OK, my turn! Recommend me some spring rates!

[auxilary]

I have the oddball setup... light wankel, shoved way back in the engine bay. I'm going to probably hav 45/55 setup (guesstimating, could be wrong, but at least 48/52). It's a midengine setup since motor sits behind the strut towers/ crossmember.

So you guys have an idea how far back the motor is. Bare rotary motor without turbo and manifolds is about 200lbs. With transmission a little under 300. I'd estimate turbo, radiator, IC, oil cooler, piping, alternator, and misc stuff will add on another 150 lbs.

 

My old setup with the L24 was:

 

-GC coilovers, Eibach 10" springs, 200lb/in all around.

-Tokico Illuminas

-msa 1" front sway bar

-autopower rollbar bolted (not welded) in with 2 extra bars (jmortensen's old unit)

-unsprung weight consists of toyota vented 4x4 setup.

-car was lowered about 1.5-2", strut housings are NOT sectioned.

 

My new setup is going to also incorporate a ST 3/4" sway in rear with 1/2" offset spacer (already installed).

 

Now, I did some research and found out (courtesy of johnc) that my mistake was having the same spring rates all around, and this created more or less an odd rebound effect that I experienced on some bumpier turns

 

A while back I picked up a pair of hypercoil (i think? they're blue) 10" springs in 175lb/in. Can I run hypercoils in front, and 200lb Eibachs in rear? Is there a reason I should not mix them?

 

I think the Z will weigh about 2200-2300lbs when it's back on the road. I tried to leave as much weight on the crossmember as possible by mounting the motor in the front to the crossmember directly.

 

What should my spring rates be? The car's a weekend driver/road course/autox in that order, weekend driver being used the most.

[Here comes trouble]

The 175/200 # combo sounds fine to me. I am planning a 180/225 combo on my GTO project by mixing Carrera (now owned by Qa1) and Hypercoil front and rear. You could probably use your other hardware with suceess. I plan to use the slightly thicker 2+2 front sway bar.http://pg.photos.yahoo.com/ph/larryjohnson97438/album?.dir=8223&.src=ph&store=&prodid=&.done=http%3a//pg.photos.yahoo.com/ph/larryjohnson97438/my_photos

[Forrest]

My opinion is - don't take anyone's opinion. (Except maybe John's heh)

 

Put in your shiznit here:

http://members.cox.net/forrest280z/springrateselector.xls

[auxilary]

that formula spit out something like 150 front and 310 rear, lol.

 

So can one mix front hypercoils and rear eibachs?

[Here comes trouble]

if the poundage is accurate, the name should not mean much since a lot of the American name brands may have the same domestic manufactuer if not foreign. I doubt if AFCO makes their own springs and Carrera is now owned by Qa1.. Ground Control may use Hypercoil etc..Eibach , BEM, Spax, Hyperco, Stock Car Products, Hal, Howe, Skunk

[Modern Motorsports Ltd]

Auxiliary, what's the rwhp/tq curve look like for your intended motor buildup? AT what rpm etc to what degree is this motor getting nazty?

[auxilary]

It'll look something like this:

 

 

The setup belongs to a buddy, same motor as I have, just in a different chassis. He's using a mitsubishi td07 turbo which is very close to the t04 garrett that I'm using in spec. Same fuel system, same injector setup, intercooler's roughly the same. Running 12 psi boost (which is what my wastegate spring is set to)

[Forrest]

Once you have your weights input correctly, change the avg speed and ride parameters around until you see something you feel is more appropriate.

[tube80z]

I have the oddball setup... light wankel' date=' shoved way back in the engine bay. I'm going to probably hav 45/55 setup (guesstimating, could be wrong, but at least 48/52). It's a midengine setup since motor sits behind the strut towers/ crossmember.

 

I think the Z will weigh about 2200-2300lbs when it's back on the road. I tried to leave as much weight on the crossmember as possible by mounting the motor in the front to the crossmember directly.

 

What should my spring rates be? The car's a weekend driver/road course/autox in that order, weekend driver being used the most.[/quote']

 

Here's a standard procedure that can be use to determine spring rates for a car that you have no experience with.

 

1. Start with weighing the car on corner weight scales.

2. Determine front and rear axle percentage

3. Determine front and rear motion ratios

4. Pick spring rate factor (radial tires for autox/track are in the range of .5 to .7 of corner weight)

5. Calculate spring rate

6. Pick bars to give you 70 percent roll stiffness on the front (educated guess)

7. Test setups +/- 20% from this to find the optimum

 

Here's an example with the numbers you gave for springs.

 

total weight 2250 (splitting the middle)

46/54 distribution 1035/1215 (axles)

1035/2=517.5

1215/2=607.5

 

Guesstimate for motion ratio (0.95) but you'll need to measure and put in yours. Spring rate factor on the low end (0.5)

 

Calculate (per wheel rate divided by motion rate squared times spring factor)

517.5/0.95^2*.5 = 286.7 (so I'd try a 275 for the front spring)

607.5/0.95^2*.5 = 336.6 (so I'd try 325 for the rear spring)

 

I've never tried this approach with less than a .5 spring factor but I don't see why it wouldn't work. Remeber that your car should have at leat 5 times the torsional stiffness of the entire wheel rate (spring+bar) for changes to work correctly).

 

You'll have to decide if you want to run that stiff or not. Street ride can be good on stiff springs if you have shocks valved correctly to deal with it. I know this isn't necessarily common accepted practice.

 

Cary

[Mikelly]

Alex, Are you planning to drive the car a lot on the street? If so, you might want to play with those spring rates. JIm's V8 Zcar is very HARSH with 300-325# rear springs... I was just on the phone with Ross last night and we're gonna order a bunch of springs and try to dial Jim's car in with a rear sway bar and some softer springs in back and front. For a track car, I really like Jim's setup, but I'd be towing to the track a LOT and Jim drives his cars on the street TO track events.

 

Mike

[auxilary]

mostly street with occasional track/autox. with 200lb/in springs it was fairly stiff in stock form for me

[Here comes trouble]

Go with what you have....... with coilovers .. you can switch to different weight springs fairly easily if you are not satisfied... 150 pound 10 inch coilover springs come up regularly on eBay..and 150 may be the ticket for your frontend since stock 280 Z springs are 103 # front and 127 # rear

[Modern Motorsports Ltd]

Auxiliary, a lot of opinions offered on this one to date, here's mine:

 

Depends on your driving/shifting habits etc:

• this car is not a stump puller with torque smacking you off idle
  
• if you're not powershifting and putting great shock load to the rear (ie. 2-3 power shift, not sure if your turbo would keep the boost for an insane power shift?) then I see no reason for your setup to have a rear spring rate greater than 200 lb/in.
  
• You don't have excess torque to control at the rear (power rolling on smoothly is quite different) so no point adding unneeded stiffness. (assuming you're at a ride height and have appropriate suspension travel your Z's rear is within proper travel etc, lower rate = more travel under torque, not necessarily bad)
  

Up front it's up to you and how good your roads are in combination with your other inputs etc:

• your car's lighter and you intend to enjoy street and autox, for autox especially you'd like nice/nimble turn in
  
• I may have missed it but I didn't see any mention of a strut bar?
  
• Crisp front brakes along with a tight front end can make your turn in a lot more enjoyably IMO. (My 280ZX was quite a different beast but I loved 375's up front in that car, too bad the Tokico's didn't like that! It was very neutral 375/250 f/r)
  

You may prefer your front springs one step below rear for slightly improved ride quality but I'd like to see you try the reverse with at least one stage (ie. 25 ft/lbs) different and preferably two if you really get into enjoying heavy front braking or even good taps to initiate the transfer etc. I'd suggest 225/200 f/r. A powerful car with strong braking is wicked when you've got very tight nose control minimizing nose dive, helps maintain improved suspension alignment (combined with strut bar) and even steadier confidence in harsh braking as speed increases

 

If you stick with Eibach's then use 10" length's for reasons I noted before in this thread or a similar one ongoing right now on spring, (they're not favourable near coilbind and reduce available travel to coilbind). If you go Hyperco's, the 225's I can put you into a set of 8's, got 'em on the shelf. Just options.

 

Feel free to drop us a line directly to discuss any other questions you may have.

[johnc]

We can calculate the ideal spring rates all we want, but for a Z application shock selection ultimately determines what spring rates you CAN run. Right now, unless you can find some leftover Koni 8610-1149s you are looking at:

 

150 to 250 lb. in. - Tokico Illuminas at around $140 each.

250 to 350 lb. in. - Koni 8611 doubles at around $300 each.

200 to 300 lb. in. - Bilstein custom revalved at around $200 each.

 

Right now I'm doing the suspension on a customer's car and have installed Illuminas with 200F and 225R Hyperco springs and ST 1" front and 3/4" rear bars. And, I did not shorten the struts because of the tires sizes the customer plans to run (275/40-17) and because its primarily a street car that will be running a 3" exhaust.

[Here comes trouble]

After you get it all together with whatever combination of suspension parts and take your first test drive....the final indicator for a correct spring solution should be the "seat of your pants" Not technically precise but an accurate assumption.

[auxilary]

Thanks for the input, Ross, and everyone else. I'll give it a shot combining front 10" 175 lb hypercoils and rear 10" 200lb eibachs and see how that works out first, since I already have all those. My biggest concern was whether manufacturers should be mixed, but I think I'll be alright.

 

If not, I'll get some hypercoils for the rear

[Forrest]

Just a note - Illuminas are about 90$ a piece on ebay right now. They've come down a lot.

[auxilary]

ok, i already have 4 + a spare one?

[cameron]

Just a side note........ but kool setup....