Speed bumps

[Osella]

Hi, I know this isn't specifically a racing tech question - however it's where I expect to find an answer.

Speed bumps -such as those that adorn the roads of the UK - are they best approached under acceleration so as to transfer the weight from the front wheels? - or is any benefit from doing that negated by the increased load on the rears by the time they hit the bump? Or does the bump slow the car enough?

I'm not a physicist but would appreciate a technical explanation -even if I then need that explaining to me!!

thanks - I've asked the Head of Physics but they don't know!

[MGDavid]

you don't stae your objectives, it depends what you are trying to achieve -
max stability
max comfort
minimum stress on vehicle / components
max speed
etc

[ss_collins]

taxis approach the bump turn one way then the other on the wheel - this smooths it out a lot. My method is to brake on the approach and then accelerate over them so the nose is up reducing the bump. However in Hitchin many of the speed bumps are fine at 30mph...

what a bizzare topic!

[phoenix]

I think it depends on a lot of things!

In my Jeep I just hit them at any speed - doesn't seem to make much difference. Taxi's maybe trying the one-wheel-followed-by-another approach, which may give a more comfortable ride for passengers, or not, as both rear wheels hit the bump at the same time!

Low cars, with short travel in bump need a slower approach so as not to ground out or hit the bumpstops - or both.

In an empty Transit, as fast as you like with the front wheels but SLOW for the rear wheels, or they jump all over the place. Towing your precious race car on a typical trailer - slow or the jockey wheel gets bent! (Experience talking!)

Short answer is, whatever suits you and you car and the bump in question, as no two seem to be the same height or have the same on/off ramp angles.

[Chris Y]

I think this is better suited to the Road Car forum.

[Dave Brand]

The best approach is to dab the brakes just before the front wheels hit the speed bump. The front will dip, so if it's timed properly the front of the car will be rising as the wheels hit the bump, reducing the shock loading on the front suspension & giving a more comfortable ride over the bump. Accelerating as the rear wheels hit the bump also helps.

[Osella]

Originally Posted by Dave Brand

The best approach is to dab the brakes just before the front wheels hit the speed bump. The front will dip, so if it's timed properly the front of the car will be rising as the wheels hit the bump, reducing the shock loading on the front suspension & giving a more comfortable ride over the bump. Accelerating as the rear wheels hit the bump also helps.

this sounds right. I was taught to brake until you feel the bump and then accelerate, which sounds like this method

[Dennis.Doyle]

Surely the optimum technique is a wheelie followed immediately by a stoppie -should be able to miss the bump altogether whilst getting maximum points for artistic interpretation & style?

Should be possible to practice on a mountain bike beofre moving onto a fireblade & maybe even in a car with line-lock brakes .... but preferably only inside a lunatic asylum.

[johnh875]

To minimise the impact brake to slow down, let brake off just before bump and a touch of throttle to raise the nose and minimise bump impact, then as the rear wheels are approaching bump use the brakes to transfer some weight away from them. Or you could just slow down a bit more and achieve the same thing with a lot less hassle.

Taking the bump on a diagonal so each wheel on the axle hits it separately will help the ride but not the impact on the suspension.

Another tip if possible (without going to a silly extent) is "dodge" the speed hump with the near side wheels in the gutter or vacant carpark.

[Al Weyman]

Interstingly I discovered something by accident the other day in my Chevy Blazer. There are some really horrible rubber strip type bumps behind Wickes in Watford and if you take them at more than 5mph they jar yer dentures or at least I thought they did, I hit them at about 25mph the other day (minor oversight) and she just sailed over the bumps with hardly a tremor. Bit like the old whipping a table cloth quickly and leaving the crockery intact on the table.

[JimW]

They seem allright providing you don't drop below 50.

Regards

Jim

[Cryos]

Lads just get good ol diesel suspension, or a Jetta. Sure the quicker ya go over them the less ya feel

[GORDON STREETER]

AL you are right in what you say but only a certain hight. I use a lot of dirt roads in Spain mostly with bulldozer track imprints in them . There is always an optimum speed where you can cancel them out. As for the big speed bumps if you hit them fast enough you can miss out the next one . This is only recomemded in a hire car !!

[Cougar]

If the the bump isnt the full width of the road but too wide to fit between the wheels I usually let the passenger side go over the bump... More comfortable for the driver.

Still not much of a scientific answer from anyone which the OP asked... where are the diagrams and maths? :P

[Suze]

If the bump is designed to fit between the wheels I tend to go over about 25 - 30...if it's one of those nasty little jolty ones (eg multi-storey car park) tend to go over as slow as possible...if it's big ones, eg elongated (over a zebra crossing or something) will brake before it and accelerate over it - does that help??!! Unfortunately the ones designed to fit between the wheels don't really "fit" between my car so it tends to be a bit of a bump! If there's the option I do also try to get the left wheel on the left hand bump and the right hand side wheel on the bump in the middle of the road...

[strider]

Originally Posted by Suze

if it's big ones, eg elongated (over a zebra crossing or something) will brake before it and accelerate over it - does that help??!!

Sounds good, but don't forget to check if there's anyone on the zebra crossing. They could be fooled by the braking before into thinking that you actually intend to stop!

[Suze]

Thanks for that, strider....

[garcon]

If the suspension can take it, most road humps are best taken as quickly as possible. Although I did getsome significant 'air' by doing that once. And nearly landed in a garden.

[Suze]

When they introduced new bumps in my old town, they recommended 20mph as the best speed to go over them (there were the between the wheels type) - never agreed with that to be honest, used to take them between 25 - 30 which seemed a little smoother.

[garcon]

And 80 mph is smoother still.


Er, apparently.

[peenuts]

i use a large van and cable trailer there is a road near to my work that has 17 speed bumps in just over half a mile take these at the speed limit it states
and the noise is anoying to the local residents. now they are starting to remove these it works a treat when you have 6 of us doing it in the early hours the moring

[Bluebottle]

Humps have been removed from a road near us, the road leads to the local dump so there were skip lorries making lots of noise on the humps!

[GORDON STREETER]

The next village to us in Spain have just put in 7 new metal bumps within a quarter of a mile and you have to go slow or wreck the suspension . They only go across half of the road so most people go over the other side . Now I may be a little senile in my old age but not as daft as the person who designed those !!!!!!

[Suze]

They'd got rid of some near us in our local town a couple of months so were quite pleased as they were disintegrating - however some more appeared over night this week and these are properly vicious, no "good" way over these, they're the sort which (are supposed to) go "through" your wheels.

[Craig]

A few residents at the other end of the estate started bleating and whining about 'cars speeding past our house as our children are playing' (shame, shouldn't have bought a house on a main road then) and got a petition up demanding humps. They even started knocking on doors crying about it. As you can imagine, they didn't call at my house a second time :lol:

They eventually got their wish, the council came and spent six weeks digging up the road to build a new roundabout (fair enough, it was needed, it used to take me ages to turn out of the side road!) and a dozen humps. They were really savage bolt-down prefabricated platform type humps and I had to slow to almost a complete stop and crawl over them at 2mph to avoid ruining the car totally.

People soon got fed up with this and started experimenting on new methods of crossing them - some would gun the throttle at one end of the road and not let off for the entire 3/4 mile stretch, getting air over every hump! Others would stand on the brakes as they approached a humpslow to a crawl, then gun the throttle wildly until they reached the next hump. Others would simply bump their inside wheel up onto the grass verge and drive round the thing without slowing.

After a couple of weeks, the same morons who were crying about how they were vital were in the local paper demanding they be removed due to, get this, 'cars speeding past our house whilst our children are playing!' Obviously someone in the council was as unimpressed as the rest of us and told them they were staying put. So, and this has yet to be proved, those whingy residents apparently removed the humps themselves one night!

Whilst I'm sad to think of them getting their own way again, you have to hand it to them for using their initiative.

Of course the council have been back since and replaced them, this time with tarmac humps, but at least you can drive over them without risking an oil slick and a wrecker.