Wheel Rates and Frequencies

[CadillacMazerolle]

I would love to see a thread here that includes useful information that is not vehicle specific. That being said, providing spring rates of your current setup without the motion ratio and corner weights is not useful information.

What suspension frequencies are you all currently running? How is the ride quality versus performance? Are you running staggered tires? Swaybar?

[David Pozzi]

I'm going to move this to the Advanced Forum section.
I see quite a few Pro-Touring cars in the 1.4 Hz to 1.6 Hz range

[Twentyover]

Front and rear the same? Or dre they different?

[CadillacMazerolle]

Bump

[CadillacMazerolle]

I know I'm looking for free information here but is there anyone out there that doesn't mind sharing their secrets?

[alphaenvirmgt]

Find copy of Detroit Speed's catalogue. They discuss frequencies there.

[CadillacMazerolle]

One would think, with pro-touring being one of the most serious car mod forums, that SOMEBODY one here would know. I mean your suspension frequency is kinda the most important part of the way your "pro touring" car handles.

....Bump...

[Ryanater]

Hi guys,

I have a done a lot of research on this myself. It seems like every source I can find recommends frequencies around 2hz for "non-aero" performance cars. In addition, they recommend a slightly higher frequency in the rear to avoid pitch problems over bumps.

That being said, it doesn't seem like anyone out there is following these rules when setting up their cars. I have talked to many people on the autocross course as well as some members of PT (including Ron Sutton), and they don't really pay attention to natural frequencies when setting the suspension up.

Personally, I run 800lb front springs and 300lb rear springs on my 69 Camaro with full Ridetech suspension. This calculates to about 1.7hz in the front and 2.0hz in the rear. If I wanted to get to 2.0hz in the front, I would have to run a spring rate over 1,000lbs/in! I only have a couple of years experience with this car on the track, but it seems like I would seriously hurt my low speed grip if I went to that stiff of a spring! If anything, I might want to go a little softer for autocross.

So I've finally gave up on paying too much attention to natural frequencies. But being an engineer, this has been hard :)

Sources I've found that mention natural frequency.
http://farnorthracing.com/autocross_secrets5.html
http://www.optimumg.com/docs/Springs%26Dampers_Tech_Tip_1.pdf

- - - Updated - - -

I know I know, I just brought this thread back from the dead...

[CSG]

I'm nobody but I use frequency for initial spring choice and then work from there pretty much ignoring frequency from that point forward.

[MonzaRacer]

Heck just swap in some Shockwaves in track quality version and drive. Wanna ad or subtract spring add air or for tuning adjust the shocks differently.
And dont say air wont work cause John Hotchkis found out that was a line of bulls--t. I remember in one article he claimed it wasnt for performance and Bret started showing up and proceeding to hang it out in autocross across the USA!
As for street cars, getting tooooo technical tends to complicate.
I know one fella who spent 6 months and $20k on his suspension and got beat, by a guy with jy car, jy driveline, and some decent Ridetech shocks.
Setup the basics, then tune for the track conditions. Heck I set up buddies drag car with new spring perches reinforced spring padswith slapper bars from S10 modified and welded to it. Car was super consistent. Tires or slicks.

[CSG]

For an air car to work great it has to be engineered up front. If you decide to "add spring rate" by adding air you have now changed roll center, roll axis inclination, weight bias, etc

[MonzaRacer]

For an air car to work great it has to be engineered up front. If you decide to "add spring rate" by adding air you have now changed roll center, roll axis inclination, weight bias, etc

Dont get me wrong, there is more to it than bolting something in BUT I have driven an air ride equipped vehicle and so far it has whooped ass on a fairly well set up 4th gen on GY F1 tires and my vehicle was a 78 C10. Now dont get me wrong, I feel I was better driver but a set up LS powered Camaro should have walked off from me. My truck was Ridetech CoolRide, the blue monroe made shocks in front a nd carquest 67-72 coil sprung c10 shocks in back. For tires I had Firehawks in 255 70 15 and Hoosier Radial DT 30/9.50-15C in back. Truck has great track it would simply roll/load on turns and pull right through. Heck I would have figured it would swing back out and it never did. And road was twisty country road. On few straights I couldnt get ahead with my roller 350(HOT CAM) but truck would catch up and hang with on curves. He was ahead of me when we started racing. And he was pissed as I sold him the F1 tires and he thought his car was so quick.
And I only have 3 paddle switches! My rear springs are not divorced from each other but truck never acted like it wanted to "trade" air.
Oh well maybe I am just so less ingrained with technical aspects and got lucky.
Still Truck rode and drove awesome and handle d great. Hope next spring I can get her back up and running again. I miss driving her.

[67King]

Okay, so obviously this forum doesn't get a lot of traffic, but I'm meandering through here finding my way, and maybe I can give some sort of feedback.

Both of my race cars, a 944 Turbo and a 968, have used similar setups. The 968 is sold, but it held a few track records at Road Atlanta, and I think Summit Point, when my business partner drove it. Very little aero on either - just a splitter and the OEM wing/spoiler. You'll notice the numbers are higher than what is commonly published out there.
F - 3.37Hz
R - 2.06Hz

Those numbers are a bit high for a street car, but the roll couple may be useful, and we always went for about 62%. That one is 61.8%. I'm a little irritated that that is the 944T, and I don't have the 968, but all the race cars were pretty similar. These cars are all around 49/51, and the rears are independent, so that will factor in, too. But since there isn't much info in the thread, I figured I'd give something.

[hquackenboss]

I would encourage you to check out the Tech Tips on Springs and Dampers at the Optimum G website. If you go to the main website, and explore what is available under the "Technical" heading, there is a lot of information there. David Pozzi posted previously in this thread that many Pro Touring cars are in the range of 1.4 to 1.6 Hz, which is in line with the Optimum G tech tips guidelines, which ballparks passenger cars at .5 to 1.5 Hz, and passenger-based race cars at 1.5 to 2.0 Hz.

Their tech tip makes another point. While passenger cars typically have higher rates in the rear in order to provide a pleasant ride (and of course passenger cars, SUVs and pickups typically carry loads in the rear. However, for race cars, it isn't uncommon to have higher frequencies in the front.

Having said that, here is something else to think about. Most production cars actually don't have constant ride frequencies. They pretty much all use some form of jounce bumpers (AKA bump stops), which create the effect of a multi-rate, and in many cases, continuously variable rate spring, where the rate increases as the suspension compresses. I am not talking about a small rubber stop that provides a little cushion just before the suspension bottoms out. I am talking about things 2- 3 inches tall that start engaging very early in compression. Crawl around the underside of a high-end high horsepower Mercedes AMG or BMW M series, and you will see what I mean. In fact, the Tesla Model 3, which has gotten pretty good reviews, has compression bumpers that are engaged almost half the time.

Every successful NASCAR team has at least one engineer who is a specialist in these. Bump stops are what has allowed the Cup cars to be controllable yet be able to run with the front splitters to be barely off the track at high speed.

Compared to swapping springs and shocks, they are cheap, easy to swap, and can be cut or drilled to soften them. In fact, I know a suspension engineer for one of the high performance manufacturers who races a Chump Car with some friends, who uses a 3D printer to make his own.