Parking brake force
FTE Chapter Leader
Joined: Jan 2005
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From: Henderson, NV
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A lot of utility companies and municipalities have given up on the mechanical parking brakes (especially the ones like ours having such a small surface area that is the limitation of the drum in hat type).
Instead, they've retrofitted a Mico Line Lock. I've presented some visual details about several models of Mico line lock options that are specific to our vintage of Super Duty in a past thread... hang on a sec and I'll find it.
See this thread here: Parking Brake Upgrade
Still, I'm subscribing to your thread to see what you come up with as far as a new spring.
In roundabout answer to a part of your question, the FMVSS regs that require vehicle manufacturers to meet minimum standards for mechanically applied parking brakes are quoted and sub-linked below:
Title 49 - Transportation Subtitle B - Other Regulations Relating to Transportation
CHAPTER III - FEDERAL MOTOR CARRIER SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION
SUBCHAPTER B - FEDERAL MOTOR CARRIER SAFETY REGULATIONS
PART 393 - PARTS AND ACCESSORIES NECESSARY FOR SAFE OPERATION
Subpart C - Brakes
§ 393.41 Parking brake system.
§ 393.41 Parking brake system.
(a) Hydraulic-braked vehicles manufactured on or after September 2, 1983. Each truck and bus (other than a school bus) with a GVWR of 4,536 kg (10,000 pounds) or less which is subject to this part and school buses with a GVWR greater than 4,536 kg (10,000 pounds) shall be equipped with a parking brake system as required by FMVSS No. 571.105 (S5.2) in effect at the time of manufacture. The parking brake shall be capable of holding the vehicle or combination of vehicles stationary under any condition of loading in which it is found on a public road (free of ice and snow). Hydraulic-braked vehicles which were not subject to the parking brake requirements of FMVSS No. 571.105 (S5.2) must be equipped with a parking brake system that meets the requirements of paragraph (c) of this section.
(b) Air-braked power units manufactured on or after March 1, 1975, and air-braked trailers manufactured on or after January 1, 1975. Each air-braked bus, truck and truck tractor manufactured on and after March 1, 1975, and each air-braked trailer except an agricultural commodity trailer, converter dolly, heavy hauler trailer or pulpwood trailer, shall be equipped with a parking brake system as required by FMVSS No. 121 (S5.6) in effect at the time of manufacture. The parking brake shall be capable of holding the vehicle or combination of vehicles stationary under any condition of loading in which it is found on a public road (free of ice and snow). An agricultural commodity trailer, heavy hauler or pulpwood trailer shall carry sufficient chocking blocks to prevent movement when parked.
(c) Vehicles not subject to FMVSS Nos. 105 and 121 on the date of manufacture.
(1) Each singly driven motor vehicle not subject to parking brake requirements of FMVSS Nos. 105 or 121 at the time of manufacturer, and every combination of motor vehicles must be equipped with a parking brake system adequate to hold the vehicle or combination on any grade on which it is operated, under any condition of loading in which it is found on a public road (free of ice and snow).
(2) The parking brake system shall, at all times, be capable of being applied by either the driver's muscular effort or by spring action. If other energy is used to apply the parking brake, there must be an accumulation of that energy isolated from any common source and used exclusively for the operation of the parking brake.
Exception: This paragraph shall not be applicable to air-applied, mechanically-held parking brake systems which meet the parking brake requirements of FMVSS No. 121 (S5.6).(3) The parking brake system shall be held in the applied position by energy other than fluid pressure, air pressure, or electric energy. The parking brake system shall not be capable of being released unless adequate energy is available to immediately reapply the parking brake with the required effectiveness.
70 FR 48048, Aug. 15, 2005
CHAPTER III - FEDERAL MOTOR CARRIER SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION
SUBCHAPTER B - FEDERAL MOTOR CARRIER SAFETY REGULATIONS
PART 393 - PARTS AND ACCESSORIES NECESSARY FOR SAFE OPERATION
Subpart C - Brakes
§ 393.41 Parking brake system.
§ 393.41 Parking brake system.
(a) Hydraulic-braked vehicles manufactured on or after September 2, 1983. Each truck and bus (other than a school bus) with a GVWR of 4,536 kg (10,000 pounds) or less which is subject to this part and school buses with a GVWR greater than 4,536 kg (10,000 pounds) shall be equipped with a parking brake system as required by FMVSS No. 571.105 (S5.2) in effect at the time of manufacture. The parking brake shall be capable of holding the vehicle or combination of vehicles stationary under any condition of loading in which it is found on a public road (free of ice and snow). Hydraulic-braked vehicles which were not subject to the parking brake requirements of FMVSS No. 571.105 (S5.2) must be equipped with a parking brake system that meets the requirements of paragraph (c) of this section.
(b) Air-braked power units manufactured on or after March 1, 1975, and air-braked trailers manufactured on or after January 1, 1975. Each air-braked bus, truck and truck tractor manufactured on and after March 1, 1975, and each air-braked trailer except an agricultural commodity trailer, converter dolly, heavy hauler trailer or pulpwood trailer, shall be equipped with a parking brake system as required by FMVSS No. 121 (S5.6) in effect at the time of manufacture. The parking brake shall be capable of holding the vehicle or combination of vehicles stationary under any condition of loading in which it is found on a public road (free of ice and snow). An agricultural commodity trailer, heavy hauler or pulpwood trailer shall carry sufficient chocking blocks to prevent movement when parked.
(c) Vehicles not subject to FMVSS Nos. 105 and 121 on the date of manufacture.
(1) Each singly driven motor vehicle not subject to parking brake requirements of FMVSS Nos. 105 or 121 at the time of manufacturer, and every combination of motor vehicles must be equipped with a parking brake system adequate to hold the vehicle or combination on any grade on which it is operated, under any condition of loading in which it is found on a public road (free of ice and snow).
(2) The parking brake system shall, at all times, be capable of being applied by either the driver's muscular effort or by spring action. If other energy is used to apply the parking brake, there must be an accumulation of that energy isolated from any common source and used exclusively for the operation of the parking brake.
Exception: This paragraph shall not be applicable to air-applied, mechanically-held parking brake systems which meet the parking brake requirements of FMVSS No. 121 (S5.6).(3) The parking brake system shall be held in the applied position by energy other than fluid pressure, air pressure, or electric energy. The parking brake system shall not be capable of being released unless adequate energy is available to immediately reapply the parking brake with the required effectiveness.
70 FR 48048, Aug. 15, 2005
Butt-Head
Joined: Apr 2004
Posts: 9,448
Likes: 2,934
From: Reed Point, MT
I spent many years fixing parking brakes on these things as the place I used to work had 9 of them and all except 2 were manuals. I gave up putting time, effort, and money into them as it was a lost cause. No matter how much "pedal" they had they would not hold on an incline. The actual issue is not the physical size, but the lack of a "wedge effect" built into normal hydraulic drum brakes. As a normal hydraulic drum brake is applied, the shoes will work in tandem...the primary shoe will pivot and push the bottom of itself into the bottom of the secondary shoe and wedge both into the drum. The parking brakes on these pickups has an anchor at the bottom of each shoe - this means that the only force applied to the shoe is from the top pushing outward, not from the tops of each and the bottoms being linked and "wedging".
Butt-Head
Joined: Apr 2004
Posts: 9,448
Likes: 2,934
From: Reed Point, MT
@ESwift and a couple of others have a line lock installed on their truck. They seem to be happy with it.
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