The Effect Of Vehicle Weight On Stopping Distance

Topic 30077 | Page 4

Page 4 of 4 Previous Page Go To Page:
Matt M.'s Comment
member avatar

My personal experience says an empty trailer stops sooner. I have locked up the brakes on a fully loaded trailer at 55 mph (construction zone where they had trucks run the left lane closer to the construction, dump truck whipped right out in front of me at 5 mph). I've never locked em on an empty trailer, but I have braked hard enough to make the trailer skip as some folks have pointed out. The empty definitely stopped sooner.

The formulas for braking distance referenced here make mass a wash (essentially they set the kinetic energy formula equal to the work done by braking formula and since both formulas contain mass they wind up cancelling each other out). What they don't account for is that the braking systems in use cannot supply enough force to match static frictional force.

Thus a formula 1 car stops faster than an escalade, which stops faster than a semi, which stops faster than a train.

That said I always want to be heavy in inclement weather.

Robert B. (The Dragon) ye's Comment
member avatar

I’ll be curious to see the outcome of Errol’s test and prefer a scientific outcome over assumption as many do but I do want to point out a huge flaw in the comparisons some are making on race cars vs passenger vehicles and semi trucks. You can’t even make those comparisons simply because of the factors involved. A race car uses much larger braking surfaces, has a massive contact patch with the road surface in comparison utilizing heat and friction, aerodynamics and downforce as well as special compounds in the tires. If an engineer worked out the math and equipped a large suv identical in every way to the tech involved in a formula 1 or Indy car, the results could be matched. The same would go for a semi but you would see much larger braking surfaces, modified tire compounds to maximize grip etc. The reason a race car decelerates isn’t specifically based on weight alone.

HOS:

Hours Of Service

HOS refers to the logbook hours of service regulations.
Errol V.'s Comment
member avatar

As Robert Dragon says, you can't compare trains, semis and motor scooters' stopping powers. They have different requirements and systems.

The original question, whether a loaded truck or an empty truck stops quicker is based on the truck, tires, brakes, road, even the driver, and all other conditions save freight weight being same.

Soon I might have to get a pickup load of gravel for my place. If I do, I'll do this experiment with my pickup (Dodge RAM 2500 with a Cummins 5.9 doing the honors).

Matt M.'s Comment
member avatar

NHTSA Test (pdf)

Here's an actual test of different types of brakes on a couple of class 8 tractors in two configurations. They are tested at Light Load Vehicle Weight vs Gross Vehicle Weight Rating. LLVW was tested bobtail and GVWR was tested using an unbraked trailer.

The LLVW stopping distances were all considerably shorter than the GVWR (check page 8 for LLVW stopping distances and page 11 for GVWR stopping distances).

The peterbilt took 38% longer to stop at GVWR and the Volvo took 25% longer to stop when tested with s-cam drum brakes than at LLVW.

Maybe the handbook was written before ABS was prevalent?

Bobtail:

"Bobtailing" means you are driving a tractor without a trailer attached.

GVWR:

Gross Vehicle Weight Rating

GVWR is the maximum operating weight of a vehicle as specified by the manufacturer, minus any trailers.

Matt M.'s Comment
member avatar

Https://www.nhtsa.gov/document/class-8-truck-tractor-braking-performance-improvement-study-report-1-straight-line-stopping

For some reason hyperlink above isn't working for me so that's the address of the study. Sorry I'm not good with computers, that's why I drive a truck!

Errol V.'s Comment
member avatar

Matt reports on the DOT/NHTSA test:

They are tested at Light Load Vehicle Weight vs Gross Vehicle Weight Rating. LLVW was tested bobtail and GVWR was tested using an unbraked trailer.

This is true. The study was about different truck braking systems (conclusion: disk brakes on steer and drive axles are way better than S-cam or any mix of them.) This did include the "loaded" and "unloaded" braking on two different power units (Pete and Volvo). The unloaded test was bobtail, and the "loaded" version - adding an unbraked trailer weighing 4,500-lb.

Guess what? the loaded test took longer to stop, both with S-cam and disk brakes!

STOPPING DISTANCES

Brake System   Unloaded   Loaded
S-Cam 221 ft. 291 ft.
Disk 184 ft. 232 ft.

The test trailer was simply added to add weight for the test (only 4,500 lbs - hardly a load for an 18 wheeler), and the trailer braking system was not used.

It looks like the original idea ("Empty trucks require greater stopping distances") may be incorrect.*

*The asterisk: This test was for braking power, not stopping power. That test would need the same truck, trailer and road conditions to compare the loaded stopping distance and unloaded. But I'll shut up now. I still want to run a better real-life test of my own. Any takers?

Note to Matt:

For some reason hyperlink above isn't working for me so that's the address of the study.

The easiest way to enter complicated URL addresses here is to fill the "Link" form address with "www.google.com", and press "Submit". Then in your text box paste your complicated URL in where the www.google.com is:

< a href="www.google.com">Test link
Here: > > > /\ /\ /\

Bobtail:

"Bobtailing" means you are driving a tractor without a trailer attached.

DOT:

Department Of Transportation

A department of the federal executive branch responsible for the national highways and for railroad and airline safety. It also manages Amtrak, the national railroad system, and the Coast Guard.

State and Federal DOT Officers are responsible for commercial vehicle enforcement. "The truck police" you could call them.

GVWR:

Gross Vehicle Weight Rating

GVWR is the maximum operating weight of a vehicle as specified by the manufacturer, minus any trailers.

BMI:

Body mass index (BMI)

BMI is a formula that uses weight and height to estimate body fat. For most people, BMI provides a reasonable estimate of body fat. The BMI's biggest weakness is that it doesn't consider individual factors such as bone or muscle mass. BMI may:

  • Underestimate body fat for older adults or other people with low muscle mass
  • Overestimate body fat for people who are very muscular and physically fit

It's quite common, especially for men, to fall into the "overweight" category if you happen to be stronger than average. If you're pretty strong but in good shape then pay no attention.

Matt M.'s Comment
member avatar

"The test trailer was simply added to add weight for the test (only 4,500 lbs - hardly a load for an 18 wheeler), and the trailer braking system was not used."

They were tested at GVWR plus the 4500 lb axle weight of the unbraked trailer. GVWR happened to be 50,000 lbs on both of the tractors in the study.

GVWR:

Gross Vehicle Weight Rating

GVWR is the maximum operating weight of a vehicle as specified by the manufacturer, minus any trailers.

Page 4 of 4 Previous Page Go To Page:

New Reply:

New! Check out our help videos for a better understanding of our forum features

Bold
Italic
Underline
Quote
Photo
Link
Smiley
Links On TruckingTruth


example: TruckingTruth Homepage



example: https://www.truckingtruth.com
Submit
Cancel
Upload New Photo
Please enter a caption of one sentence or less:

Click on any of the buttons below to insert a link to that section of TruckingTruth:

Getting Started In Trucking High Road Training Program Company-Sponsored Training Programs Apply For Company-Sponsored Training Truck Driver's Career Guide Choosing A School Choosing A Company Truck Driving Schools Truck Driving Jobs Apply For Truck Driving Jobs DOT Physical Drug Testing Items To Pack Pre-Hire Letters CDL Practice Tests Trucking Company Reviews Brett's Book Leasing A Truck Pre-Trip Inspection Learn The Logbook Rules Sleep Apnea
Done
Done

0 characters so far - 5,500 maximum allowed.
Submit Preview

Preview:

Submit
Cancel

This topic has the following tags:

High Road Training Program Tips For Braking
Click on any of the buttons above to view topics with that tag, or you can view a list of all forum tags here.

Join Us!

We have an awesome set of tools that will help you understand the trucking industry and prepare for a great start to your trucking career. Not only that, but everything we offer here at TruckingTruth is 100% free - no strings attached! Sign up now and get instant access to our member's section:
High Road Training Program Logo
  • The High Road Training Program
  • The High Road Article Series
  • The Friendliest Trucker's Forum Ever!
  • Email Updates When New Articles Are Posted

Apply For Paid CDL Training Through TruckingTruth

Did you know you can fill out one quick form here on TruckingTruth and apply to several companies at once for paid CDL training? Seriously! The application only takes one minute. You will speak with recruiters today. There is no obligation whatsoever. Learn more and apply here:

Apply For Paid CDL Training

About Us

TruckingTruth was founded by Brett Aquila (that's me!), a 15 year truck driving veteran, in January 2007. After 15 years on the road I wanted to help people understand the trucking industry and everything that came with the career and lifestyle of an over the road trucker. We'll help you make the right choices and prepare for a great start to your trucking career.

Read More

Becoming A Truck Driver

Becoming A Truck Driver is a dream we've all pondered at some point in our lives. We've all wondered if the adventure and challenges of life on the open road would suit us better than the ordinary day to day lives we've always known. At TruckingTruth we'll help you decide if trucking is right for you and help you get your career off to a great start.

Learn More