Calculating ride frequency for the Mustang

[TeeLew]

I'm curious, what is everyone using the calculated frequencies for other than the flat ride concept? Excessive damping does reduce compliance at some point, but don't be so willing to reject high damping in certain areas of the curve. We carry those things around for a reason.

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[TeeLew]

Ride frequencies were 2.4 front and 1.7 rear.

That's a fairly big split to the front. I'm not so concerned about flat ride, but that is a pretty stiff front end for a non - aero car.

 

[Norm Peterson]

I'm curious, what is everyone using the calculated frequencies for other than the flat ride concept?

It's a better guideline than picking spring rate numbers out of thin air.

Especially in a street-driven car, but even in a dual-purpose street/occasional track car, it's OK to let the suspension move more than just tiny bits. Looking only at spring rate numbers can lead to a temptation that reads something like "if some's good, more's better, and too much is just enough".


Norm

 

[TeeLew]

I find it a good way to compare dissimilar cars. Comparing similar cars, say a Mustang & Camaro, on spring rates can be confusing enough with different weights, motion ratios, etc. Looking at the rates in this manner allows you to compare the relative vertical stiffness of dissimilar cars. A Mustang & a Miata might have different everything, but both be at the similar relative stiffness of X Hz.

That's one of reasons I like to use this approach.

 

[Brian@BMVK]

I find it a good way to compare dissimilar cars. Comparing similar cars, say a Mustang & Camaro, on spring rates can be confusing enough with different weights, motion ratios, etc. Looking at the rates in this manner allows you to compare the relative vertical stiffness of dissimilar cars. A Mustang & a Miata might have different everything, but both be at the similar relative stiffness of X Hz.

That's one of reasons I like to use this approach.

Yep, this.

I still think overlooking flat ride completely isn't necessarily going to get you the best handling car, though it really heavily depends on your driving style. I've noticed that the totally ham-fisted/less precise drivers tend to favor inverse flat ride. For an aero-heavy application I have done a couple with minimal flat ride or slightly under 1.00, but the goal being to get as close as possible.

 

[Norm Peterson]

Fortunately, flat ride isn't an all-or-nothing phenomenon. In terms of how fast it deteriorates either side of the theoretically 'perfect' flat ride speed, I'm pretty sure it's not symmetric.


Norm

 

[Brian@BMVK]

Fortunately, flat ride isn't an all-or-nothing phenomenon. In terms of how fast it deteriorates either side of the theoretically 'perfect' flat ride speed, I'm pretty sure it's not symmetric.


Norm

Absolutely.

 

[Järn]

My search for ride frequency on other automobiles is not turning up much relevant data. I find general statements about ride frequency and no specifics.
I did find some numbers for 15 to 20-year-old cars, nothing relevant to us.
What would be relevant to us? 2016+ Camaro and Corvette, Audi RS3, RS5; BMW M2, M3, M5. I will keep looking...

I did add in the GT350 and GT350R I am still looking for GT500 data.


in this post NightmareMoon made the following comment:
https://www.mustang6g.com/forums/th...d-looking-for-advice-on-my-next-steps.146727/

FWIW, the Steeda Min Drop springs are sporty but streetable, and about half way between the base springs and what Ford puts on the GT350R.

The ride frequency math shows that this is true:
Base GT ride freq = 1.36
Steeda Min Drop RF = 1.5 (+.14)
GR350R RF = 1.63 (+.13)


Question: I updated the chart on the first post. I added a column for Average Ride Frequency by just averaging Front and rear rates. Is that a valid number?

 

[Norm Peterson]

Question: I updated the chart on the first post. I added a column for Average Ride Frequency by just averaging Front and rear rates. Is that a valid number?

I suppose it'd be a valid number, but I can't offhand think of any use for it.

Personally, I think flat ride speed would be more useful even if you didn't include the effects of damping.

I think the cell formula for calculating undamped flat ride speed given wheelbase and front and rear ride frequencies would look something like this . . .

0.0568 * [Wheelbase] ÷ { ( 1/[FrontRideFrequency] - 1/[RearRideFrequency] ) }

Wheelbase in inches. You already have the ride frequencies. No point in displaying these answers any closer than to the nearest whole mph.


Perhaps Brian can review the above equation. 0.0568 comes from the conversion of inches to feet and feet/second to mph.


Norm

 

[Norm Peterson]

Separate comment - I think you should add input variables for front and rear unsprung masses while you're adding a wheelbase input parameter. 100 lbs might be a reasonable default value for each side of an independent suspension if you can't determine anything better. Maybe 300 lbs total rear unsprung weight if you ever use this sheet for a stick axle car

I'd also center the numerical tabulations like the numbers in the input cells are.


Norm

 

[Brian@BMVK]

My search for ride frequency on other automobiles is not turning up much relevant data. I find general statements about ride frequency and no specifics.
I did find some numbers for 15 to 20-year-old cars, nothing relevant to us.
What would be relevant to us? 2016+ Camaro and Corvette, Audi RS3, RS5; BMW M2, M3, M5. I will keep looking...

I did add in the GT350 and GT350R I am still looking for GT500 data.


in this post NightmareMoon made the following comment:
https://www.mustang6g.com/forums/th...d-looking-for-advice-on-my-next-steps.146727/

FWIW, the Steeda Min Drop springs are sporty but streetable, and about half way between the base springs and what Ford puts on the GT350R.

The ride frequency math shows that this is true:
Base GT ride freq = 1.36
Steeda Min Drop RF = 1.5 (+.14)
GR350R RF = 1.63 (+.13)


Question: I updated the chart on the first post. I added a column for Average Ride Frequency by just averaging Front and rear rates. Is that a valid number?

GT500 CFTP front springs are 265 lb/in...though I suspect they may have adjusted strut length to compensate.

I guess the question is, outside of just curiosity, what are you looking to do with the information? FWIW C5 Z06 Corvettes sit around 1.3-1.5 Hz with a ~20% higher rear RF. I'm not sure on C6 or C7 but I don't believe they are a lot stiffer. Lack of weight makes the 'softness' a lot less of a penalty.

 

[TeeLew]

Yep, this.

I still think overlooking flat ride completely isn't necessarily going to get you the best handling car, though it really heavily depends on your driving style. I've noticed that the totally ham-fisted/less precise drivers tend to favor inverse flat ride. For an aero-heavy application I have done a couple with minimal flat ride or slightly under 1.00, but the goal being to get as close as possible.

I'm not necessarily shooting for the best handling car. I'm looking for whatever makes the watch run in the right direction. Those aren't necessarily the same thing. We all have compromises, mine is generally mid-corner understeer. The driver preference you've noticed is the exact opposite of what I've experienced.

For an aero-heavy car, having a 1.0 or greater F/R ride ratio implies a gain in front aero % as speed increases. Be careful with that.

 

[Brian@BMVK]

I'm not necessarily shooting for the best handling car. I'm looking for whatever makes the watch run in the right direction. Those aren't necessarily the same thing. We all have compromises, mine is generally mid-corner understeer. The driver preference you've noticed is the exact opposite of what I've experienced.

For an aero-heavy car, having a 1.0 or greater F/R ride ratio implies a gain in front aero % as speed increases. Be careful with that.

I think you misunderstood what I was saying on both counts.

 

[NightmareMoon]

What's this "Flat Ride Concept"? Is it about the ratio of the ride frequencies front to rear or something else?

 

[Järn]

I guess the question is, outside of just curiosity, what are you looking to do with the information?

I want to fill in some specific cars into these categories so that these ranges become more understandable/relatable, for the average Mustang owner:
Standard Road Car: < 1.3 Hz
Sporty Road Car ("ST- Versions"): 1.3 Hz - 1.5 Hz
GT PP1 = 1.4 Hz
Very Sporty Road Car ("RS-Versions"): 1.5 Hz - 1.8 Hz
GT350=1.53 Hz, GT350R= 1.62 Hz
Super Sports Car (Ferrari, Lambo etc): 1.7 Hz - 2.0 Hz

(Thank you again...)

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