I don't understand coilover spring rates.

[steverife]

Originally Posted by Lincoln Logs

Take any modern Super-200TW tire, install a 245 or 255 on a 17x9 and pair it with soft suspension (ex. Flex-A). Enjoy cornering on bump stops. These cars need way more spring rate to support a sticky tire, it's not rocket science. I've tested a bunch of spring rates from 4k-9k and anything less than 8k you are into the bump stops a lot more than you realize.

I'm not familiar with the Flex-A. Top STX cars with a Giken seem to be running as low as 5k up front and the stock diff folks seem to have gravitated to around 400/350.

Softer springs may cause the car to roll more than you want, but between ride height and camber plates up front and top mounts in the rear, you should be able to put together a suspension where you aren't forced to set up your car around hitting bumpstops under normal circumstances.

[Racecomp Engineering]

Since it hasn't come up yet, this is your reminder that the stock suspension is very bumpstop active. You're hitting the bumpstops early and often (not just during performance driving). This is intentional. There's a difference between "bottomed out" and just hitting the bumpstops.

Some coilovers will ride the bumpstops as well, depending on how they're set up and the spring rates used. Sometimes it's very noticeable, sometimes it's not. For example, the bumpstops on BC coilovers are (were?) very hard. Other coilovers may use much softer/progressive bumpstops and it may be more difficult to tell when you're hitting them.

Spring rates certainly aren't irrelevant, but they are just one part of the system.

- Andrew

[Clutch Dog]

There's also the whole topic of "bumpstop tuning" as they are being used more and more in how a car settles on compression

[Lincoln Logs]

Originally Posted by steverife

I'm not familiar with the Flex-A. Top STX cars with a Giken seem to be running as low as 5k up front and the stock diff folks seem to have gravitated to around 400/350.

Softer springs may cause the car to roll more than you want, but between ride height and camber plates up front and top mounts in the rear, you should be able to put together a suspension where you aren't forced to set up your car around hitting bumpstops under normal circumstances.

Looking at the 5k springs is only looking at a SINGLE part of the equation. There are so many other elements that need to be considered. Those same cars are running larger front sway bars and have double or triple adjustable coilovers, etc. Bumpstops are just as much of the equation and another element for tuning. See RCEs response for even more insight.

Originally Posted by Racecomp Engineering

Since it hasn't come up yet, this is your reminder that the stock suspension is very bumpstop active.

Thanks for bringing this up. OEM tuning from Mazda on the new MX-5 is VERY bump stop active too.

[Spacemane969]

Originally Posted by Clutch Dog

I like my 6k as a compromise between street use and track use and yess you "can" race on them at the track. but they are compromised.

for me Im enjoying it thouroughy! it forces you to drive the chassis and not tire


I dont give starbucks my money though .

What do you mean by compromise at the track?
That setup seems optimal for me. Stock wheel width and spirited street driving with one or two track days per year.

[Spacemane969]

Originally Posted by Racecomp Engineering

Since it hasn't come up yet, this is your reminder that the stock suspension is very bumpstop active. You're hitting the bumpstops early and often (not just during performance driving). This is intentional. There's a difference between "bottomed out" and just hitting the bumpstops.

Some coilovers will ride the bumpstops as well, depending on how they're set up and the spring rates used. Sometimes it's very noticeable, sometimes it's not. For example, the bumpstops on BC coilovers are (were?) very hard. Other coilovers may use much softer/progressive bumpstops and it may be more difficult to tell when you're hitting them.

Spring rates certainly aren't irrelevant, but they are just one part of the system.

- Andrew

So a harder bumpstop would be more correlated with stock feel? I just remember feeling the stock setup as diving into a corner and planting itself until you came out of it. AKA the "on rails" feeling. That's the feeling I'm after.

[Racecomp Engineering]

Originally Posted by Spacemane969

So a harder bumpstop would be more correlated with stock feel? I just remember feeling the stock setup as diving into a corner and planting itself until you came out of it. AKA the "on rails" feeling. That's the feeling I'm after.

No not really. The stock bumpstops are progressive (which is why you don't necessarily "feel" when you start getting into them). Hard bumpstops are noticeable and can cause an abrupt change in behavior, generally not good.

- Andrew

[Lincoln Logs]

Originally Posted by Spacemane969

What do you mean by compromise at the track?
That setup seems optimal for me. Stock wheel width and spirited street driving with one or two track days per year.

For a sticky 200tw tire you need more spring rate even with the relatively small width, generally speaking tire compound > size. A high performance summer tire, RE-71 or BFg Rival-S, sized as a 225/45/17 tire will create more lateral grip than a Michelin Pilot Sport 4S or Continental Extreme Contact Sport size in 255/40/17 on a 17x9.

Throw on something less sticky then perhaps you can optimize for that tire. 6kg is not enough spring rate if you want to optimize for maximum grip from a modern 200tw tire. If we are talking about a car that is turning laps a few times a year and you don't care about ultimate lap times then perhaps it is perfect.

[Clutch Dog]

Originally Posted by Lincoln Logs

For a sticky 200tw tire you need more spring rate even with the relatively small width, generally speaking tire compound > size. A high performance summer tire, RE-71 or BFg Rival-S, sized as a 225/45/17 tire will create more lateral grip than a Michelin Pilot Sport 4S or Continental Extreme Contact Sport size in 255/40/17 on a 17x9.

Throw on something less sticky then perhaps you can optimize for that tire. 6kg is not enough spring rate if you want to optimize for maximum grip from a modern 200tw tire. If we are talking about a car that is turning laps a few times a year and you don't care about ultimate lap times then perhaps it is perfect.

Originally Posted by Spacemane969

What do you mean by compromise at the track?
That setup seems optimal for me. Stock wheel width and spirited street driving with one or two track days per year.

It's "optimal" only be definition of what the intended goal is.

Which lincoln just stated. few track days a year for self improvement without regard to setting lap times or competition.
If you want to compete you'll go to a more serious set up.

You also wouldnt be running 18x8 225's at a track event if you were serious.

[Spacemane969]

Thanks guys. One last thing. With adjustable dampers would running soft settings have the effect of feeling like the springs got softer as a whole? I'd rather start a little higher on spring rate and adjust them softer if I start losing too much grip.

So for instance if I bought 8k springs and the softer setting would bring them down to feeling like 6k, relatively, with all of the components at work.

[CrowsFeast]

Originally Posted by Spacemane969

Thanks guys. One last thing. With adjustable dampers would running soft settings have the effect of feeling like the springs got softer as a whole? I'd rather start a little higher on spring rate and adjust them softer if I start losing too much grip.

So for instance if I bought 8k springs and the softer setting would bring them down to feeling like 6k, relatively, with all of the components at work.

I'm not a professional in this area but:

Short answer: yes.
Long answer: not really. As stated springs are only part of the equation. From what I've been reading and my discussions at the track it seems shock valving has a much higher effect ride quality, especially with (3 way? 4 way?) adjustable shocks. From my understanding for track use you typically want the low velocity bump damping to be high and high velocity bump damping to be low. Low velocity bump would be from driver inputs. If the shock only allows slow movement for these then the car can react faster to the driver inputs because you don't have to wait on the suspension re-settling. The high velocity bump will be from the actual road imperfections, curb, etc. With low damping on the high velocity bump then the suspension can soak up these imperfections much better without upsetting the car.

Once again I am not a professional/expert in this area but I do have a lot of interest/discussions about it. PLEASE correct me if I'm wrong. That said I am also talking about a 'typical' situation for any car and as we know nothing in racing is really typical and every car is different.

[RayRay88]

With one or two track days a year it would be better to go with softer spring rates and invest in a high quality shock/coilover system, that can stiffen up quite a bit at the track. Either way you're going to compromise, it just depends on which side you favour more, comfortable on the street or capable on the track.


Expensive and more advanced coilovers like the upcoming Xida, CSG Flex A, JRZ, Ohlins etc. will be the closest you can get to having your cake and eating it too. Digressive valving will likely be your friend.

[Lincoln Logs]

Originally Posted by Spacemane969

Thanks guys. One last thing. With adjustable dampers would running soft settings have the effect of feeling like the springs got softer as a whole? I'd rather start a little higher on spring rate and adjust them softer if I start losing too much grip.

So for instance if I bought 8k springs and the softer setting would bring them down to feeling like 6k, relatively, with all of the components at work.

Kinda.

You need to spend big money to come close to having your cake and eating it too. I have MCS 1WNR coilovers, and yes for 8kg/450lb springs, it does ride well but it still gets busy over really torn up pavement at city speeds. Up the pace and start hopping curbs and the track and everything is right in the world. Adjusting your damping on a high end shock goes a long way but you can't hide the fact you are running spring rates 3 times stock.

Sway bars will also have an impact. Stock sways will ride better than big beefy sway bars. Another massively overlooked area when it comes to ride quality is the tire selection. Rolling around on sticky RE-71r? Cabin noise jumps up and the stiff sidewalls make the car ride worse. Throw on a set of ECS or Pilot 4S tires and your ride quality will increase. Likewise, tire/wheel width also will have some impact.

For me, I run around on a set of TRD 17x7.5 wheels with the stock tires when I'm not running the car at competition and drop the damping. When autocross time comes around I swap wheels and change my damping.

[Spacemane969]

Originally Posted by Lincoln Logs

Kinda.

You need to spend big money to come close to having your cake and eating it too. I have MCS 1WNR coilovers, and yes for 8kg/450lb springs, it does ride well but it still gets busy over really torn up pavement at city speeds. Up the pace and start hopping curbs and the track and everything is right in the world. Adjusting your damping on a high end shock goes a long way but you can't hide the fact you are running spring rates 3 times stock.

Sway bars will also have an impact. Stock sways will ride better than big beefy sway bars. Another massively overlooked area when it comes to ride quality is the tire selection. Rolling around on sticky RE-71r? Cabin noise jumps up and the stiff sidewalls make the car ride worse. Throw on a set of ECS or Pilot 4S tires and your ride quality will increase. Likewise, tire/wheel width also will have some impact.

For me, I run around on a set of TRD 17x7.5 wheels with the stock tires when I'm not running the car at competition and drop the damping. When autocross time comes around I swap wheels and change my damping.

So would you still recommend a stiffer rate in the rear? What happens to this platform when they are both equal?