Ch 11-14 Flashcards
1
Q
Hydroplaning
A
- rain-soaked roads can induce a hydroplane, losing all steering and braking control
2
Q
Contact patch
A
- where the rubber meets the road
- properly inflated tire: flat contact patch
- under inflated: will start to cup, less rubber touching = smaller contact patch, can lead to blowout
- overinflated: U shape, wear rings around center of tire, stiff ride
3
Q
Tire tread
A
- bald tires will have better traction on dry roads than treaded tires, more rubber touching the road
- tread is designed to channel and push rain, slush, and snow out of the way
- when driving too fast in bad weather, not enough time to push the water out of the way, wedge of water build, eventually being on top of it, causing hydroplane
4
Q
3 factors of the speed at which a vehicle will hydroplane:
A
Tire Tread Depth
- NFPA 1911 requires
1. front tread = no less than 4/32” at any 2 adjacent major grooves
2. non-steering axle: no less than 2/32”
- Studies show less than 5/32” will have significantly longer stopping distance
- check tire tread regularly
Air Pressure
- underinflated: not enough pressure to properly push water out of the way
- lower threshold for hydroplane speed
Depth of Water
- Deep water can overwhelm the tread cause tire to float and rise on top
- avoid standing puddles/ deep pockets of water
- follow other vehicles tracks, have already swept some water
5
Q
Hydroplaning Speed Formula
A
Hydroplaning Speed =
(10.35)√Inflation Pressure
6
Q
Handling a hydroplane
A
- avoid slamming on brakes
- firm grip of the wheel, remove foot from accelerator, use as little steering as possible and allow vehicle to slow on its own
- if you have to apply the brakes:
1. w/ ABS: brake normally
2. w/o ABS: light/rapid presses, threshold braking
7
Q
Tire blow outs
A
- the rubber is not meant to bear the weight of the vehicle, the pressure is
- when underinflated, tire sidewalls will over-flex, generating more heat than the tire can handle, causing blowout
- if overweight, not enough pressure to properly support it, can cause blowout
- NFPA 1911 requires apparatus to be weighed yearly
8
Q
Proper tire pressure
A
- check tire pressure w/ calibrated pressure gauge on all tires (include inside dual tires)
- in tubeless tires, improper seal can cause air to escape
- small leaks from nails, screws, and other road hazards
- air can actually leak through rubber membrane at a rate of 1-2psi per month
- tire pressure printed on tire is NOT the recommended, its the MAX
- method for determining proper pressure: vehicle weighed to see how much each tire needs to support, then refer to the specific tire’s load and inflation chart
- measured based on COLD AIR PRESSURE, don’t check if driven in the last 3 hours
9
Q
Dual tires
A
- should differ by no more than 1/4” in diameter and 3/4’ in circumference
- same size and make
- kept at same pressure
- a 5psi difference can cause a 5/16 in difference in circumference
- recommend metal valve stem caps w/ strong rubber gasket
- NFPA1901 requires each tire to have a visual indicator or monitoring system that indicated pressure
10
Q
Handling a tire blowout
A
- result in 23,000 collisions w/ 535 fatalities
- usually caused by improper reaction
- NFPA 1451 states drivers must be trained in proper handling of a blowout
- natural reaction is to slam on the brakes and try to get over to side of road
- proper response: accelerate and keep vehicle in a straight line to regain forward momentum, then gently reduce speed
- if driven at governed speed, their will be no more room to accelerate
11
Q
Fatal truck crashes by a blowout can be divided into 3 scenarios:
A
- If front left blows, truck loses control to the left, veers into oncoming or adjacent traffic, and rolls immediately or after collision w/ another vehicle. 15/22 of the crashes involve multiple vehicles
- if front right blows, loses control to the right, veers off the road and rolls or collides into structure, or both. Typically single vehicle (10/13 of crashes)
- if any rear tire blows, typically, remains under control
12
Q
Life of a tire (years)
A
- overtime will begin to age and crack
- NFPA 1911 states max life shall be no longer than 7 years
- most tire manufactures recommend every 6-10 years
- can depend on climate, use and wear
- manufacture date printed on sidewall in a 4-digit code: 1st two: week of the year, 2nd two: year
13
Q
Information printed on sidewall of a tire
A
- P: passenger vehicles
- LT: light trucks
- Next 3 digits: width in mm
- Next 2 digits: aspect ratio, tires ratio of height to width (70 and lower indicate short sidewall for improved response and handling)
- R: radial ply construction has been the standard for 20 years
- Next 2 digits: wheel diameter in inches
- Next 2 or 3: load index
- M+S or M/S: some mud/snow capability
- US DOT Tire ID Number: begins with “DOT” indicates that tire meets all federal standards. Next 2 number are the plant code
- Last 4: week and year the tire was built
- Tire Ply Composition and Material Used: number of layers of rubber coated fabric. Could be steel, nylon, polyester, and others
- Max Load Rating
- Max Inflation Pressure
- UTQGS Info-Tread Wear Number: tire’s wear rate, higher the number, longer it lasts
- Traction Letter: ability to stop on wet pavement, high to low: AA, A, B, C
- Temperature Letter: resistance to heat, highest to lowest: A, B, C
14
Q
Snow tires
A
- M/S doesn’t mean it’ll handle well in deep snow
- different rubber compound, more pliable for cold weather
- recommended where temp is regularly below 45 degrees
- more aggressive tread pattern
15
Q
Impaired driving defined
A
- same legal limit in every state
- non-commercial: Blood alcohol concentration (BAC) greater than 0.08%
- commercial: weight over 26,001lbs, BAC greater than 0.04%
- considered to be a “per se” rule, means if driver’s over the limit, they can be criminally charged regardless of the circumstance
- general impairment: if it can be demonstrated that cause of the crash/unsafe driving was due to ingestion of alcohol, narcotics, or prescription meds, charges can still be made, regardless of BAC
- under 21 y/o, prohibited from driving w/ any BAC
refer to table in pics
