Progress II coilovers - but which spring rate for a potential B-swap.

Id prefer the rear spring rate to be slightly stiffer than the FRONT

For a good daily driver, your car will drive awesome with 200-250 up front and 250 or so in the rear.

Stock is somewhere around 100-150 up front, depending on if it was a 2dr, 4dr, manual, auto, etc...


Stiffer is not always better. But if the coilovers you are thinking about are built specifically based on your spring rate choice. I would want you to ride around in someones car with certain springrates to see if you are in the ballpark.


*slo edit * wanna try again my guy?

"NOPE" nothing to see here slo <whistles>

B16 EF, easy answer is Whitener setup.


Note the USDM cars have the D's and B's mounted on the wrong side of the car, that plus the drivers weight is the reason Andy Hollis ran 50 lbs heavier on the left side. Even when he went to the K swap he kept them the same way IIRC. I'll ask him when he's in town and I'm building his transmission for next years OLOA


He used to have "notes" on Facebook, but no idea where FB is hiding them now.

Andy is also the tire tester for GRM. Also when ST class needed certain block measurements Andy's info aligned with mine.

Link to the Hollis notes, I know what I'll be reading tonight....

You never really explained the application this car will see, or I couldnt tell. It says you dont daily the car, but still want it to be comfortable. What is this mystery application? What types of things will this car see?

I only ask because I've learned a shit ton about spring rates over the last year, and honestly for our honda's, average vehicle speeds and vehicle sprung weight have the most to do with their selection.

Many of our suspension/driveshaft/braking components themselves (i.e. unsprung weight components) arent all that heavy from stock, and any mods we do in thia area with aftermarket parts typically remove unsprung weight, so for simplicity sake, we wont discuss unsprung weight.

Average vehicle speeds are very important in selecting a good spring rate for two important reasons:

1) increasing vehicle speed increases overall sprung weight due to downforce, even on a stock body.

2) increasing vehicle speed increases the rate/frequency at which changes/bumps/obstacles/weight transfer/etc will present themselves to your suspension components.


That last point means that when vehicle speed increases, we must have a higher spring rate to allow the suspension to react and push the wheel into the ground in the same way a lower vehicle speed and lower spring rate will, in order to maintain good control.

In your application, will the car ever see, or need to operate over 100mph for extended periods of time, have downforce adders (i.e. a wing, splitter, etc.), while also doing other repetitive maneuvers at that speed (i.e. cornering, braking)? If so, you'll want a higher spring rate to up the natural peak oscillation frequency that the spring can operate at.



This chart will help you understand what I mean. A lower spring rate has a lower natural peak oscillation frequency, compared to a higher spring rate.

Your typical street spring might operate at a max ability of 1hz, or one cycle per second. This means it can only deal with forces trying to compress and expand it at a rate of 1 time per second. Oscillations from the road surface or vehicle weight transfer entering the wheel/lower control arm then into the spring at a rate higher than 1 cycle per second, the spring will end up clashing with second order harmonics. Imagine two separate forces trying to enter the spring, one entered at the right time so the spring is busy dealing with that force, and another suddenly appears when the spring wasnt ready to take anything else. The spring could only deal with the one force, but not the other that also appeared, because the spring cannot accept or repel any more energy than it already has during that 1 cycle per second.

This is an oversimplification, but helps explain that spring operating frequency is tied to spring rate selection. And the frequency need of the spring is tied to the operating environment of the vehicle.

A higher spring rate, and the spring can do or handle more compression/expansion events per second, along with higher initial weights imposed on it.

Spring frequency is a very important trait to consider based on your application.

• If you're tracking this car with downforce adders, you need higher spring rates.
• If your front end is heavier than the rear, you need higher rates in the front compared to the rear.
• If you have high rate springs compared to stock, you need shocks that are designed, valved and tuned to manage higher spring rate oscillating frequencies.

For my EG, KTuned offered their K1 Street setup with 10k/600lb fronts and 6k/350lb rears. With the damper adjusters set to about half way, this setup rode amazing on the street, and did very well in corners until vehicle speeds exceeded 100mph.

I've since gone to 14k/800lb front and 10k/600lb rears, 100tw tires, gone B series and added a rear wing. Still on the same KTuned K1 shocks set to half way, its absolutely phenomenal how well the car handles now at 120+mph. The driver mod behind the wheel now needs to adapt to it with more seat time.

Hope this offers a decent starting point.