TRD shocks and springs

[NoHachi]

Now take a look at this badly made picture:
pic one: stock AE86, 150mm stroke. At full extension of the shock the spring is still not fully stretched. At full dynamic compression the spring would just barely hit the strut. (its stopped by the bumpstop that I didn't draw)

Pic two: TRD spacer The car is lowered significantly. The top of the strut (aka the car) is now just 20mm away from the strut. 8kg/mm springs have a stroke of ca 75mm's. Loving contact will be made by topmount and strut.
Also notice that we have tons of extension left in the shock..more then the spring has available. So the spring is no longer captive.

pic3 T3 spacer: Same problem with compression travel as TRD 60mm spacer. About 55mm to little of it. Less of a problem at full extension (but according to robo still to much extension and still no captive spring.

Pic 3: 40mm shorter housing and 20mm spacer: Still have a bit to much extension and slightly too little compression. A bumpstop will add enough rate to prevent topmount/strut contact. Extension problem is worse then with the T3 spacers (20mm worse to be exact, I did not draw this correctly yet).

[img name=]http://www.aeu86.org/download/ae86/id/13377[/img]

[Uzelac]

Whay you raised coilover spring at PIC4 ?

If you left it at original perch position, wouldn't both compression and extension be near perfect ?
With pretty lowered car.

[NoHachi]

Fixed it...the reason is the captive spring problem. That is something that you can probably never solve with springs that have a free length that is shorter then the total stroke of the damper.

The free length is probably a compromise TRD had to make to get the spring rate that they wanted in combination with ride height they wanted, within the given constraints of the stock spring perch position. Either that or they made a bit of a **up.
This is the reason that we have helper springs with coilovers. They simplify the process of spring selection significantly.

[4000GT]

Top explanation!

[Uzelac]

Please, correct me if i'm wrong:

It looks that if someone is going to use TRD sized springs with original perch they should cut 25-30mm and go with 30-35mm spacer.
It gets 70-75mm of compression and 65-70mm of extension.
Just as reminder "Short Strokes" as TRD/SS Konies/HTS have ~148mm of travel.

[NoHachi]

No, the forces on a 8kg spring result in a compression stroke of around 75mm. So you need around 75mm between the position of the spring at rest (with sprung+driver weight) and the top of the strut. Your solution leaves too little compression stroke and will leave the spring free in rebound. Check your numbers again and you'll see.

I found measurements of around 165mm of travel for AE92 shocks. The true free length of TRD springs is also uncertain. If the measurements were 100% accurate, then the best solution would be to cut 60mm from the top of the strut, above the perch and leave the perch where it sits. No spacer needed.
Since I don't have a guarantee on these numbers, the "normal" approach with a 40mm cut and 20mm spacers seems to be a safe and tested solution. I predict bottoming for experienced track drivers on slicks, but its no worse then what the AE86 came with stock. Keep the bumpstops in place and it should be ok.

[4000GT]

Ill get the free length of the springs when they arrive, should be today. Nothing like accurate data.

[Uzelac]

NoHachi Wrote:No, the forces on a 8kg spring result in a compression stroke of around 75mm. So you need around 75mm between the position of the spring at rest (with sprung+driver weight) and the top of the strut. Your solution leaves too little compression stroke and will leave the spring free in rebound. Check your numbers again and you'll see.

Whats wrong with my math? Look pic4.
Raise shock for 15mm (bigger spacer (35mm), smaller cut (25mm)) and leave perch at same position.
You will get 75mm of comprssion and 72,5mm of extension for HTS 102 damper which have 147,5mm of travel.
What is wrong with that?

NoHachi Wrote:I found measurements of around 165mm of travel for AE92 shocks. The true free length of TRD springs is also uncertain. If the measurements were 100% accurate, then the best solution would be to cut 60mm from the top of the strut, above the perch and leave the perch where it sits. No spacer needed.

Stock AE92 have 160+ mm of travel, but SS Konis (Koni sports for AE92) and HTS 102 have just under 150mm. 50:50 proportion for extension:compression makes it around 73mm for both.

[4000GT]

Ok my gear arrived! The Shocks are 48511 AE031 seems to be 5 way adjustable (believe thats the AE92 shock). The Springs are 210mm unsprung.

[4000GT]

Ok suspension is in. Assuming there isnt a left and right spring?