JagoBlitz

noodels

Fantastic

noodels

Have you calculated above post from Junky for 03 arb on your proposed set up ?

JagoBlitz

Acc. to the excel sheet there is no harm in going to ARBs from 2000 all around.
The coils have a greater effect on the balance than the ARBs.
Out of the three setups my current one seems to tend most to oversteering.

s2000Junky

There is nothing to calculate. Common knowledge is if you apply a stiffer sway bar to the rear of the car its going to over steer more compared to the ap2 rear bar your currently running. If you want to calculate your stock spring rate change to the current you are now running thats another matter. As a sum of both spring and sway weight your going to arive at a different bias then factory yes, but my comment is simply on where you are at right now with the rear sway swap and what thats going to achieve for you = more rear bias to over steer.

My first s2k was an 01 so I am familiar first hand with how that handles along with currently owning an 02 and running after market 10k and currently 14k spring rates front and rear and changing out the rear sways from all years. I currently swap from 02-03 to ap2 rear sways depending on if im trackng the car. I like the added sharper more responsive turn in feel of the 02-03 rear sways over the ap2, but the softer ap2 is more effective for proper traction bias on High speed track duty. But as I said before you should experiment yourself so you can see what you prefer. Fundamentally though pring rates should be match to G load/ tire adhesion to get most out of tire which is based on width and compound and stagger or no stagger, then you can tweak bias to preferential handling characture. I run 255/315. And no aero/downforce and I have my own preferences. There is multiple ways to skin a cat.

Car Analogy

I am the originator of that spreadsheet wheel rate calculator. Its based on the spring and swaybar rates calculated by TwoHoos in his legendary research paper, and the Motion Ratios calculated by Sake Bomb Garage.

All it does is calculate wheel rates of springs and bars combined, then express the rates as percentages Front vs Rear. It lets you compare any possible configuration of aftermarket or stock springs and bars from any year, with the stock rates for any production year.

Suspension setup is very complicated, and this is simply a tool that can help put a frame around contemplated changes or to help interpret results from a chance.

For instance, on my '06 I replaced both front and rear bars with '00-'01 bars. I went from 300/311 bars to 392/427.

It looks like I went way more rear bias, right? Nope. On my '06, with stock springs, the effect was:

Swaybar rates vs bias:
Stock:
300/311 = 56.4%/43.6%

'00 bars:
392/427 = 57%/43%

I actually shifted bias slightly forwards! The reason is the motion ratios front vs rear. The front swaybar motion ratio increases much faster than rear. So a bar stiffness increase of 92 in/lb front has a larger effect on wheel rate than the 116 in/lb bar increase at the rear!

This is why the calculator is such a valuable tool. Intuition would make you think the rear bar increased much more than front, so bias must have shifted rear. Not the case.

The spring motion ratios work tbe other way around. As you increase rates, you shift bias rearwards.

For example, consider the following spring rates on, say, an '04 ap2, with stock swaybars. The following values are F/R spring rates = F/R bias percentage. Lets see what happens as we increase rates in lock step:

Spring rates vs bias:
300/300 = 56.4%/43.6%
400/400 = 55.4%/44.6%
500/500 = 54.7%/45.3%
600/600 = 54.2%/45.8%

As you can see, bias shifts rearwards as you go up in rate. So to keep the same bias with stiffer springs, you need to increase front more than you increase rear (the opposite for swaybars).

So lets say we liked the bias we had at 300/300, but we wanted to increase spring rate significantly. What rear spring would we need to keep bias the same if we increased front springs to 600? (On this example '04 with stock swaybars)

600/540 = 56.4%/43.6%

Again, not intuitive. Spreadsheet calculator helps put things in proper perspective.

JagoBlitz

Thank you for your input.

So, does the calculation match your experience when driving the car with the new sway bars?

Car Analogy

Yes. When I got the bars I was hoping for more rear bias.

My '06 understeers more than I'd like (I grew up in rwd era). I was hoping the stiff rear bar would shift bias. It didn't. I then experimented with using some stiffer rear springs from another year. That worked.

Then I switched to some lowering springs (not to lower, but for their progressive rate, which I prefer for the street. I went with H&R, which barely lower the car at all, and added custom spacers in front as it still lowered more than I like.) Most lowering springs were designed when ap1 came out, and are based on ap1 rates (but a bit stiffer, and usually progressive). This means they're heavily rear biased. So basically I have rates similar to what I experimented with, but progressive.

H&R doesn't publish their spring rates for lowering springs (but oddly, do publish rates for their coilovers). But I built a rig to measure their spring rates, to confirm bias.

s2000Junky

Don't forget the OP is currently running 10/10k spring rate, not factory springs but with factory sways. Moving to a stiffer 00-01 rear sway as it stands will increase oversteer bias from current configuration. That is what he is trying to verify as I understand it. ^^^ Adding the stiffer front from the 00-01 as well brings back into closer to current balance but stiffer all around.

noodels

All ok if on straight roads