Coilover Custom Build

[Flash]

I'm ordering some new coilovers Wednesday and I need to pick a spring rate. I'm unsure about a good spring rate I should get.
Standard is: Front: 9 kg/mm Rear: 6 kg/mm

But I do not want the standard spring rate. I'm looking for a spring rate that is a little stiffer to go to the track with.
I do not drive my car daily. So it is not a daily driver by any means. So I'm not looking for 'comfort'. I want a rather aggressive spring rate.
Idea's and help please... I'm asking for rather experienced help.

 

[drivemusicnow]

Do you want to do this right, or do you just want a general idea of what you should have?

If you go to the far north racing site (for the most part it is still up, even though they don't race or sell parts anymore) there is a book that is listed that has the proper equations to solve for spring rate.

Essentially you'll need to corner weigh your car, weigh the unsprung mass, mechanical advantage of the suspension on the spring/strut, and the motion ratio? i think it's called.

Or you could just ask JTMCinder what he has on his car. This would be much easier, however he is AWD. I don't know any Auto-x FWD cars that know there stuff off-hand.

either way, that rear spring rate seems a bit low. Depends on how the shocks are valved as well. You may need to ask them at what point do they change the valving in the shocks. Also make SURE you can get shock dyno data for YOUR shocks.

 

[asian312]

Are you taking this on racetracks or auto-X in parking lot?

 

[eclipsegsx1736]

A pretty common setup that will get you pretty close would be 12kg/8kg with a stiffer rear bar. This is a pretty aggressive setup, plenty of lift-off oversteer and a pretty neutral car on-power, although there are so many factors involved as mentioned above. This is for AWD too, and this is assuming the shocks are matched correctly to the rates. RRE uses a setup very similiar to this on their 2g's.

 

[Flash]

I get a choice of spring rates up to 20kg.
Where's Greg Collier when I need his opinion? FWD-wiseman.

12kg/8kg sounds good.

 

[jtmcinder]

In metric, I have around 12/8, but I'm probably switching to something closer to 15/8 for next year.

Part of this decision should be made with the front diff in mind. If it's still open, then stay down at 12 or so; if you have a helical, then you can go higher.

Tune the rear via the swaybar. I would not go higher than 8 in the rear of a street-driven car.

- Jtoby

ps. Far North Racing never sold parts; instead, Dennis worked (for a while) for a racing-parts business

 

[silvah_gsx]

Wow 20 is pretty high. 14 up front reduces the lift-off oversteer, but if I were you I'd worry about that only on canyons, not on a track...I'm sure you can understand why.

 

[Flash]

I think I'll go with 12/8.

Any other suggestions?

 

[jtmcinder]

Is it too late to say that you might not be happy with Asian shocks that adjust compression and rebound together?

Yes?

OK, then I'll keep it to myself.

- Jtoby

ps. damn that unfreezing process