What options to achieve flat ride?

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VisualKei
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What options to achieve flat ride?

Post by VisualKei » Thu May 02, 2019 12:14 pm

I recall doverosx had a cornucopia of info on the dead forum on flat ride data and different paths to achieve it at various budgets, but unfortunately Google's cache of it is all gone now. Most people just toss on a massive rear torsion bar to tighten up the rear end, but it also reduces whatever left/right independence the rear suspension has with it's limited design architecture of being a twist-beam axle design.

The purpose of this thread is to inquire: what are the simpler/cheaper paths available to us to get flat ride behavior? That is, short of jumping into custom FCM coilovers, Ohlins, Motons, and all sorts of high-end race-oriented goodies, what can the spirited driver do with off-the-shelf or easily moddable/adoptable components available to the general consumer?

If I remember from old discussions, Bilstein's B14 PSS coilover kit will do it, but people were snapping their coilovers at the shock tower mounting locations, unless they ran the DNA tophats because of some mechanical binding issue? That ends up putting the cost at $1,500+.

Vogtland has a set of lowering springs for a reasonable price, and I recall it possibly being mentioned that they would get you into flat ride territory, and coupled with Koni yellow sports @ full soft (assuming the shocks you get dyno similarly) would get you get improved performance without changing daily ride quality too much, and significantly cheaper to execute than going to Bilsteins. I just heard back from Vogtland today and was told the following technical data:

"Here are the rates for the 954026 kit
F 19N/mm (108 in/lbs), R 20-40 N/mm (114-228 in/lbs)"

The rear spring rate seems a bit too soft to get flat ride, if I am interpreting the variables correctly, as it looks like you need to push it into the 500in/lb rate for optimal bounce frequency. I am using this spreadsheet to play with values: http://www.fatcatmotorsports.com/FCM_Ri ... ne_new.htm

doverosx also had an older spreadsheet here: http://brodeydover.ca/index.php/2016/06 ... sheet-yet/

The comment/notes on flatride combos are a bit brief or vague. Several entries state Bilstein rear springs will get you there, but I don't know if one can just order Bilstein rear springs alone. I'm not sure if one spreadsheet supersedes the other, or there is newer data that I just haven't come across yet. Help and discussion would definitely be a plus.

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texanbrit
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Re: What options to achieve flat ride?

Post by texanbrit » Thu May 02, 2019 12:26 pm

I think the binding and failure with the Bilstein's is from using aftermarket rigid top-hats rather than the stock ones.
2013 Abarth 500c (NGen Turbo'd) - Isabella
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VisualKei
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Re: What options to achieve flat ride?

Post by VisualKei » Thu May 02, 2019 3:13 pm

texanbrit wrote: Thu May 02, 2019 12:26 pm I think the binding and failure with the Bilstein's is from using aftermarket rigid top-hats rather than the stock ones.
I believe you're right. I think mneuman916 had an analysis on the dead forum and came to the conclusion that the DNA tophat allowed the proper axes of movement and the failures must have been with any number of aftermarket options that were flawed in design...definitely a costly repair bill for parts and labor, from what I recall. Sometimes an "upgrade" isn't an upgrade.

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Re: What options to achieve flat ride?

Post by texanbrit » Thu May 02, 2019 3:27 pm

VisualKei wrote: Thu May 02, 2019 3:13 pm
texanbrit wrote: Thu May 02, 2019 12:26 pm I think the binding and failure with the Bilstein's is from using aftermarket rigid top-hats rather than the stock ones.
I believe you're right. I think mneuman916 had an analysis on the dead forum and came to the conclusion that the DNA tophat allowed the proper axes of movement and the failures must have been with any number of aftermarket options that were flawed in design...definitely a costly repair bill for parts and labor, from what I recall. Sometimes an "upgrade" isn't an upgrade.
Although I've run the CPR and NGEN top hats for years on my cars and nothing has broken (touch wood). Maybe the Bilsteins are just weaker.

Anyway, back to the OP. What do you mean by flat ride? Less bouncing? Less roll in the corners? Visually the car is flatter when parked (rather than the stock butt in the air look)?
2013 Abarth 500c (NGen Turbo'd) - Isabella
2012 500 Pop (broken, engine rebuild on hold) - Popabella
2014 500L (Daily workhorse) - The Hulk
2013 Abarth 500 (broken engine, current project) - Abby

Romanoaf
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Re: What options to achieve flat ride?

Post by Romanoaf » Thu May 02, 2019 4:02 pm

Flat ride is a term used (coined) by fatcat motor sports, that is for optimizing spring rates to get ride frequency higher in the rear than in front.. Shaikh from FCM has a lot of suspension setup videos on YouTube; seems to be able to backup his research with test and race Miata’s.
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VisualKei
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Re: What options to achieve flat ride?

Post by VisualKei » Thu May 02, 2019 4:16 pm

It's a specific terminology (most commonly seen used in the MX-5 world and FCM. Not sure if there's another synonym for flat ride) regarding the natural bounce frequency where the rear of the car has a slightly higher frequency than the front. The rear bias oscillates it quicker so the rear end of the car settles quicker after the front end handles whatever road condition puts it to work, instead of bouncing at an identical or slower rate. It reduces pitching (the opposite where the front has a higher frequency than the rear), and is more predictable through corners and handling uneven terrain (dips or bumps in roads, hitting rumble strips on a track, etc.) Flat ride also allows one to reduce overdamping or use excessive rebound as a crutch, so it improves ride quality. Springs, torsion/sway bars, bump stops, and other suspension elements also end up influencing "flat ride" overall. Doverosx is a huge proponent of it and a suspension guru, and his descriptions of the concept made a lot of common sense.

For the most part, suspension elements are a mystery for customers, myself included. We just buy them without knowing spring rates, or asking for a dyno chart of shocks (even the same shock models from one brand can have significant valving variations, so they don't necessarily have the same response curves side-by-side, so "three clicks from soft" on a pair of Konis might have completely different rebound/damping figures from one another). I don't normally see suspension manufacturers sell products with shock dyno plots, spring rates, or offer various linear or digressive response curve options, and so on for customers. When a company sells an exhaust, intake, or ECM tune, typically they'll typically provide an engine dyno plot and data, or the customer can get it tested and see what effect it has. We just assume the proper engineering is done for our application and we have a degree of trust when we buy a suspension product. It's hard to sell suspension with a quantitative or tangible value, other than "it drives/handles better".

Suspension being a fairly technical subject, it can become difficult to make educated decisions without extensive study of the topic and analyzing what our current suspension does, and how adding or changing parts affects everything else. I'm not shy in saying I'm pretty ignorant about it, and I think having more data out there in general would be beneficial.

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Re: What options to achieve flat ride?

Post by MadFiat » Thu May 02, 2019 6:01 pm

I am far from a suspension expert.

I believe Brody said that the vogtlands are the closest you can get w/o going to a custom bilstein coilover. I do not know if his spreadsheet is using just vogtland springs or coilovers though.

However, I have to say I was extremely impressed with how the Vogtland springs handled the Sisters. If that's what Brody calls "Flat Ride" then I'm all for it. MAD FIAT had poise and balance like I did not have when I did this event in the past.

My setup fwiw, is Vogtland Springs front & rear, Stock struts front, Koni Yellow at 1/2 setting rear, 30mm torsion bar rear, chassis braces and lower cross brace front. Rear top isolator replaced with hose for slight levelling.
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VisualKei
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Re: What options to achieve flat ride?

Post by VisualKei » Thu May 02, 2019 6:20 pm

I'm currently sitting on factory suspension. I was thinking of doing Vogtland springs and Koni rears on full soft. I picked up some Energy bump stops to install at the same time for the rear, if beneficial, but don't know how they affect the data on the spreadsheets. I have the DNA side braces, DNA under chassis cross brace, and considering adding the DNA brace that ties to the actual shock towers. I'm hoping DNA comes out with the rear trunk brace that ties to the lower seat mounting position (only available for Euro Abarths currently).

Of course, a full set of Koni yellow sports and Vogtland springs ends up being around the same price as a set of Billstein B14 PSS coilovers on sale, and if the coilovers can be used on the factory shock tower hardware without risk of damage to the coilover's upper perch bolt, then I might go that route. It looks like some of the example cars on the spreadsheets that achieve flat ride also experiment with OE hardware and just replacing the rear coils with Bilstein springs that are pretty stiff.

I definitely noticed rear-end squirreliness on The Sisters, especially transitions from left turns to right turns in rapid succession (or vice versa). Under hard braking before approaching a curve, it starts to get a little loosey goosey on the arse end. This is my first sporty car so I have no other points of reference to compare it to. I currently have no road track time or track education, so I'm at a novice level with maybe 10 hours experience on Sodikart 6.5hp GT5 gas karts. I felt like the suspension was a bigger issue than the grip, because I don't recall pushing it hard enough to scrub tires (Continental ExtremeContact Sport summer tires) but I was already pushing my comfort level. I was running about 40/32psi at operating temperatures. The rear seemed more skittish the first day when it heated up to 34psi so I dropped it a bit for Day 2.

I'm hoping a properly tuned suspension upgrade will make the car feel more planted and inspire more confidence.

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Re: What options to achieve flat ride?

Post by MadFiat » Thu May 02, 2019 7:07 pm

VisualKei wrote: Thu May 02, 2019 6:20 pm I'm currently sitting on factory suspension. I was thinking of doing Vogtland springs and Koni rears on full soft. I picked up some Energy bump stops to install at the same time for the rear, if beneficial, but don't know how they affect the data on the spreadsheets. I have the DNA side braces, DNA under chassis cross brace, and considering adding the DNA brace that ties to the actual shock towers. I'm hoping DNA comes out with the rear trunk brace that ties to the lower seat mounting position (only available for Euro Abarths currently).

Of course, a full set of Koni yellow sports and Vogtland springs ends up being around the same price as a set of Billstein B14 PSS coilovers on sale, and if the coilovers can be used on the factory shock tower hardware without risk of damage to the coilover's upper perch bolt, then I might go that route. It looks like some of the example cars on the spreadsheets that achieve flat ride also experiment with OE hardware and just replacing the rear coils with Bilstein springs that are pretty stiff.

I definitely noticed rear-end squirreliness on The Sisters, especially transitions from left turns to right turns in rapid succession (or vice versa). Under hard braking before approaching a curve, it starts to get a little loosey goosey on the arse end. This is my first sporty car so I have no other points of reference to compare it to. I currently have no road track time or track education, so I'm at a novice level with maybe 10 hours experience on Sodikart 6.5hp GT5 gas karts. I felt like the suspension was a bigger issue than the grip, because I don't recall pushing it hard enough to scrub tires (Continental ExtremeContact Sport summer tires) but I was already pushing my comfort level. I was running about 40/32psi at operating temperatures. The rear seemed more skittish the first day when it heated up to 34psi so I dropped it a bit for Day 2.

I'm hoping a properly tuned suspension upgrade will make the car feel more planted and inspire more confidence.
Yeah, if you're doing it all at once, coilovers are definitely an equivalent priced option. I haven't done the front Konis, which are the biggest expense on that route. The stock struts on the Abarth do have FSD technology though, but it's not as good as branded Konis nor are they adjustable.

The squirrely rear-end issue... I've either become a better driver, or more likely, my car is better than it used to be. In the past it was a real issue for me at all speeds. Rear could step out even if the car felt otherwise planted on 2nd gear corners. Now it seems like I only have to fight it a little on high speed corners, which is a matter of knowing what speed to enter the corner at to prevent hijinx. The hairpins and medium speed switchbacks the car was totally planted. Even with my NeoGens hitting about 41/37 psi hot.
2015 Rosso Abarth 5MT - MAD FIAT - EC Phase 2 + Supporting Mods
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Re: What options to achieve flat ride?

Post by Romanoaf » Thu May 02, 2019 7:22 pm

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