Suspension Spring Rate questions

[D'Ecosse]

I just purchased a set of JIC-Magic FLT-A2 coilovers

http://www.jic-magic.com/productsjic_susp_flta2.htm

The supplied springs are 10Kg Front & 12Kg Rear - per most performance applications (including the Honda OEM Type R's, S and Zanardi's) all have balance with higher spring rates in the Front

Also mentioned here

Comments please on whether it might be advisable to swap out the springs between the front & rear? (They are both the same length)

 

[Larry Bastanza]

Can you swap them? Will they fit? If so I would. Ask Docjohn in the NE about his NSX-R setup. It is killer. If you talk to Peter Mills or Andrie Hartanto, they will tell you the same thing, stiffer in front. The Comptech setup is 1000lbs front, 600lbs rear. That would equal of 12f/7.2r The NSX-R suspension would be equal to 12/9.5, so swapping would be pretty close.

HTH,
LarryB

 

[fkong777]

why is it that both Tein and JIC have 10 / 12 ?

Can it be that JDM like to tune handling with more oversteer than what US drivers are use to.

I have tein HA on my is300. and it is 12 / 12. it is pretty balance with a hint of oversteer. but it oversteer can be corrected using damper adjustment.

Im going to pickup a NSX within this month and I'm debating to go with Tein Flex or JIC. JIC are very nice but also very pricey.

 

[D'Ecosse]

why is it that both Tein and JIC have 10 / 12 ?

Can it be that JDM like to tune handling with more oversteer than what US drivers are use to.

Not when you consider the Type R's which aren't even avaible here and they have bias on front

 

[D'Ecosse]

.... The Comptech setup is 1000lbs front, 600lbs rear. That would equal of 12f/7.2r ...

Your math is a little off Larry - the comptech Pro is actually quite monstrous!

1000lb/in ~ =17.8 kg/mm and 600 lb/in ~= 10.7 kg/mm

12/10 is ~= 675/560, much less aggressive.

Math:

1 kg ~= 2.2lbs; 1 inch ~= 25.4 mm

=> 10 kg/mm ~= 10 x 2.2 lb/mm = 22lb/mm;

=> 10kg/mm ~= 22lb/mm ~= 22 x 25.4 lb/in = 558.8 lb/in

=> 10kg/mm ~= 560 lb/in


=> 1kg/mm ~= 56lb/in

=> 6kg/mm ~= 336lb/in

=> 8kg/mm ~= 450lb/in

=> 12kg/mm ~= 675lb/in

I may follow Chris Willson's suggestion on the TEIN's and leave the fronts at 10kg and get 8 kg's for the rears. This actually quite close to the 02+ type R

The NSX-R suspension would be equal to 12/9.5, so swapping would be pretty close....

I hate to do it to you again Larry, but ......

Courtesy of Science Of Speed

Front is 102 N/mm ~= 102/9.81 = 10.4 kg/mm
Rear is 81.4 N/mm ~= 81.4/9.81 = 8.3 kg/mm


A range of different suspension spring ratings is actually in the Suspension FAQ

 

[D'Ecosse]

Looks like I'm talking to myself for the most part here - Maybe I'll think of an answer too.

Anyway, quick update - I checked the spring rates on the shocks by loosening up the bottom perches (nice thing about coil-overs!) and they were stamped on the tops. Interesting (& convenient as it turns out!) the rates are 9kg/mm & 10 kg/mm (not 10 & 12 as the JIC-Magic web-site states - however in looking through some of their vendor sites, some of them are listing in their applications tables the 9/10 set-up, so I think it was maybe changed recently).
However I'll probably go with the 10's on the front & the 9's on the rear as concensus (did a lot of reading through archives today!) suggests that bigger spring on rear creates a lot of oversteer. I would imagine that should give a reasonable neutral steering effect & I can should be able to swap them around without any fear of not being matched to the damping, since they are pretty close already.

 

[Larry Bastanza]

Ken,

Thanks, damn math teacher, he must have taught me wrong!LOL.............

BTW, my numbers were just absolute ratios, not the spring specs. You did a way better job

LarryB

 

[D'Ecosse]

BTW, my numbers were just absolute ratios, not the spring specs. ...

Aaah, I wondered what the little "r" was for - now I see what you meant.