What ride frequency is best for you?

[mndude07]

This might warrant a sticky.

I'm bored and alot of people don't seem to get this concept, so here we go.


What is ride frequency and what does it mean to me?

The ride frequency of a car is the rate in Hertz (Hz) that a suspension oscillates up and down. The higher the ride frequency (RF for now on), the stiffer the ride usually is. RF and spring rate are related, but not how most people think. Technically speaking, you can't compare spring rates between cars to gauge ride harshness. Example: A 500lb spring on your CB7 and a 500lb spring on Joe's mustang will not feel the same.

Why is that?
RF is influenced by several factors which include total weight, unsprung mass, spring rate, and motion ratio (and technically tire spring rate). Now for some definitions:

Lets focus on a single corner of the car...

Total weight: Weight on that corner, self explanatory

Unsprung mass: Things not supported by the suspension. This includes wheels, tires, brakes (rotors, calipers, pads, etc) and a portion of the spring, shock, and control arm. The entire upright (aka knuckle) and hub and bearing is counted though.

Spring rate: Given in lbs/in or kg/mm. This is how stiff your spring is. Example: A 500lbs/in spring means it takes 500 lbs on the spring to compress it 1 inch....you maybe start to see how to calculate how much a spring of given dimensions will lower the vehicle.

Motion ratio: This is a number between 0 and 1. It is the ratio of how much the spring & damper moves vs how much the wheel moves upward. Example: If your tire moves up one inch, and the suspension moves up 0.7 inches, you have a motion ratio of 0.7.

Tire spring rate: Same idea as normal spring rate, but many factors of the tire itself determine this, including air pressure inside the tire. Sometimes you can find this info for tires like Hoosier's, but a typical street tire you just have to either calculate it directly, estimate, or leave it out of your calculations.

So, you can see that if two cars with different motion ratios and different unsprung weights have the same springs, the ride frequencies will be different. While you cannot compare spring rates between the CB7 and the mustang, you CAN compare ride frequencies. A ride frequency of 1.7 Hz in the CB7 and the mustang will feel the exact same(provided the dampers are the same).

Ok that's great, why do I care about ride frequency?

We'll tackle this with a pro's and con's list:

<1.0 Hz, for typical street cars)
1.0 - 1.5 Hz, high performance cars probably where alot of us want to be that care
>1.5 Hz, race cars only, your kidneys will hate you forever.

Low ride frequency
Pros:
Ride comfort
More mechanical grip
Aids in damper effectiveness

Cons:
Too low may result in bottoming out
Less responsive
Decreased roll stiffness

High ride frequency
Pros:
Safer to go lower
Faster transient response
Increased roll stiffness

Cons:
Decrease in mechanical grip, car may begin to "skate"
Decreased ride comfort
Damper adjustments become less precise/effective

As you can see, there are compromises. The one thing that is almost never a compromise though is reducing unsprung mass. Less unsprung mass allows you to retain the same RF with a softer spring, and in the case of wheels and brakes, less weight makes it easier to accelerate the rotating components as well as slow them down. The only downside is if you sacrifice braking performance by going to a lighter, smaller braking system. If you can get a lighter caliper, lighter wheels, lighter control arms, etc...do it. It's almost always a good idea.

I'm not going to say what suspension you should get, hopefully you can decide that on your own and this helps you to do that.

I'll probably add more later.

[steelbluesleepR]

i figured you'd post something like this eventually. great write up!

[marcusv8thunder]

Spot on dude, some basic Engineering concepts here that would be useful for everyone into suspension.

You could add in the Motion ratio bit, that the motion ratio is related to the angle of the strut. If its 100% vertical then it will have a motion ratio of 1. The more angled the top of the strut is inwards the motion ratio reduces. For example ||=1 /\=0.5 --=0

The cb front and rear stuts tilt in slightly so the motion ratio would be just less than one. A single seater racing car, will be not far off 0 with thier near horizontal strut layout.

Hope this helps also

[MikeW]

Adam, I love your passion and I commend you for writing it all out but....this stuff makes my head hurt, lol. I know it's important to know but I just cant keep up with it. It starts to get garbled and looks like numbers to me. And I hate numbers.

EDIT: I read the whole thing, lol. I understand the concept and, as you mentioned, some people really like to dial it in to get it perfect. I want to, but as I mentioned, doing all that configuring and number crunching...makes my head hurt. I will say this though, if I ever have a car that I want to get really serious about, on the suspension, I'll hit you up for sure, lol.

[mndude07]

i figured you'd post something like this eventually. great write up!

Thanks man!

Spot on dude, some basic Engineering concepts here that would be useful for everyone into suspension.

You could add in the Motion ratio bit, that the motion ratio is related to the angle of the strut. If its 100% vertical then it will have a motion ratio of 1. The more angled the top of the strut is inwards the motion ratio reduces. For example ||=1 /\=0.5 --=0

The cb front and rear stuts tilt in slightly so the motion ratio would be just less than one. A single seater racing car, will be not far off 0 with thier near horizontal strut layout.

Hope this helps also

Yeah, I'll add more details later, I just got tired of writing...it was like 3am when I wrote it. Also, not only the angle effects the motion ratio. The shock can be vertical and still not have a motion ratio of 1 because the shock/spring is located somewhat inboard of the upright, creating a level-arm effect. It is very uncommon if not impossible to have a motion ratio of exactly 1. Also, race cars often use a rocker arm setup, which changes things quite a bit. The damper position itself no longer directly influences motion ratio in that case.

Adam, I love your passion and I commend you for writing it all out but....this stuff makes my head hurt, lol. I know it's important to know but I just cant keep up with it. It starts to get garbled and looks like numbers to me. And I hate numbers.

EDIT: I read the whole thing, lol. I understand the concept and, as you mentioned, some people really like to dial it in to get it perfect. I want to, but as I mentioned, doing all that configuring and number crunching...makes my head hurt. I will say this though, if I ever have a car that I want to get really serious about, on the suspension, I'll hit you up for sure, lol.

Mike, if you have questions ask me for sure. I tried to water this down to make it all simple and concise. If you can get me some corner scales, hit me up and we'll do some work.

I'm helping Kevin(crx08) out quite a bit with his h22 turbo cb7 build, and will be taking care of alot of the suspension and brake calculations for that car....I plan on getting alot of data about motion ratio and unsprung weight for the CB7 so that I can eventually make sort of an algorithm. This will ultimately let me just write out a table for everyone that says "This spring will give you this ride frequency, and this shock will work with it".

[MikeW]

Eh...dont think corner scales are gonna be easy to come by. Sorry.

I dont know that Ill need, or be doing, any major "figuring" on the CG but who knows.

[Dirtyrice]

Great write up man.

[marcusv8thunder]

Yeah, I'll add more details later, I just got tired of writing...it was like 3am when I wrote it. Also, not only the angle effects the motion ratio. The shock can be vertical and still not have a motion ratio of 1 because the shock/spring is located somewhat inboard of the upright, creating a level-arm effect. It is very uncommon if not impossible to have a motion ratio of exactly 1. Also, race cars often use a rocker arm setup, which changes things quite a bit. The damper position itself no longer directly influences motion ratio in that case.

Yep true also. And yes rocker arm is another piece of suspension that can change things.

Ill be interested in the findings from the CB

[gloryaccordy]

I think this might be beyond the scope of what the avg CB7 tuner needs to know.

Only shocks worth buying: Konis, Tokico Illuminas
Only coilovers worth buying: Koni/GC, D2, Tokico RAK, Progress, maybe Nex GTs
Keep all bushings/balljoints fresh
Rotate your tires w/every oil change
Alignments are necessary, camber kits aren't
Best drop for best compromise of comfort + performance + UCA clearance is about 1.5"

I commend the effort but it may have been unnecessary.

[mndude07]

I think this might be beyond the scope of what the avg CB7 tuner needs to know.

Only shocks worth buying: Konis, Tokico Illuminas
Only coilovers worth buying: Koni/GC, D2, Tokico RAK, Progress, maybe Nex GTs
Keep all bushings/balljoints fresh
Rotate your tires w/every oil change
Alignments are necessary, camber kits aren't
Best drop for best compromise of comfort + performance + UCA clearance is about 1.5"

I commend the effort but it may have been unnecessary.

If you don't care, then don't comment. We don't need any 100lbs = 1/10th of a second b.s.

[gloryaccordy]

If you don't care, then don't comment. We don't need any 100lbs = 1/10th of a second b.s.

It's not that I don't care; as an engineer I enjoy the technical aspects. But I don't see this as something that would help a noob who knows nothing in any way. A "CB7 Suspension Guide for Dummies" would prob make more sense in that aspect. People barely understand the concept of spring and damper rates, so IDK how ride frequency guides would help. Not to mention, while ride frequency is important, IMO damping curves are more important when talking about response and ride comfort. You can get the perfect ride frequency, but if you have stiff springs on stock shocks it won't matter.

I'm all for technical discussion though.

[megarock15]

with a little more info i would vote this as a sticky! And as far as cb7 Noobs go, they should read up on every bit of useful info they can find. I wouldn't call myself a Noob, and i have been looking into upgrading my suspension and any piece of info i can get to properly install and tweak my suspension helps. I really appriciate the write up!

Bang Up Job Mate

[marcusv8thunder]

I think this might be beyond the scope of what the avg CB7 tuner needs to know.

Only shocks worth buying: Konis, Tokico Illuminas
Only coilovers worth buying: Koni/GC, D2, Tokico RAK, Progress, maybe Nex GTs
Keep all bushings/balljoints fresh
Rotate your tires w/every oil change
Alignments are necessary, camber kits aren't
Best drop for best compromise of comfort + performance + UCA clearance is about 1.5"

I commend the effort but it may have been unnecessary.

I find this completely unbelievable, I thought you said your were an engineer?

If someone tries to up the level of technical info on this forum, this surely can only be greeted with a yes and thanks.

[gloryaccordy]

I find this completely unbelievable, I thought you said your were an engineer?

If someone tries to up the level of technical info on this forum, this surely can only be greeted with a yes and thanks.

Part of my job as an engineer is to design applications that are easy for the user.

What's the hopeful result of this exercise? If it is to learn about suspension design then yes the sky is the limit. But if it is to aid in merely picking a good suspension for a DD CB, learning about second order systems and then designing/dynoing/tuning/reinstalling shocks/springs is well beyond the point of diminishing returns. Possibly reasonable for a dude that plans on building a few track cars in his lifetime, but well beyond overkill for a daily driver. I would wager big $$$$ that no individual could design a subjective overall better DD setup than a Neuspeed Sport or Skunk2 + Koni Yellow kit; ESPECIALLY if considering overall price and effort. Even if you just went with custom Koni Yellows, for the street their stock rates are so perfect the added cost of revalving is unnecessary.

Not to mention, much of suspension response is subjective & relative to the application. The ride frequency and damping curves for a DD in an area with shitty streets would be much different than that for a DD in like Palm Beach or w/e.

And of course ride frequencies can (and in some cases should) vary at each end of the car. There are a lot of ins and outs.

Plus ride frequency is just one small piece of the puzzle; a more interesting discussion IMO would be what one's ideal damping curves look like for rebound and compression, and once spring rates are normalized they pretty much look the same. Motion ratios would help us understand why 500lb in car X is not the same "spring" as 500lb on car Y. But again in the discussion of picking a good suspension for a CB, all we care about is what 500lb is at each corner of a CB; understanding what goes into that response is ancillary

I think info like motion ratios, spring rates and damping curves are of great use. We should compile all that before delving into suspension design concepts

[mndude07]

Ride frequency is exactly the base of how a car rides. If it is pointless for a DD to care about it, then why is it carefully chosen for each car from the factory? Knowing ride frequencies can help out all the people that are worried "I don't want too stiff/too soft of a ride". In the design process, ride frequency is first chosen, then using the suspension data, and on-track feedback, etc, damping curves are made, adjusted, and fine-tuned.

You almost make me want to custom valve some yellows with my own chosen springs to show you that you CAN make it better than off the shelf parts, for cheaper than a set of KW or AMR coilovers....so I wouldn't say that it isn't worth it. Too bad my accord is no more.

As for the whole thing about it being subjective, there are widely accepted rules of thumb. You match your dampers to your chosen spring and chassis, not the other way around. You pick your ride frequency and then adjust dampers as needed. Ride frequency selection gets you in the ballpark for the ride of the vehicle, mechanical grip and transient response. The rules of thumb, that's where the street/race decision has to be made in terms of critical damping. A stock road car is typically in the range of 20-30% critically damped, while race cars are on the order of 60-70%. You can find this info on many, many sites and books. Its just what works the best. If you disagree, tell that to people like Claude Rouelle.

Your critical damping percentage is also a large part of ride quality, and in some ways, what defines the suspension as a race, street, or DD setup. You seem to forget that just because it is a race car, that doesn't mean it has to be stiff as all hell. Like I wrote in my original post, an increase in ride frequency increases response, but decreases mechanical grip. This is why a softer spring on a bumpier track might actually be faster.

The ride frequency is how quickly the car "reacts", so you generally want the rear end to have a slightly higher (a couple tenths of a Hz) higher, so the rear is "in sync" with the front. Ride frequency is a product of spring rate, motion ratio, and others as we know, and that is the reason civic guys that run higher rates in the rear are wrong. They have the right idea that you want the rear to react quicker, but the greater number for the rear should be ride frequency, not spring rate.

Ideal damping curves...you can set a base through calculation, and then at that point, alot of it comes down to data-logging. F1 teams make damper changes for each different track because they have suspension velocity histograms for each track. Basically, treat the street as your track. Drive around until you fill up your data logger, and observe at what velocity most of you suspension movements are at. You will most likely find that it is at and below the 3in/sec mark, so slightly after that is where your digression knee would want to be.

We can start compiling more info and i'll put it into the first post as it comes up. We have a good start. Its a bit sad that its only the same 3 or 4 guys talking about this stuff though. If anyone else has questions, even a simple one, please ask. I promise I won't call you stupid.