The Strut thread - Koni / Illumina / Tokico / Carrera / Bilstein / Ground Control

[mom'sZ]

... a peek into the mind of a genius.

[tube80z]

For the ITS 240Z I hadn't been through Claude Rouelle's course yet (we had data acquisition but no shock pots), so I developed the ShockTek the old fashioned way- I paid a Phd in Vibrations with a ton of shock experience to get me close. Then it was a lot of testing and long term trend analysis (tire wear, for instance is a long term trend). The ITS E36 Bimmers I did most recently were the same way.

 

Thanks for the info Keith. I'm not sure if it's easier or harder to do this for autox versus a road racer. Up to now I mostly used subjective feedback, a stopwatch, and tire temps. After going to Claude's seminar I invested in enough datalogging to be able to measure this on the car. I have yet to put this in actual practice beyond experiments in the shop. And from playing with this you can use ordinary linear rotary pots and linkage and seem to get data that's good too (low buck version). Where I'm really headed is being able to get real-time tire temps via IR sensors, which should help answer some of these questions.

 

On the GC advance designs. Do you think the issues you've seen are unique to road racing? Why I ask is that I find them to work very well for me in a SoloII environment but they weren't valved right when I first go them. They feel much better than the tokicos and Koni (DAs) I've used before.

 

Cary

[katman]

A lot of people seem to be really happy with the GC shocks and personally I'm a big fan of Jay's hardware- camber plates and such. Very nice pieces. But the AD shocks I gave more than the benfit of the doubt- even sent one of the Bimmer sets back to have him check them on his dyno- and my opinion of the ones I've had to work with is, well, momma always said if you don't have anything nice to say.... In road racing there weren't a lot of guys with the AD shock in Z's- most of us had developed the car long before the AD was available. The bimmers was a different story. WHen the E36 became legal for the class GC was one of the first with a complete bolt in suspension so lots of bimmers run them. I have never been one to do what everybody else is doing, especially when they are behind me on the grid. But I did give the AD's a shot.

 

I would think autox would be a tough app to hone in on since your sessions are like a minute long and it would seem to be impossible to get enogh repeatable data with all the other variables constant to make any real judgements. Technically I don't see why on the same terrain that road racing and autox would have any difference in shock requirements. Keep in mind when you get somewhere close to critically damped for the bumps (high speed valving- faster than 5in/sec) the rest of the characteristic of the shock are really for tuning transitional handling. In autox the transitions are such short duration I imagine it would be tough to tune without some sort of data system- but I know in Pro Solo lots of folks have exotic double adjustables and somehow do it. Best of luck.

[oatmilk]

If you need some Tokico info just let me know and I'll ask around. Hitachi owns Tokico so they are literally in the next cubicle.

 

thanks,

[Guest dherde26]

I have a quik question as I read threw this I found alot of the info very useful but i want to know is there an exact list of what is needed to run the bilstiens becuase I havent heard of a whole lot of people running them so I dont really now.... i mean getting them revalved to 300/100 and then running 375f 325r

 

does that sound like a good balance i will be using the car for track days and mountain rd. driving and i dont mind gettin beat up on the road

 

also i am running the s/t sways and i plan on getting the t3 rollcenter adjusters and the camber plates as well as the tension rods

 

so tell me what u all think

 

thanks

[katman]

To do the Bilstein converesion with the P30-0032 struts you need 4 P/N 450424 (M48x1.5) gland nuts. Then you need to cut your strut housings 2.0 inches front and rear. The fronts require a 9/16 thick spacer under the Bilstein, and the rears require a 2-1/16 spacer under them.

 

However, for anything resembling a street car, I wouldn't run anything near those spring rates. You can have 99% of the fun with something on the order of 115 lb/in front and 145 lb/in rear springs, Suspension Techniques bars, the appropriate bushings all around, and a real tire (Khumo or Hoosier for example) for track days. These rates would allow you to get away with a Koni or Tokico Illumina shock and a streetable ride height. At the ITS level spring rates you pound the chassis and will be foreverer chasing around cracks in your dual purpose street car. Whether your kidneys are good for it or not, its not worth it IMHO.

 

I have driven our ITS race car and a street car set up like the above paragraph on the same road course and been within a second of my ITS time with a negligible difference in fun quotient. And could play the radio and hear it.

[OlderThanMe]

I have the standard 225f/250r and that is as stiff a you would want to go on the street. With my Illuminas on 5 it is hard like a go cart and can lock up a front wheel pretty easily.

[Guest dherde26]

To do the Bilstein converesion with the P30-0032 struts you need 4 P/N 450424 (M48x1.5) gland nuts. Then you need to cut your strut housings 2.0 inches front and rear. The fronts require a 9/16 thick spacer under the Bilstein' date=' and the rears require a 2-1/16 spacer under them.

 

However, for anything resembling a street car, I wouldn't run anything near those spring rates. You can have 99% of the fun with something on the order of 115 lb/in front and 145 lb/in rear springs, Suspension Techniques bars, the appropriate bushings all around, and a real tire (Khumo or Hoosier for example) for track days. These rates would allow you to get away with a Koni or Tokico Illumina shock and a streetable ride height. At the ITS level spring rates you pound the chassis and will be foreverer chasing around cracks in your dual purpose street car. Whether your kidneys are good for it or not, its not worth it IMHO.

 

I have driven our ITS race car and a street car set up like the above paragraph on the same road course and been within a second of my ITS time with a negligible difference in fun quotient. And could play the radio and hear it.[/quote']

 

ok so what if i went like in the 300f 250r what bound rebound do u suggest

 

thanks

Drew

[katman]

I don't recommend 300/250 either, so you're on your own. But the Bilsteins should work with that too.

[JMortensen]

The strut has a lot to do with how the car rides, dherde26. As olderthanme points out, Illuminas on 5 ride a lot different than Illuminas on 1 (5 on the street is ridiculous BTW, try 1 or 2). So even if the spring rate were reasonable I'm guessing that the way the strut is valved is not reasonable for the street.

 

225/250s with Illuminas is a good compromise setup and I wouldn't want to go too much farther than that for a street car. I have 200/250 with Illuminas and I didn't pee blood when I drove it daily, but it was definitely on the stiff side.

[Guest dherde26]

The strut has a lot to do with how the car rides' date=' dherde26. As olderthanme points out, Illuminas on 5 ride a lot different than Illuminas on 1 (5 on the street is ridiculous BTW, try 1 or 2). So even if the spring rate were reasonable I'm guessing that the way the strut is valved is not reasonable for the street.

 

225/250s with Illuminas is a good compromise setup and I wouldn't want to go too much farther than that for a street car. I have 200/250 with Illuminas and I didn't pee blood when I drove it daily, but it was definitely on the stiff side.[/quote']

 

ok one other question why stiffer in the rear than in the front

[JMortensen]

That's what works on my car to get the front end to turn. Search spring rates and you'll find that in sweeping overly general terms east coast road racers with their high speed super smooth tracks tend to like stiffer front springs, while out west we have bumpier tracks with tighter slow sections so we like it set the other way. It's an overgeneralization, but that seems to be the trend.

[driftz240]

I just ordered a kidney belt...lol

my drift setup is finally complete, i put together a 1 3/4 sectioned strut with custom kyb real sport dampers 4 click adjsutable front,8 click rear, brp coilovers, 450 front / 350 rear spring rates, dp racing camber plates, 35mm bumpsteer spacers.

ill be shaking it down at beaverun drift event very soon. ill get video of the super slide action.. now off to the body shop...

[Guest dherde26]

That's what works on my car to get the front end to turn. Search spring rates and you'll find that in sweeping overly general terms east coast road racers with their high speed super smooth tracks tend to like stiffer front springs, while out west we have bumpier tracks with tighter slow sections so we like it set the other way. It's an overgeneralization, but that seems to be the trend.

 

ok

so what are the tokico good to spring rate wize

[johnc]

Tokico engineers will tell you that the BZ3015 and the BZ3099 (typical 240Z shortened strut inserts) are good to 250 lb. in. I have run 275 lb. in. springs with them but you're basically stuck on adjustment 5 where the comrpession damping is way too stiff.

[Guest dherde26]

Tokico engineers will tell you that the BZ3015 and the BZ3099 (typical 240Z shortened strut inserts) are good to 250 lb. in. I have run 275 lb. in. springs with them but you're basically stuck on adjustment 5 where the comrpession damping is way too stiff.

 

so what do u suggest john

i was leanin toward the bilstiens but stock valving what are they good to

anyone??

 

thanks

drew

[JMortensen]

Tokico engineers will tell you that the BZ3015 and the BZ3099 (typical 240Z shortened strut inserts) are good to 250 lb. in. I have run 275 lb. in. springs with them but you're basically stuck on adjustment 5 where the comrpession damping is way too stiff.

I gotta disagree with this. I ran mine on 1 or 2 on the street and it was fine. At autox I'd put it up to 3 or 4 and occasionally tried 5, but mostly 4 on the track. For the street 1 or 2 works just fine with the 200 to 250 rates and doesn't bounce or buck or do anything stupid IME.

[OlderThanMe]

right now I have mine set on 4f/3r and it is just to where it doesn't kill you on the street...I am going to drop them down to 2 in the morning. my spring setup feels like a new sports car so on a car that is 34 years old that is not bad. It is not as crazy hard as my dad's 944T with bilsteins that just kills. I think my z is better anyway than that bent, expensive, overweight car...plus you can throw the Z around better and feel the road. His has all the luxury stuff...not that it isn't fun to drive it is just that the shocks are rock hard.

My Z used to be like riding a rodeo...too much power for 4 DEAD shocks...

[Guest JAMIE T]

This is hands down the best thread on this subject anywhere. Zcar specific.

[mom'sZ]

I don't recommend 300/250 either, so you're on your own.

Well since the subject of spring rates has come up Keith, I'd like to ask a question. From what I've read of your opinion on spring rates, for a strictly road race Zcar, SCCA ITS class, the idea seems to be to use spring rates to balance the car. I imagine to run at the pointy end of the field you must use the brakes HARD, which dictates somewhat hard rates, at least on the front, with something reasonably close in the back to maintain balance. Of course the condition of the racing surface trumps everything else, and one must choice a stiff enough rate that allows the driver to not bottom the suspension during normal driving. Then from that baseline, front to rear balance would be adjusted using spring rate. Then sway bars would be used to make adjustments to the best compromise rate wise. (I already know your opinion of sway bars) Is that about it or I'm I all at sea here?

So to answer another reader's question, stiffer in the front or back would depend on what works that day, with that car at that track and that driver in a purely race situation. IMHO coil overs are kind of over kill for a street car. But they would allow switching to higher rates on a dual purpose car and adjusting ride hieght. And maybe a decent choice of rates is not available in OEM size replacement springs. With 200 lbs. in the front and 225 lbs. in the back with my Konis set to full soft, the rear never squats on acceleration, the front never dives on braking, the car is stiff but not obnoxious on the street and the handling in corners... well, you have to throw the car wildly into a corner, at what at first seems retarded fast speeds to even get it to skate or step out, and when it does, it's predictable and easily reeled back in. Now that drifto set up, that's an entirely different bird...