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rear coilovers vs jtr perch relocation


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I cant decide what to do. I plan on running

235/45/17's on 8's. I want the lowered look

but dont want to give up rear suspension

movement for launches at the strip. I want

it to handle good but not so stiff that it

wont hook hard off the line!

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The combination you want - good launch, decent ride and big tires would seen to indicate coilovers - keep the length for wheel travel/squat/ride and the narrowed springs allow for bigger tires.

 

Otherwise your weight transfer w/relocated perches won't be a good (shorter/stiffer springs) and ride will suffer.

 

Am I wrong here guys?

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Brad I believe you're correct. I'm running coil-overs with 245 tires on 17X8 wheels and it just barely fits. I cannot imagine what a super short spring using a relocated perch would feel like but I'd imagine it would be stiff. My car presently squats like mad with 200lb springs and I may even be moving up because it feels a touch soft. Seems to handle fine although I'll admit to not pushing it very hard. I'd actually be happier if it didn't squat quite so much to be honest, rolling into the gas is enough for it to squat a bit. I've got 225lb springs up front that seem to be fine but I think I'm hitting the bumpstops some judging from where I find the stopperd all the time. I believe I should section the front struts..

 

P.S. Removing the thin spacer on the driver's side rear has been fine - no rubbing. I'm going to do the same on the passenger side next time that wheel is off. Just an FYI for those considering using the measurements I've published. icon_wink.gif

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I didn't know about putting stiffer springs in the rear until after I'd done my setup - doh! I think that 250s would probably be good but I'm not looking to do it just yet. The bumpstops are stock thickness up front and that's where I find them pushed to the top. Sectioning those could be done without moving my coil-over perch and I don't think I'd go more than 1inch anyway. What's considered "normal" to use a decent strut? I guess I'm just not sure I want that trouble just yet - especially with brand new struts all around. Oh, and the "old" struts I pulled out were toast completely - I ASSume it was from bottoming as they didn't look heavily used. They were silver and I think bottom of the line Tokicos. Still have them if you want me to look (shrug).

 

Anyway, the car seems to launch well and a bump in spring rate would probably be perfect for what Z'ya wants. With 225 up front it doesn't seem to ride harsh at all. Maybe I can get someone to take a pic of it launching to see how much it squats...

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I'll have to take a harder look at rear Z tire's fitment sometime. This spring/summer I saw 225/50/16's on 16x7 zero offset fit fine on my dad's 240. He had to roll the inside of his rear fender lips as his tires were rubbing slightly, then we realized his struts were blown and springs were weak. But rolling them alone made it fine and he had lots of room behind his tread to the rear strut, 235's would've fit no trouble. He went to coilovers for the optimal spring choice and ride height for spirited driving. I'll be curious to see how much room is their....I know Pete's documented his fully etc but are all Z's the same out back for clearance? Is their a simple top perch mod/swap to lower it 1/2" or so? If current setup is fine doing coilovers for a 1/2" drop seems a bit of work and dough. If you're adept at welding I was thinking of sectioning the strut below your spring perch and thus retaining full travel....assuming you can fit your 235's (if that's the size you have to have...seems a bit low profile for a strip launch IMO if strip is a big priority) beside stock perch/springs.

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Working on my fuel pump today I noted that I've got maybe two fingers worth of space on the passenger's side - that's the one with a spacer. I didn't get a good look on the other side but I expect it was closer. I HAVE found that my rear suspension seems to be shifted slightly to the driver's side by a touch - just enough that when both were setup the same the driver's side rubbed slightly. (shrug) I'll try to snap a pic of my setup under there next time I get a chance just for folks to compare...

 

P.S. I always thought it was best to weld and section struts above the spring perch? Wouldn't making mods below it put added stress on the welded area? icon_confused.gif

 

[ September 30, 2001: Message edited by: BLKMGK ]

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the coilover sleeve will NOT slide over any weld, you would have to grind it all off OR have the sleeve in place prior to welding..

 

i always weld/section as low as possible - as far in as i can get the tube cutter anyway... then at least the weld will interfere the least as possible

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Jim if you want a rouger ride just bump up the rears to 250. then the fronts are already 25 lighter

 

i know its a PITA but the other choice is to swap your fronts and rears, as i really think that on the street the stiffer should be at the assend..

 

did you reinstall the bumpstops? if so cut them in 1/2 or remove completely. some think that they should be there but only konis get junked from bottoming out (AFAIK) and there isnt a lot of travel on a z strut as it is.

 

or shorten the struts and swap the springs??

 

on the rear dont shorten the full amount, only take out about 1" of tube,or you wont be able to get the car high enough up again.

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I am not advocating the JTR spring perch mod, but I must say it works. Remember, you are not using a cutdown stock 1st-gen, but a 280ZX 2+2 which is a very tall spring. I found the ride to be just right and with Illuminas I could adjust the shocks as needed.

 

If you are starting from scratch and have to spend $$$ for used 20ZX 2+2 springs and welding, I would suggest looking at coilovers with a not too stiff spring rate with adjustable Illuminas. However, no one should knock this mod because it does not sound exotic. It flat works.

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Several places sell them. MikeSCCA has them for sale at http://www.fonebooth.com/suspension.html His setup his what I've used on mine at all four corners. Requires some welding and some cuttinggrinding of the old perches but the ability to adjust ride height in minutes is awesome!

 

I think MSA may also sell coil-overs as does Ground Control. Mike posts and conributes here though icon_smile.gif Hrm, Ross may also sell a coil-over setup, I'm not sure. Ross? I'd buy from one of those two guys...

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"... Ross may also sell a coil-over setup, I'm not sure. Ross? I'd buy from one of those two guys..."

 

Sure, I sell coilovers...been to busy pushing the rear CNC disk bracket & CV adaptor to production and meeting other custom Z package goals to update my web though. But most anything legal I'll sell you icon_wink.gif For those daunted by welding/grinding you don't have to do any if you're satisfied running 225 width treads at near stock height (ie. not lowered 2"). You can simply slip your threaded collar and nut over your OEM unaltered tube leaving the OEM perch their. Not a showstopper but it's a very easy install and leaves you the option of throwing OEM springs etc back on with little trouble if ever needed (ie. an all original car) for a comfortable ride in the off-track season or for sale (and keep coilover setup for next Z...). My dad got in a time pinch and had the local Z mechanic install his setup and the mechanic never altered the struts, it all clears fine as it cleared with OEM struts so my dad's fine with how it is. He's right around stock height or possibly a bit below. 3.75" clearance to his mid-car bottle/muffler.

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