I have heard several stories of springs failing at low millage eg 20-50 k. Hiowever all these cases i have heard of it seems to be confined to French models fords and Gm. Is springs failure with cars beter known for their reliability eg jap and german manufactures at this low millage common???. i would also appreciate a responce to the aforementioned question in realtion to suspension bushes
It seems poorer quality of metal and the amount of speed bumps is the main reason for the increase in broken springs i would also like to know do springs wear with age eg corrosion and if so at what sort of age would you expect to see springs to show signs of terminal wear??
Cheers
Andy
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Bit an odd question Andy
www.eibach.de/index_start.php?SPA=1&spz=en&LID1=2&...0
You may find this site of interest
As well as speed humps I'd also suggest anti skid road surfaces, lower profile tyres and ever more grip from road tyres also contribute to failure (even if the road is flat the springs will be oscillating). Just my thoughts though, may be wrong. Personally I would'nt worry until they break and need replacing :-)
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Corrosion doesn't tend to affect coil springs in the usual sense; i.e., by gradually reducing the effective section. However, the presence of a corrosive atmosphere does affect the response of steels to fatigue loading.
In a corrosive atmosphere, as well a reduced SN curve, the assumption of the presence of a safe stress range, below which fatigue does not occur becomes an unsafe assumption. In a design sense, the slope of the SN curve is reduced at low stress, but does not become flat.
In a mechanistic sense, the presence of products of corrosion prevents crack closure, and accelerates inter-grain crack growth.
So, if you design a spring assuming a non-corrosive atmosphere, you can use a superior SN curve and you may disregard all the low stress cycles. If the corrosion protection is compromised, the assumption of a non-corrosive atmosphere may no longer be sound, and all stress cycles become potentially damaging.
My understanding is that the corrosion protection offered to springs has been so compromised, thus accelerating their demise.
Rubber bushes are way too complex for me to consider!
Number_Cruncher
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In HJ's section in The Telegraph of 13th May, there was a letter pointing out an article from 'Professional Engineering' regarding the common practice now to use 'open toe' springs. Apparantly this causes a stress concentration compared to closed coils.
see
(www) telegraph.co.uk/motoring/main.jhtml?xml=/motoring/2006/05/13/mrjon13.x
ml
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A complex subject. I would add Mercedes Benz to the list of spring breakers - several models are prone to this, especially A-class rears. I think that apart from the valid points made concerning low profile tyres, road conditions and a lack of corrosion prevention treatment, there is a tendency for car designers to use springs which are either too short (A-class) or too tightly wound in relation to the wire gauge (W124). This results in a hopelessly overstressed spring in either case.
A glance at a few pattern parts catalogues will identify the spring-breakers (GSF sell A-class rear springs and W124 both ends).
If you want to know the weak spots of any vehicles, a look in these catalogues is always revealing. If you see any odd items stocked, you have your answer.
659.
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190E's used to break rear springs too.
Springs normally snap near the ends. It seems to be more common nowadays. probably down to cost and materials savings - they're more 'marginal' than hitherto.
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There was a very similar thread to this just the other day;
www.honestjohn.co.uk/forum/post/index.htm?t=43666&...f
Number_Cruncher
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There have been alot-and I mean a lot-of VW failures.
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This has been a sufficiently serious problem for Citroen to issue a recall for many of their vehicles.
Not to replace the springs but to fit a shield so that if (when??) a spring breaks it doesnt puncture the tyre!
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