Post by Steve on Feb 9, 2010 13:48:15 GMT 10
This was first published in 2000, hope you all get something out of it. It was from the ShadowRiders.org Tech page on
//www.shadowriders.org/index.html
Worth a gander around
From: Honda Sabre and Magna Motorcycle Owners
[mailto:SABMAG@MITVMA.MIT.EDU]On Behalf Of Phil Ross
Sent: Tuesday, July 18, 2000 4:45 PM
To: SABMAG@MITVMA.MIT.EDU
Subject: Re: Maggot sightings at WIMC; Mid-O races (long) (fwd)
OK, question time. My feeling is that a stoppie really isn't maximum deceleration--or is it? Wouldn't a front brake at 3/4 lockup (vs impending lockup, which is going to put the tail in the air) together with the rear at impending lockup (thus larger contact patch) give you a quicker stop than a stoppie? But yet, if you can loft the tail of a VFR with linked brakes ... would ABS work any better? Hmmm.
--
Cheers--Phil
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Phil Ross pwr(a)infinet.com Columbus, OH
AMA#637232 COP#0016 IBA SS1K, BBG, 50CC
1985 VF1100S V65 Sabre, "The Couch Rocket"
==============================================
ANSWER:
From: Honda Sabre and Magna Motorcycle Owners
[mailto:SABMAG@MITVMA.MIT.EDU] On Behalf Of Marc W. Mauss
Sent: Tuesday, July 18, 2000 4:49 PM
To: SABMAG@MITVMA.MIT.EDU
Subject: Re: Maggot sightings at WIMC; Mid-O races (long) (fwd)
The answer is: You're right. I sent the following off-list the other day. It explains how and why you're right. BTW, size and number of contact areas have NOTHING to do with it.
Let's assume that the total weight of bike and rider is 700 lbs.
Let's assume an initial front/rear weight distribution of 50/50.
Let's assume a coeficient of friction of 1.00 (just to make the numbers simple) and that both tires have the same coeficient of friction.
In this situation, before applying brakes, each wheel has 350 lbs of downward pressure (50% of 700), and therefore (with c of f = 1) will maintain traction with up to 350 lbs of braking force. Each wheel will slip on the road surface (lock up) if MORE THAN 350 lbs of brakeing force is applied.
When you start braking, weight is transferred to the front wheel.
You soon reach the point of 60/40 weight distribution - 420 lbs on the front and 280 lbs on the rear. At this point, (again with a C of F = 1) the front wheel can sustain 420 lbs of braking force before locking up, while the rear can only handle 280 lbs of braking force.
You then reach a point of 80/20 weight distribution, with the front wheel bearing 560 lbs and the rear bearing only 140 lbs. At this point, the rear wheel can only take 140 lbs of braking force before locking, while the front wheel can take 580 lbs of braking force.
By the time you reach a weight transfer of 100/0 (all the weight on the front wheel, as in a stopie), the rear wheel will lock with any braking at all, while the front can take 700 lbs of braking force before locking. At all times, the sum of rear wheel breaking and front wheel braking is 700 lbs (using the 700 lb weight and a C of F = 1), but as more weight transfers to the front, the front wheel gets more traction, while the rear wheel gets less.
If you're trying to stop in the shortest possible distance, you want that 700 lbs of braking force applied until you stop. When you start braking, the front can only provide 350 lbs, increasing to 700 by the time the rear wheel lifts. But up until that point, you're "wasting" available braking traction by not using the rear brake.
Merlin
(formerly Marc W. Mauss)
RRR01
Honorary CSA Consul to Cyberspace
MSF Instructor
Coram (Long Island), NY
//www.shadowriders.org/index.html
Worth a gander around
From: Honda Sabre and Magna Motorcycle Owners
[mailto:SABMAG@MITVMA.MIT.EDU]On Behalf Of Phil Ross
Sent: Tuesday, July 18, 2000 4:45 PM
To: SABMAG@MITVMA.MIT.EDU
Subject: Re: Maggot sightings at WIMC; Mid-O races (long) (fwd)
OK, question time. My feeling is that a stoppie really isn't maximum deceleration--or is it? Wouldn't a front brake at 3/4 lockup (vs impending lockup, which is going to put the tail in the air) together with the rear at impending lockup (thus larger contact patch) give you a quicker stop than a stoppie? But yet, if you can loft the tail of a VFR with linked brakes ... would ABS work any better? Hmmm.
--
Cheers--Phil
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Phil Ross pwr(a)infinet.com Columbus, OH
AMA#637232 COP#0016 IBA SS1K, BBG, 50CC
1985 VF1100S V65 Sabre, "The Couch Rocket"
==============================================
ANSWER:
From: Honda Sabre and Magna Motorcycle Owners
[mailto:SABMAG@MITVMA.MIT.EDU] On Behalf Of Marc W. Mauss
Sent: Tuesday, July 18, 2000 4:49 PM
To: SABMAG@MITVMA.MIT.EDU
Subject: Re: Maggot sightings at WIMC; Mid-O races (long) (fwd)
The answer is: You're right. I sent the following off-list the other day. It explains how and why you're right. BTW, size and number of contact areas have NOTHING to do with it.
Let's assume that the total weight of bike and rider is 700 lbs.
Let's assume an initial front/rear weight distribution of 50/50.
Let's assume a coeficient of friction of 1.00 (just to make the numbers simple) and that both tires have the same coeficient of friction.
In this situation, before applying brakes, each wheel has 350 lbs of downward pressure (50% of 700), and therefore (with c of f = 1) will maintain traction with up to 350 lbs of braking force. Each wheel will slip on the road surface (lock up) if MORE THAN 350 lbs of brakeing force is applied.
When you start braking, weight is transferred to the front wheel.
You soon reach the point of 60/40 weight distribution - 420 lbs on the front and 280 lbs on the rear. At this point, (again with a C of F = 1) the front wheel can sustain 420 lbs of braking force before locking up, while the rear can only handle 280 lbs of braking force.
You then reach a point of 80/20 weight distribution, with the front wheel bearing 560 lbs and the rear bearing only 140 lbs. At this point, the rear wheel can only take 140 lbs of braking force before locking, while the front wheel can take 580 lbs of braking force.
By the time you reach a weight transfer of 100/0 (all the weight on the front wheel, as in a stopie), the rear wheel will lock with any braking at all, while the front can take 700 lbs of braking force before locking. At all times, the sum of rear wheel breaking and front wheel braking is 700 lbs (using the 700 lb weight and a C of F = 1), but as more weight transfers to the front, the front wheel gets more traction, while the rear wheel gets less.
If you're trying to stop in the shortest possible distance, you want that 700 lbs of braking force applied until you stop. When you start braking, the front can only provide 350 lbs, increasing to 700 by the time the rear wheel lifts. But up until that point, you're "wasting" available braking traction by not using the rear brake.
Merlin
(formerly Marc W. Mauss)
RRR01
Honorary CSA Consul to Cyberspace
MSF Instructor
Coram (Long Island), NY