silicone boy Posted October 7, 2003 Share Posted October 7, 2003 Thunder, I would go with the coilovers from Ross if you can "spring" for it (pardon the pun). You'll get the ride height adjustment that you want (trust me, this is can save a lot of headache if you are dropped too low by non-adjustable springs-this can happen with if your frame isn't straight, or with an "incorrect" tire and wheel combination). You sound as if you are not sure about spring rates. It's a personal taste-I like 225 lbs. If you find that your spring rates are not right, you can always switch them out for other springs. As an added bonus, you get more space for wider tires. It's the best of all worlds for about $200-$300 more than regular springs that are only marginally stiffer than stock (such as the ones you mention). Quote Link to comment Share on other sites More sharing options...
THUNDERZ Posted October 7, 2003 Author Share Posted October 7, 2003 Is a higher Lb. stiffer or softer? Quote Link to comment Share on other sites More sharing options...
silicone boy Posted October 7, 2003 Share Posted October 7, 2003 Higher rated springs are stiffer. A stock Z has springs at about 140 lb/in I believe (actually, that's not quite right, but I never use stock rate springs anyway, so I don't really know the exact number-its in the ballpark). 225 lb/in springs are therefore 60% stiffer than stock (approx.). That's about as stiff as is comfortable on the street. Street prepared autocross and improved touring racers usually go much stiffer-sometimes double these rates (ouch!) Quote Link to comment Share on other sites More sharing options...
brokebolt Posted October 7, 2003 Share Posted October 7, 2003 I'll add my $0.02. I like what John C. states about not mixing and matching. My brothers '75 280Z had this and the rear bounced something feirce on hard bumps (also stock shocks). I currently am using a soft 225 front and 200 rear on 5 way Tokico Illuminas. Ok for street on 1 and nice performance on 5. My tires are too splashy on 5 I really need a stiffer sidewall. To answer you last post higher spring rate in lbs means stiffer. 225 lbs. is softer than 400 lbs which is harder. A softer spring will offer a softer more forgiving ride while a harder spring will not be as "road freindly". I personally like the combo I'm running and I'm 99% on street, well really it's back hick country roads with lots of pot holes and road kill. See more old beat up farm trucks than sport cars on the back roads. What can I say I live in a cow town. Mike Quote Link to comment Share on other sites More sharing options...
Guest cowboy6280 Posted October 7, 2003 Share Posted October 7, 2003 brokebolt - you have the stiffer springs up front? I thoguht if you dont have even front and rear you would go with the softer in the front? or am I totally wrong with this? Just from what I have read I thought that was how it went or is this just a personal preference kinda thing? thanks Quote Link to comment Share on other sites More sharing options...
JMortensen Posted October 7, 2003 Share Posted October 7, 2003 Seems like there are a couple of people who like stiffer front springs, I think 260DET is one also. The general consensus seems to be stiffer in the rear. FWIW, I started with 250's all around and went down to 200's in front because of the unbelievable plow. I think a LOT of this has to do with the driver. To each his own! Jon Quote Link to comment Share on other sites More sharing options...
johnc Posted October 7, 2003 Share Posted October 7, 2003 Regarding 240Z spring rates... In the ITS racing community there is an "East Coast" and a "West Coast" line of thinking. Both work and I think the differences have to do with the types of tracks each group normally races on and how they like to corner and put the power down. An example of an East Coast ITS spring package is: 350 lb. in. front 275 lb. in. rear 27mm front anti roll bar no rear anti roll bar Smooth tracks so bump compliance isn't as important. Give up corner entry and mid corner speed so that the driver can power hard out of the corners. Allows the driver to pass at the end of the next striaght. POwer is king on the faster tracks. An example of a West Coast ITS spring package 275 lb. in. front 300 lb. in rear 25mm front anti roll bar 19mm rear anti roll bar Bumpy tracks so compliance is important. Braking, corner entry speed, and mid-corner speed is important because most passing occurs on corner entry and through the turn. Except for one track (Willow Springs) most courses are medium speed with more technical turns. Handling is rewarded. All the above are just one man's biased opinion and are very broad generalizations. Quote Link to comment Share on other sites More sharing options...
Tim240z Posted October 7, 2003 Share Posted October 7, 2003 If you want a cheap 'ghetto' setup, I heard from Scott (ZR8ed here on the board), that you can use the springs from a 4 door chevette. They are quite a bit stiffer than the stock Z springs, drop the ride height by ~1", and are a bolt on conversion. Tim Quote Link to comment Share on other sites More sharing options...
THUNDERZ Posted October 8, 2003 Author Share Posted October 8, 2003 Hey guys thanks for all of your advice. I am going with the set up off e-bay (illuminas ) and some relatively mild springs. Couldnt pass the deal. It was worth it for the shocks alone. I can always buy coil overs in future. I am really getting my z in shape all over at the moment and not pushing the limits like some of you guys(no offense...your cars blow my mind). Quote Link to comment Share on other sites More sharing options...
brokebolt Posted October 8, 2003 Share Posted October 8, 2003 I think my logic went something like this; Engine big and heavy needs much help to keep it from sagging front. Nothing in rear, need soft to frimly plant power to road to make speed. I feel that the softer spring allows the rear to recover from bumps better that a stiffer rear; relative to the front ofcourse. Back country roads are full of this bump and pot hole business. As for the fronts, I was thinking that if I stiffened the front the less plow with a slightly softer rear. I'm running a stock 1973 7/8" rear sway bar and a big fat 1 1/8" front. All urethane with solid differential and transmission mounts. As soft as granit tile but fun on tight twisty motorways. Mike Quote Link to comment Share on other sites More sharing options...
260DET Posted October 8, 2003 Share Posted October 8, 2003 Seems like there are a couple of people who like stiffer front springs' date=' I think 260DET is one also. The general consensus seems to be stiffer in the rear. FWIW, I started with 250's all around and went down to 200's in front because of the unbelievable plow. I think a LOT of this has to do with the driver. To each his own! Jon[/quote'] Just about finished finalising the springs, looks like they will be 275 lb all round, one more test to go. Had 300's on the front but the front of the car tended to react just a bit too much to bumps. But my car is not stock weight distribution. Front sway bar almost certainly will be 22mm, rear presently 14mm but not finalised, that may go up a bit. With Koni Sports shocks she is firm but certainly not rough to ride in. IMHO with springs up near 300 very good shocks are absolutely crucial, can't emphasise that enough. Quote Link to comment Share on other sites More sharing options...
johnc Posted October 8, 2003 Share Posted October 8, 2003 Just about finished finalising the springs, looks like they will be 275 lb all round Careful... with identical wheel rates (the Z wheel rates are about 98% of the spring rate) you can get into fore-aft pitching problems. Basically the front and rear have the same oscillation frequency and they will amplify each other. Shocks have trouble controlling this kind of pitch problem. Quote Link to comment Share on other sites More sharing options...
260DET Posted October 9, 2003 Share Posted October 9, 2003 In what sort of situation is a pitch problem likely to show up, John? On the undulating road test this morning it felt as solid as a rock although on that particular public road it was impossible to push the car anywhere near its apparent limits. Car feels like it would have to be pushed up to at least 150kph through dips etc on a second/third rate road before the suspension performance could be properly evaluated. Shock bump valving has been changed, so that the rears have 25% less than the fronts, if that is relevant. Quote Link to comment Share on other sites More sharing options...
johnc Posted October 9, 2003 Share Posted October 9, 2003 Mostly hard braking. The chassis will oscillate a little leading to some uncertainty about which end is going to lock up. You always want the fronts to lock up just a micro-second before the rears. With a pitch oscillation you might have the rears locking up first in corner A and the fronts locking up first in corner B. Then on lap two the situation may reverse. It depends on the track, the bumps, and driver input. You may also see it in a fast sweeper where the chassis is upset by a bump and starts to oscillate a bit. You'll feel the oscillation (and maybe even see it) and the car will feel like it doesn't want to take a set, or maybe it looses the set it took. Some people describe it by saying, "The car is vague, doesn't want to keep a line." Its a subtle problem if you have good shocks, its a scary problem if you have bad shocks. Quote Link to comment Share on other sites More sharing options...
ZROSSA Posted October 9, 2003 Share Posted October 9, 2003 Richard, Your car has the fj20, right? I would asume that you have a rear weight bias. This would mean that your actual wheel rates would still be different front to rear. I think John is working on a car with 50/50 weight distribution. You would also have to have a car with the same unsprung weight on the front and rear. Douglas Quote Link to comment Share on other sites More sharing options...
johnc Posted October 9, 2003 Share Posted October 9, 2003 I think we have a terminology issue. Wheel rate as I define it is the spring rate at the wheel. Its the actual spring rate divided by the lever arm (the distance from the spring to the wheel center). On a strut suspension, wheel rate is almost identical to actual spring rate. On a control arm suspension the wheel rate can be 1/2 or even less of the actual spring rate. Weight distribution doesn't affect wheel rate. Quote Link to comment Share on other sites More sharing options...
260DET Posted October 10, 2003 Share Posted October 10, 2003 Thanks John, a proper track test will follow so I'll look out for the condition you have mentioned. The effective spring rate at the front is likely to be a bit less than 100% of the actual spring rate due to caster, track and camber changes which have resulted from moving the bottom of the struts out and forward? Hope to get the whole car and it's front and rear axle loads weighed next week so as to put this spring rate thing in perspective. Quote Link to comment Share on other sites More sharing options...
THUNDERZ Posted October 10, 2003 Author Share Posted October 10, 2003 How do you guys have the time to be so good at this? Dont get me wrong....I love the Z....But you guys blow me away! Quote Link to comment Share on other sites More sharing options...
awd92gsx Posted October 10, 2003 Share Posted October 10, 2003 By playing alot of Nascar 2003. Seriously, though...when I bought my car it was actually pre set-up as a road racer by a local place here in town... Sometimes I wish i had more of a stock suspension, it looks ultra bad ass and handles just as well, but...with rough roads it gets kinda old...plus I have a severe left hand pull I need to fix (I have a bad bushing that is causing the camber to go completely out of whack) Quote Link to comment Share on other sites More sharing options...
260DET Posted October 13, 2003 Share Posted October 13, 2003 How do you guys have the time to be so good at this? Dont get me wrong....I love the Z....But you guys blow me away! Dunno about anyone else but I wag school a lot. Now about how revalving the rear shocks to increase the compression damping dramatically improved rear end grip..................... Quote Link to comment Share on other sites More sharing options...
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