Nate SERE Posted July 22, 2014 Author Share Posted July 22, 2014 It's a steep approach angle. I teetertop on 3 tires. Have to have speed or back tire gets stuck up in the air and spins. No lsd for me yet. Quote Link to comment Share on other sites More sharing options...
NewZed Posted July 22, 2014 Share Posted July 22, 2014 Droop limiters? Quote Link to comment Share on other sites More sharing options...
Leon Posted July 22, 2014 Share Posted July 22, 2014 (edited) My terminology was incorrect, I did not mean "not at all" I should have said "not very much" I hope it is alright if I drop some math for my reasoning, I know that you are fully aware of this as you have in the past educated me, so it would be nice to have someone glance over my reasoning. k = (Gd^4)/(8nD^3) k =spring rate G = modulus rigidity n = number of active coils d = spring wire diameter D= coil diameter The value we will be changing will be n, from pictures it shows 11 coils, and since the top and bottom coils are not necessarily part of the active coils we can say either 10, or more likely 9 active coils in the system. Removing 1/2 a coil would change the number down to 8.5 and 1 whole coil would be 8. G, d, D all stay the same, our variable is n and k Solving one side for in terms of G, d, D we get n*k = (Gd^4)/(8D^3) If we use the supplied spring rate of 185lb/in using a roughly estimated value set from above of n = 10 (math is easier) coils and k = 185 we get 10 * 185 = (Gd^4)/(8D^3) = 1850. Modifying that to solve the rate difference, we get k = 1850/n Thus if we remove 1/2 a coil we get k ~195lb/in Change - original / original * 100 = % change (195lb/in - 185lb/in) / (185lb/in) *100 = 5% Not all that much I think statistically insignificant in a very rough kind of way (5% cutoff) Granted if we used the active coil number of 9 we would get a 6% change to 196 for 1/2 a coil removed and 208 if we removed a whole coil a 12% change, which starts to make a difference (statistically) Oh I agree, it is not the end of the world, but I just have reservations of sticking my hand in-between the wheel and the fender to settle the spring. Pretty sure it is unjustified, but it seems like a good way to walk away without hands. Typical coil springs have closed ends, meaning there are 2 inactive coils. From pictures found here, Tokico 280Z springs have 8 turns and 6 active coils. Using k1=185lb/in, n1=6 coils, n2=5 coils, and k2 is the unknown: k2 = k1*n1/n2 k2 = 222 lb/in This is a 20% change, which is a bit more than "not very much". Edited July 22, 2014 by Leon Quote Link to comment Share on other sites More sharing options...
seattlejester Posted July 22, 2014 Share Posted July 22, 2014 (edited) Ah I must have been looking at a stock photo, in my defense it looks like 9 coils in the rear, but looking at every other picture looks like the from does have 8 turns. To be fair my response was to 1/2 a coil, which would work out to 9%, which is still indeed significant. Before I retract my statement completely, one thing I thought when I was looking at the spring was the lack of an actual grounded end. Yes the spring does have less of a gap at each terminal coil then the coils in-between (the cause of my seating issue), but it was neither ground down or touching the next coil up which is why I originally wanted to only retract 1/2 a coil from each end. And technically if we were to cut off one end, wouldn't the first coil cut be removing the inactive coil? If my memory serves it says if you have a spring with a closed or ground down terminal ends, then removing both the terminal ends should actually maintain the number of active coils no? Edited July 22, 2014 by seattlejester Quote Link to comment Share on other sites More sharing options...
johnc Posted July 22, 2014 Share Posted July 22, 2014 That coil spring calc is for a complete spring as built. Cutting coils, in actual practice, does not get the results the calc indicates. You generally get about 60% of the increase in rate the calc says you should. At least that's from my experience using a spring tester after cutting coils. Quote Link to comment Share on other sites More sharing options...
Leon Posted July 23, 2014 Share Posted July 23, 2014 That coil spring calc is for a complete spring as built. Cutting coils, in actual practice, does not get the results the calc indicates. You generally get about 60% of the increase in rate the calc says you should. At least that's from my experience using a spring tester after cutting coils. Which could probably be attributed to the fact that most people who cut coils don't close the ends, as posted above. Quote Link to comment Share on other sites More sharing options...
johnc Posted July 23, 2014 Share Posted July 23, 2014 Yup. Quote Link to comment Share on other sites More sharing options...
ktm Posted July 23, 2014 Share Posted July 23, 2014 (edited) Oh I agree, it is not the end of the world, but I just have reservations of sticking my hand in-between the wheel and the fender to settle the spring. Pretty sure it is unjustified, but it seems like a good way to walk away without hands. How so? I don't know when you are seating the spring, but I let the car down slowly until the upper perch just touches the spring. I then seat the spring (it takes very little effort) by wrapping my hands around the spring and continue lowering the car. I do not place my fingers between the coils for the same reason you cite. Edited July 23, 2014 by ktm Quote Link to comment Share on other sites More sharing options...
seattlejester Posted July 23, 2014 Share Posted July 23, 2014 Learning something new everyday, thanks john and leon. How so? I don't know when you are seating the spring, but I let the car down slowly until the upper perch just touches the spring. I then seat the spring (it takes very little effort) by wrapping my hands around the spring and continue lowering the car. I do not place my fingers between the coils for the same reason you cite. Oh I do the same, I mean when you lean in to stick your arms in-between the fender and the wheel to push the spring into place, I am just acutely aware that if the jack decided to go or something of that nature, my arms would probably be cut off if not severely injured by the fender and the wheel. Quote Link to comment Share on other sites More sharing options...
Nate SERE Posted July 29, 2014 Author Share Posted July 29, 2014 (edited) Got everything installed this weekend including all new bushings. I love the way that it handles now and the ride is much better as I don't bottom out on everything. Its sitting much higher in the front right now and I am hopeful that it will settle some more. I am looking at adding camber plates to the front to get another inch or 2 of drop to level it out with the back. Here are before and after pics..... Edited July 29, 2014 by Nate SERE Quote Link to comment Share on other sites More sharing options...
Hypertek Posted July 31, 2014 Share Posted July 31, 2014 add more weight to the front (i.e. put the bumper back on), that should bring the nose down =) jk Are you running the staggered 15x9 15x10.5 ataras? Quote Link to comment Share on other sites More sharing options...
seattlejester Posted July 31, 2014 Share Posted July 31, 2014 I really don't know maybe the picture/angle is misleading, but it looks alright to me if you turned the wheel back to center. Yes a pillow ball camber plate should bring you down in height, although I am unsure if there are any on the market for the stock sized spring perch. I know there was talk about machining a piece to replace the stock insulator, but if what johnc says is true regarding polyurethane being too hard on the mounting studs, I can only imagine a solid bushing would be much much worse. Maybe time to get the dremel out for the fronts? I cut my front ones from the top, and secured them at the bottom so they actually don't have to be set every time even though I cut I think more than 1 coil. Quote Link to comment Share on other sites More sharing options...
logr Posted July 31, 2014 Share Posted July 31, 2014 Cutting lowering springs is not a good idea since that would take away the little bit of shock travel there still is. Lowering it from the top is the best idea. A 240Z isolator will lower it about an inch but it seems that it would be possible to modify a stock top hat to work with camber plates. Anybody done this? Your tires are so far away from the springs that the spring perch could be lowered but not without sectioning the tubes which would mean shorter struts or you will be back to riding on the bump stops. Quote Link to comment Share on other sites More sharing options...
osirus9 Posted August 3, 2014 Share Posted August 3, 2014 (edited) get coilovers. If there is any doubt in your mind then just go for it and never look back. That's what I did and I've never regretted it. I use my car for mostly daily, and the occasional autoX Farting around with lowering springs and cutting coils will get you to the same height as coilovers but with none of the handling. Just go for it, it's really not the expensive if you consider the amount of time you;ll spend messing with your current suspension. Do it once, and do it right. Edited August 3, 2014 by osirus9 Quote Link to comment Share on other sites More sharing options...
seattlejester Posted August 3, 2014 Share Posted August 3, 2014 He already went with the springs so that is kind of a moot point, and as long as the spring and strut are matched, the handling characteristics will still be there. Iogr has a really good suggestion, the 240z top insulators should drop you about an inch compared to 280z insulators. Quote Link to comment Share on other sites More sharing options...
rturbo 930 Posted August 3, 2014 Share Posted August 3, 2014 240z isolators will only lower the rear, so instead of your car looking like a 4x4, it will just look ridiculous. Nate, what size are your tires? Bigger tires will help fill your wheel wells, and also give you a little more ground clearance. Honestly though, the 'before' ride height looks perfect to me. You just need a better spring/shock combo to get there. What was the 'before' ride height, and what is it now? It doesn't look low enough to scrape. My BMW is at about 4-4.5" inches off the ground, measured from the crossmember (I think), and I NEVER scrape anything, mind you I have stiff springs, and Bilstein sport shocks. To keep your wheels from rubbing the flares, you need to mount them higher. They look too low to me. Ultimately, I would get coilovers and sectioned struts. It will be the most expensive route, but worth it IMO. Quote Link to comment Share on other sites More sharing options...
logr Posted August 4, 2014 Share Posted August 4, 2014 (edited) My mistake, Porschephile is right. I had measured 240 fronts and 280 rears but not 280 fronts until checking them now. The front flares cannot be lowered without new fenders as Nates are cut. You might have liked the look before but everything was riding on the shock to top hat( I would say bumpers but there were none). The handling was probably not optimum that way. Edited August 4, 2014 by logr Quote Link to comment Share on other sites More sharing options...
johnc Posted August 4, 2014 Share Posted August 4, 2014 Farting around with lowering springs and cutting coils will get you to the same height as coilovers but with none of the handling. Aftermarket coil overs, by themselves, do not improve handling. A spring is a spring. What aftermarket adjustable coil overs give you is the ability to change springs a bit easier and corner height adjustability. Quote Link to comment Share on other sites More sharing options...
jhm Posted August 4, 2014 Share Posted August 4, 2014 ....and they allow you to install camber plates, as well....negative camber is a must for any kind of competitive driving! Quote Link to comment Share on other sites More sharing options...
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