Initial Spring Setup - How To?

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1

This seems to be one thing I struggle with, I don’t have any real idea of how to set my springs initially. Is there a calculation for FM6?

Or can someone share a process for setting the spring weight, I guess this is the first thing you should do on a build.

Thanks

2

One method I saw posted here recently seems effective:

Take your car’s weight and split it by weight distribution (Front %), then divide those 2 numbers by 2.

3

FM6 already has a built in calculator . . . but it is usually set too high/stiff.

Found out on the Celica that I have been running that it was sprung way too high. So I continued to soften the springs until the brake/acceleration issue became manageable.

Test to see if springs are too soft/stiff: Push the car relatively hard, but in control, for few laps AFTER the tires have warmed up.

If the wheels are locking up easily + having difficulty exiting corners + driving over curbs bounce the car around . . . then the springs are too stiff. Reduce front/rear by about 10% and retest. Continue until the braking/acceleration/driving over bumps feel more grippy and less skittish.

If the car bobs forward/back and side to side and difficult to control through esses then it is probably too soft. Continue to increase front/rear by about 10% until it feels comfortable.

In both cases, you should see small improvements on your laptimes + noticeably better braking/cornering/exit grip.

My rule for front/rear balance is:

  1. Set spring rates roughly based on weight distribution
  2. Reduce the power side spring rate by another 5%, i.e. for FWD, reduce front spring rate by another 5% or so. For RWD, reduce the rear. For me, this seem to give a little better grip.

Very ROUGH guide that I use for starting point is:

Examples #1:

FR 2000 lbs, 55% front wt, 45% rear = rear is 90% of front

  1. Front spring = (2000/10) = 200 lb/in
  2. Rear spring = (200) x (0.9) = 180 lb/in
  3. Rear spring adjust for RWD = (180) x 0.95 = ~170 lb/in

FF 2500 lbs, 58% front wt, 42% rear = rear is 84% of front

  1. Front spring = (2500/10) = 250 lb/in
  2. Rear spring = (250) x (0.84) = 210 lb/in
  3. Front spring adjust for FWD = (250) x 0.95 = ~235 lb/in (I adjust to nearest 5 lb/in)

MR 3000 lbs, 45% front wt, 55% rear = rear is 110% of front

  1. Front spring = (3000/10) = 300 lb/in
  2. Rear spring = (300) x (1.10) = 330 lb/in
  3. Rear spring adjust for RWD = (330) x 0.95 = ~315 lb/in (I adjust to nearest 5 lb/in)

These are for road cars only; have not evaluated for supercars or race cars. These are just starting points . . . the car will be pretty supple. Then use ARB to stiffen up the ride for cornering.

If the spring rates are in good range, you’ll see good movements on the telemetry screen. Seeing up to 80%~90% offset is good. What you want to avoid is seeing too many 100% (too soft) or never seeing 80% (too stiff).

1 Like
4

Are you sure these numbers are correct? 300 front spring for 3000 lbs car seems way too soft from my experience.

Provided 50% weight distribution I would set it around 750 (3000/4) and ARBs around 20 to complement.

5

300 would be a bit on the low side. I would likely stay at/under 400 lb/in front. 750, for me, I find too stiff.

It’s whatever you find comfortable. It’s like cooking; if it tastes good to you, that’s a good meal. I like mine spicy and a touch salty!

6

Thanks guys, I’ve put some of this into practice. My springs settings were slightly too stiff on the Supra, softened them and what a difference. Still fairly firm, front and back in the 500lb/in area but a big difference.

Thanks all, some really useful replys.

Mark

7

Out of curiosity I played around with much softer springs and it works if you use higher tire pressure. On my setup I use 28 which requires a stiffer setup. However if you dial in 29 all of a sudden you can run much softer springs, in my case around 500.

The interesting question is now: is there a best (fastest) way to tune? E,g. soft tire pressure / stiff springs or vice vwrsa

8

I use the weight X distribution + aero /2. after that i immediately take off anywhere from 20 - 40 % from both front and back because going by the formula alone the sprigs are always too stiff. It takes all of 30 seconds to calculate