Motorycle Braking Distance

[Z_Fanatic]

Do motorcycles generally stop at much shorter distance than most cars? I figure it depends on which motorcycle and which car... although in motorycycles, the rider can cut off the momentum quicker than a driver hitting the brake in a car or downshift (manual). But let say cruising on 60 mph, and suddenly had to stop where the rider didn't have much time but to disengage the clutch and apply the brakes, compared to a car, with same velocity stomping its brakes, which would require more distance to come to a full stop? Just wondering what is the general consensus for sportbikes vs car braking power ratio? Thanks.

[Auto_newb]

Bikes would stop faster, they are lighter and the contact patches are more concentrated. If the biker were to use full power and squeeze the handle as hard as he can, The rider would probably fly over the handlebars.

[Z_Fanatic]

Yeah, causing brake-locks. The front brake power is immense, that's why endos are possible. But a friend and I got into argument about it, he's a a year or year and half old rider in a '03 F4i, and he claimed the stopping distance is more, given if you don't downshift to neutral first.

Hehe, locking which brakes is potentially less dangerous? lol. Front will either catapult you or send the rider to a spilled power slide. And locking the rear can cause also cause spill or highside during lean.

[speediva]

Locking the rear is more dangerous.... if you lock the rear and you let back off before you stop, you're damn near guaranteed a high side. You should just keep the rear locked if you ever do it... it is hard to keep your balance (I've done it) but it's doable. Locking the front, you just let off and reapply brake (carefully, of course). Since your steering comes from the front, you can control where it goes when it's locked.

A bike can stop more quickly on a straight, but a car could stop faster in a turn. Bikes don't stop well in turns, thus the reason you have to stand the bike back up to vertical before applying brakes.

[Z_Fanatic]

thanks for the tip Saturn, how do you umm practice these timings and reactions? intentionally lock the bike in a closed circuit? lol, i hope never wilingly in the streets. a friend of mine told me after locking the brake, release it asap (within 1-2 sec) and apply it again, but most people panic since never done it before. i hear it's even more difficult to recover if the rear brake is locked during a turn.

[speediva]

Basically, the only way you'd ever get "used" to it is to practice it like you said... They used to teach you how to lock/recover in the MSF, but it became a liability issue. I personally hope to not have it happen again. It scares the crap out of you... especially in traffic.

[aussieidiot]

actually in tests there bugger all in it. between a wrx and an R1 there could be around 1/2 a meter

[Z_Fanatic]

probably because the WRX sti is one mean stock rally ricer? and R1 is heavier compared to below 1 liter bikes? i suppose it really depends.

[aussieidiot]

In the test i was thinking of, they pitted a WRX in the hands of a local pommy rally champ and an R1 ridden by a SBK rider. The test was about normal 'city' hooning. The WRX beat the bike at some things and vice versa. Ultimately the WRX could stop as quick due to ABS and other electronic help. The final result was even over all tests but the WRX had gone through a set of tyres where as the bike had not.

In another test had a GSXR 1000 against a 4WD twin turbo 4 cyl pommy wierd thing and it came back that the bike stopped in a faster time but in a slightly longer distance. My basic physics and relationships of velocity, time and distance says this can't be done but hey, I'm no scientist.

[aussieidiot]

i forgot to add. The brakes on my 954 are to good for general use. if i need to use the front brakes i must be flying. generally I only need to down shift and rear brake with slight front if required but if i did use the fronts to their full potential chances are the guy behind would hit me.
as for locking the rear as Tangie said its dangerous but can be fun if you pull it off

[Z_Fanatic]

Originally Posted by aussieidiot

In another test had a GSXR 1000 against a 4WD twin turbo 4 cyl pommy wierd thing and it came back that the bike stopped in a faster time but in a slightly longer distance. My basic physics and relationships of velocity, time and distance says this can't be done but hey, I'm no scientist.

I could be completely off, but could it be because the Gixxer was travelling at faster velocity than the twin turbo? Perhaps in that sense, Gixxer stopped quicker relative to whatever velocity twin turbo was in, but required more distance due to higher speed. That's the only I can figure it would make sense given the info. Plus there could be many other affecting variables - weight of the vehicles, differences in the speed (even if slight), torque, shifting, etc.

[Beast22k]

In terms of the gsx stopping faster yet with a longer distance is probably because they were going at the same speed when they went to stop but the gsx's brakes would be to powerfull to put at full force so the brakes were applied slowly causing them to be in the higher speed range for a longer period of time and gradually applying more brake causing them to slow down extreamely fast once the brake could be used to a higher potential... on the otherhand the 4wd had to have been some sort of car so they could apply full brakes without worrying about flying over the front of the vehicle thus allowing them to get into the lower speed range sooner yet slowing down at a constant rate that took more time while the bike slowed at an increasing rate that slowed down faster but kept them in a higher speed range longer. I tried to say that as clearly as possible... if you don't quite understand and want me to explain better I will... .

Later

[Z_Fanatic]

nope, got it! thanks.

well Blayne said it sort of violated the laws of physics... as I understand now, it didn't; it was a consequence of the rider and mechanical application; i.e. deterrant variables from going quasi-full kinetic to maintain consistency. and I had no idea whether they were exact same speed or off by a little.

Another words, my guess is a bike in lower speed stop quicker than cars, where as higher speeds take a bit longer. but only if the brake is applied closer to full potential.

[speediva]

Originally Posted by aussieidiot

i forgot to add. The brakes on my 954 are to good for general use. if i need to use the front brakes i must be flying. generally I only need to down shift and rear brake with slight front if required but if i did use the fronts to their full potential chances are the guy behind would hit me.
as for locking the rear as Tangie said its dangerous but can be fun if you pull it off

Aussie, you do realize that 75-80% of your stopping power is in the FRONT brakes, right? I almost NEVER use my rear, unless I am "emergency braking" and need a little extra stopping power.

[aussieidiot]

two parts to this
1. To tangie.
I do realise that the majority of stopping power is in the front but what I tried to say was that I don't tend to ride at speeds requiring the full use of the fronts. When in built up areas I don't feel the need to go more than 20k's over limit just in case (45 mph in a 30) and the fronts are so powerful that only slight pressure is all thats required. Even on the track I never used the full potential because it felt as if I'd lose control.
That said I know that I can use it when needed with confidence because I still practice emergency stops every now and then. usually with full hard fronts emergency stop the back is in the air slightly.oops : )

2. To Beast and Z

ok I'm not the best at physics (passed higher school cert and 1st year uni) but if both parties are travelling at the same speed (velocity is only speed in a direction). both apply brakes at the same time but at a variable due to braking abilities. Wouldn't it be that the shorter the distance equal a shorter time. Braking variables aside due to abs and driver ability and all that, in my mind the shorter the distance the shorter the time. I do get what you are saying about the speed range. We have road safety adverts saying half your speed is taken off in the last 5m (16 feet) therfore a car can decelerate evenly to a stop whereas a bike takes most of its speed of later but at a much higher deceleration to be "quicker"