Ark Posted September 23, 2009 Share Posted September 23, 2009 So my car has HSD coilovers on it, at the same ride height as my old suspension, set to be stiffer than before, but now I get the tyres bouncing off the wheel arch on big compressions round the 'Ring. Is this because the HSDs are allowing the wheels to travel too far, or just because they aren't suitable? Short of spending out on a load more suspension, what can I do to reduce or stop this? (driving slower through the compressions is not an option ) Quote Link to comment Share on other sites More sharing options...
bignum Posted September 23, 2009 Share Posted September 23, 2009 Hi chris, the only thing i can think is the springs are actually softer than your original ones and under large compressions are compressing to much, even though you can adjust the shock for compression/rebound rate which will make the car feel "bumpy" stiffer, under a prolonged compression ie the foxhole its the spring taking the load. Quote Link to comment Share on other sites More sharing options...
Paul Whiffin Posted September 23, 2009 Share Posted September 23, 2009 Dont know that much about the HSD's but cant you just the amount of travel they allow? Pretty sure you can with them. Quote Link to comment Share on other sites More sharing options...
Scott Posted September 23, 2009 Share Posted September 23, 2009 As Paul said, you can adjust the stiffness of the spring as well as the height. You would need to do this carefully though as you would want both sides to have the same stiffness. The collar under the spring needs to be screwed up the way to compress the spring. You won't need to go nuts with this to notice a difference 10mm would probably make a big difference. Quote Link to comment Share on other sites More sharing options...
bignum Posted September 24, 2009 Share Posted September 24, 2009 If you adjust the collar under the spring won`t it just higher the car? Quote Link to comment Share on other sites More sharing options...
imi Posted September 24, 2009 Share Posted September 24, 2009 Isn't there one collar for the spring stiffness and a lower collar for the height Quote Link to comment Share on other sites More sharing options...
Swampy442 Posted September 24, 2009 Share Posted September 24, 2009 Theres a collar for spring preload and the bottom of the shock is threaded into the housing that mounts on the lower arm. You unlock the locking collar and adjust the height that way. If theyre the same as mine. Ill get a pic if you want as theyre sat in my dining room right now lol Quote Link to comment Share on other sites More sharing options...
Swampy442 Posted September 24, 2009 Share Posted September 24, 2009 There you go Quote Link to comment Share on other sites More sharing options...
Andy-No-Knee Posted September 24, 2009 Share Posted September 24, 2009 Them they is nice......... soooooooo sweeeeeet! Quote Link to comment Share on other sites More sharing options...
Swampy442 Posted September 24, 2009 Share Posted September 24, 2009 I know, they should be on my bloody car, not sat in their boxes! Quote Link to comment Share on other sites More sharing options...
Ark Posted September 24, 2009 Author Share Posted September 24, 2009 The spring rate is reportly the same on HSDs as on the HKS springs I had before. The ride height can be changed and the bump/rebound stiffness, but the spring stiffness is fixed. The instructions say that you should set the pre-load by winding the spring-base collars up so they are hand-tight, then one more rotation, basically to stop it from rattling. I suppose I could wind up pre-load up further which would lower the car, and compensate by raising the ride height on the coilover. I would rather the spring run out of travel before the tyre hits the wheel arch, but I don't know whether that would cause me other problems... Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted September 24, 2009 Share Posted September 24, 2009 As Paul said, you can adjust the stiffness of the spring as well as the height. You would need to do this carefully though as you would want both sides to have the same stiffness. The collar under the spring needs to be screwed up the way to compress the spring. You won't need to go nuts with this to notice a difference 10mm would probably make a big difference. You cannot adjust the stiffness of a spring, it's fixed and finite. Using spring rates and ride height to stop tyre to arch contact is totally arse about face. Stop the tyre contacting the arch in the first place. The suspension must travel from full droop to full bump stop contact with the springs off, without getting near to anything. It sounds like a wheel size / offset or tyre size issue, nothing to do with suspension per se. Quote Link to comment Share on other sites More sharing options...
Scott Posted September 24, 2009 Share Posted September 24, 2009 If you wind the pre-load up it will lift the car up though, not down. It will mean the car will settle higher up due to the pre-load being higher. If the springs have the same stiffness then the pre-loads must be different. It has to be one or the other. Quote Link to comment Share on other sites More sharing options...
Scott Posted September 24, 2009 Share Posted September 24, 2009 You cannot adjust the stiffness of a spring, it's fixed and finite. Using spring rates and ride height to stop tyre to arch contact is totally arse about face. Stop the tyre contacting the arch in the first place. The suspension must travel from full droop to full bump stop contact with the springs off, without getting near to anything. It sounds like a wheel size / offset or tyre size issue, nothing to do with suspension per se. I didn't actually mean the stiffness, i meant the pre-load. I doubt the spring is being fully compressed and reaching the end of its travel when cornering. Surely if everything is the same other than the suspension, and the springs are the same length and stiffness it can only be down to the pre-load? Quote Link to comment Share on other sites More sharing options...
Ark Posted September 24, 2009 Author Share Posted September 24, 2009 You cannot adjust the stiffness of a spring, it's fixed and finite. Using spring rates and ride height to stop tyre to arch contact is totally arse about face. Stop the tyre contacting the arch in the first place. The suspension must travel from full droop to full bump stop contact with the springs off, without getting near to anything. It sounds like a wheel size / offset or tyre size issue, nothing to do with suspension per se. Tyres are 235/45 x 18, wheels are +32 offset, which is more than stock, I know, but still... Quote Link to comment Share on other sites More sharing options...
Ark Posted October 3, 2009 Author Share Posted October 3, 2009 So for comparison, I've got these pictures: http://homepages.tesco.net/christopher.nixon/Radiator/thm3.JPG http://homepages.tesco.net/christopher.nixon/Radiator/18-09-2009-TF0589.jpg From the hub-centre to the wheel arch lip is ~36cm, so the same ride height as I had on stock shocks with HKS springs on them. I'm starting to think these HSDs are upside-down! No travel when I lift the car, and too much when under compression. Quote Link to comment Share on other sites More sharing options...
Bon Bon Posted December 15, 2009 Share Posted December 15, 2009 You can adjust the travel to sit the shock where you want it, lower the spring perch and raise the bottom mount and you'll have it sitting farther down in it's travel. Having said that, resorting to making the suspension bottom out to stop the wheel from hitting the arches is a horrible solution and will make the handling when the suspension bottoms "interesting". If you want to try a slightly stiffer spring rate for track work then that would be a preferable option, ~20% stiffer wouldn't be a problem for the dampers and would reduce suspension travel greatly. To be honest though, I'd suggest beefier anti-roll bars if that's your problem, since stiffer doesn't always = better. Quote Link to comment Share on other sites More sharing options...
Kirk Posted December 15, 2009 Share Posted December 15, 2009 look at that machine if your ever change them wheels i will kill you! on another note, sell the hsds and get something better Quote Link to comment Share on other sites More sharing options...
Bon Bon Posted December 16, 2009 Share Posted December 16, 2009 on another note, sell the hsds and get something better It's not a "fault" of the suspension though, the damping setup may well be softer than the old HKS ones and making the effective wheel rate lower, but this is just a case of having enough suspension travel for the wheels to catch... I'd be interested to hear if Ark has any other issues with track use? Ok, if they're a little soft for his purpose then fair enough, but it's not an issue of "better", maybe just stiffer. It's not uncommon to have to play around with spring rates, arbs, etc, etc for track work, I know the Nordschleife in particular requires some very careful thinking about to deal with heavy compressions and the violently bumpy karussell... General rule I work off is you spring the car stiff enough to not bottom out, then roll, pitch, etc are controlled by playing with arbs, damper settings, etc. If you can't stop the car from pitching with a combination of spring choice/damper setting without spoiling the car's feel and composure then arbs, beyond that it's a case of tweaking for feel. If it's bottoming in some compression situations but you wouldn't want it damped more aggressively and body roll isn't an issue then definately think about a slightly stiffer spring, a small change that the dampers will be fine with can make a big difference to the amount of compression travel possible in a given situation. Quote Link to comment Share on other sites More sharing options...
Kirk Posted December 16, 2009 Share Posted December 16, 2009 (edited) constant scrubbing is his problem, ive been out with him quite a few times at the ring and everytime you can hear the wheels scrubbing the inners. To me its to soft but if comfortable but thats not what you need on such a track like the ring. Cant say ive had much experience with HSDs so i cant realy comment on things it could be Edited December 16, 2009 by Kirk (see edit history) Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted December 16, 2009 Share Posted December 16, 2009 It's a wheel / tyre size / offset problem, period! Quote Link to comment Share on other sites More sharing options...
Bon Bon Posted December 16, 2009 Share Posted December 16, 2009 Thanks Chris, obviously there is that underlying issue there... Quote Link to comment Share on other sites More sharing options...
Ark Posted December 16, 2009 Author Share Posted December 16, 2009 look at that machine if your ever change them wheels i will kill you! on another note, sell the hsds and get something better It's a wheel / tyre size / offset problem, period! Ooh, two incompatible points of view! To move the goal-posts further, the car's had stiffer ARBs since raising this thread, and big stoppers on the front so I can't even sling on a set of OEM wheels to test the theory. I don't think there's enough adjustment in there to raise the shock body and lower the piston enough to stop this problem by running out of suspension travel before hitting the arches...sounds like an ugly cludge anyway. Stiffening the dampers provides some respite, and the rest, I guess I just have to see how it goes. PS. Martin, are you angling to buy some used HSDs by any chance? I can read you like a book! Quote Link to comment Share on other sites More sharing options...
Chiefgroover Posted December 16, 2009 Share Posted December 16, 2009 So my car has HSD coilovers on it, at the same ride height as my old suspension, set to be stiffer than before, but now I get the tyres bouncing off the wheel arch on big compressions round the 'Ring. Is this because the HSDs are allowing the wheels to travel too far, or just because they aren't suitable? Short of spending out on a load more suspension, what can I do to reduce or stop this? (driving slower through the compressions is not an option ) I had HSD on my Z, same problem, rear didnt seem any harder, but I got various wheel rubs on bumpy roads. Typical of "coilover kits" over sprung and poor dampening. My HKS hypermax 2 used to do this on one part of the ring except it broke through the front inner arch and damaged the wiring loom, twice on the old silver car. My CW isnt expensive, its top quality german Bilsteins, sensible spring rates and adjustable ride height by circlips, so you get both sides dead even every time. Can wait to try out this weekend. I have now gone the CW route, just the fronts to fit, so I will report in due course. Quote Link to comment Share on other sites More sharing options...
Chiefgroover Posted December 16, 2009 Share Posted December 16, 2009 BTW your car looks very low at the front, and you seem to have very little wheel drop. I'd make sure that the struts are the correct length for full wishbone travel by adjusting the bases. I think you problem is too much spring (prob 14 and 10kg) and not enough dampening, and like the HKS hypermax 2 if you give it enough dampening the car wil prob just drift and float eveywhere. Quote Link to comment Share on other sites More sharing options...
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