Jim Clark

The next step is to include different size brakes, like 15- and 12-inch diameter brakes and even air disc brakes, says Jim Clark, CoC director, Bendix Spicer Foundation Brake.Clark heads the committee working on the lining test program.Clark was also the chairman of TMC's original task force.

Bumpy RoadInitially, TMC proposed that lining makers submit three samples of each aftermarket product for testing on a single, precisely calibrated brake dyno and test fixture, to be monitored by SAE's Performance Review Institute.

Using a single dyno, says Clark, would have leveled the playing field and produced good, comparative data, but lining manufacturers insisted on selecting their own brake dynos and fixtures.
...
At first, nearly 10 percent of the aftermarket linings that were submitted to SAE either failed to meet FMVSS-121 standards or were rejected due to unacceptable documentation, says Clark.

Dana Corp.'s Jim Clark is rather blunt in his assessment of disc brakes."They're a better animal," he says, comparing the designs to their S-cam counterparts.
...
"This new rule is going to define stopping distances, and that's going to define the brakes that we use," Clark said, during a recent seminar held by the Technology and Maintenance Council of the American Trucking Association.
...
"Manufacturers want a 10% margin," Clark said, suggesting that smaller designs may no longer be offered as a vehicle option once the shorter distances become a reality.
...
Meanwhile, a steer axle equipped with disc brakes will shed almost 10 feet from the minimum stopping distances enjoyed by those equipped with 16.5 x 5 S-cam designs, says Clark.

But that's all about to change according to Jim Clark, chief engineer in charge of foundation brakes at Dana Corp.He insists a major push from the U.S. National Highway Transportation Safety Administration (NHTSA) to improve truck stopping distances, combined with the never-ending need to bolster productivity, will soon make disc brakes a more common component on this side of the pond.

"Government agencies throughout North America are keenly aware of the fact that trucks don't stop as well as cars do and that something needs to be done to close the gap," notes Clark."In the U.S., NHTSA is calling for a 30 per cent reduction in stopping distance in new rulemaking planned to take effect by 2007.They believe that this improvement alone will achieve a 50 per cent reduction in truck-related highway fatalities."

Clark believes these braking distance changes will be formally defined in about three years and then the rule will take full effect in the U.S. by 2007.He predicts Canada's governing agencies will follow a similar timetable - perhaps only one year later than the U.S. implementation.

Proactively responding to this emerging opportunity, major brake suppliers have recently introduced new air disc brake systems for Class 7 and 8 trucks.For several years, brake makers have been working to Americanize European disc brakes by making them lighter and easier to both install and maintain.

These systems will still offer a range of benefits over the S-cam option, including reduced stopping distance; increased brake pad life - 30 to 50 per cent better in some cases; car-like braking and steering; as well as overall lower life-cycle costs.

According to Clark, the most likely configuration for disc brakes will be on steer axles, with today's drum brakes still on the drives and trailers.

Why? The performance level for the vehicle rises significantly when a disc brake is used on the steer axle because this is the axle receiving most of the weight transfer in a braking application.

In addition, disc brakes reduce the chance of steering pull from brake torque.Clark reports during Dana's field tests, drivers literally fell in love with disc brakes.One veteran test driver claims he could perform a panic stop from 60 mph without touching the steering wheel.That level of performance can certainly be used by fleets to attract and retain drivers.
...
"Disc brakes are currently used in motor coaches, fire trucks and city buses but also in tankers," says Clark."Now that disc brakes are readily available in the U.S, we are starting to see an increased level of interest from all kinds of fleets during the specification process.And a greater number of owner/operators, who typically keep their vehicles longer, are also exploring both the life-cycle costs and safety benefits of disc brakes."

Table of Contents

But Jim Clark of Bendix Spicer Foundation Brake LLC, a joint venture between Bendix Commercial Vehicle Systems and Dana Corp., believes that to consistently meet a 248-foot requirement, a 10 percent safety margin is needed, making his target 220 feet.
...
Applying Clark,s 10 percent margin, the target could be 239 feet.

"The rules are expected to require up to a 30% reduction in stopping distance at 60 miles per hour," said Jim Clark, chief engineer for commercial vehicle systems at Dana Corp.

Jim Clark, Dana Corporation's chief brake engineer, points out several other key issues that truckers need to consider, especially in the selection of replacement brake shoes and linings.Aftermarket parts do not have to meet the same DOT FMVSS-121 performance standards as new.So there are varying quality levels, driven by competitive pricing.

Clark says brake shoe paints and/or coatings have changed a lot over the years and this has impacted resistance to "rust jacking."He says some manufacturers and jobbers paint or dip shoes; that with the change in EPA regulations pertaining to paint VOCs, water-based paints have become more popular as have dips.When asked what's most durable, Clark said, ". . . Epoxy coatings are the best.You'll find that the premier brake products we sell to our OE customers are e-coated."This is not to say, however, that all new S-cam foundation brake shoes are e-coated.

Clark shares the same recommendations all the experts we interviewed have: Inspect brakes thoroughly on a schedule.Pull brake drums on a regular basis, especially on vehicles five years and older.

Jim Clark, Dana Corporation's chief brake engineer, points out several other key issues that truckers need to consider, especially in the selection of replacement brake shoes and linings.Aftermarket parts do not have to meet the same DOT FMVSS-121 performance standards as new.So there are varying quality levels, driven by competitive pricing.

Clark says brake shoe paints and/or coatings have changed a lot over the years and this has impacted resistance to "rust jacking."He says some manufacturers and jobbers paint or dip shoes; that with the change in EPA regulations pertaining to paint VOCs, water-based paints have become more popular as have dips.When asked what's most durable, Clark said, ". . . Epoxy coatings are the best.You'll find that the premier brake products we sell to our OE customers are e-coated."This is not to say, however, that all new S-cam foundation brake shoes are e-coated.

Clark shares the same recommendations all the experts we interviewed have: Inspect brakes thoroughly on a schedule.Pull brake drums on a regular basis, especially on vehicles five years and older.When replacing shoes and linings, thoroughly examine the ones coming off, don't just scrap them.

Don't ignore automatic slack adjusters.If "rust jacking" is a problem, make sure ASAs are thoroughly lubed and that there's no evidence of internal rust/corrosion.

In conclusion, "rust jacking" produces short lining life, sometimes 50% less than is expected.

Jim Clark, Dana Corporation's chief brake engineer, points out several other key issues that truckers need to consider, especially in the selection of replacement brake shoes and linings.Aftermarket parts do not have to meet the same DOT FMVSS-121 performance standards as new.So there are varying quality levels, driven by competitive pricing.

Clark says brake shoe paints and/or coatings have changed a lot over the years and this has impacted resistance to "rust jacking."He says some manufacturers and jobbers paint or dip shoes; that with the change in EPA regulations pertaining to paint VOCs, water-based paints have become more popular as have dips.When asked what's most durable, Clark said, ". . . Epoxy coatings are the best.You'll find that the premier brake products we sell to our OE customers are e-coated."This is not to say, however, that all new S-cam foundation brake shoes are e-coated.

Clark shares the same recommendations all the experts we interviewed have: Inspect brakes thoroughly on a schedule.Pull brake drums on a regular basis, especially on vehicles five years and older.When replacing shoes and linings, thoroughly examine the ones coming off, don't just scrap them.

Don't ignore automatic slack adjusters.If "rust jacking" is a problem, make sure ASAs are thoroughly lubed and that there's no evidence of internal rust/corrosion.

In conclusion, "rust jacking" produces short lining life, sometimes 50% less than is expected.