Suspension spring rates?

[EVO-00X]

Hi guys, what sort of spring rates would I be looking at for the rear coils to aide against bogging down so much on hard launches?
On the weekend a 7,000rpm launch saw all 4 tyres light up with smoke belching out the fronts, but the ass end bogged down a bit too much, even with aftermarket coilovers with what I thought was pretty stiff suspension :lol: Driver's rear tyre caught and pulled out the inner guard behind the sideskirt area and shredded the outer edge of the tyre. The inner guard is an easy fix with some decent rolling, however the spring rate will need some beefing up Apart from that inconvenience, it launched pretty hard and gets a thumbs up from Frankie B)

 

[ONPSI]

Do you know what spring rate your springs are now?
My old III has 10's or 12's in the rear, sorry can't remember but that seemed ok..However it's still going to bog hard when you launch at 7k rpm
King Springs here on the GC will custom make stiffer springs for you

 

[rob323]

Just bump your rear tyre pressure right up, then traction won't be a problem

Depending on which coilovers you have, some only adjust the rebound. You need to firm up your compression stroke, this will make a bigger difference than hard springs will.

 

[EVO-00X]

Thanks. I'll have to find out what spring rate I have now. I have the steel Fulcrum Formula coilovers all round. They are cloned on Bilstein struts and inserts and use h/duty King springs.
Suspension is hard enough for cornering yet civil enough to drive on without bouncing around like a looney. Im extremely happy with the ride when compared to friends cars running more of the mainstream alloy bodied racing suspension. Fulcrum obviously now are Tien distributors and dont deal with their own stuff anymore, but I might pick their brain in the meantime.
Thanks Rob, I'll see what my options are.

 

[rob323]

Talk to Quadrant or Heasmans down your way, they have plenty of experience with Billies from what I hear, and should easily be able to bump up the compression valving a little to suit.

 

[EVO-00X]

Thanks Rob I'll do that. Props to Fulcrum suspension and their exceptional customer service. I had a response from my enquiry already.

The spring rate on the rear is currently 170/220 lbs progressive, which explains for the nice ride.These kits haven't been made for around 6 years but they did know of another spring rate that they said might do the job though at 220/260lbs progressive.The extra rate might be enough to keep the rear from bogging down as much, but I would have thought something around 300lbs would have been the max you'd want to go on a street car without hopping around on bumpy roads around bends. Anyhow, just waiting on a price and weighing up my options.

At the end of the day if it means I have to give up the ghost on these (even though they feel great on the road for a daily driver) and step it up to the next level, its only money right?!??!?? :lol:

kg/mm to lbs/in
-----------------------------
16 = 896
15 = 840
14 = 784
13 = 728
12 = 672
11 = 616
10 = 560
9.0 = 504
8.5 = 476
8.0 = 448
7.5 = 420
7.0 = 392
6.5 = 364
6.0 = 336
5.5 = 308
5.0 = 280
4.5 = 252
4.0 = 224
3.0 = 168
2.0 = 112

 

[rob323]

Chuck some 4kg/mm or 6kg/mm linear rate springs in the back and see how they go. I don't think they will make any difference though if the valving in the billies is still soft.

 

[bazeng]

We need a video for a better analysis!

 

[EVO-00X]

lol... and shred my other tyres right Baz? lol :lol:
Gotta get the lips rolled more before trying that again B)

 

[JETGSR]

yes I would agree with Rob D if your shock only has rebound, the car will squat then lift slowly, Go too hard and you'll need a mouth guarg and a kidneybelt.(for the street)

I've been looking into a bit of suspension at the moment and the avaerage rear rate is about 6 some pushing to 8.<- i tink is a bit hard
I've had my Olins revalved and they dont seem to squat anywhere near what they used to. and handle awesome on the track.

Troy

 

[DOUGMO]

I run 400lb linear fronts and 350 linear rear - I just changed to them from progressive of the same rates.

My car hardly squatted at all with the progressives. mind you my shocks are pretty hardcore and have bump and rebound adjustment.

 

[EVO-00X]

UPDATE:
Well, the time has come and Im currently looking at new suspension and selling my existing coilovers.
I've got a choice of any spring rate I desire for up front and rear, with say 30 level damping and full length height adjustment.
If I play it safe with 8 fronts and 6 rears I should be right with enough to keep me happyish on bumpy streets with a low damper setting, then for fun days on the track and hillclimbs I can increase damper to stiffen it up yes?
George, I'm better off keeping my fully adjustable K-mac pillow ball front strut tops arent I? http://www.k-mac.com.au/ . Spending extra $$ on camber-only tops that most manufacturers offer as an option to their kits would be a waste of $$ if I already have the Kmacs.

 

[evopwr]

Rob,

I run Teins with stock springs (front 6kg, rear 5kg), and have scrapage issues on the back. thinking of going 8kg rear..

Definitely keep your Kmacs and get different springs. in theory you should revalve the shock according to the spring rate, but I guess it just depends on how perdantic you are.

 

[DOUGMO]

yes rob, those kmacs are the go, i run them too.

with those rates it will be good for both but it depends on the shock as to weather the
bump adjustment will firm it up, cheap and chearfuls you wont notice much difference.
thats why the cheaper coilovers have stiffer springs.

 

[GSRWRC]

Rob,

I run Teins with stock springs (front 6kg, rear 5kg), and have scrapage issues on the back. thinking of going 8kg rear..

Definitely keep your Kmacs and get different springs. in theory you should revalve the shock according to the spring rate, but I guess it just depends on how perdantic you are.

I have the same, thinking about swapping the springs front to rear though. The ride is still a bit too firm for the cars intended use grrr.

 

[evopwr]

^ Compared to what i used to have its like riding on air :lol:

 

[EVO-00X]

OK I'll get some 8/6's before the end of the month. I'm not looking to spend big bucks this time though, so Im going bang for buck with names like GBR, BC and GAB SS who all R&D their own suspension plus offer decent warranty. The GBR's are manufactured with quality components and are a nice unit with 12 months guarantee followed by lifetime warranty thereafter. They are making a good name for themselves at the moment and feedback has been positive from user reviews. I was really tossing up between the GAB SS and GBR's if anybody would like to chime in and offer their opinion on either. Both have very similar features. Its also interesting to note that the GABs have titanium threaded area on them for strength now so they've matured a bit over the years and offering a better product. Both the GAB's and BC's are manufactured by the same plant in Thailand, but they are not clones of eachoither and are individual. Im definitely not getting any of those rebadged clones like D2's etc.

 

[EVO-00X]

As luck should have it, one of the members in this forum listed a brand new set of BC Racing RM Inverted Series coilovers for EVO I-III with 8/6kg setup - I jumped straight on them
They get some good reviews so looking forward to comparing them against what I currently have.
Specs hof the RM inverted series can be read here: http://www.bc-racing.co.uk/coilovers-series-rm/?popUpClose=1

 

[rob323]

As luck should have it, one of the members in this forum listed a brand new set of BC Racing RM Inverted Series coilovers for EVO I-III with 8/6kg setup - I jumped straight on them
They get some good reviews so looking forward to comparing them against what I currently have.
Specs hof the RM inverted series can be read here: http://www.bc-racing.co.uk/coilovers-series-rm/?popUpClose=1

Just remember that inverted shocks are not set and forget. They require maintenance. The MCA website has a good page on regreasing inverted shocks.

 

[7zark7]

I have some Race Logic Coilovers ( 8F, 7R) in my Evo 3 tarmac car with a custom Whiteline 23mm rear sway-bar running 205 R-Specs.
The car launches quite flat with very little bog down but it does spin all four wheels easily, especially if I do 7k launches. (My normal launch is 6 - 6500 rpm)
Wheel spin is prob not so good if you're a drag racer but it's good for standing starts out on closed road sections and for a bit of mechanical sympathy.
The car feels quite firm and tight but it handles really well with little understeer. I did have to do quite a bit of playing around with the front to rear ride-height and front compression/rebound but I think I've got there now.
I would recommend them as a good cheaper suspension system to anyone who is starting out and using their car for competition. I personally think that they would be a little too firm for a daily driver.
Hope that helps.