Spring setups for AE86

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InitialB
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Spring setups for AE86

Postby InitialB » Tue Dec 03, 2013 7:00 pm

I can build an engine with my eyes closed, however, I've never been good at calculating suspension. I have researched various N2 builds and I plan on putting swift 12kg in the front and 10kg in the back. Now I'm lost on spring length. The sizes range from 5" to 11". My idea was 9" up front and 8" in the back?

With that said, I want the car as low as functionally possible for time attack so what lengths do you guys recommend for front and rear?

REMINDER THIS CAR WILL BE FOR TRACK USE, NOT STREET USE.

Sorry if I sound like an idiot... it's because I am an idiot.
Last edited by InitialB on Wed Dec 04, 2013 1:12 pm, edited 1 time in total.

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Re: Spring setups for AE86

Postby kuroki86 » Tue Dec 03, 2013 7:03 pm

thats way stiffer rates than most people run, but most of us see some street use i guess

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Re: Spring setups for AE86

Postby InitialB » Tue Dec 03, 2013 7:05 pm

Yeah it's a lot stiffer than most, but it is the most commonly used in N2 spring setups. I know most of the guys that daily their cars run like 8kg and 6kg at most.

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Re: Spring setups for AE86

Postby yoshimitsuspeed » Tue Dec 03, 2013 8:04 pm

I am no master of suspension tuning myself but I can say that lower and stiffer does not mean faster and this is a very common misconception among people who want to look fast and those who are new to trying to go fast.

If you are interested in proper setup I'd start reading. I know books like tune to win and others by Carroll Smith are highly recommended in the racing world. I have bought it but haven't gotten around to reading it yet lol.

This thread is about the AW11 but there is a lot of technical discussion and some comparison to front engine cars and the importance of weight distribution.
http://www.mr2oc.com/showthread.php?t=298272

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Re: Spring setups for AE86

Postby InitialB » Tue Dec 03, 2013 8:08 pm

Well I know that lower and stiffer don't directly mean faster, however, stiffer does mean better traction and handling if I'm not mistaken.

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Re: Spring setups for AE86

Postby gotzoom? » Wed Dec 04, 2013 9:00 am

What tires do you plan to run?

I've been tuning my suspension for track use for the past couple years and here's what I've found. First off, I agree with what yoshimitsuspeed said. However, the big problem with our cars is that, in race trim, the roll center is too low and the center of gravity is too high. What you read about in books generally assumes that the center of gravity and roll center are closer together, so you may have the tendency to second guess the data that you get from the car. I certainly did for a period of time.

I've used street tires (Hankook RS2) and normally run R Compound tires (Nitto NT01.) While a stiffer setup works better with R comps, I don't really feel that there is a significant difference in setup needed when you go back and forth between "normal sized" street tires and R comps. This is especially true if you have adjustable shocks/struts. Based on my experience, I feel that the car will be slow (really slow) with rates that high. I've experimented with rates as high as 600lb/in (10.7kg/mm) springs up front and 8kg/mm springs in the stock locations in the rear. With rates that high, even with 205 width Nitto NT01 tires, the car has no grip and is slow. It is fun to drift with, though. My opinion is that you aren't too far off base with 8kg/mm (450lb/in) springs up front and 6kg/mm springs in the rear. I don't feel that combination is ideal for the car based on my setup, but it's close enough to tune from. If you plan to run wide wheels and bias ply race slicks, you may be able to get away with those high rates, but I'm certain they won't work with "normal sized" tires. I think you should really be focused on the dampers you run. There aren't a lot of good options available for the car and most of what directly bolts up is junk or not suited to the car. Spend your money on the rear shocks. They are the key to going fast in an AE86, imo. If you're really interested in going fast, I wouldn't consider any shocks/struts that you can't get revalved easily. I hope that helps.

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Re: Spring setups for AE86

Postby gotzoom? » Wed Dec 04, 2013 9:02 am

Forgot to mention one thing. You raise spring rate to reduce traction, not increase it.

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Re: Spring setups for AE86

Postby InitialB » Wed Dec 04, 2013 11:44 am

Well these other parts might help you understand why the rates are so high.

1. The car has an SS Works Watt's link.
2. It also has UEO STYLE Pro 4-link.
3. It is running 235 Dunlop slicks all around.
4. It also sports a pretty awesome GT wing.

When i say it's racing use only, I'm not kidding :lol:

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Re: Spring setups for AE86

Postby InitialB » Wed Dec 04, 2013 11:47 am

The car is going to be using TRD Race Shocks with 8-way damper adjustability all around.

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Re: Spring setups for AE86

Postby burdickjp » Wed Dec 04, 2013 12:28 pm

To determine spring length:

Find an average front and rear corner weight. That is to say: how much weight will the spring support?
Find the distance between spring perches for the ride height you want.

The total length will be the at rest length + the corner weight divided by the spring rate.

Be sure your units work out:
distances in meters
mass in kg
spring rate in kg/m

OR
distances in inches
weight in lb
spring rate in lb/in
Pursuing the ideal

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Re: Spring setups for AE86

Postby yoshimitsuspeed » Wed Dec 04, 2013 1:19 pm

gotzoom? wrote:Forgot to mention one thing. You raise spring rate to reduce traction, not increase it.

That is true in relation to front to rear balance and in the same way for sway bars. If you just make the front stiffer it will take more of the load and forces causing it to loose traction earlier. If you raise stiffness equally between the F&R then the balance will stay the same. Whether it's overall faster or not depends primarily on the road surface. If you raced on an absolutely flat and smooth surface you would not need suspension. As soon as you encounter any uneven or rough surface then your tires will begin to reduce pressure on the road or even loose contact altogether at the low spots. Suspension allows the wheel to come up on high spots and go down on low spots. It also starts to introduce roll and other attributes that can become very detrimental. The goal and the balance is suspension soft enough that it can maintain as even a pressure as possible on the road over the varying conditions it will see while keeping roll, suspension geometry and alignment as ideal as possible.
At higher levels different cars, different tracks and different drivers will all need suspension tailored specifically to them.
You will also need enough travel to allow the suspension to absorb those inconsistencies without bottoming out or digging into unpridictable areas of the spring and shock travel or suspension geometry.

I wish I could help you more as far as actual numbers but that's out of my league. I just know that there is such a thing as too low and too stiff.
Your rates do seem to be within the realm of others I have seen on more dedicated track cars though. I suspect it's a decent starting point but if you are trying to be competitive you would want to start branching out to other variations and start getting a feel for what variations are fastest in different condition, tracks and so on.

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Re: Spring setups for AE86

Postby InitialB » Wed Dec 04, 2013 1:28 pm

Thanks for the lesson :D . I think I'll be going with 9 inch 11k springs in the front and 8 inch 9k springs in the back.

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Re: Spring setups for AE86

Postby Zissou » Wed Dec 04, 2013 5:29 pm

InitialB wrote:Well these other parts might help you understand why the rates are so high.

1. The car has an SS Works Watt's link.
2. It also has UEO STYLE Pro 4-link.
3. It is running 235 Dunlop slicks all around.
4. It also sports a pretty awesome GT wing.

When i say it's racing use only, I'm not kidding :lol:

Pics?

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Re: Spring setups for AE86

Postby miswuevos » Wed Dec 04, 2013 8:40 pm

gotzoom? wrote:What tires do you plan to run?

There aren't a lot of good options available for the car and most of what directly bolts up is junk or not suited to the car. Spend your money on the rear shocks. They are the key to going fast in an AE86, imo. If you're really interested in going fast, I wouldn't consider any shocks/struts that you can't get revalved easily. I hope that helps.



You have any examples on what directly bolts up and is junk?

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Re: Spring setups for AE86

Postby totta crolla » Thu Dec 05, 2013 3:24 am

You may have already seen this thread but it does make it clear that a very rigid platform is needed for stiff (8kg+) springs:
http://www.aeu86.org/viewtopic/nohachis ... +ramblings