I'm sold on light steady pressure rather than snubbing

Discussion in 'Experienced Truckers' Advice' started by Reaper'sTrucking, Nov 27, 2022.

  1. Reaper'sTrucking

    Reaper'sTrucking Light Load Member

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    Well guys I gotta be honest I'm more fond of the light steady pressure method going down hills. After years of preaching that snubbing is the right way I've come to find that going downhill when in the right gear my brakes were way less hot than when I would snub. My Peterbilt is having an engine rebuild so I'm using my backup truck that I bought off an old farmer for $5k it's a 1988 freightliner flc112 with a m11 Cummins 13 speed and no Jake brake, I converted it to auto slack adjusters and here in Washington and Oregon I run upwards of 105k but at the moment I'm pulling a 3 axle spread reefer running 90k pounds and after going down 3 miles of 6% grades then immediately after 2 miles of 8% the first run I would snub it in 5th gear from 30 down to 25 all the way down and came to a stop at the bottom to make sure my brakes aren't over heating and the drums were fairly hot to the touch and the hubs were warm but on the 2nd run same weight I dropped down to 4th low and ran the engine fan and kept it at 20mph with 15psi of pressure all the way down and stopped and the hubs were cold and all my drums were room temperature with no brake fade, no smoke and no hot spots. Yesterday I was going down a 2 mile hill in cowiche that's roughly 13% then halfway down levels out to 10% the rest of the way and I did the same light steady pressure in 4th gear to the bottom and came to a stop and just as before the brakes were barely room temperature. I was totally against light steady pressure and always thought snubbing was the way but I've proved myself wrong, the mistake I made before when trying light steady pressure was that I was in too high of a gear but once I was in low range it was perfect
     
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  3. staceydude

    staceydude Road Train Member

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    What motor do you have I. The Peterbilt? Are the Jakes as strong as the Cummins?

     
  4. D.Tibbitt

    D.Tibbitt Road Train Member

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    Great to hear it has worked for someone hauling heavier than normal, on big mountains.
     
  5. Reaper'sTrucking

    Reaper'sTrucking Light Load Member

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    The Peterbilt is a 2005 379 but the acert engine was swapped for a 6nz cat, on a 6% normally the Jake's hold me around 30mph if I'm 80k or less and about 25mph if I'm running upwards of 105k
     
  6. Chinatown

    Chinatown Road Train Member

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    I've done light steady pressure my whole career and never had a problem. I was told to do that in cdl school years ago.
     
  7. CargoWahgo

    CargoWahgo Road Train Member

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    The universities out in California tested stab vs steady hold.

    Steady hold proved superior. So you'd be right according to the university tests on their big hill.
     
  8. tscottme

    tscottme Road Train Member

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    Letting the speed increase going downhill and then braking, snubbing, puts more heat into the brakes than maintaining a safe speed at all times. The amount of heat or energy the brakes need to get rid of can be calculated by a simply formula that considers the mass of the truck, which does not change while going downhill, and the speed. Lookup the formula for Kinetic Energy. Ke = 1/2 Mass multiplied by velocity squared. So ANY additional speed is multiplied by itself and increases the kinetic energy much more than expected. Say you let speed increase by 5 mph the speed portion of the formula goes up by 25, 5 times 5, not five. There is also the consideration of what steady speed should be used. A too-high steady speed will also introduce too much heat into the brakes. I was taught and drove my first 3 years to use the snubbing technique and all of my trucks had NO JAKE. After that I had trucks with jakes and experimented because I would travel the same roads, at the same times, for 2-5 years at a time. I was able to prove to myself what I expected to not work worked better than what I wanted to work.

    Anyone can use the online Kinetic Energy calculators and input their own numbers for the mass (weight) of their truck and speeds. If you usually let your speed increase by 5 or 10 mph before slowing down, use those speeds and see the raw numbers. It never is less kinetic energy to let a vehicle speed up and the amount of kinetic energy that must be converted to heat by the breaks doesn't increase a little bit for a little bit of speed increase. The Kinetic energy/heat increase a lot for a little increase in speed. The math is not even close. Light steady pressure and maintaining a constant speed produces less energy/heat than the alternative. If I used brake pressure I would only use just enough for it to register on the brake application gauge, not enough brakes to even feel their application.
     
  9. azheavyduty

    azheavyduty Light Load Member

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    Steady is how the old time log truckers all did it. Before jakes they were going off hills on roads that would make a lot of todays truckers cry for their moms.
     
  10. REO6205

    REO6205 Trucker Forum STAFF Staff Member

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    Exactly right. When I started driving loggers we had water tanks to help cool the brakes. I was taught by the old timers to use gentle steady pressure. Those old guys knew their stuff.
    When I drove tanker for PIE we didn't have any trucks with jake brakes and everybody I knew used the steady pressure. We ran all over the Sierras and the PNW with no problem.
    Patience is key.
     
  11. Old_n_gray

    Old_n_gray Medium Load Member

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    Haven't heard PIE mentioned in a while. Old fart. ;)
     
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