jonD6B 0 Posted February 12, 2006 I have after market struts on my 1.9 8V that are of unknown origin and therefore I don't know what poundage the spring rates are. Is there any way of testing them to find out? Share this post Link to post Share on other sites
Anthony 1,000 Posted February 12, 2006 You can get them properly tested at most motorsport setup places I suspect, or you can work it out for yourself - can't remember the formula off the top of my head (I know Adi posted it a while back if you do a search) but basically you need the thickness of the coil, the number of coils, and the uncompressed height from what I recall... Share this post Link to post Share on other sites
buchanan84 1 Posted February 13, 2006 heres an online calculator spring rate calculator any probs give me a shout as i've just been doing stuff on this at uni Share this post Link to post Share on other sites
PumaRacing 1 Posted February 13, 2006 heres an online calculator spring rate calculator any probs give me a shout as i've just been doing stuff on this at uni The main problem being that the number of active coils is not a number that anyone will be easily able to determine by measuring the spring. It isn't the same number as the fully compressed length divided by the wire diameter and on a suspension spring you wouldn't easily be able to fully compress the spring anyway. I have an empirically determined program which calculates spring rates for suspension sized springs and valve sized springs and the correction factor for active coils v total coils differs quite markedly between the two. Share this post Link to post Share on other sites
SPGTi 2 Posted February 13, 2006 Get a drill stand that you can use as a press, a set a bathroom scales and a ruler. Use the drill press to compress the spring onto the scales over a known distance. This should then give a rate. Steve Share this post Link to post Share on other sites
buchanan84 1 Posted February 14, 2006 The main problem being that the number of active coils is not a number that anyone will be easily able to determine by measuring the spring. It isn't the same number as the fully compressed length divided by the wire diameter and on a suspension spring you wouldn't easily be able to fully compress the spring anyway. I have an empirically determined program which calculates spring rates for suspension sized springs and valve sized springs and the correction factor for active coils v total coils differs quite markedly between the two. my understanding of the active coils was number of complete coils, i.e. not flattened or ground flat for the stuff i'm doing at uni i'm looking at a removed spring, so can measure free length and count the coils I dont suppose there's any chance you could give me a copy of your program? sounds like it could be useful for what i'm doing (typical lazy student looking for the easy way) cheers Share this post Link to post Share on other sites
jonD6B 0 Posted February 14, 2006 O.K. It seems as though it isn't going to be a straight forward test so let me advance my question slightly. Once the spring rates are determined, is there actually any difference between springs from different manfacturers if the poundage rate and the length of the spring are identical? Simplified, I mean what would seperate springs made by 'Tein' (for example) and springs half the cost? Share this post Link to post Share on other sites
jonD6B 0 Posted February 15, 2006 Just to ask again, do springs with the same drop and rates vary in performance? What makes people choose Bilstein over Spax for instance? Share this post Link to post Share on other sites
PumaRacing 1 Posted February 15, 2006 Just to ask again, do springs with the same drop and rates vary in performance? What makes people choose Bilstein over Spax for instance? If they are both have the same length and rate then they will perform the same. The wire that springs are made of is a basically standard material called music wire because it was designed for making pianos. It's not generally the springs that make people choose different suspension suppliers it's the dampers. However springs can also be made with a non linear rate by tapering the coils, spacing them non linearly or thinning the wire at one end. That can give a comfortable ride over small bumps but a firm one under hard cornering. The state of the art in valve springs is moving towards elliptically drawn wire rather than round wire which allows greater compression and valve lift for a given spring rate. Anyway I'm sure this and more is all on Google somewhere. Share this post Link to post Share on other sites
Rippthrough 98 Posted February 15, 2006 If they are both have the same length and rate then they will perform the same. The wire that springs are made of is a basically standard material called music wire because it was designed for making pianos. It's not generally the springs that make people choose different suspension suppliers it's the dampers. However springs can also be made with a non linear rate by tapering the coils, spacing them non linearly or thinning the wire at one end. That can give a comfortable ride over small bumps but a firm one under hard cornering. The state of the art in valve springs is moving towards elliptically drawn wire rather than round wire which allows greater compression and valve lift for a given spring rate. Anyway I'm sure this and more is all on Google somewhere. There's also some use of stainless purely for looks. On a side note there are a few experiments with shape memory alloys for valve springs - you can make them so they increase preload at high temperatures (/rpms) although there are obviously a few problems with that! Share this post Link to post Share on other sites
