suicyclists again
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From: Brent P on 9 Jul 2008 22:04 On 2008-07-10, DanKMTB(a)gmail.com <DanKMTB(a)gmail.com> wrote: > Anyone else care to join us in this threshhold braking experiment? My > numbers will either prove my claim or show that I was mistaken, but it > would be nice to have other peoples data as well. Ok... I couldn't find a spot where I could get up to 30, do a full decel stop and then spend time measuring... so I did 25mph on residential roads. I did 4 runs. The first run I braked hard and kept the rear on the edge of lock. 36 of my size 13s. On the second run a woman in an SUV pulled out in front of me and stopped in my path with a deer in the headlights look. Needless to say I aborted. 3rd run the rear wheel locked and lifted I eased back and then found the threshold. 46 of my size 13s. Third run was really from 26mph and change. Again I locked the rear wheel but I think I kept it from actually lifting. 52 of my size 13s. So... this converts to 39 ft, 49.8 ft, and 56.3 ft respectfully.
From: Brent P on 9 Jul 2008 22:05 On 2008-07-10, Brent P <tetraethylleadREMOVETHIS(a)yahoo.com> wrote: > On 2008-07-10, DanKMTB(a)gmail.com <DanKMTB(a)gmail.com> wrote: > >> Anyone else care to join us in this threshhold braking experiment? My >> numbers will either prove my claim or show that I was mistaken, but it >> would be nice to have other peoples data as well. > > Ok... I couldn't find a spot where I could get up to 30, do a full decel > stop and then spend time measuring... so I did 25mph on residential > roads. I did 4 runs. > > The first run I braked hard and kept the rear on the edge of lock. 36 of > my size 13s. On the second run a woman in an SUV pulled out in front of > me and stopped in my path with a deer in the headlights look. Needless > to say I aborted. 3rd run the rear wheel locked and lifted I eased back > and then found the threshold. 46 of my size 13s. FOURTH run was really correction in caps. > from 26mph and change. Again I locked the rear wheel but I think I kept > it from actually lifting. 52 of my size 13s. > > So... this converts to 39 ft, 49.8 ft, and 56.3 ft respectfully. > >
From: Larrybud on 10 Jul 2008 13:32 >> > unless you're on a sandy,dirty,oily,or icy road,bikes can >> > stop in very short distances. Without tossing yourself over >> > the handlebars.... >> >> Um... bicycles take longer to stop than most cars from the same >> speed. > > Do you really think so? I can stop my bikes pretty darn quick. > In approximately one bike length if I don't mind tumbling over > the handlebars, but even without the tumble I can stop very > shortly. Bicycle stopping distance calc: http://www.exploratorium.edu/cycling/brakes2.html 25mph in 23ft using the default values. Average car stop about 100-130 feet. A Vette can probably stop in 40 feet. I suspect Brent real problem is that he was going to blow through the red light like I see most bicyclists do, and is pissed a vehicle caused him to stop.
From: Larrybud on 10 Jul 2008 13:33 "DanKMTB(a)gmail.com" <DanKMTB(a)gmail.com> wrote in news:c157c134-8158-44f7-9fd5-dc462835bff2(a)t54g2000hsg.googlegroups. com: > On Jul 9, 12:23 pm, Brent P <tetraethylleadREMOVET...(a)yahoo.com> > wrote: >> On 2008-07-09, Jim Yanik <jya...(a)abuse.gov> wrote: >> >> > unless you're on a sandy,dirty,oily,or icy road,bikes can >> > stop in very short distances. Without tossing yourself over >> > the handlebars.... >> >> Um... bicycles take longer to stop than most cars from the same >> speed. > > Do you really think so? I can stop my bikes pretty darn quick. > In approximately one bike length if I don't mind tumbling over > the handlebars, but even without the tumble I can stop very > shortly. All the weight back, but over the rear tire, and grab > the front brakes. Pull until rear wheel is airborne and > approaching flipover point, modulate as necessary. How long do > you figure it takes the average car to stop from 25mph? I'd bet > I could stop shorter on a bicycle. Very high performance cars > may give me a run for my money. > >> Basic physics of contact patch and swept braking area are in >> play. A road bicycle has very little of each. > > You forgot mass you're bringing to a stop. Since the bicycle > also has very little mass in motion, it needs much less of a > contact patch. CORRECTION! Sorry, my car distances were not for 25mph.
From: Matthew T. Russotto on 10 Jul 2008 16:00
In article <b1624b5b-3d52-4442-8e26-75288f24510a(a)34g2000hsh.googlegroups.com>, gpsman <gpsman(a)driversmail.com> wrote: >On Jul 9, 5:49 pm, Brent P <tetraethylleadREMOVET...(a)yahoo.com> wrote: >> Remember, I ride and drive. I know full well the limitations of the >> bicycle brakes. > >Except you don't know those limitations are yours. Do the physics, GPSTroll. -- There's no such thing as a free lunch, but certain accounting practices can result in a fully-depreciated one. |