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Old 12-05-2010, 11:30 PM   #1
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Default Suspension Basics (Pre-101)

I've had the chance to flog a number of exotic cars this year (R8, Gallardo, 997 Turbo, Vantage, others) and the experience really changed my perception of how a car can (should?) handle at the limit. I would like to understand the specifics of what makes the handling on an exotic car so impressive.

The most impressive of the bunch was the Ferrari 360 I had to chance to autocross. Even though the ride was compliant over uneven pavement, when pushed the car exhibited nearly no brake dive or body roll and slid through corners with what really felt like even grip from all four contact patches. While I'm used to cars which steer with the throttle, I'd never driven anything so neutral. It was exhilerating to drive, and that's not even counting the amazing engine.

Not only was the handling of the Ferrari a night and day difference from the way my turbo Miata feels at the limit on its stock suspension, but is substantially different from my BMW M3 as well.

Utimately, I'd like to learn what combination of factors mix to create a ride which is streetable, yet neutral at the limit - and whether or not that feeling could be replicated on a miata without exotic components.
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Old 12-05-2010, 11:46 PM   #2
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Quote:
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I would like to understand the specifics of what makes the handling on an exotic car so impressive.
.

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Originally Posted by nderwater View Post
exotic components.

JK.

If you've only ever tried a Miata on stock suspension you're in for a treat as far as how far you can take a Miata. LOTS of info on proper setups for higher horsepower cars here. While the stock Miata has a great suspension compared to most production cars, age isn't kind to the Showas, and the spring rates and bump travel both leave something to be desired, especially on an NA.

First step is to raise springs rates, and lower the car. Easy....well, except for now losing travel. So if it's an NA (sorry, haven't checked out your intro thread yet), then you get NB shock mounts and call Shaikh at FatCat Motorsports for a recommendation on proper bumpstops.

Ok, so you want stiff springs...but how stiff...and on OTS shocks or a coilover* setup? With a turbo setup, while it will depend on sway bars and such, you generally want raise the F/R rate ratio to about 3/2...a good bit higher than most of the packages out there. The FM springs are one of the few spring sets out there that works for almost any Miata, and are nearly ideal for a street car. The fleaBay coilovers and most of the Teins are way too stiff in the rear for the front spring rate...and you'd either need to order the Teins with stiffer fronts, or make your own combo using generic 2.5"ID springs on the eBay collars.

Best thing you can do is play around with FCM's spreadsheet and find a setup with the kind of spring rates you're looking for and proper roll ratio and travel etc.

Anecdotal advice: Spend as much as you can. I went through a half dozen of the popular shock and spring combos before finally trying a $1K+ setup (which I miss greatly). It was a night and day difference. For a little more than that now guys like Emilio at 949 Racing and Bernie at Stewart Development have some phenomenal options that can make a Miata handle like the exotics.

Last edited by gospeed81; 12-06-2010 at 12:04 AM.
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Old 12-05-2010, 11:49 PM   #3
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Old 12-06-2010, 12:09 AM   #4
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Read the Shock Tech 101 thread.

This week I will be posting pictures of each part in a typical Bilstein shock. I have a test shock that I have dedicated to the thread that will be used to help people understand the effect of each part and what to change to achieve a desired graph. This will include everything from the bleed to the top off shim, to the type of oil.

Quote:
Originally Posted by nderwater View Post
I've had the chance to flog a number of exotic cars this year (R8, Gallardo, 997 Turbo, Vantage, others) and the experience really changed my perception of how a car can (should?) handle at the limit. I would like to understand the specifics of what makes the handling on an exotic car so impressive.

The most impressive of the bunch was the Ferrari 360 I had to chance to autocross. Even though the ride was compliant over uneven pavement, when pushed the car exhibited nearly no brake dive or body roll and slid through corners with what really felt like even grip from all four contact patches. While I'm used to cars which steer with the throttle, I'd never driven anything so neutral. It was exhilerating to drive, and that's not even counting the amazing engine.

Not only was the handling of the Ferrari a night and day difference from the way my turbo Miata feels at the limit on its stock suspension, but is substantially different from my BMW M3 as well.

Utimately, I'd like to learn what combination of factors mix to create a ride which is streetable, yet neutral at the limit - and whether or not that feeling could be replicated on a miata without exotic components.
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Old 12-06-2010, 02:03 AM   #5
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I rode in Sam Strano's national championship Camaro. That car had a lot of body roll but he could wheel it around incredibly well. Next I rode in a national championship Corvette with Penske's(I don't remember the woman's name but she was a Cadillac executive) that car felt as if it had practically no roll or dive-it was just fast and smooth. Even though they felt worlds different the times weren't too far off from each other.
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Old 12-06-2010, 02:22 AM   #6
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Now that the laughter has died down, let me elaborate.

We all how a stock Miata handles - good steering feel, immediate direction change - yet lots of body roll, brake dive and not much overall grip. My previous Miata was a '99 R Package which had awesome grip when being hustled through the corners, but still exhibited way too much body movement and the ride was punishing on the street. My M3 has more grip still, but at the cost of steering feel and responsiveness.

I've driven many other excellent sports cars in anger - Vettes, 350Z's, S2000's, Boxster's, 911's - and yet none of them felt as flat, neutral and responsive as the Ferrari I drove. What is it that makes it so different?

I've read the Tech 101 thread. What I'm looking to understand is not the specifics of high-speed vs low speed compression or spring preload. I'm looking for a high-level explanation of what makes a Ferrari handle so well. The center of gravity can't be that much lower than a Miata. The weight distribution is very slightly more rearward in the Ferrari, but the roll center can't be too far moved. Both cars have double wishbones with coil-over shocks, and the suspension geometry doesn't appear to be *that* different. The wheelbase is proportionally longer in the Ferrari - but less so than my M3. So what is it exactly that makes the handling characteristics so different between the cars?
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Old 12-06-2010, 07:09 AM   #7
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Quote:
Originally Posted by nderwater View Post
I'm looking for a high-level explanation of what makes a Ferrari handle so well. The center of gravity can't be that much lower than a Miata. The weight distribution is very slightly more rearward in the Ferrari, but the roll center can't be too far moved. Both cars have double wishbones with coil-over shocks, and the suspension geometry doesn't appear to be *that* different. The wheelbase is proportionally longer in the Ferrari - but less so than my M3. So what is it exactly that makes the handling characteristics so different between the cars?
i'm gonna wager chassis rigidity plays a major factor
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Old 12-06-2010, 10:19 AM   #8
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So your more interested in the whole picture and not the shocks. If so i will have to try to give you some info that i can remember from my vehicle dynamics class.

Ok so i am not going to research a ferrari so i will just guess that it prob has a wider track than a miata, stiffer stock springs, and wide tires.

Body Roll

So there is a million things to learn about this so i will try to keep it simple
A car has a center of gravity above the ground and that is where the forces act on the car. During a turn the car wants to rotate around this point, so think of a car flipping. The resistance to this rotation is the roll stiffness of the car. It can be simplified in an equation roll stiffness=((t^2)/2)*K . In this equation t is track width of the car and K is the spring rate. If you increase t or k you increase roll stiffness. As you can see track width is squared so as you increase it roll stiffness increases exponentially. Spring rates should also be as high as possible while still maintaining tire contact on the road. All sway bars have there own roll stiffness and this is just added to the overall roll stiffness. You would like to keep roll in check because your using more of our outside tires for grip, with less roll the cornering forces can be more evenly distributed.

Now to understand tires is a whole different game. Tires are the most complicated things you have on your car and can only be computer modeled by a select few tire manufactures. A lot of testing is done on tire machines.

http://www.youtube.com/watch?v=nmo_dkNZIHM

Tires perform best when there contact patch is flat against the ground. You want as much dynamic camber to keep the contact patch flat to the ground. A miata is good at this and i dont know much about ferrari suspension types.

If you have any questions about suspension just ask and i will tell you or if i dont remember i can look it up in my textbook(Race car vehicle dynamics).
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Old 12-06-2010, 11:20 AM   #9
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........So what is it exactly that makes the handling characteristics so different between the cars?
Shocks and springs.
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Old 12-06-2010, 11:43 AM   #10
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I'd also bet that the Ferrari has a lower CofG than any other stock car, and the moment arm between the CofG and roll center is very short. They are designed to have little to no body lean. More mass-consumer oriented cars have lean partially to generate some feedback to the driver.
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Old 12-06-2010, 02:02 PM   #11
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I'd also bet that the Ferrari has a lower CofG than any other stock car, and the moment arm between the CofG and roll center is very short. They are designed to have little to no body lean. More mass-consumer oriented cars have lean partially to generate some feedback to the driver.
There's no need to build in lean; it's an inevitable result of limited space to package the suspension arms.
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Old 12-06-2010, 02:15 PM   #12
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Well, if track width is important to the argument:

F360 track width 65.7 in
Miata track width 55.3 in

The Miata is 10+ inches narrower. But I'm sure the reasons are much deeper than that.
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Old 12-06-2010, 03:54 PM   #13
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For my own geekyness, I'm working on a spreadsheet comparing the stats for the Ferrari 360 Spyder I drove against the numbers for my '99 Miata and '99 M3. Specifically comparing the 360 and Miata, here's some food for thought:

Track/Wheelbase Ratio - 63.2% Ferrari, 62.6% Miata
Overall Height - 48.6" for both cars
Suspension Design - Double-wishbone w/ coilovers F&R for both cars

The biggest difference so far is the F/R weight distribution, which is more dramatic than I suspected. While the Miata is pretty balanced, The Ferrari is 43%f 57%r and has 215f 275r section-width tires to match.
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Old 12-06-2010, 04:04 PM   #14
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The biggest difference so far is the F/R weight distribution, which is more dramatic than I suspected. While the Miata is pretty balanced, The Ferrari is 43%f 57%r and has 215f 275r section-width tires to match.
That's a significant deficit on the Ferrari's side of the ledger, and the staggered width tires are a less than optimum work-around.
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Old 12-06-2010, 04:05 PM   #15
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consider

3600 - Moton Club Sports
3700?- JRZ Double Adjustable
3800 - Xida
3960 - Koni 2812

for the Miata
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Old 12-06-2010, 05:18 PM   #16
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For the record, reading through Ferrari forums is a bigger embarrassment than import forums. None of the members seem to know much about their cars, asside from a few track rats whose race crews tinker with the settings on their Challenge Stradales. As for the regular forum members, dealers and tuning shops maintain and mod their cars for them and the owners don't really care about the details.
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Old 12-06-2010, 05:58 PM   #17
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This is not a simple subject.

There are dozens or hundreds of books written about chassis, suspension, NVH, tire, damper, brake, and frame design. If you are really interested in this stuff I can recommend a fair amount of reading. When I went about setting up my miata, I spent about a year researching and reading. I went through several thousand pages of material.

Again, this is not a simple subject. You cannot point to any specific component, everything has to work together even down to the level of molecular structure of the materials.
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Old 12-06-2010, 07:22 PM   #18
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If you are really interested in this stuff I can recommend a fair amount of reading. When I went about setting up my miata, I spent about a year researching and reading. I went through several thousand pages of material.
That's pretty exactly how this started. After the harshness of my R-Package NA, I kept my NB on its stock suspension because I was spending two hours a day commuting in it. Now that I take the express bus to work, I'm interested in putting a suspension under the car which is a better match for its performance... but my idea of what a better suspension should feel like has become more complicated.

The first time I drove an S2000 in anger I thought "Wow, this is what a well tuned Miata must feel like." Flogging a 911 was even better - it's as if a talented shop tweaked an S2000, then gave it more *****. But unlike even a 911, the mid-engine cars I've driven recently didn't feel heavy on the front tires under breaking, and on turn-in didn't seem to rotate around a planted front tire.

Now I'm not interested in just firming up the ride of my Miata. As much as possible, I'd like to replicate that planted, neutral (yet compliant) feel of a mid-engine exotic... so before I buy any parts, I'd like to understand the general mechanics of the suspension design on those cars. My thought was that if I better understood the mechanics of the suspension I would like to replicate, the easier it would be to make decisions about the specifics of the suspension setup I'm looking for.
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Old 12-06-2010, 07:32 PM   #19
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Most street cars are designed with road clearance in mind. That's a big diffierence between a street car and a track rat.
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Old 12-06-2010, 07:41 PM   #20
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