240Z Turbo Posted April 10, 2001 Share Posted April 10, 2001 Strut Turbos, HEHE! Anyway, the only reason I propose this is so I can still have enough strut tube to raise my spring perch above the tire so that I can run a 5.5" backspacing. Here is what I propose. Remove the stock isolator and drill out the hole where the strut currently bolts. I will then machine a sleeve(1.5") with a seat to slide into the isolator from the bottom(through drilled hole) and will stop at the seat and is secured from the top with a nut(OD of sleeve is machined for threades). This will essentially allow for the point at which the strut is bolted to be 1.5" above its current location. YOu will just slide the strut from underneath isolator as usual, but its new bolting point will be 1.5" higher than its current location. I hope this makes sense? Quote Link to comment Share on other sites More sharing options...
240Z Turbo Posted April 10, 2001 Author Share Posted April 10, 2001 THREADES=THREADS this is the morons language conversion table Quote Link to comment Share on other sites More sharing options...
Drax240z Posted April 10, 2001 Share Posted April 10, 2001 Maybe I am not following quite right... But wouldn't you basically be rendering the isolator useless as far as isolating noise/vibration goes? If that is the case, why not just make camber plates instead? I think I may have misinterpreted this, please clarify. ------------------ "Nothing is fool proof to a sufficiently talented fool." Richard Lewis - 1972 240z, Powered by a Nissan 2.8L Turbo Inline 6. Drax240's Turbo Site Beginners Turbo FAQ & Answers Quote Link to comment Share on other sites More sharing options...
Guest needwaymorespeed Posted April 10, 2001 Share Posted April 10, 2001 I think I understand-you want to raise the chrome shaft of the strut up 1.5 inches and retain the isolator in stock position??? The spring would still be in the stock position on the struts and this is what hampers the offset of wheel-have to get the lower mount on the spring above the wheel-this would require also moving the rubber isolator up or running 8 inch springs ala pete paraska. moving the chrome shaft obly would give you the whole travel of the strut back without sectioning youre struts. If misunderstood please correct. Curtis Quote Link to comment Share on other sites More sharing options...
240Z Turbo Posted April 10, 2001 Author Share Posted April 10, 2001 Exactly, you would still retain the isolator so you don't have the noise, but would raise the mounting point of the strut top up 1.5". Now to get the spring perch above the tire you would need to get a shorter spring. Scottie GNZ took the 2+2 spring and cut x # of coils off and then moved the spring perch up above the tire. He can now run a 5.5" backspacing. Moving the point at which the strut bolts to the isolator up 1.5" gives you back the stock travel(if car was lowered 1.5") while not having to section the strut tube and also allows me to move the spring perch up above the tire which might not be possible on a sectioned strut tube. Quote Link to comment Share on other sites More sharing options...
Mikelly Posted April 10, 2001 Share Posted April 10, 2001 OK< I think I understand this, but I have to ask: This seems like an aweful lot of work to do when you could go ahead and do the coil over conversion while you have the car appart... If you just wanted to do the rear conversion, just order the parts from Mike/scca to do the rears...cost would be about $200. Mike Kelly ------------------ http://hometown.aol.com/dat74z/myhomepage/auto.html "I will not be a spectator in the sport of life!" mjk Quote Link to comment Share on other sites More sharing options...
jeromio Posted April 10, 2001 Share Posted April 10, 2001 It seems like your talking about something like this: This would keep your strut from bottoming out, which is a good thing, but you won't have much suspension travel. Also, if you simply move the stock perch up and use a cut down stock spring, you're going to be pretty likely to hit those bump stops alot. Springs are rated as a unit, so if you take a 150lb, 10 inch spring and cut 2 inches out of it, you're left with a 120lb spring - much softer. In my opinion it would be easier and more effective to either buy or fabricate some camber plates. But then, if you retain the stock springs, they're too fat to allow very much camber adjustment. Still, you'd be able to lower the car by almost 1.5 inches without cutting the strut. ------------------ 240Z.jeromio.com Quote Link to comment Share on other sites More sharing options...
Drax240z Posted April 10, 2001 Share Posted April 10, 2001 Springs don't work quite that way. The spring rate is inversely related to the number of coils in the pring, so if you cut one coul off you are actually raising the spring rate. For example: This spring: Diameter of wire: .5in Diameter of spring: 4 in Free length of spring: 12in Number of active coils: 8 (I am going to use the same material for these comparison, just to eliminate variablse. Letting Youngs modulus equal 200GPa, Poisson ratio equal 0.3, density of material 7500kg/m^3) This would give you a spring rate of approximately 254lbf/in. Now lets say I cut 1 coil off, and therefore reduce the free length of the spring by 1". Diameter of wire: .5in Diameter of spring: 4 in Free length of spring: 11in Number of active coils: 7 Now we get a spring rate of: 290lbf/in. A significant increase in spring rate. ------------------ "Nothing is fool proof to a sufficiently talented fool." Richard Lewis - 1972 240z, Powered by a Nissan 2.8L Turbo Inline 6. Drax240's Turbo Site Beginners Turbo FAQ & Answers Quote Link to comment Share on other sites More sharing options...
jeromio Posted April 10, 2001 Share Posted April 10, 2001 Dunno anything about that formula, but from my experience, if you remove a coil, the chances of bottoming out go up. As a teenager I cut the coils on my 78 Celica to lower it. I cut it down by about 2 inches and that sucker was a kidney mangler. Bouncy bouncy - on the bumpstops all the time. I suppose it makes sense that to compress the cut spring vs. the uncut by the same distance would require more force. Hrm. I dunno - I still don't really even understand how Backspacing and offset apply to wheels ferkrysakes. ------------------ 240Z.jeromio.com Quote Link to comment Share on other sites More sharing options...
Evan Purple240zt Posted April 11, 2001 Share Posted April 11, 2001 KIDNEY MANGLER... damn thats funny stuff Quote Link to comment Share on other sites More sharing options...
Guest Rick Johnson Posted April 11, 2001 Share Posted April 11, 2001 There are two problems with cutting the stock springs short enough to raise the lower perch above the rear tire. First the rate will end up well over 200 lbs / inch making the ride harsh. Second the spring will not have enough stroke to allow full compression without coil binding. I solved these problems by designing a custom rear spring that ended up at 190 pounds / inch and had enough stroke to prevent coil binding. It fit the stock perche diameter. I used the stock top insulator (short version from a 73. I did remove the rubber washer between the spring perch and the insulator which saved me about 1/4 inch. For the bottom perch I threaded some pipe but next time I would buy the threaded aluminum pipe the suspension houses sell. The adjusting nut then provides a surface for the customized lower perch. The lower perch was modified by cutting off the "welded on" perch and then welding a large washer to it so it would be strong enough to sit on the aluminum adjusting nuts. The custom short spring fit between the two perches. This is an adaptation of the JTR manual ideas. My rear tires (24.8" tall) fit under the perch allowing 245/45 x 16 to fit under the stock wheel wells with much room to spare. 255's could fit. Rick Quote Link to comment Share on other sites More sharing options...
Drax240z Posted April 11, 2001 Share Posted April 11, 2001 Sure it makes sense that you may have hit the bumpstops. You have to figure that you put the car ~2" (less, because the spring rate increases as you have less coils) closer to the bumpstops. Remember that it is not a linear relationship between spring rate and length. Its entirely possible to cut 25% of the length of the spring down, and only raise the springrate by 10%. (depends on the spring specifics) Usually lowering is acompanies by the trimming of bumpstops to give you back a little travel. (or so I've read/heard) ------------------ "Nothing is fool proof to a sufficiently talented fool." Richard Lewis - 1972 240z, Powered by a Nissan 2.8L Turbo Inline 6. Drax240's Turbo Site Beginners Turbo FAQ & Answers Quote Link to comment Share on other sites More sharing options...
240Z Turbo Posted April 11, 2001 Author Share Posted April 11, 2001 OK, you all are missing something about the spring I was going to use. I proposed to use the 2+2 spring which has a different spacing between windings. If only Scottie GNZ would chime in on this one. It allows you to cut the coils to make an effectively shorter spring, but will retain enough spacing between windings to that it will not bind. The only thing I wonder about is whether raising the point at which the strut bolts will affect the point at which the bump stops contact. By the way, the picture above is exactly what I was proposing. Also, no matter what spring combo is used I will have to raise the spring perch up so that it can clear a 26x11.5" slick. Quote Link to comment Share on other sites More sharing options...
240Z Turbo Posted April 11, 2001 Author Share Posted April 11, 2001 Also, Jeromio that is what I proposed in your pic and thanks for the drawing. You said, "This would keep your strut from bottoming out, which is a good thing, but you won't have much suspension travel." This would not adversely change your suspension travel at all but effectively increase travel because you would now have 1.5" more travel on the strut. Also, by using the 2+2 spring I believe the compressed height of a shortened 2+2 spring will be the same as a compressed uncut tokicko spring because of the winding spacing. I would have to have Scottie verify this. Quote Link to comment Share on other sites More sharing options...
jeromio Posted April 11, 2001 Share Posted April 11, 2001 Yes, you will increase travel vs. merely lowering the car, and that's what will keep your strut from bottoming (which is apparently really hard on them). But, compared with the other options, camber plates or strut sectioning, you will have less travel. This is because you will be effectively "shortening" the cartridge shaft. With sectioning, you use a smaller cartridge. With camber plates, you lower the car by effectively lowering the top point. You still have to deal with your spring perch issue for the increased tire width/height though. With strut sectioning, you can lower the car, not lose any travel, but your perch may be too low and interfere with the wide tire. If you convert to coilovers and camberplates, you will squash all birds with your stone. The car will be lower, your perch will be higher (using an 8 or possibly 7 inch spring) and you will have many spring rates to choose from. Also, the camber will be adjustable - added bonus. There's a couple different vendors of camber plates, but I can't imagine they'd be all that hard to fabricate - in my opinion less difficult than making the part you are describing. ------------------ 240Z.jeromio.com Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted April 11, 2001 Share Posted April 11, 2001 Sorry guys, but every spare moment for the last 2 days have been in or under car. The shifter replacement ended up being a MAJOR project. James, after I spoke with you last night, I went to bed (frustrated) 2:30a and woke up with the blue flu by mere coincidence. What should have been a 3-hr job turned into AAARGH!. Spent most of the time damn-near rewiring the car because I tugged on the flimsy fuse block removing the console (must have been 100 times) and broke a major connection that was not visible. I am OK now, shifter is in and ready to run tonight. That shifter is SWEEEET!!! Oh yeah, the post . Some folks think what I have done is sacrilige but I would not do it if was not recommended by JTR, for whom I have great respect. James is correct in that the 280ZX 2+2 is unlike the stock Z spring and when cut as recommended, ends up with about 190lbs and does not bind. Believe me, if they are not binding with my banzai launches, they never will otherwise. The ride is no different than the generic performance springs I replaced. With this mod, I have plenty of clearance for my 26" DRs that is on a 15x8 with a 4.5". If I ever go back to a "normal" street tire I could easily fit a 5.5" backspace with a taller tire than is normal for a Z. Would I recommend this setup? Probably not, unless like me, you have access to the springs and a welder. If you have to go to the boneyard and pay to have the springs removed and cut, you are probably better off springing for a few more bucks and get a set of SCCA's coilovers. ------------------ Scottie 71 240GN-Z Scottie's GNZ Quote Link to comment Share on other sites More sharing options...
pparaska Posted April 13, 2001 Share Posted April 13, 2001 James, I like your idea, but I think you will still have problems with the bumpstop as you noted, as it will still be at the same height relative to the top of the spring. Since the strut tube is still the same length and the spring is shorter, that means the bumpstop will be closer to the top of the strut tube and gland nut, so it will bottom sooner. Of course, you can shorten it, but that makes it stiffer. The above all assumes that the spring perch will sit at the same relative height compared to the bolting surface at the top of the isolator. If you can raise that somehow, you'll raise the bump stop. I have a Z buddy that did something on a similar vein. He modified the stock isolator as follows: Started with a 240Z isolator. Heated the metal shell of the isolator until the rubber melted enough to separate the rubber and inner portion of the isolator and the outer shell. He then cut about 1/2" to 3/4" off of the top of the rubber portion, leaving a 1/4" or so of rubber between the metal insert that the strut shaft goes through and the top of the rubber. He then cut slits in the outer shell from the bottom toward the top about as long as the amount of rubber removed above. Then he inserted the cut down rubber/center portion of the isolator into the shell, and bent over the tabs created by the slits in the outer shell to capture the rubber/center. A few tack welds on the tabs could be added to ensure the tabs don't unbend. This took 1/2" to 3/4" out of the isolator height, and raised the strut shaft and spring perch a like amount. HTH, ------------------ Pete Paraska - 73 540Z - Marathon Z Project pparaska@home.com Pete's V8 Datsun 240Z Pages Quote Link to comment Share on other sites More sharing options...
240Z Turbo Posted April 13, 2001 Author Share Posted April 13, 2001 The spring will not affect the overall travel even though it is shorter. Remember, the 2+2 springs are said to have the windings spaced further apart. Therefore, a compressed tokicko spring will have the same length as a compressed cut 2+2 spring because it has fewer windings. now the question is how this will affect the bumpstop. Quote Link to comment Share on other sites More sharing options...
pparaska Posted April 13, 2001 Share Posted April 13, 2001 I know it's hard to communicate geometry with words, but I think I answered that above. Even though the spring won't coil bind, the top spring perch will be closer to the top of the strut housing/glandnut. Since that's what positions the bumpstop, it will hit sooner if you use shorter springs (loaded) with the lower spring perch in the stock location. ------------------ Pete Paraska - 73 540Z - Marathon Z Project pparaska@home.com Pete's V8 Datsun 240Z Pages Quote Link to comment Share on other sites More sharing options...
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