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R1 vs semi trailer braking distance?

Discussion in 'General Motorcycling Discussion' started by gunnin' it, Apr 24, 2008.

  1. Hi

    Was talking with a mate the other day, and he was trying to tell me that If a test was conducted to determine braking distance from a given point at a given speed of both an R1 and a semi trailer, then the semi would stop in less distance.

    I disagreed, the bloody thing weighs tonnes! It has more wheels on the ground though..

    Anwyay, can you help me out so I can PWN him?

  2. Good question. Trucks have a heap more rubber on the road - probably 50-100 times more, and bigger brakes. They also carry massive amounts of weight, so the momentum is enormous.

    Bikes have two contact patches that probably amount to less than the size of a credit card under hard braking. But the rubber's stickier, and there's so much less weight to pull up.

    My money's on the bike, in less than half the distance.
  3. A car can theoretically outbrake a bike, but not by much.

    Does your mate think he can outbrake a car?

  4. Nothing theoretical about it Rob. Try taking a new Volvo for a test drive and stomp down on the brake pedal letting the ABS do all the work. Then tell me you could stop that quickly, easily and consistently on any bike ;).

    Of course trucks too can have issues with heavy braking since if one wheel locks then the whole rig can get dangerously unsettled. I don't think that more wheels can cancel out the excess weight since road trains take a frightening amount of road to haul up to a stop from 100kph.

    Wouldn't want to test the theory though, since if you find out you can't outbrake a truck the driver's probably not going to notice until they have to wash the squish mark from the back of the trailer.
  5. bike would outbrake a semi by a country mile. no risk. i know trucks.
  6. African or European? :grin:

    Too many variables!

    Sweeping generalisations say that a race bike will out-brake a semi trailer.

    But it's more about having good brakes, good suspension, correct weight distribution and good tyres than mass, because the same mass that needs to be slowed down creates proportionally more grip to be used for slowing down with.

    That is to say; I bet if you modified a semi trailer you could get it to stop Pretty Damn Fast. Hell, a suspension engineer friend in the US has a Dodge Ram pickup truck that can out-slalom a Corvette in cornering competitions.
  7. Bullshit, no semi truck can outbrake a motorbike.

    do the math 92000+ kg vs 180kg. = motorbike stops first.
  8. My bike will outbrake a semi and most cars.

    The brakes on the K12 with ABS are phenominal
  9. errr how about the rule of momentum.
    momentum=mv the higher the momentum the harder it is to stop. The more breaking force you need.

    Would be interested to know if that is wrong :?
  10. Oh hush. Mass is virtually irrelevant. Other factors of vehicle design are at play.

    1888kg Bugatti Veyron stops in 31.4m from 100kph -> 0
    995kg MR2 Spyder stops in 35m from 100kph -> 0

    Mass is virtually irrelevant. A factor, yes. 92000-180kg = motorcycle? No.

    cha-chaos: Correct. Except the mass of the vehicle creates proportionally more friction to stop with, effectively cancelling mass out in simple braking-distance models.
  11. Non-rigid trucks seem to be limited, not by grip or braking power (on the first stop anyway :grin: ) but by stability issues.

    Sure, cars can outbrake bikes, but not by as much as they can outbrake trucks.

    Bike wins.
  12. That's correct.
    But the formula for calculating the braking distance for a truck = Peak braking friction coefficient x tyre tread depth correction factor x braking efficiency correction factor x driver control efficiency factor (ie preventing the trailer fishtailing). Then you worry about mass and velocity.

    Found some figures that put a loaded non-articulated truck at 310 feet from 60mph. A semi-trailer from 60mph is 335 feet unloaded, 355 feet loaded (with an unbraked trailer).

    Figure I found for the R1 was 151 feet (of course a Volvo S70 sedan will stop in 134).
  13. I'll restate:

    It's extremely likely that an R1 could outbrake a semi-trailer. I'd put my $1000 on the bike. (Edit: Guess I don't need to bet, given jd's post above)

    But it is not a simple factor of "lol cars and trucks are heavy". :p
  14. It is actually quicker to stop a vehicle if ABS does not kick in. If you use the thresh-hold braking technique whereby you apply the brake as heavily as possible before ABS takes over, you have a constant braking force but with ABS the brakes let go momentarily, thus the braking force is not constant.

    I have done this in various driving courses and the difference in a falcon is about a car length.
  15. yeah, the common argument is that a truck has more surface area interfacing with the road. this means it has 18 contact patches, compared to 2 on a bike. the surface area of a truck tyre on the road is also greater than that of a motorcycle tyre.
    average semi trailer = 10T prime mover, 25T payload (inc trailer) so 35000kgs
    motorcycle = 200kgs with 100kgs rider (inc gear, and a sack of spuds :LOL: )

    lets even give the truck the advantage of having the same compound tyres (they actually run a firm compound and therefore would break traction far earlier) and lets assume a 10/100 has a contact patch twice the size of a motorcycle tyre.
    this means the truck has 36 times the ability to resist momentum through its tyres.
    the bikes weight x 36 = 10800kgs
    so a 10.8T truck with 18 wheels ( :rofl: ) mathematically stands a chance.

    however, for a semi to stand a chance, the bike would need to weigh 972kgs :grin:

    there you go, in lay terms :)
  16. Agreed. But the point is any driver can use the ABS without having to think and get exactly the same stopping distance.
    But not every rider could get the ideal stopping distance from a bike (except perhaps on the ABS equipped models).
  17. Yes, but if the rider were trained in this technique, I dont se why they would not stop consistently every time. this is how I was trained and I have never use ABS since. If you know what you are doing, it makes driving/riding much easier and more predictable.
  18. Weeeeeell.. (Offtopic for a bit...)

    Motorcycle braking tests that favour ABS (ie: tests that consider consistency) show ABS as the superior stoppererer.

    Motorcycle braking tests biased against ABS's consistency (ie: tests that consider peak braking distances) show that not engaging ABS is indeed the faster way to stop.

    The alarming bit, though, is that in the peak-distance test ( http://www.ibmwr.org/prodreview/abstests.html ), ABS stops over 100ft faster (200 feet versus 320 feet) than the best human ability when the road was wet with an irregularity in the surface.
  19. (Last multipost. Hey, speaking of ABS and wet weather... It's just started to bucket down outside, right before home time. :p )

    I'm all for practicing emergency stops - Even wif my ABS Tiger I practice a few in the back streets near my place on the way home. But I seriously doubt I could outbrake it in a true emergency panic stop in crap conditions.
  20. Yes I agree - but from a theoretical practical perspective, even though a (modern) car should outbrake a bike, the difference between the average driver and the average rider is chalk and cheese and I'd always bank on a bike outbraking a car in real world traffic scenario.

    Anyway, assuming the trucky knew he couldn't outbrake a car, and a car can only just outbrake a bike, how was he going to outbrake a bike????

    What about the routine warnings that truckies need more space than a car ahead/infront to pull up??? :-k

    So have we K.O'd the truck argument yet??