jackknifing
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jackknifing
I saw a post and someone asked what causes jack knifing.
Someone answered:
This has some valilty to it. Locked up tires do not have the same stoping power. But it has nothing to do with vehicle speeds or stoping power.
The real cause of jackknifing is that a locked wheel has "no
directional control". The tire can go in any direction. If the front wheels don't follow then they will actully over come the front wheels untill the front wheels begin to follow the rear wheels. (remember the bike skids we did as kids)
If you would like to see this actully happen take a model car and lock the rear wheels and roll down an incline. It will do a 180 and roll backwards. This is due to front wheels maintaining directional control and turning outward as rear tends to slid sideways untill car spins out.
Lock the front wheels and car will maintain a straight direction as the rolling rear tires with directional control will follow the locked front wheels. Just like your trailer follows your tow vehicle.
Lock your trailer brakes and they will not maintain direction stability and a jackknife could occur.
A question about jackknifing: I thought the cause was when the tow slowed faster than the trailer. If the trailer brakes lock up in gravel or dirt, how does this cause a jackknife situation?
I'll take a stab at the answer. When the brakes lock up, they have less braking power.....The whole purpose of Anti-lock brakes is to keep the tires from locking up so the vehicle will stop faster, thus a vehicle with locked brakes doesn't have the stopping power of a vehicle with pulsing brakes.
The real cause of jackknifing is that a locked wheel has "no
directional control". The tire can go in any direction. If the front wheels don't follow then they will actully over come the front wheels untill the front wheels begin to follow the rear wheels. (remember the bike skids we did as kids)
If you would like to see this actully happen take a model car and lock the rear wheels and roll down an incline. It will do a 180 and roll backwards. This is due to front wheels maintaining directional control and turning outward as rear tends to slid sideways untill car spins out.
Lock the front wheels and car will maintain a straight direction as the rolling rear tires with directional control will follow the locked front wheels. Just like your trailer follows your tow vehicle.
Lock your trailer brakes and they will not maintain direction stability and a jackknife could occur.
Last edited by Hellbender; Jan 14, 2004 at 08:40 PM.
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Joined: Oct 2002
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That's why the oem's always make the fronts lock up before the rears.
Any idiot can crash straight on into a wall. It takes a driver, not a glorified passenger to handle a vehicle with heavy rear wheel brake bias.
Any idiot can crash straight on into a wall. It takes a driver, not a glorified passenger to handle a vehicle with heavy rear wheel brake bias.
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