Disc brakes on a semi?

Discussion in 'Questions From New Drivers' started by Sportster2000, Apr 29, 2008.

  1. Sportster2000

    Sportster2000 Road Train Member

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    I have heard of them before and finally saw a truck that had them on there a couple of weeks back. Well I am going to be driving one. Question is, is the stopping power of the disc brake more or less than the drum brakes? Is the difference noticeable? Just wondering. :biggrin_25525:
     
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  3. Lurchgs

    Lurchgs Road Train Member

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    Gonna depend on the size of the rotor and the pads. I would *guess*, however, that it's probably shorter stopping distance. Probably noticeably so.

    The Gov't is contemplating mandating shorter stopping distances for big rigs, last I heard - to go into effect this summer, I think. In effect, requiring disc brakes - I think all around on the tractor.

    In discussion, the general response was "Gonna need a darn crane to put those rotors on! " They'll probably have to be vented and/or slotted, too.
     
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  4. Brickman

    Brickman Trucker Forum STAFF Staff Member

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    From what a mechanic told me you do not want to mix and match the drums on a trailer and disc on the tractor.
     
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  5. Lurchgs

    Lurchgs Road Train Member

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    it would definitely be sub-optimal, but it could be done - particularly if the trailer is ABS
     
  6. Sportster2000

    Sportster2000 Road Train Member

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    So what you are saying about the trailer having drum brakes and the truck having disc brakes that the truck will try to slow down faster? So then that would mean that the trailer would not really be doing that much braking at all. Am I correct on this thought?
     
  7. Lurchgs

    Lurchgs Road Train Member

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    I'd not mix/match unless the trailer had ABS.. then it would slow down just as it does now - but yeah, most of the braking woudl come from the tractor
     
  8. Lone Ranger

    Lone Ranger Light Load Member

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    Disk brakes are much better than drum brakes, both in stopping force and fade resisting.

    The disk brake system weighs less, and there are less moving parts.

    The best thing about disks is that on a long downgrade, they do not fade nearly as much or as fast as drum brakes. When drums get hot they expand and it takes more brake pressure to maintain the stopping force. The shoes have to push harder and further.

    When disk get hot they expand too, but the brakes are squeezeing the disk, so as the disks expand, they get squeezed even harder.

    As for mixing them, that doesn't seem to be an option to avoid since most of the trailers made here (USA) have drum brakes. Disks are more expensive.
     
  9. Native Dancer

    Native Dancer Heavy Load Member

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    Picked up axles at Hendrickson a few weeks ago and delivered them to a trailer manufaturer. There were some axles there with disc brakes and I was told they were available as an option. The rotors and pads didn't look that big. The brake pots were mounted perpendicular to the rotors.
     
  10. dieselhound

    dieselhound Medium Load Member

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    I would guess the pads wouldn't be big because the friction area causing heat. The heat is what would bother me. The bigger disc could cool off without cracking. I can imagine the replacement costs as to shoes and drums.
     
  11. Lurchgs

    Lurchgs Road Train Member

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    I think the pads would HAVE to be big. Keep in mind, friction is what stops that 80,000 pound gorilla. The heat, though, is why I mentioned vented or slotted rotors.. very little loss of friction, but it keeps things a lot cooler.

    As for the cost.. I'm not going anywhere NEAR that one
     
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