Flat Ride, Bounce Frequencies and Tires: A Question

[K-Dawg]

In stock form our cars are neutral with FRC around 75% but since it comes with a staggered wheel/tire set up to understeer more how much of an effect does a square wheel/tire set up play in that percentage?
Wouldn't just changing to a square set up induce more oversteer?
Then when figuring out a good FRC % shouldn't we be trying to calculate that in to the equation?

This might be the dumbest question ever but i'm over here trying to figure it out.

Larger front tires (more front grip) would tend to reduce understeer, yes. But front roll couple (FRC) isn't a simple oversteer/understeer/neutral indicator. It's a numerical representation of how much of the car's total roll stiffness comes from the front suspension. The value has nothing to do with tire size, compound, etc.

Every car is going to be different. IMO, the FCM spreadsheet is most useful for seeing how changes to a particular suspension setup will affect ride and handling.

[lvm3sm46]

In stock form our cars are neutral with FRC around 75% but since it comes with a staggered wheel/tire set up to understeer more how much of an effect does a square wheel/tire set up play in that percentage?
Wouldn't just changing to a square set up induce more oversteer?
Then when figuring out a good FRC % shouldn't we be trying to calculate that in to the equation?

This might be the dumbest question ever but i'm over here trying to figure it out.

[Nate047]

This document from OptimumG is a pretty good summary of the theory behind ride frequency selection and how it relates to spring rate.

Thanks, I'll take a look when I have some time to read and really pay attention lol.

[timmo]

Cool, I'll see if I can find it and figure it out.

This document from OptimumG is a pretty good summary of the theory behind ride frequency selection and how it relates to spring rate.

[Nate047]

It looks intimidating but it’s pretty intuitive after a while.

There’s a thread somewhere on here outlining the concept + thinking behind flat ride and how to use the spreadsheet.

Cool, I'll see if I can find it and figure it out.

[Johnvu]

I don't buy that our cars have "Snap" Oversteer. If you set up your suspension using the Flat Ride theory and your Front Roll Coupling (FRC) is within the normal range (72ish?), the car should behave in a very predictable and controllable way. Even if your tires are slightly over inflated and your back end starts to slide, it is still very predictable.

I have been in an NSX, a car known for snap oversteer, during one of these scenarios and it felt very different from my M3 at its limits. However, I am no expert and this is just what my past experiences have told me. Maybe this guy has seen an event where the tires were so stiff and the FRC was so high that the car exhibited snap oversteer qualities?

[r4dr]

Alright lol

It looks intimidating but it’s pretty intuitive after a while.

There’s a thread somewhere on here outlining the concept + thinking behind flat ride and how to use the spreadsheet.

[Nate047]

https://www.fatcatmotorsports.com/FC..._M3_Online.htm

Alright lol

[timmo]

Pretty much any, if not all OEM cars come with flat ride. Having a not-pitchy ride not only bodes well with performance but also comfort

[Str8f4c3]

Best link to how to calculate/setup flat ride? I'm interested in looking into this for both my e36 and e46.

https://www.fatcatmotorsports.com/FCM_Ride_Harmony_BMW_E46_M3_Online/FCM_Ride_Harmony_BMW_E46_M3_Online.htm

[Nate047]

There is no snap oversteer at the limit with flat ride. I've been tracking (and streeting) a flat ride setup for 2 years now with zero snap oversteer.

If you did flat ride only, and used sway pairs that are similar to what people with non flat ride setups, you would get normal (non snap) oversteer, so maybe that's what he meant? But, part of the beauty of the spreadsheet is you can also dial in sways to get a neutral setup with flat ride.

... also worth pointing out that the car, stock, is flat ride-- and doesn't snap oversteer.

Best link to how to calculate/setup flat ride? I'm interested in looking into this for both my e36 and e46.

[Obioban]

What does the spread sheet assume for COG for each axle, as this has an obvious impact on weight transfer?

You’d have to ask Shaikh— the formulas aren’t visible.

[T.J.]

If you did flat ride only, and used sway pairs that are similar to what people with non flat ride setups, you would get normal (non snap) oversteer, so maybe that's what he meant? But, part of the beauty of the spreadsheet is you can also dial in sways to get a neutral setup with flat ride.

What does the spread sheet assume for COG for each axle, as this has an obvious impact on weight transfer?

[Str8f4c3]

There is no snap oversteer at the limit with flat ride. I've been tracking (and streeting) a flat ride setup for 2 years now with zero snap oversteer.

If you did flat ride only, and used sway pairs that are similar to what people with non flat ride setups, you would get normal (non snap) oversteer, so maybe that's what he meant? But, part of the beauty of the spreadsheet is you can also dial in sways to get a neutral setup with flat ride.

... also worth pointing out that the car, stock, is flat ride-- and doesn't snap oversteer.

This makes a lot of sense, too. Especially the point about the stock setup. He did mention "rearward bias", which makes sense given the tendency for many rear sway setups to lean towards oversteer. I'm still just perplexed that he specifically used the term "snap oversteer". Like we aren't driving mr2's haha.

[Obioban]

There is no snap oversteer at the limit with flat ride. I've been tracking (and streeting) a flat ride setup for 2 years now with zero snap oversteer.

If you did flat ride only, and used sway pairs that are similar to what people with non flat ride setups, you would get normal (non snap) oversteer, so maybe that's what he meant? But, part of the beauty of the spreadsheet is you can also dial in sways to get a neutral setup with flat ride.

... also worth pointing out that the car, stock, is flat ride-- and doesn't snap oversteer.