So one of the tires on my car had a blowout on a road with a slight slope. I tried lifting the car up with a hydraulic jack but after the car got to a certain height the jack fell forward and the car lurched forward. I tried it twice and the same thing happened both times.
They say you're supposed to do them on a level surface but sometimes you're just not going to have one.
Would wheel chocks help in this situation?
Yes, wheel chocks would help in this case. Also, use of the emergency brakes as well as leaving it in gear (EDIT- Leave it in gear if a manual or park if automatic). If wheel chocks are not available, you could use a largish stone which could be wedged between the tire and the ground on both sides of the tire. This would be on a tire which is not flat and multiple chocked tires should be utilized. Leave the flat tire on the ground while breaking the lug nuts loose and again while retorquing them. This all depends on the slope of surface in question, though. There will be a point where the slope will be too great to overcome with any of these approaches. In this case, you may have to limp your vehicle to a place where it can be set level. You could also try pointing the vehicle perpendicular to the slope, with the flat tire on the high side.
If you leave the car in gear, and depending on if the vehicle is front-wheel, rear-wheel drive, don't jack both front wheels up if front-wheel drive, etc. This way you always have a tire on the ground that is in gear. So if your left-front tire blew out and your car is front wheel drive, jack it up so the right-front wheel stays fully weighted on the ground. All of Paulster2 answers help as well. Hope it helps!
A car on a jack is usually a very unstable object. Even when if are changing a wheel on a level surface, you should use everything available to stop your car moving when jacked up: handbrake, reverse gear or park, and wedge or stone or brick or whatever.
When the the car direction is more or less aligned with the slope, using everything at hand to secure your car against moving should help you out. It's advisable to always have something rigid enough in your car just for the case that you have a flat on a steep climb on a dessert road (no joke, you'll never have a flat in front of a workshop, that's granted).
On a rare occasion when your car is aligned perpendicularly to the slope, well, then it depends on what side of the car you need to change the wheel. If on the "upper" side, you need to secure your car against motion in both directions (again, with a piece of wood, brick or whatever) and try to position the jack as vertically as possible. And, again, a car jacked up like this will be very, very unstable. If the case is that the flat tire is on the "lower", than the best advice is not to try to jack the car up at all.
