So,...can you "perform?"

[ANDYVH]

Braking wise I mean.

I recently found a braking distance chart for motorcycles, on a lawyer website no less. That listed a “standard” of 134 feet to stop from a speed of 60 mph for all bikes and riders. I thought that seemed to be a very optimistic, unreal short distance so I decided to test it myself. I mean, a 60 mph stop in 134 feet calculates to an .89 G-force stopping effort, as an “average” value for motorcyclists. I thought, maybe, so lets see.

Here are my results from my somewhat accurate braking test session. I set up a 150 foot braking lane out on a rural road, running east/west, and measured with a long tape, I marked it off with paver bricks. The road was smooth, clean, grippy aged asphalt. After setting up my markers 150' apart, I paced off the distance to use as a reference from the bike to the marker when I stopped. The 150' distance took 53 strides (I have a 30” inseam), so that equaled 2.85' per stride. After each stop, I'd dismount and walk the number of strides from the leading edge of the front tire to the ending brake marker. Only two of the 12 stops were slightly longer than the 150' braking lane.

I got my bike up to an indicated 65 mph, which I know on my bike is just slightly over 60 mph, and made sure the speed was steady before I got to the braking marker. At the marker I applied both brakes as best I could. I noted when the ABS activated, which was probably 75% of the 12 stops. Each stop left a very definite stripe from the front tire on the road for the entire stopping length. But no lockup and sliding. I also felt the bike definitely squirmed around a bit but also self corrected. Here we go:

TEST DIRECTION DISTANCE SPEED (approx) NOTES
1 East 165.5 60 1st test,establish my marker start point
2 West 140.0 60
3 East 142.9 60
4 West 151.4 60
5 East 152.1 60 ABS cycling of the rear brake, over braking on rear
6 West 134.4 55 Speed was definitely lower at start of braking zone
7 East 154.2 60
8 West 150.0 60
9 East 141.5 60
10 West 141.5 60
11 East 157.7 60 Attempted stop with no ABS actuation
12 West 137.0 60
AVG 147.3 My speed was only estimated as read on speedometer

The tire marks on the pavement also helped me determine I was applying the brakes 12' to 21' before the brake start marker. My initial reaction after stopping the bike well short of the 150' marker was I thought I was doing a great job of beating the average. Ha! I adjusted my noted stop distance by adding the early application distance to the ending position. So even though this was all estimated, the repeated efforts and variables are minimal enough to determine some consistency. Some other notes, my 94 R1100RS has ABS, and the Telelever front suspension with designed in limited squat during braking. No matter how hard I apply the brakes the steering geometry remains consistent which helps to control the bike. This minimizes tracking errors by the rider and bike because the steering geometry does not get "steeper" during braking liek with a normal front fork and excessive fornt end dive. I ride my old 76 BMW to get a sense of front end dive! By the end of the testing I could sense a slight headache due to the G-loading of the stops.

The final points are unless you test and practice your braking, you'll never know what you can safely achieve. So, for my average of 147' at 60 mph, if I add one second reaction/application time (88' for 60 mph) to a real world stop, my best average TOTAL stopping distance for 60 mph stops would be 235 feet!! Eye opening to say the least! That also means that at night my headlight had better reach out at least 235' or I should slow down.

 

[pffog]

Pretty consistent results and good practice for you for sure. What most forget it the biggest factor in stopping distance is tires and road surface, not brakes, after all if is the friction of the tire against the pavement that does the stopping.


My favorite way to practice threshold braking is to pick an object, sign, pavement break, etc. ahead, then wait until the last moment I feel I can hit the brakes to stop by that mark. I think it gives a better visual picture of what you and the bike are capable of.

 

[ANDYVH]

True and thanks for the comments. What is hard to see in this picture is the paver brick on the side of the road that indicates the end of the 150' braking lane. Some other things too; in this controlled case, I knew where the braking started everytime. I knew the traction was good. I knew the road had little crown or undulations, bumps, cracks, etc. All that made it much easier to be consistent. That was my 1st goal, to see if my braking was consistent and repeatable. More of a test session than real world, to see how I did, and could I do it over and over.

Now, although things like my speed at the test start, the exact measured start of braking, the exact measured distance, are all variable in this test, the results do show some consistency so in that I feel it does indicate the performance with a bit of accuracy.

I have seen data on the web stating a braking standard for motorcycles at 60mph as 134 feet. That is very optimistic and aggressive braking that I really, really doubt most riders could attain given the wide breadth of rider skill, bike setup, tires, brake systems. Plus that distance is ONLY the actual stopped distance. It does not include any measure for reaction time and application time. 60 moh is 88 feet persecond. So allowing for one second of reaction and application to a real world braking situation, means the REAL distance, at best is 88 + 134 = 222 ft. THAT is a HUGE difference.

Check out the width of the scuffing on my front tire from deformation during braking. The contact patch width is much wider (40 psi inflated pressure), and you can sense the "sliding" aspect of the tire shown by the scuffing. Granted, with ABS, the tires do not slide enough to loose traction, but ABS systems DO work on the principle of predetermined tire "slip" to achieve maximum braking efficiency while maintaining stability. ABS systems rely on a certain amount of tire deformation during the stop to increase the size of the contact patch. During my stops I could definitely feel the front end of the bike squirm around during the stop, while it self corrected to maintain balance. Toward the ends of some stops when the ABS was definitely cycling the loading at the grips is high.

 

[Visian]

this is really interesting.

you should write up a story for the BMW ON.

ian

 

[ANDYVH]

Hadn't thought of that. Maybe I'll do some repeats of this test and see if my results are consistent or improving. Then based on that I may have something to write up.

I was published in the April 07 issue for a brakes service article I wrote. Been a while since then. But this is one subject I feel strongly about and I have seen as many BMW riders with marginal performance braking skills as on other brands. Moreso theres days it seems. I mean, years ago, how many helmetless BMW riders did you ever see. Now? Not as bad as the HD riders but certainly a LOT more of them.

 

[R184]

Any lawyer who used the 134 feet average for M/C stopping as an absolute on that web site won't last for very long in an actual court battle. A court certified traffic expert wouldn't have much trouble debunking the figure given. The test skids you did showed the "Lawyers" were wrong. Not to mention you prob. had a great time conducting your own experiment too. Great job.

There are actual certified traffic investigation classes that teach how to determine a vehicles minimum speed from a locked wheel skid. Even in the ABS world, these classes are a useful tool in traffic investigation. While ABS has changed things quite a lot, there are other factors which come in to play and can greatly alter the stopping distance.

Factors that come into play are;
1. Tire type make. pressure & rating. A non-DOT knobby behaves and skids a lot different that a V rated Sport tire.
2. Vehicle (in this case motorcycle) type and weight.
3. Type of surface the stop was made on. Stopping distance on brushed cement will be different that on old asphalt.
4. Temperature, to include relative humidity.
5. Road conditions, i.e. wet, dry, etc.

Google Skid Mark Analysis or Speed From Skid marks to get some more information.

 

[Visian]

Hadn't thought of that. Maybe I'll do some repeats of this test and see if my results are consistent or improving. Then based on that I may have something to write up.

go for it.... you've got a great idea here and i think it deserves a wider audience.

and you're right, i also see a lot of weak braking skills, this article could motivate people to get some training.

ian

 

[ANDYVH]

To the reply about skid mark analysis, it seems unfortunate that much of the web responses go to lawyer sites. Perhaps skid marks and lawyers have something in common?

Anywho, I had to paste in this from a lawyer website about motorcycle skids: "Motorcycle accidents are different from car accidents. Most bike riders have a natural tendency to hit the rear brake, largely due to the fact that a sudden application of the front brake can cause a motorcycle to flip. Unfortunately, most motorcycles are designed such that only about 40 percent of the braking power is in the rear brakes.

Largely due to a motorcycle flipping due to application of the front brake? Where do they get this stuff? Now, perhaps, on a sportbike if the knob at the grips gets the bike into a stoppie he may flip forward. But really, going over the handlebar is most likely caused by sudden overbraking of the front tire (before weight transfer is initiated) such that the front end washes out, then perhaps the rider tumbles over the bike. But NOT from actually flipping the bike, and certainly not in the case of any Harley or large touring bike. Too bad that what the jury knows is only what the lawyer tells them.

I found this interesting program to determine the braking distance for a motorcycle using more parameters that determine the actual stop distance like the road surface (friction of coefficient), wheelbase, center of gravity, etc: http://www.msgroup.org/forums/mtt/images/StoppingDistance.xls