70mph could easily lock its wheels too.
Therefore are you saying that they should both have the same stopping distance?
poppa, using TJs logic, I guess a HGV should stop a lot quicker then a hatchback as its got more tyres as well as more weight.
Sadly an all too common incident when a mincer gets out of depth.
At the point of the bike throwing stage I would have probably laughed and just ridden off for fear of really going to town on her.
Realman - try going back and reading what I wrote. You have missed the point.
the tandem stops in the same distance as a solo or less - same tyres twice the weight - so twice the momentum to stop but increased( twice???) as much grip
It does not take twice as long to stop
Your truck analogy = a truck weighs 40 times a car - it does not take 40 times as long to stop.
it looks like a viral promoting the latest in the Halo series, it is isn't it?
I see your argument TJ and I thought you had a point but then as per poppas argument HGV vs car on tarmac, doesn't take 40 times as long to stop but your theory is it should stop quicker due to more mass pushing down on the wheels. Interesting tho, I think a very overbraked bike, a long gravel section plus a rucksack full of bricks is called for.
(no brain cells or physics equations were harmed during the production of my post)
it looks like a viral promoting the latest in the Halo series, it is isn't it?
Thank you! Just after she throws the bike, and she's in that really aggressive about to pounce stance, it really reminded me of something. Halo.. Can someone photoshop one of those alien swords into her hand? That would be awesome.
a truck weighs 40 times a car - it does not take 40 times as long to stop.
I never said it would take 40 times as long, it would just take longer. Same on a bike.
the tandem stops in the same distance as a solo or less
From experience or are you just making this up?
Just to add fuel to the fire...
Arguments in favour of TJ here:
http://www.bikersoracle.com/vfr/forum/showthread.php?t=95537
From experience
so then - If yo think a heavier bike / rider takes longer why?
It is not due to running out of power in the brakes - imagine yo have v2s with vented discs and we are talking single stop from 20 mph.
After some searching, this seems like quite a hot topic, whether weight affects stopping distance. I can't find any definitive answer.
From real life experience, I would have to say the heavier you are, the longer it will take you to stop.
Shit, she can chuck some heavy stuff about, thats a 40lb sx trail shes lobbing like a soggy tampon with PMT written allll over it.
was also my first assumption* but as I said TJ may have a point, who's going to be first to get the bag of bricks and a tape measure out?From real life experience, I would have to say the heavier you are, the longer it will take you to stop
*Assuming you have adequate brakes for level of grip, with plenty of grip more mass will need better brakes obviously.
