Published - 2020

Coil Springs: Astonishing Results in Coil Spring Tests

Tech news

The coil spring, together with the shock absorber and the strut bearings, are all classified as safety components in the strut. This is exactly why the quality of the coil spring is important and especially in the winter time where low temperatures often are a contributing factor that causes coil springs to crack. After Triscan - by several of the company's customers - was presented with a competing product at an incredibly low price, an investigation was initiated. The results of the tests performed proved to be astonishing. 

 

Two specimen of the competing company's coil spring for the front axle, suitable on selected models of Citroën C4 and Peugeot 307 in the years 2000-2008, were subjected to two common tests. 

 

The purpose of the first test was to check the coil spring's conformity - ie the coil spring's ability to maintain its original shape. The test was performed by measuring the height of the spring, after which the spring was compressed, and the height again measured. The measurement for the two springs tested revealed that the height had been reduced by 10 mm. Generally, the spring must of course return to its starting point and thus have the same length. The inability to return to the starting point can be attributed to the use of low-quality spring steel.  

 

The second test was a durability test. During this cyclic test, the springs are continuously pressed together 1 million times or until the springs crack. In this case, 180 mm compression from a starting point of 875N-3833N. As can be seen from the table below, the springs cracked after approx. 95,000 and 612,000 compressions. The tests performed are done at 20 degrees and it is worth noting that the probability of coil spring cracking increases the lower the ambient temperature is. As with the first test, the inability of the springs to pass the test can be attributed to the use of low-quality spring steel.

 Test   spring   Length  of spring [mm]  Compression  [mm]

 F   start  [N]

 F
stop [N]

Cracking by

 [Compression  no.]

 OE demand
 1  441  180  875  3833   95.027  >1.000.000 
 2  440  180  875  3833   612.781  >1.000.000

 

Test spring 1


test 1

 

 

Test spring 2

test 2

 

“The durability test performed confirms that there is often a clear connection between price and quality”, explains Lars Berthelsen, product coordinator at Triscan a/s and continues: "It is therefore also particularly important for safety components to ensure that the quality meets the current standards - it is absolutely crucial and especially important in cases where failure can have very large safety consequences”. 

 

test 3

Product Coordinator Lars Berthelsen

 

All of Triscan's coil springs are manufactured by the Swedish manufacturer Lesjöfors and comply with the OE requirements specification of min. 1 million compressions. Depending on the type of spring, either spring steel EN 10270-2 FDSiCr or EN 10089 is used. The springs' corrosion protection consists of a zinc phosphating and after that a powder lacquering which is regularly checked to withstand 1000 hours in a salt spray chamber. Lesjöfors has a high-tech production and over 150 years of experience in the production of springs. All manufacturing and development take place in Sweden. The coil springs are made of high-quality spring steel and are cold wound on CNC machines, ensuring a continuous high and uniform quality. Lesjöfors is certified according to ISO/IATF 16949: 2016, ISO9001: 2008 and ISO14001: 2004. The coil springs are manufactured according to "Matching quality" and can therefore be used by repair shops without affecting the vehicle's warranty.