Safe Speed Forums

This is a direct copy from the ABD website - http://www.abd.org.uk/pr/490.htm

These things are now dotted all over Fife, where I live. 3000 miles ago I had new tyres put on my girlfriends car, the bumps have thrown the tracking out so far that they are now through to the canvas on the inside.

She was completely unaware of this, believing her tyres to be nearly new.

I put my car in for MoT last week, and it failed on the ball joints in the front wishbones being loose.. again according to the mechanic "caused by the new bumps"

Both of these faults could cause a horrific accident.. how many more motorists have similar dangerous faults in their cars thanks to these bumps?

It's insane.

Welcome to the Forums!

3000 miles is an incredibly short distance - I have still have my original tyres with plenty of tread left after 22000, and my car is not exactly known to be gentle on the tyres... They would probably say that you must have been speeding over the humps so it was self inflicted (i.e. going faster than 2mph!).

I originally thought the speed bump concept was just incompetence on behalf of the authorities, but knowing much more these days I almost suspect that it is a deliberate mechanism to throw additional costs onto motorists and if accidents occur then it is perfect for justifying additional things such as more speed bumps and speed cameras. A self perpetuating persecution of motorists....

or I could have just been right in the first place, and they are so incompetent that almost every measure that they take makes things worse.

Somebody with a more specific knowledge than myself can probably tell you whether you have a case for suing the authorities for the damage to the vehicles - you can for potholes and other disrepair so maybe there is a case?

The problem I have with them is that they are literally now EVERYWHERE in fife... not just outside schools etc.. so on a daily drive you are constantly crossing the things. There have been several petitions against them that the council have just ignored, saying if they cause discomfort or damage to your car you should just go slower over them.

From my point of view if the limit is 30, i should be able to do 30 without breaking my car.

Recently in the local press they've been going on about how much of a success they have been in reducing speeds in the area, and that despite all the objections they are a neccessary evil.

Problem is, so many people are now driving cars with lethal tyres or suspension, thanks to the bumps, in blissful ignorance.

when the components fail, causing accidents, plod will put it down to poor maintenence and the council will continue to think the humps are wonderful.

In the village where I live, there have been no speed related accidents in 30 years, so quite what the point is of the bumps i don't know!

It's the whole mentality of "everyone MUST be slowed down" regardless of whether there was ever a problem!

I'll get off my soapbox now!!

Damage to my car this year totals £350 for.....

2 new CV Joints
Tracking & Wheel Balancing needed
4 new Tyres, (which had no probs in the MOT 2 months earlier but had worn down to near slicks very soon after - presumably a consequence of the above 2 problems)

According to the garage, all due to speed bumps, (Peugeots with their soft suspension tend to not fair well over them).

So I know exactly how you feel mate. To say I was pissed off with it, would be a vast understatement.

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Why can't we just use Common Sense?

Pretty sure I reported a story in which Bolton Council ripped up a large number of humps last year

More please! Across UK ..

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Sorry to disagree, but I'm totally unconvinced that speed bumps damage suspension unless, that is, you simply ignore them and hit them at well over the posted limits.
Many people in rural areas drive cars every day over badly or unsurfaced tracks and their cars don't need re-tracking every few weeks. Suspension is designed to cope with bumps. What, exactly, is bending within the steering system to cause this problem. The rubber bushes will absorb a lot of shock loading and the dampers will absorb vertical loads. If the bumps are crossed whilst driving straight ahead or nearly so, then any potential side loads are neutral, the only loading on the suspension being vertical and straight fore-and-aft. That should cause no problems to a car that is sound to begin with. Is it suggested that the steering arms are bending? The standard ones on my Rover 214 rally car don't bend over rough forest tests driven flat out and that has heavy-duty bushes with minimum compliance, thus putting even more load into the arms themselves.
Sure, if your suspension is near the end of its service life going very quickly over speed bumps may hasten its demise, but not on a decent modern suspension system.
Speed bumps are more of a discomfort than a damage-causing feature and yes, they are a b****y nuisance. But to suggest that they cause the levels of damage suggested here is very unlikely.

I don't think you're looking at this correctly at all. Ball joints, dampers and bushes are 'disposable' components with a finite lifespan. In practice (I wouldn't mind betting) that lifespan is measurable in terms of 'events over a certain load threshold'. Clearly speed bumps will contribute to 'events over a certain load threshold' and as such will significantly shorten the life of suspension components.

Springs and suspension arms are in a slightly different class, with higher shock loading required to cause damage. Still it's entirely possible for excess loads to be caused by some speed bumps.

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

I think the truth sits somewhere between the two.

Clearly speed bumps shorten the life of suspension components, as will anything that causes the suspension to work more.

But I would agree with Peter that they shouldn't cause catastrophic component failure unless you hit them at seriously excessive speed and / or wheels locked up / steering applied.

I too have been seriously amazed by how much abuse standard suspension and steering components can take in competition use - and that has generally been on older cars. Modern vehicles tend to have heavier and stronger components as market needs have changed over the years towards stiffer, tauter handling setups.

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I haven't had tracking or alignment issues, but I did have a shock failure on a brand new Mondeo (ST200) where the springs had such a high rate that the car didn't fail the simple "bounce test". The main dealer kept telling me that there was nothing wrong, despite me complaining of bad under-steer at speeds that it had previously had no problems with, and what I thought was oil down the outside of the shock (driver side rear; 3 separate visits to main dealer).

Then I had a nail in that tyre, so I took it to Kwikfit to get it repaired, and while the wheel was off I got the fitter to test the shock. He lifted the wheel and let go, and it dropped like a stone with no damping at all - with this new evidence I went back to the Frauds main dealer, and after a further 3 weeks delay (parts not in stock) the shock was replaced, and all was well again.

The conclusion was that speed bumps had been a factor in the premature failure (12 months old and 18,000 miles) but the ones that would have most likely caused the problem were on the works site where they used those heavy plastic ones that are 4" high and only 10" wide.

The thing about many speed bumps is that they are extremely uncomfortable at the posted limit or at most speeds below - most public road ones are OK at about 5mph, but private ones such as the steep plastic things cannot be taken comfortably at any legal speed. However, as I and many others have discovered, taking them at much higher speeds allows the suspension to treat them more like a pothole and absorb the bump. So on a speed bumped 30mph public road the most comfortable speed is often 40mph or more.

Cooperman, your argument has merits for full across the road speed bumps, however it is much more likely these days to come up against speed cushions that are positioned to (in theory) allow buses, trucks etc to pass unimpeded while cars are forced to straddle them with all the force hitting the inside of the wheels and nothing on the outside, or one wheel passes unimpeded while the other takes the full hit. As the cushions appear to be less of a problem, many people take them at the speed limit, and I can see that with repetition, damage or misalignment could occur.

It also should be considered that a very large number of vehicles are not privately owned, and therefore the driver has no incentive to be careful. It was true in my case where the ST200 was a leased company car, so I chose (where safe) to drive at a speed over the bumps that caused minimal pain to my injured neck (whiplash), and I was going over 10 wider speed table types and 20 of the steep plastic ones every working day. So yes, maybe it was my fault, but that doesn't stop the real world consequence that the shock failed prematurely and degraded dramatically the handling of the car. Had I listened to the main dealer I would have been driving around in an MOT failure for two more years before the failure might have been spotted.

I would go as far as saying that the drivers of most cars that are not relatively new and privately owned will be doing everything that they can to minimise the discomfort over speed bumps, and bugger the consequences; except that the consequences are damaged suspension components that have a real world impact on handling, and especially braking from high speed.

<shrug> That was really the substance of my point.



But when you measure the high stress competition use in miles or hours it's absolutely tiny compared with road use - that's the basic reason.

I know that you're also thinking of massive shock loads - but there are massive shock loads in road life too - it's just that it's once in a few months instead of once in a few minutes.

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

Sorry...

There may be some truth in that as regards component wear, but I don't think it holds up for catastrophic failures.

For the most part I don't think steering / suspension links suffer from fatigue fractures, as the design and materials selection will be geared around eliminating this very problem.

So the only way in which such a component is likely to fail is when it is subjected to an extreme load that exceeds it's elastic limit. Whereas as long as you stay under that limit you can repeat the load as many times as you like without a problem.

Thus I believe that short term competition use is actually a good measure of how much shock loading the suspension components will withstand in normal use.

But wear rate is a different topic

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No problem at all. I'm sure we all agree completely once we've sorted out the definitions.

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

Are they driving the same kinds of cars though? If I lived/worked in an area that required me to regularly drive along rough tracks (as opposed to merely badly potholed roads) then I'd have chosen a different car to the one I currently own.

Also, do the types of suspension disturbance make a difference? Hitting a pothole, the suspension is extending beyond its neutral position then retracting back to neutral, whereas hitting a speed hump it's being forced to compress further than the neutral position before then being allowed to extend back - wouldn't this place differing stresses on the components?




That's a big if though, especially in areas where those multiple smaller humps are used rather than a single full-width one. With the multiple humps, it's difficult (or even impossible depending on the hump width and track width of your vehicle) to have both wheels on an axle affected the same - generally one wheel ends up passing through the gap between hump (or hump and kerb), and the other then rides up the far side of the hump you're trying to straddle. Parked/oncoming traffic can also hinder optimum vehicle placement for minimising hump effects.

Edit: beaten to it by Rewolf, I see!

And for all hump types, having them placed right on junctions makes it a certainty that some vehicles will have to cross them at an angle...

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Chris

I think that in order to truly appreciate the massive difference between driving over speed humps and covering a rough rally stage at competitive speed you would have to experience the latter! Having once done the latter you'd never again even consider the possibility of hitting a speed bump at moderate speed causing any component damage. Wear yes, failure no.

Similarly, the times I've known people say that after touching a kerb whilst parking they've upset the tracking of their vehicle. No, they're not that fragile. Sliding into a big kerb sideways at 20mph+ with the wheels locked would probably do some damage, but anything less is unlikely.

Another thing that springs to mind from competition experience is that when you do "overdo it" and break something, the first thing to fail is usually a tyre sidewall, and next after that broken or buckled wheel rims. It would be very unusual to break a steering component without incurring fairly severe damage nearer the point of contact.

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I thought that we were talking about the extra wear causing premature failure of components that wear over time such as shocks, bushes, bearings etc, and bending of steering arms or minor shifts in alignment rather than outright failure. A few degrees of misalignment can cause serious wear on the tyres, and can be caused by a single curbing incident.

For most people, who quite frankly don't check anything unless a light comes on or the tyre is flat, this means that they can wear the insides of their tyres down to slick without noticing. Then when they do need the grip it just isn't there. This link is about how accident investigators are being taught about the contribution that worn shocks alone can have towards accidents, and it isn't just the obvious (see lower down the page) http://www.prnewswire.co.uk/cgi/news/release?id=64998

I used to do business with MIRA, the Motor Industry Research Ass'n, at Nuneaton. If you have ever seen test vehicles on their rough-road course and their 'Belgian Pave' sections, where these test vehicles do literally hundreds of miles, you would never be worried about a few bumps or speed-humps on ordinary roads.
Modern suspension is really so very strong and, as JT rightly says, fatigue failure is virtually non-existant. Wear rates for suspension are also low in normal use compared to 30 or more years ago. Take, for example, the ball joints on a Mini front suspension. In the early 60's these would last only about 20,000 miles in normal use. The lower arm ball joints on a Fiesta I know of lasted 50,000 miles. Similarly tyres last so much longer now due not only to better tyre technology, but to better control of suspension movement.
As a general rule it is wise, maybe, to get the track checked every 25000 miles or every year, whichever comes soonest, but it should not ever be a problem and it's hard to see how speed bumps will knock the tracking out.
On the competition side, I do get my rally cars tracked before each event, but unless I've gone off or hit something a bit hard whilst travelling sideways, it's not usually far out.
However, speed bumps are a bit of a pain-in-the-a**e.

The problem in our case is that Fife council has gone berserk with these bumps in the last couple of years. I do a fairly high mileage and have to constantly cross the things. While I was in the MoT station, the tester told me that bumps were without question causing all kinds of problems.. he had seen a huge increase in tracking problems, suspension component failure etc. That is proof enough for me. While I was in the station a mondeo was also being tested.. and failed on anti roll bar bushes and a dislocated front strut.. again, the tester said caused by the speed bumps.

Everyday cars are not designed to deal with the pounding from these bumps day in day out.. those who think otherwise should come and live here for a few years, and watch the deterioration in their cars.

I have no objection to the things outside schools, but to put them on every street, everywhere is just asking for trouble.

A local taxi firm actually put in a letter to the council regarding the wear in their cars.. components designed to last 100,000 miles were wearing out in less than 20,000. They backed this up with written confirmation from the manufacturer. The council ignored the letter.

Wrote to the council RE the bumps, expressing my concerns... recieved this reply...

DAVE

There was consultation with the Community Council and with residents who live where the speed cushions were proposed at the design stage. The leagal adverts were placed in the Glenrothes Gazette and notices were put up on street lights before the work was approved.

The Transport Research Laboratory has reported that if driven at the correct speed then no increased maintenance will result from the use of speed cushions.

The Scottish Executive are funding the 20 mph zones to help reduce the number of child casulaties and on that basis the residential areas served by all schools in Central Area are being provided with 20 mph zones - most will also have speed cushions.

Speeds have reduced where the 20 mph zones are in place and there is now a waiting list from other areas asking for more speed cushions. Evidence from Hull City showed that casualties fell by two thirds when the 20 mph zones were used - it is hoped that casualties will fall across Fife when the programme of 20 mph zones is completed.

A meeting is planned in the 252 Hall on Betson Street on 31 May from 3 pm to 5:30 pm to look at the proposed extension of the existing 20 mph zone to include the rest of Markinch.

This meeting will be the first of probably 3 or 4 over the next few months as the design of the 20 mph zone for Markinch is completed.

Dont know if you can make it to the meeting tomorrow, but we can discuss the issues you raised if you are able to be there.

Regards Ian

Ian B Smith
Lead Officer - Central Area
Traffic Management
Transportation Services
Scottish Transport Local Authority of the Year 2004
Room 112 Townhouse
Kirkcaldy
Fife
KY1 1XW
Tel 01592 411586 Fax 01592 411592


Nice of them to arrange the meeting when neither I (nor anyone else) can go... right in the middle of the working day!

The timing of your post coincides perfectly with the middle of their meeting (albeit of course on a different day). If you feel strongly, do consider taking an afternoon off annual leave. The issue is important.