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

[johnc]

Drew,

 

Honestly, if I was building a car like yours for myself (which I actually am) I would do the following:

 

1. Shortened struts with coil overs.

2. EMI Racing camber plates.

3. Hyperco springs 200F and 225R.

4. Tokico Illumina shocks BZ3099 front and BZ3015 rear.

5. Suspension Techniques ARB kit 52095 (25mm front 19mm rear).

6. Off the shelf 15 x 7 wheels with 225/50-15 Toyo Proxes RA1s.

7. Replace all the suspension bushings with polyurethane except the rear bushings on the TC rod. Use rubber there.

 

This is a good starting point. You can experiment with spring rates withing a 200 to 250 lb. in. range (go bigger on the front, remove the rear ARB, etc.) to see what you prefer as a driver.

 

But, as Keith inferred above, going fast around a race track has much more to do with the driver then any particular spring combination.

 

BTW... the only difference between what I recommend above and what I'm actually going to install is spring rates. I'm using 175F and 200R. I've gotten older and I want my daily driver/autox/instructor car a little more comfortable.

[Guest dherde26]

Drew' date='

 

Honestly, if I was building a car like yours for myself (which I actually am) I would do the following:

 

1. Shortened struts with coil overs.

2. EMI Racing camber plates.

3. Hyperco springs 200F and 225R.

4. Tokico Illumina shocks BZ3099 front and BZ3015 rear.

5. Suspension Techniques ARB kit 52095 (25mm front 19mm rear).

6. Off the shelf 15 x 7 wheels with 225/50-15 Toyo Proxes RA1s.

7. Replace all the suspension bushings with polyurethane except the rear bushings on the TC rod. Use rubber there.

 

This is a good starting point. You can experiment with spring rates withing a 200 to 250 lb. in. range (go bigger on the front, remove the rear ARB, etc.) to see what you prefer as a driver.

 

But, as Keith inferred above, going fast around a race track has much more to do with the driver then any particular spring combination.

 

BTW... the only difference between what I recommend above and what I'm actually going to install is spring rates. I'm using 175F and 200R. I've gotten older and I want my daily driver/autox/instructor car a little more comfortable.[/quote']

thanks john

currently i have the s/t sways but the bigger set 1 1/8 in the front and 7/8 in the rear i believe and my other question is this, i have budys who drive s13's and s14s and they are all in the 300-400 spring rate range and i kno the datsun may be a shade lighter but i wouldnt think that much but i guess iwill have to take your word considering you have been around it more than me...also does anyone kno what the stock rate is

 

and johnc what is the max rate you can run on the illuminas and will it make any diff is i end up using the t3 camber plates instead and are u saying section the struts 2 inchs as well

 

also about the tires i was gonna run yoko avs es100 any comment on those i am just not a toyo guy thats all

 

thanks

drew

[katman]

For road racing we do use spring rates to balance the car, but the initial rates are based on how much spring we think we can get away with before the car skips over bumps or won't put power down, or slides without warning, or locks up tires easily. The goal is to preserve contact patch geometry- which for a Mcpherson strut means try not to let it move much. Then try to find shocks to control those rates. Hoosiers are a lot more sensitive to lockup under braking than most street tires, and that was probably the limit (and chassis stiffness) that kept us from going over 400/350 on the ITS car.

 

I'd do what JohnC says, or a little softer. His is a good plan. I mentioned 115F/145R as something I've had a blast with, but I did have a daily driver at 185/185 that was also equal fun and still streetable (albeit with Recaro's to cushion my derierre).

 

Couple data points on Tociko's: Some people seem to get away with it, and maybe the newer ones are better, but we destroyed Illumina's at 240 lb/in rates. For ITS we used to also use a Tociko BZ3099 I think (not an Illumina) that was a strut originally designed for the Dodge Colt Rallye team or some such other nonsense, that Tokico told us would be good for 200 lb/in rates and marginal at the 240 we were running at the time. They held up well, but we were running bias ply Hoosiers back then.

[johnc]

i have budys who drive s13's and s14s and they are all in the 300-400 spring rate range

 

Don't compare spring rates from one car to another. The rear multi-link suspension on the 240SX is not a strut suspension like the 240Z. What we are actually tuning when adjusting springs rates is Wheel Rate. This is the force per unit (lb. in.) measured at the wheel as opposed to what the spring rate is and takes into account the lever arm distance between the spring and the spindle/hub

 

On a strut equipped car (like the 240Z) the motion ratio is around .97 . So, a 250 lb. in. spring on a strut works out to a wheel rate of 243 lb. in. On a multi-link or unequal length control arm suspension where the spring is mounted inboard, the motion ratio may be .30 to .70. A 250 lb. in. spring installed in a suspension that has a .50 motion ratio would work out to a wheel rate of 125 lb. in. You would need to double the spring rate to get close to the wheel rate of a strut equipped car running 250 lb. in. springs.

 

and johnc what is the max rate you can run on the illuminas and will it make any diff is i end up using the t3 camber plates instead and are u saying section the struts 2 inchs as well

 

I've already answered that question above.

 

also about the tires i was gonna run yoko avs es100 any comment on those i am just not a toyo guy thats all

 

Run whatever tires and camber plates you want. I was just offering a suggestion based on what I was building for myslef.

[Guest dherde26]

Don't compare spring rates from one car to another. The rear multi-link suspension on the 240SX is not a strut suspension link the 240Z. What we are actually tuning when adjusting springs rates is Wheel Rate. This is the force per unit (lb. in.) measured at the wheel as opposed to what the spring rate is and takes into account the lever arm distance between the spring and the spindle/hub

 

On a strut equipped car (like the 240Z) the motion ratio is around .97 . So' date=' a 250 lb. in. spring on a strut works out to a wheel rate of 243 lb. in. On a multi-link or unequal length control arm suspension where the spring is mounted inboard, the motion ratio may be .30 to .70. A 250 lb. in. spring installed in a suspension that has a .50 motion ratio would work out to a wheel rate of 125 lb. in. You would need to double the spring rate to get close to the wheel rate of a strut equipped car running 250 lb. in. springs.

 

 

 

I've already answered that question above.

 

 

 

Run whatever tires and camber plates you want. I was just offering a suggestion based on what I was building for myslef.[/quote']

 

ok thanks for all the help i apreciate it very much

so i now kno what i am goin with

 

Thanks

Drew

[mom'sZ]

For road racing we do use spring rates to balance the car, but the initial rates are based on how much spring we think we can get away with before the car skips over bumps or won't put power down, or slides without warning, or locks up tires easily. The goal is to preserve contact patch geometry- which for a Mcpherson strut means try not to let it move much.

So the stiffer rates (on an ITS car) come mostly from the desire to keep the suspension from moving to much and staying in the 'sweet spot' of the travel where alignment geometry is optimal, thus being less effected by bump steer inherient to the strut suspension?

 

grasshopper begins to see the light....

[JMortensen]

Bump steer isn't inherent in strut suspension. It's designed in from the factory and can be tuned out (check the FAQ section). Camber change is the big one here, and big camber curves ARE inherent to Macpherson strut suspension. There is also dynamic caster change as well in the front end.

[mom'sZ]

Bump steer isn't inherent in strut suspension. It's designed in from the factory and can be tuned out

 

within the limitations of improved touring rules? (stock suspension arms and pick up points, no bending of the tie rod ends or moving of the rack)

So... if I'm getting this, the stiffer rates help keep the camber in the 'sweet spot'. Using camber plates and other legal available means and a tire pyrometer to tune by you set the car up to optimize contact patch... correct?

[JMortensen]

within the limitations of improved touring rules? (stock suspension arms and pick up points' date=' no bending of the tie rod ends or moving of the rack)

So... if I'm getting this, the stiffer rates help keep the camber in the 'sweet spot'. Using camber plates and other legal available means and a tire pyrometer to tune by you set the car up to optimize contact patch... correct?[/quote']

OK you have a point. You will have some bumpsteer if you keep the stock pivot locations. BTW bending the tie rods won't change the bumpsteer, only the angles that the tie rods run at. You've got the camber part right.

[v8dream]

 

Honestly' date=' if I was building a car like yours for myself (which I actually am) I would do the following:

 

1. Shortened struts with coil overs.

2. EMI Racing camber plates.

3. Hyperco springs 200F and 225R.

4. Tokico Illumina shocks BZ3099 front and BZ3015 rear.

5. Suspension Techniques ARB kit 52095 (25mm front 19mm rear).

6. Off the shelf 15 x 7 wheels with 225/50-15 Toyo Proxes RA1s.

7. Replace all the suspension bushings with polyurethane except the rear bushings on the TC rod. Use rubber there.

 

BTW... the only difference between what I recommend above and what I'm actually going to install is spring rates. I'm using 175F and 200R. I've gotten older and I want my daily driver/autox/instructor car a little more comfortable.[/quote']

 

Wow! Substitute the Tokicos for Koni Sports (for a Rabbit) and EMI camber plates for a set from Design Products and you just spelled out exactly what I'm putting into my car. I am also going with the 175/200 spring rates. I haven't driven it yet, and was feeling a bit of anxiety about how the combination would work out. I'm feeling much better now. Thanks!

[katman]

within the limitations of improved touring rules? (stock suspension arms and pick up points' date=' no bending of the tie rod ends or moving of the rack)

So... if I'm getting this, the stiffer rates help keep the camber in the 'sweet spot'. Using camber plates and other legal available means and a tire pyrometer to tune by you set the car up to optimize contact patch... correct?[/quote']

 

Yup. The pyrometer was always my best tool (next to good records and a good test driver) and I was always amazed at how many guys didn't do tire temps after every session (no wonder they were losing). Of course knowing how to take them properly and what to do with them is another story. I had to evolve my temperature targets as we moved from bias ply to radial, and as Hoosier changed their radials over the years. They were little help because we were usually one of the first on new constructions and compounds and nobody else was going as fast. The rules said we could replace the struts or inserts, so our replaced struts had some bump steer correction in them, but the big thing is camber control in roll and shocks to keep the tires planted.

[clarkspeed]

For those of you contempating race set-ups, Katman posted an excellent set up guide on ImprovedTouring.com that explains many of the questions above. I am giving it a shot and so far the results look very promising. Search for "240 set up".

 

Katman,

Care to post some insight into tire temp measurment? I felt like I was "chasing" things at Road Atlanta a couple of weeks ago. I ended up backing quite a bit of camber out with the heaver spring rates. I think the long back straight was messing with the measurments.

[katman]

Well here's some hints.

 

1. I never change anything based on temps from one session. I need repeatable data before I make an adjustment.

2. I check in this order- LF LR RR RF

3. I go inner-middle-outer on each tire in that order and use a needle probe that I can get a good 1/16th below the tread.

4. We try to get a 20-25 degree bias toward the inside. Hoosiers respond well to camber thrust so the inside should run hotter. In the old bias ply days we were even to 10 degrees bias.

5. If your setup is right, especially the shocks, all 4 tires should be close to the same- like there shouldn't be more than 20 degrees difference between the average temps of each tire. On an ITS 240Z at Road Atlanta your highest temp will be the left rear, followed by the left front, right rear, and then right front. I dare say most setups proly have a 40+ degrees spread between the left rear and right front.

6. If you're not getting 160+ minimum it's too cold outside or you're too slow to make any worthwhile adjustments.

7. Follow the Hoosier rep around your ties and compare your temps to his. They round things off but generally trend propely, so if you're not seeing the same trends as the numbers they give you there's something wrong with your technique.

8. There's generally a big gradient around the corners of the tread, especially with big camber, so be consistent with where you measure.

 

YMMV.

[clarkspeed]

Awesome. I guess I'm not too far off then. It was a little cool at the Mitty so my temps ended up around 150 but I measured them with a IR gun. I know, not as accurate. Ended up 20 degrees different LR to FR. Around 10 degrees hotter on inside vs. outside. 3 out of 4 anyway. Took too much camber out of rear and LR ended up 14 hotter on outside, last sesson. Still, much better than where I started at. Another good track day should get them real close. And yes, the Bilsteins seemed to reduce tire wear but time will tell.

 

Katman,

Do you shoot for the same temp spreads front and rear? ie. 20-25 bias toward inside? In the past I've run a little less camber in the rear to increase traction out of slower corners.

[katman]

I wouldn't use an IR gun. Surface temps change too quickly.

 

A Z will need up to a degree+ less camber on the back and the temp bias will be the same.

 

Long term keep track of tire wear. For us that bias produced best handling and even tire wear. Counterintuitive- you'd think the hotter insides would wear faster.

 

One last thing- when in comes to engine or chassis, never assume the basics are still right just because so and so hasn't been changed and hasn't been a problem before. When diagnosing either I always start back at square one to verify everything is still where I think it should be. For chassis, the progression would be hardware (is everything tight and uncracked?), corner weights, toe, tires (as in throw on another set and see if the problem is still there). Only then do I start looking at springs/bars/adjustments.

 

Oh, and 20 degrees for 150 degree tires is proly a lot worse at the 190-210 you should be at on a normal day....

[JMortensen]

A Z will need up to a degree+ less camber on the back and the temp bias will be the same.

Please clarify. This looks like it says you ran more neg camber on the back than the front. Hard to argue with success, but that is really backwards from what has worked on my car.

[clarkspeed]

Damn this is a good thread. Now I know what I didn't know or something like that. Thanks all!

[katman]

Please clarify. This looks like it says you ran more neg camber on the back than the front. Hard to argue with success, but that is really backwards from what has worked on my car.

Degree+ less. Less camber on the rear, by a degree or more.

[Cal Poly Zmanaustin]

Wow! Substitute the Tokicos for Koni Sports (for a Rabbit) and EMI camber plates for a set from Design Products and you just spelled out exactly what I'm putting into my car. I am also going with the 175/200 spring rates. I haven't driven it yet, and was feeling a bit of anxiety about how the combination would work out. I'm feeling much better now. Thanks!

 

 

I'll chime it here. John's recommendation is exactly what I was running before my Z got totaled (rear ended on the freeway) except I did run the polyurethane bushings on the rear TC rod. I had the aluminum bushings on the inner rear control arms in the beginning. I do not recommend those at all. I swapped them out for urethane later. I am only going to change to larger wheels on my next one.

 

I can also vouch for the 5 way Illuminas with this set-up. I too was running 175f/200r and changed to 200f/225r. I found the movement of the car to be very predictable and nuetral. I was looking at additional power upgrades (just a mild L28 before) which is why I went stiffer to avoid the rear from squatting as much. Also, the #1 setting is welcomed after a day of road racing at the track and needing to drive 300 miles home. Don't be fooled this setting makes the car so much more tolerable to drive on the street without sacrificing handling.

[JMortensen]

Degree+ less. Less camber on the rear, by a degree or more.

OK so you mean you run 3 degrees neg in front and 2 degrees neg in rear for example.