Can someone explain to me why my car wouldn't automatically stall when left in first gear on a hill with the parking brake on? A co-worker started my car for me and didn't shift it to neutral and somehow the front right tire spun down to the threads. My manager doesn't believe it's possible, and insists that it would have stalled right away. Can anyone help me with an explanation?
1Welcome to the site. We need more information. Is the car FWD? What was the condition of the tires to begin with? How old was the front-right tire? How old is the car? Was the steering wheel turned fully to the left?– ZaidDec 19, 2016 at 19:45
How long did he let it spin??? And if the drive tire(s) were spinning, it wouldn't stall.– 3DaveDec 19, 2016 at 20:04
@Zaid why do you ask if the wheel was turned to the left specifically? Are you thinking the tread/shoulder was pressing into a kerb/curb, or pointing out into the roadway ?– CriggieDec 20, 2016 at 6:33
2@Criggie I was thinking of contact patch. Turning the steering to full lock affects how much surface area is in contact with the ground, which will influence how easily the wheel would break away– ZaidDec 20, 2016 at 7:51
1How were the weather conditions? Ice, rain? Did they generously lube up your tires with some water and a lot of soap? Was the car facing uphill or downhill? Yes, in general the car should have stalled unless there was some super special circumstance. I would suspect foul play; does your co-worker have a grudge against you?– MonkeyZeusDec 20, 2016 at 14:44
Tires are rugged by design
It takes several minutes of abuse to get a tire in relatively decent condition to pop and expose its steel ply.
The additional load of the drivetrain with the car being in gear should have resulted in the car stalling.
Even if the vehicle was running for a few moments the co-worker would've seen some tire smoke unless the car was on ice.
In my opinion, one of the following scenarios is applicable if what you say is true:
- the tire was in appalling condition to begin with
- the clutch is in appalling condition
- the car was somehow started and run in gear for several minutes at medium-to-high engine RPMs
- the tire that is now on the vehicle wasn't present at the time of the jump-start
3If the clutch was in bad shape then I'd expect it to slip rather than the tire to spin. Dec 20, 2016 at 12:13
1@dlu I was hoping someone would say that :). You're right, if the clutch slips the tires don't get roasted. If it doesn't the car should stall. Either way the facts don't add up.– ZaidDec 20, 2016 at 12:17
Unless the engine has a lot of torque, if the tire was able to keep spinning as it wore through a slippery surface and built up a lot of heat before actually getting to a point where there would be traction then the melting (and smoking) rubber might have provided enough lubrication to allow the tire to keep spinning with relatively little traction. Dec 20, 2016 at 12:21
Generally, parking brakes only affect the rear wheels of a car. Since your question implies that you have a front-wheel-drive car, the drive wheels weren't affected by the brake, and were able to spin (essentially) freely. But, the car couldn't move due to the rear wheels being stopped, so the front wheel with the lowest traction (the front-right) spun and wore itself down.
1Great point - this knowledge can be used to crab the front of a FWD car sideways without moving forward, but its hard on tyres and makes you look like a poor driver.– CriggieDec 20, 2016 at 0:15
The surface must have been slippery, or the engine must have had a lot of torque – or perhaps we're being used to develop support for a plot device :-) Dec 20, 2016 at 12:15
It is possible to do a "burn out" whereby a FWD car is run with the handbrake fully applied which can mean that one or both of the front wheels spin whilst in gear. If the car has an open differential, one wheel will spin. If it has a limited slip or lock diff, both wheels will spin.
I've seen that many times at the Worthersee Treffen Volkswagen meet in Austria. However, in order to take a tyre down to the treads you've got to give the car a significant amount of throttle for a sustained period. This Video shows the kind of abuse you've got to give a car and you'd have to do this for several minutes.
Indeed a car started in gear with the handbrake applied and, crucially; no throttle applied, will stall. I fear that your co-worker is telling porkies about what happened. Watch the video and decide for yourself.
Cars are designed to allow the drive wheels to spin at different speeds – this is to allow for the difference distances that the inside and outside wheels travel while turning or going around a corner. The part that allows this to happen is called the differential and it will also allow one wheel to spin freely while the other is locked.
So, based on what you've told us, this is how I think happened:
Your car either lacks a clutch interlock (which should have prevented starting the car unless the clutch was depressed), the interlock is broken, or your coworker wasn't thinking and didn't notice when s/he let the clutch out the tire started spinning.
You car must be front wheel drive (and not a SAAB, or other car where the parking/emergency brake acts on the front wheels). Or the car may have been resting against a curb with a brake that was unable to hold the wheel either because it was only partially applied or because it was out of adjustment (or moved forward until it hit a curb, but that would cause me to really wonder about your coworker). But somehow the tire was able to spin without moving the car.
The wheel with the damaged tire must have been on a relatively slippery surface and able to start spinning when the car was started or when the clutch was let out. If the surface was slippery enough, the spinning tire might have been relatively silent and hard to notice – especially if it was a noisy environment.
This is where it gets puzzling. For the tire to wear there needs to have been friction between the tire and the surface it was sitting on. The same friction that was wearing the tire should have provided traction that would have caused the car to try to start moving – but it sounds like you found the car in the spot where you left it. But if the tires had traction and the car didn't move then I would have expected the engine to stall. But perhaps the tire was sitting on a surface with some friction but not enough to stall the car or maybe the tire was already on its last legs (but unless something else is wrong, like an alignment problem, I would expect that other tires on the car would also be very worn down if this was the case) or perhaps the tires were sitting against a curb or something else was stopping the car from moving – then if the engine had enough torque perhaps it could spin the tire without stalling.
1I've had a quite a few (British/European built) cars, all with manual transmission. None of them has had a clutch interlock.– Chris HDec 20, 2016 at 15:46
Fair enough, my older cars didn't either, but I think it is fairly common in the US at least for the last 20 years of so (if SAABs and VWs a representative samples). Dec 20, 2016 at 15:59
1@ChrisH, yes it would be almost reflexive for someone who drives a stick, but then so would putting it in neutral – or so I'd think. Dec 20, 2016 at 16:06
1I do both, so I agree with you. Strictly speaking I check it's in neutral by waggling the stick. If parked on a hill in gear I drape something over the steering wheel (e.g. a windscreen cloth, a map).– Chris HDec 20, 2016 at 16:09
1Another thought - a lot of weight in the boot/trunk, and/or a non-level parking surface to de-load that front wheel ?– CriggieDec 20, 2016 at 19:14
Assuming your car is front wheel drive, if the right front tire was on a low friction surface (ice, mud, or wet clay for instance), it suppose it is possible. Not sure how you could prove it though without reproducing it again.
If the coworker's claim is true, he/she managed to start the car while it's in gear. You can move a car using the starter motor, but moving it against a parking brake AND getting enough rpm for the engine to start seems unusual.
Everything that lands on a road surface (oil, grease, antifreeze, window washer fluid, gasoline, diesel fuel, battery acid, tire repair sealant car wax, beer, urine, dead rats, etc.) usually ends up next to the curb, and you were parked on a hill with the e-brake on which usually only applies to the rear wheels. Your coworker starts your car for you because its cold (I am assuming). The engine is racing on fast idle, the defroster fan is turned on high, who knows what the radio is up to. They let out the clutch and dont notice that the right front tire is spinning so they assume it is in neutral. Your tire starts wearing, your engine control computer keeps the engine from stalling.