So can a average car turn quicker....
- Thread starter stosh
- Start date
Doughnuts in the parking lot of course.
biggins said:
Why would the turning radius be tighter? Isn't that dependent on the steering lockout. Seems that would be independent of driving fw or bw....I'm assuming that there's no skidding/powersliding involved...........
-S.S.-
stosh said:
Reruns of the Rockford Files.....
Think about it. Turn your steering all the way to the right and go forward 10 feet, then withought moving the wheel go in reverse 10 feet. The car will end up in the same spot you started at, the turning radius is the same. To make this thread bike related do the same with a bike.
Must be one of those weird fizziks things, eh?biggins said:
-S.S.-
Because in reverse your cars front end is sliding around to make that more abrupt turn....kind of like overstearing with the front end.
Is isn't relying solely on teh tires and to make the turn is it sliding along with it. I guess if you did forward donuts in the parking lot it the action would be similar.
Rhino
Is isn't relying solely on teh tires and to make the turn is it sliding along with it. I guess if you did forward donuts in the parking lot it the action would be similar.
Rhino
you will have to do a complete circle going forward first, then in reverse. going backwards will have a shorter circle do to the fact that the axis {like biggins said} is closer to the center of the circle, it is simple physics. why do you think most of the little cars in asia (the little two seater motorcycle things) turn in the rear. It just like driving with a trailer on a vehicle, you can make sharper turns in reverse than forwards.
Stosh, I think the company should take their lunch outside and perform this forward-circle-backward-circle test. Then we will all know for sure 
Oxymoron! OXYMORON!!! :mumble:drt_jumper said:
-S.S.-
the turning radius of the car is the same whether in forward or reverse, that's determined by how far the wheels can deflect. however, note that the point about which the car pivots (red point on my probably-flawed diagram) is not in the middle of the car. <--- this is key.
why? when you pull into a parking space going forward you start turning before you reach the spot. when you turn, however, you are pivoting about this point far back on the car (which is already behind the spot since you started turning early).
when you pull into a parking space going backwards, on the other hand, your car pivots around a point closer to the spot you wish to occupy.
this is probably easier in pictures:
car 1
car 2
empty spot
car 3
car 4
assume you approach the empty spot from the bottom, going forwards. your turn will pivot around car 4, roughly (see diagram again).
assume you are still facing upwards but now are backing in from "above". your turn might now pivot around car 2 instead. voila.
why? when you pull into a parking space going forward you start turning before you reach the spot. when you turn, however, you are pivoting about this point far back on the car (which is already behind the spot since you started turning early).
when you pull into a parking space going backwards, on the other hand, your car pivots around a point closer to the spot you wish to occupy.
this is probably easier in pictures:
car 1
car 2
empty spot
car 3
car 4
assume you approach the empty spot from the bottom, going forwards. your turn will pivot around car 4, roughly (see diagram again).
assume you are still facing upwards but now are backing in from "above". your turn might now pivot around car 2 instead. voila.
So what's the answer, Dr. Science??Toshi said:
-S.S.-
Ahahaha this thread cracks me up....
on this note i go to watch Milla Jacofftohernakedpictureov go blast zombies.
on this note i go to watch Milla Jacofftohernakedpictureov go blast zombies.
Nicely said.Toshi said:
true you turn early for one way, and late for the other.
Drt_jmpr,
The trailer example adds a whole other dimension to turning as anyone learning to back up a trailer can attest.....but it has nothing to do with anything being discussed here.
At low speed, with only two wheels steered, the only factors in turning radius are wheelbase and steering lock (max steered angle of the steered wheels). Front vs. rear steer only changes the "steer center". Toshi's diagram is correct.
At high speed, rear-steer (out of phase) is unstable, so yes, it turns more quickly (than you want). This is why it's so much fun to do reverse donuts in FWD cars...
At high speed, rear-steer (out of phase) is unstable, so yes, it turns more quickly (than you want). This is why it's so much fun to do reverse donuts in FWD cars...
for some reason caster of the wheels is coming to mind here. I'm not a mechanic and I've been battling with my current crappy car trying to get it aligned properly and kept that way so I'm not really sure what caster is but I do know that it's totally direction dependant, you can drive a much straighter line forward than you can in reverse because of caster.
Toshi, you lost me at "flawed diagram" 
http://www.ozebiz.com.au/racetech/theory/align.htmlKornphlake said:
"Caster is the angle to which the steering pivot axis is tilted forward or rearward from vertical, as viewed from the side."
like denny, i would argue that this effect (along with any difference in, say, bushing deflection depending on the direction) is negligible at low speeds compared to the effect i tried to describe. an interesting side note is that something in the suspension geometry on my pathfinder makes the tires rub on the fender liners at full lock in reverse but not when going forwards...
That has to do with stability not turning radious, right? Unless you figure in under/over stear as part of the equation.Kornphlake said:
at slow speed a car will turn the same....right? At spead....forward may push some and in reverse (becuase it isn't as stable in that direction) the front end will over steer and come around.
I think people are argueing two slightly different questions.
1- does a car stear sharper one way than another (front to back) at speed, and
2- does a car stear sharper one way than another (front to back) when going slowly.
at speed the wheels are not able to stick tot he ground and hold their line like at a slow speed.
I know on my RC racing truck it made no difference but at speed the front end would whip around. in reverse. I saw whip because the front end would slide (negating much of the slow speed arc determiners) pivoting on the rear wheel.
I don't think any of that made sense.....I get to go home early.....later. Have a good weekend.
for some reason caster of the wheels is coming to mind here. I'm not a mechanic and I've been battling with my current crappy car trying to get it aligned properly and kept that way so I'm not really sure what caster is but I do know that it's totally direction dependant, you can drive a much straighter line forward than you can in reverse because of caster.
CANTER is the independent tilt of each wheel as if it were on an imaginary axle that was shaped like a v.
ie the top of each wheel tilts in, the bottom out. Reverse that for underloaded big trucks without air ride suspension. It does make a difference
CANTER is the independent tilt of each wheel as if it were on an imaginary axle that was shaped like a v.
ie the top of each wheel tilts in, the bottom out. Reverse that for underloaded big trucks without air ride suspension. It does make a difference
i think its simply because when the car is turning the front end follows a wider radius than the rear. so if you are turning in reverse the leading end of the car is following a tighter radius than the rear. think if you could turn your wheels totally sideways. you would pivot around the center of the rear axle. the front of the car would swing in a circle equal to the wheelbase. in forward or reverse. so the tighter radius is what makes it seem to turn tighter in reverse