Ke36 Posted December 10, 2008 Share Posted December 10, 2008 im starting to get really fucked off with my front coilovers had 300mm length coil over springs in it had them wound all the way down to the bottom of the thread and was at a nice ride height but the springs were about 10-15mm uncaptive so i took the shocks out and got them shortened 20mm and at the same time swapped the springs over for some in the same spring rate that were 250mm length so that i had some ability to go lower if i wanted so i put it all back in and had the lower spring seat 30mm form the bottom (50mm shorter springs - the 20mm of shock ive had chopped off) and the thing is way higher than it was before, ive takin it for a few drives so it should all be settled ive had to drop the spring perch but another 15-20mm to get it to sit at the same height so my springs are even more uncaptive than they were before?? what the farks going on the maths just doesnt add up to me?surely i dont have to take another 20mm off my shocks?im sick of taking the damn things in and out and stripping them down Quote Link to comment Share on other sites More sharing options...
OSM Garage Posted December 10, 2008 Share Posted December 10, 2008 Whats it like with the 300mm springs in it with the shorter insert? Did you try? You mite have no more height adjust left but atleast you know it was good with the nut wound all the way down. And with the shorter insert, surely it would keep the spring captive. But i know what you mean, i dont quite get it myself Quote Link to comment Share on other sites More sharing options...
Ke36 Posted December 10, 2008 Author Share Posted December 10, 2008 nah had to swap the 250mm springs for the 300mm ones with autolign, that way it dont cost me anything so i cant recheck them unfortunately if i have to machine the shocks ill do it be i have no idea why the hell it isnt sweet as is, just wondering if im missing something only other thing i can think of is the springs are a different rate maybe, but they still had the sticker on them saying what they were and that was the same as my old ones Quote Link to comment Share on other sites More sharing options...
shizzl Posted December 10, 2008 Share Posted December 10, 2008 common prob with coilovers,theyr mainly for stiffness rather than height adjust..most youll probably get out of a coil over with a single spring would be 30-40mm drop.. to get it sacked you need keeper springs so you can wind all the tension off the spring... which basically means the shock has already travelled most of its availability.. best thing to do is to get shorter shocks and keeper springs.. Quote Link to comment Share on other sites More sharing options...
fuel Posted December 10, 2008 Share Posted December 10, 2008 I can only imagine the longer spring length is going to compress more and have a tendency to be more captive. Going to a shorter spring with the same spring rate it's going to be a bit more stiffer. Thing is with coilover springs, especially short and stiff ones is they're not going to be captive easily - you really need keeper springs in there. If you shorten your inserts further you may start to run out of travel if you want it to be boned - it's the same problem I'm faced with at the moment. Ideally I should have found shorter length inserts (which are heavy duty) and shortened the strut casing an inch or two to suit (much like what we did to the rears of mine). Quote Link to comment Share on other sites More sharing options...
Ke36 Posted December 11, 2008 Author Share Posted December 11, 2008 common prob with coilovers,theyr mainly for stiffness rather than height adjust..most youll probably get out of a coil over with a single spring would be 30-40mm drop..to get it sacked you need keeper springs so you can wind all the tension off the spring... which basically means the shock has already travelled most of its availability.. best thing to do is to get shorter shocks and keeper springs.. nah dont think you quite get what im saying the coilovers are custom made not off the shelf, they got me as low as i wanted, weve chopped 3 inches out of the strut when the sleves were fitted and fitted shorter inserts theyve got massive amounts of travel then when i put them in the car realised i wanted to go a bit lower than that so figured wind them down a bit (ended up being at the bottom) and shorten the shock to keep them captive no problems there, i imagine if i had put these back in the car there would have been no problems??? excpet i would have had no adjustment at the same time i got the springs swapped for shorter length ones the exact same spring rate (fuel this is where it shouldnt matter in relation to what ur saying i think ) this means they should compress the same amount as any other spring with the same spring rate, when they have the same weight applied to them, no matter what the length of the coil is (spring rate is calculated using number of turns, coil diameter and length) so maybe the wrong spring rates?fucked if i know what im talking about, physics was a few years ago now thing is now i dunno if id fit a keeper in there as ive only got 10-15mm before i run out of adjustment again and the keeper i imagine would be larger than that size on full compressed so it will effectively raise the car again Quote Link to comment Share on other sites More sharing options...
isnowi Posted December 11, 2008 Share Posted December 11, 2008 Are the springs the same poundage? or the same size wire? cos 2 springs of the same diameter and wire size will be different spring rates. think of the springs as one long bit of wire, the taller the spring and the more coils in it, the longer the wire, and the easier it is to bend. Also remember that the spring rate becomes exponentially higher with every coil that becomes coil bound ( not usually an issue with race coils as they are normally linear, but this is one way how the they make progressive rate springs) A linear spring will be the same poundage up till the point that it's rate becomes infinite when the coils are bound. Apologies if i am rehashing stuff you already know. Cheers, Dan Quote Link to comment Share on other sites More sharing options...
Ke36 Posted December 11, 2008 Author Share Posted December 11, 2008 nah exact same spring rate thats whats got me farked they should compress the same amount no matter what length they are if there the same spring rate correct? but if that was the case i wouldnt have a problem would i? maybe these springs are a different rate than the others?thats the onlt conclusion im coming to but just wanting to make sure my maths inst farked up or im missing something else Quote Link to comment Share on other sites More sharing options...
Truenotch Posted December 17, 2008 Share Posted December 17, 2008 This is really confusing! Obviously there would be no point in running a Keeper spring to keep the coils captive, because you could compensate for that by lifting the perch up a bit (keeper springs would have the same effect). So it's a shorter shock, a 50mm shorter spring and the perch is 30mm higher than where it was with the 300mm springs? Which means it should be around 20mm lower then it was before... but isn't. Are the springs seating at the top properly? Only thing that I can think of is that the spring is fouling up on something when you lower the car, due to the spring not being captive. So they could be off on an angle and holding the body up somehow.... Although then you wouldn't expect it to drive right. hmm... Quote Link to comment Share on other sites More sharing options...
Testament Posted December 18, 2008 Share Posted December 18, 2008 If its not hanging up on something I'm guessing the springs are stiffer - they are the key change you have made. maybe the old springs were softer than you thought so when you asked for "x" spring rate its actually more than what the old springs were. Quote Link to comment Share on other sites More sharing options...
isnowi Posted December 18, 2008 Share Posted December 18, 2008 I wonder if the swaybar is having some effect on what you are seeing, it could be hanging up on something? Quote Link to comment Share on other sites More sharing options...
Ke36 Posted December 18, 2008 Author Share Posted December 18, 2008 cheers guys yea its had me stumped it definately wasnt hanging up on anything as i could wind them down as low as i wanted and it would drop springs just wernt captive i got the springs rated by autolign this week they came out dead on 250lbs so thats not the problem my solution was to take the shocks in and get them shortened another 20mm like you said truenotch keeper springs just wernt going to do the job im peicing my cooilovers back together now, good news is the springs are captive when there just sitting there now i just gotta see what height it turns out at Quote Link to comment Share on other sites More sharing options...
Testament Posted December 18, 2008 Share Posted December 18, 2008 but were the old springs 250lbs when they came out of the car? Quote Link to comment Share on other sites More sharing options...
Ke36 Posted December 18, 2008 Author Share Posted December 18, 2008 dunno never tested them swaped the ones i have in there now for them they were meant to be 250 Quote Link to comment Share on other sites More sharing options...
Testament Posted December 18, 2008 Share Posted December 18, 2008 dunno never tested them swaped the ones i have in there now for themthey were meant to be 250 thats what I mean, if you cant find anything else - maybe the old springs were softer than they were supposed to be. Quote Link to comment Share on other sites More sharing options...
Ke36 Posted December 18, 2008 Author Share Posted December 18, 2008 yea thats about the only thing i can think of causing it its all sorted now anyways Quote Link to comment Share on other sites More sharing options...
Steelies Posted December 19, 2008 Share Posted December 19, 2008 this means they should compress the same amount as any other spring with the same spring rate, when they have the same weight applied to them, no matter what the length of the coil is (spring rate is calculated using number of turns, coil diameter and length)so maybe the wrong spring rates? just a thought... if the spring rate is calculated per coil, and youve swapped spring lengths (this is where i presume longer spring has more coils than short one), would that actually change the overall rate/amount of force required to compress the spring? Quote Link to comment Share on other sites More sharing options...
Testament Posted December 19, 2008 Share Posted December 19, 2008 this means they should compress the same amount as any other spring with the same spring rate, when they have the same weight applied to them, no matter what the length of the coil is (spring rate is calculated using number of turns, coil diameter and length)so maybe the wrong spring rates? just a thought... if the spring rate is calculated per coil, and youve swapped spring lengths (this is where i presume longer spring has more coils than short one), would that actually change the overall rate/amount of force required to compress the spring? no spring rate is constant force/distance compressed (or stretched) - it doesnt matter how long it is bar the extremes e.g compressed up to coil bind or stretched past the yield point of the spring material. Quote Link to comment Share on other sites More sharing options...
Ke36 Posted December 19, 2008 Author Share Posted December 19, 2008 yea a 250lb spring that is 300mm long is actually physically different to a 250lb spring that is 250mm long (i.e differnet size wire different number of turns etc) but they both compress identically thats what the 250lb bit is if you cut the 300mm long spring down to 250mm it would no longer be a 250lb rated spring Quote Link to comment Share on other sites More sharing options...
Chrome_GT Posted December 30, 2008 Share Posted December 30, 2008 im starting to get really fucked off with my front coilovershad 300mm length coil over springs in it had them wound all the way down to the bottom of the thread and was at a nice ride height but the springs were about 10-15mm uncaptive so i took the shocks out and got them shortened 20mm and at the same time swapped the springs over for some in the same spring rate that were 250mm length so that i had some ability to go lower if i wanted so i put it all back in and had the lower spring seat 30mm form the bottom (50mm shorter springs - the 20mm of shock ive had chopped off) and the thing is way higher than it was before, ive takin it for a few drives so it should all be settled ive had to drop the spring perch but another 15-20mm to get it to sit at the same height so my springs are even more uncaptive than they were before?? Hey I quickly sketched this out. Your first try: 300mm springs, shock min thread at equivalent 315mm => 15mm clearance Second try: 250mm springs raised at bottom so effectively 270mm springs. Shock shortened 20mm So.... 270mm springs, shock min thread at 295mm => 25mm clearance To me it makes sense you've made them more uncaptive. Shortening the shocks by 20mm woul've only been ok if you'd kept the 300mm springs. Because you changed to shorter spings you need to take at least another 25 off (with rasied lower seat) or even more if you keep lower seat lower. Another way to think about it: If you 'hadn't touched the shocks or the lower seat, but you shortened the springs 50mm then you would have 15+50mm clearance =>65mm uncaptive. Basically the problem was you went for shorter springs which worsens the uncaptivity. Quote Link to comment Share on other sites More sharing options...
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