I live in an area with speed bumps that have breaks in them that give one the option of driving the two wheels on one side of the car through a break, while the wheels on the other side go over the bump.
Which has less wear and tear on the car: All 4 wheels over the speed bump, or just 2?
They have the same type of speed bumps where I work. I just alternate. One day I let the left side go over the speed bump, the next day I let right go over.
Tester
Two is less than four. If you can, let two wheels pass through the breaks. You should ALWAYS slow to a near-crawl to negotiate a speed bump. The speed at which you pass over the thing is more important than how many wheels move up and down. Slower is better.
It makes perfect sense to bump only one-half of your wheels if possible. Why on earth would anyone consider bumping all four of them?!
I just ride my motorcycle and go between the bumps.
Seriously, I don’t really think it matters unless you are driving much too fast.
I agree with Craig58. It doesn’t make a difference whether it is two or four wheels. Roll over the bumps, don’t bump over them. In other words, slowly.
Most like this setup are in a 2 lane drive. so if a car is in the other lane, you’ll hafta use 4 tires over it.
All four wheels, this imposes less tortional stress on the body shell and suspension system.
Higher speed negotiation technique is to pre load the front and rear suspension systems. It takes a little practise : Drive up to the speed bump and primary brake just as your front wheels are about to hit the speed bump, this will cause the car nose to compress the shocks and springs and should occur just prior to hitting the speed bump, take your foot of the brake, the front suspension system will start to extend but the pre load will stop unwinding as you hit the bump recompressing the front suspension, the front will again unwind as your front wheels exit the far side of the bump and will preload the rear suspension for the same cycle. This is the method taught on the advanced police driving course in Hendon and works well for traversing speed bumps at higher speeds, it works well once you get the hang of it.
As I said it takes a little practise, and never hit speed bumps at higher speeds with only 2 wheels.
You’re kidding, right?
Most police cars I’ve seen don’t even bother to slow down when they drive over 6-inch curbs, leaving a trail of sparks.
Nope, not kidding, but this is Hendon police driving school, England.
Strangely enough, the technique is part of the advanced high speed drivers course for highway patrol…who never encounter a speed bump throughout their whole working lives.
That’s a new one for me, I think most US police learn to drive in a demolition derby someplace.
Yeah I know but the Brit police have to drive Euro boxes, one hard impact and your either in orbit or your wheels have just fallen off ~ still attached to the engine and transmission…
If you slow to 15 MPH or less (depending on the way they are constructed), it won’t make a difference. I’ve noticed that the wide bumps on the street are OK at 15 MPH but the parking lot variety (narrow) are best done at about 5 MPH. It shouldn’t matter whether you use 4 or 2 wheels.
The “wide bumps” that you refer to are technically called speed humps. When properly installed, they have a very gradual ramp-up and down cross section that causes very little jolting and at their designed speed, will allow the car to roll smoothly across, even at 15-20 mph. They operate on the principle of allowing enough time (e.g., slower speed) for the fluid in the shocks to bleed through the orifice without causing the jolt when the shock is required to expand or retract at too fast a rate. Unfortunately, not many highway/street contractors know how to properly install them. I’ve seen what should have been humps that were built wrong, and merely function like 5-foot wide speed bump.
Anyone who drives over speed bumps at more than a crawl (police excepted) is going faster than they should. And done at a crawl, movement of the suspension is extremely small and your vehicle is well capable of handling it without wear of damage.
Scudder, I’d argue that tortional strength of all modern cars capable of meeting modern crash testing standards is easily capable of handling speed bumps. I love the old BL ragtops, especially the Spitfire, but I have to admit that you might induce some rattles driving a Spitfire over a speed bump every day, two wheels OR four.
Speed bumps aren’t designed to reduce traffic speeds to a crawl, their actual construction when built by incompetent contractors is totally another thing.
Crash testing has little to do with repetitive stresses, all torsional stresses are transmitted through the roof of the car, these stresses are transmitted up the vehicle pillars placing significant loads on door hinges and latch assemblies,the firewall and body shell in general. If you cross a speed bump every blue moon, no problem but if you encounter a large number of them and consistently traverse them with 1 wheel per axle you can expect stuff to work loose and stuff starting to get out of shape. Windshield leaks are a favourite.
As for Triumph Spitfires, I wouldn’t trust it under any circumstances over speed bumps, if the door mirrors didn’t fall off you’d probably leave the exhaust system behind.
The ones I’m familiar with, the ones in parking lots, reduce traffic to a crawl, at least momentarily. Based on the OP’s description I thing those are the types he/she is alluding to.
Well, actually the structural members surrounding the passenger cabin are designed to be able to transmit the forces of a frontal impact up over the body through the A pillars and around the cabin while the front of the car’s structure absorbs much of the energy by crumpling as well as directing it to the A pillars and the undercarriage. One of the things that design manifests itself as is tortional strength.
Much of the tortional stress is also managed by the rest of the overall framework of the unibody as well as the pillars. The pillars are part of an overall structure, not the only parts that manage tortional stresses.
But I submit that we’re arguing technical points that we’d need a very expensive finite element analysis to really answer. I’d also submit that repeatedly crawling over parking lot speed bump won’t hurt any modern car no matter you’re chosen method of doing so. The design validation testing and accelerated life testing that the vehicles are subjected to submits the structures to far more than we ever could. And have you seen the computerized stress analysis models they’re working with these days? Simply Marvelous!
I love Spitfires. But I agree. If the mirrors didn’t fall off the Lucas electrical system would probably short out.
How about the non-split bump/hump? I work at a place that has three bumphumps in one of the parking lots. Maybe this is one for the Myth Busters, but I follow many people down the path of crossing all three, and quite a few people approach the bump at an angle, so each of their four tires crosses the barrier one-at-a-time.
I was thinking about the physics of this… with both tires “in parallel” and crossing the barrier together, the whole front weight gets lifted X inches on two suspension segments (R & L). Crossing at an angle, some portion of the front weight gets lifted X inches, and then the other. Torsion! At the same time, I think (though haven’t measured it) that the shocks have greater compression.
So, to protect your car: go perpendicular to the bump, or at an angle?