Why do we need tyre data

[Mar-1]

hey everyone,
Ok i know that my question is noobish but i really need help. I keep hearing that to start the design we need the tyre data to be able to decide on the suspension system and other things. The thing is that i dont know why do i need the tyre data in 1st place, like how will it help me and most importantly how to utilize it.

Thanks for your time and help in advance.

[Matt S]

Mar,

The tires are the single most important piece of equipment on a race car. All of your lateral and longitudinal forces are reacted through the tires. Without proper tires, or proper knowledge of the tires' behaviour, you car will not reach its full potential, no matter how awesome the rest of it may be.

That being said, your understanding of tire dynamics and tire data treatment is hugely important when designing a suspension system. Your tire data will tell you things like load sensitivity, coefficient of friction against slip angle, camber thrust, etc. It's up to you to decide how to best use the data.

You'll find that in many aspects, suspension design is a compromise. There is no one single "best" suspension geometry, it's about finding what works best for your application.

If you're interested in learning more about tires (and you should, they're awesome), check out chapter 2 of "Race Car Vehicle Dynamics" by Milliken & Milliken

[exFSAE]

You don't need it.

[cvargas]

Originally posted by exFSAE:
You don't need it.

Then why was it created?

[,4lex S.]

I guess everything is a choice, but tyre data would seem to rank as a big potential gain.

Then again, I have to tack potential onto that.

Makes me wonder though, if Goodyear has changed their tyre compounding and construction this year, what are the teams using them going off of without a TTC run?

Mar-1: The Tyres chapter of Carroll Smith's Tune to win is a good place to start for introductory Tyre information, moving on to RCVD and other more in depth resources afterwards.

[Adambomb]

Originally posted by cvargas:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by exFSAE:
You don't need it.

Then why was it created? </div></BLOCKQUOTE>

I'm going to take a stab and guess that he meant "if you have to ask, then you don't need it."

Just like all the teams that "need" pneumatic shifters, turbos, etc.

[exFSAE]

Kinda.

"Need" is a strong word. You need 4 wheels and an engine. You need an impact attenuator.

Ultimately the goal of all this prep work leading up to a competition is to have a car that's fast / balanced / driveable / reliable / etc etc. Tire data and vehicle simulations can help you learn some things which hopefully lead to this end. However, it isn't necessary. Could get your car sorted by extensive track testing if you like.

I'll also say that this kinda stuff can hurt you as much as help if you take everything at face value and/or rely on your simulations to just "optimize" some lap time or give you the end-all-be-all answer.

[Edward M. Kasprzak]

You do not "need" the TTC tire data.

Since this is an engineering competition, though, you need to understanding something (many things!) about your tires. There are other ways to gain this knowledge, but the TTC data fills a pretty large hole. Data on all other significant parts of the car can be obtained more easily. For example, you can dyno your engine or dampers at much less cost than force & moment testing your tires.

Remember, a major goal of your vehicle design is to make best use of all four of your tires. They put the "F" in F=ma, so tires are very important.

Here's another reason why the TTC exists: It has prevented a tire testing "arms race". When we founded the TTC in late-2004 there were several teams looking for ways to obtain data on their tires. By creating the TTC we have gone a long way toward eliminating "rich teams" having tire data while others do not. In short, tire F&M data was going to happen in the Formula competitions one way or another. We've tried to make a broader and more level playing field than would have happened without us.

As exFSAE likes to remind everyone, the TTC data (like all tire force & moment data) has its quirks. There are as many pitfalls and ways to go wrong as there are positive applications of the data.

The TTC data is one of the tools available to you. It can be very informative. It can give you a basis for many engineering calculations. It can add to an organized design --> build --> test --> evaluate cycle, but it cannot replace it. You certainly don't "need" it, and if you have it then you need to decide how to make good use of it. There are many possible ways to use the data.

[ben]

Do you need tyre data to build a competitive FSAE car that can win dynamic events - no.

If you have the tyre data and understand it, can it help you make your car quicker - yes

Will proper analysis of tyre data as part of the design event score you points - yes

Will understanding the tyre data and how to process it help you justify why you should be employed in a vehicle dynamics role post FSAE - yes

Ben

[Xeilos]

They put the "F" in F=ma, so tires are very important.


Stealing a line from Claude here. "Tyres are 'F' important".

[AxelRipper]

Makes me wonder though, if Goodyear has changed their tyre compounding and construction this year, what are the teams using them going off of without a TTC run?


We've been attempting to plan for them by using a dartboard, 10 sided die, and averaging the data from other Goodyears. Really hoping they're planning to run an oval for endurance at MIS this year though due to the left side positive camber and amount of wedge we have planned in at the current time.

[JDS]

You can build a very competitive car without having tire data. As long as you design your suspension paying attention to your roll centers, being mindful of your camber gain, and other kinematic factors, your car doesn't NEED the tire data necessarily. Especially with Formula style cars that have very little suspension travel.

With that said however, you can learn SO much from the tire data and you can score a lot of points in design with the judges if you can show them how you used the tire data to design your suspension. Not to mention with the knowledge you gain you will be much more prepared to design a proper suspension for your formula car or any other car in the future after you graduate.

I spent a LOT of time in my years designing FSAE suspension with the tire data and optimizing my kinematics to fully utilize the tires. In retrospect, the time I spent certainly didn't pay off in terms performance increase, but with that knowledge I learned how to write my own vehicle dynamics simulations, I learned a TON about kinematics, tire modeling and testing procedures, etc... So in those respects, having and using the tire data was invaluable.

[Mike Cook]

If you're asking than you don't need it. Don't feel bad. I think this is the first year my team has really even looked at the tire data much. And we're not slow pokes.

[flavorPacket]

Originally posted by Edward M. Kasprzak:
Here's another reason why the TTC exists: It has prevented a tire testing "arms race". When we founded the TTC in late-2004 there were several teams looking for ways to obtain data on their tires. By creating the TTC we have gone a long way toward eliminating "rich teams" having tire data while others do not. In short, tire F&M data was going to happen in the Formula competitions one way or another. We've tried to make a broader and more level playing field than would have happened without us.

Dr. Kasprzak, are you aware that a team conducted private tests on the Hoosier LC0 18x6-10 tire back in 2006? As far as I know, the TTC still does not offer data on this tire today, yet it's used by many of the fastest teams in the series. In fact, several of these teams have used data from the R25B instead, which is far from similar, and they've still been successful at competition.

Tire data is not required to win the design event, dynamic events, or anything else. Can it help? Of course. But just like in professional series, FSAE events are not won and lost on tire data, but rather on the cumulative performance of the driver, vehicle, and team, meaning that a comprehensive balance of capability across all vehicle subsystems must be achieved and then executed.

[Edward M. Kasprzak]

We have heard about some teams doing various types of private testing.

The 10" LC0 is on our list for Round 5 in early 2012.

[JT A.]

I think there are 2 major missing pieces needed to bridge the gap between the TTC data and real life conditions before teams can actually make a legitimate attempt to "optimize" their suspension for the characteristics of the tires.

1) Compliance. You must know how much you have, and how much it changes your camber/slip angles from a completely rigid link assumption. I see a lot of talk about designing the perfect amount of bump steer in the rear 5th links, or designing an ackerman geometry for perfect slip angles at the front wheels. Compliance turns all your hard work into garbage. A lot of this is coming from first year or fairly new teams that should really be focusing on other things anyways.

2) Scaling the data to match real track surfaces. If you're looking at the slip angle vs lateral force graph of raw TTC, the lateral force is significantly higher than what you will see on real surfaces. The tricky thing is that you cant just scale the peak of the curve, it changes the whole shape of the curve. So this requires some knowledge of tire models and probably also some physical testing.

Without these things you can still compare & select tires based on the TTC data, or get a conceptual understanding of their characteristics, but you won't be able to "optimize" anything based on the data. And you can still build a very competitive car without it.

[BBolze]

One thing I began to notice is Tire data is most useful for insights into a tires sensitivity.

If your a new team and mostly want Loads information your better off to use corner weights and accelerations (maybe measured from a MyChron) we've recorded 2g braking and 1.6g lateral. If you assume balanced handling, it would follow that lateral loads are balanced too, so about 0.8*weight front and rear axle, how you proportion that left to right is up to you. (This KINDA gets you around point 2 of JT A's post)

In Hoosiers FAQ they have a lot of generic tire properties, in particular the 2deg camber for peak grip is a good baseline for trying to choose a camber gain deg per unit jounce, assuming you have a static camber value in mind which can give you a starting place for kinematic development

JT A's comment on compliance shows the benefit of spring rate data which is one of the easier values to test for (a cleated drum & a strain gauge) The comment on slip angle compliance though, that one I thought WOULD be accurately reflected. Lateral tire deflection though, and it's effect on scrub radius, that's a shot in the dark.

But as JT A mentioned, I found TTC data most useful in comparing tire properties against eachother ie) Camber sensitivity of Goodyear vs Hoosier, how FY drops off after peak and how that would affect driveability at the limit, how much ackermann should we use for a car this light? One of the first things I actually engineered from the data was choosing a Mechanical Trail for the most steering feeling

[Spetsnazos]

My current team adviser believes that tire data is hocus pocus magic and its not relevant at all. The team is building a car w/o even looking tire data so you definitely don't "need" it.

But what the hell is the point of the competition anyways? To drive around or understand and learn something? I rather learn, but that's just me.

[DougMilliken]

Originally posted by Spetsnazos:
My current team adviser believes that tire data is hocus pocus magic ...

Let's follow the money and look at a simple economic argument only (others can make various technical and educational arguments). Most of professional racing has been spending millions of dollars on laboratory tire testing, starting in the 1980's. If there was no benefit, 30 years should be enough time to figure this out and save the money!

[MCoach]

Originally posted by Spetsnazos:
My current team adviser believes that tire data is hocus pocus magic and its not relevant at all. The team is building a car w/o even looking tire data so you definitely don't "need" it.

But what the hell is the point of the competition anyways? To drive around or understand and learn something? I rather learn, but that's just me.


So, just to throw some non-existent person under the bus...
What if everything else for something that people seem to care a lot more about was treated as 'hocus pocus'? What I have in mind is calling the engine a magic box, just like some people treat tires. So you pick an engine based on how it looks on the outside. Wider is better, right? More cylinders is more power? What if your advisor asked you to design a car based around an engine. You had no idea what the rpm limit was, what the power band was, what type of valve train it had (cam profile, etc), or it's lifetime? What would drive the design decisions? That it's a box and we can fit it into the car?


I don't want to sound like I'm attacking anyone, but that's my view when people say stuff like, "we picked these tires because they were popular and we picked the widest because that lets us put the most power to the ground."

Tires may be extremely complex if you want to get to the bottom of them, and sometimes a bit misunderstood. However, they are one of the most vital parts of a car and necessary to design around to reach target goals. Hell, you might as well use old ceramic tires/wheels as the original skateboards once used. A little tire development there changed the entire sport.

[exFSAE]

Originally posted by Spetsnazos:
My current team adviser believes that tire data is hocus pocus magic and its not relevant at all.

Test data is test data is test data. Doesn't matter if it's an Instron load frame, K&C rig, flat track, engine dyno, whatever. Whether your adviser likes it or not, tire specimen 'X' did create forces and moments 'Y' under test condition 'Z' as is presented in TTC data.

Now at this point, to be blunt I'd say your adviser is either a genius or a fool. On one hand, you can use tire data to dive down some rabbit hole while not really knowing what you're looking at or how to use it.. and make no better decisions (maybe even worse decisions!) than if you had no data at all. Depending on where your team is at, using some caution and putting off in depth data analysis until a later time could be a pretty smart move. Same could be said of say a first year team trying to dive into ADAMS modeling.

On the other hand, if you have a truly good understanding of tire test data it can be very useful in the design phase without having to do extensive track testing yourself. So to write it off immediately as bullshit without giving it a good objective assessment is quite foolish.

I'm not gonna judge which category your adviser falls into.

[Claude Rouelle]

To Spetsnazos,

Just a simple question to your faculty adviser: how do you solve engineering problem without engineering input / data?

That buying and using tire data should not be your priority is understandable especially if you are a new team; you do have many other challenges.

However.... The FSAE challenge gives you the possibility to develop your engineering and team work skills by understanding, analyzing, solving, testing, developing.... Also, the design judges will evaluate your engineering skills not only on your car quality build and apparent performance potential but mainly on your understanding of the how, the why and the how much of your design.

As the tires are the only elements of the car in contact with the ground (Well... hopefully!) and cornering, braking and acceleration performances as well as driver's feedback pass through the tires, I don't see how you can quickly and smartly develop a car without basic tire understanding and tire data.

Unless you want to make hocus pocus engineering!

******

One more thing a bit out of this topic but still about tire data.

FSAE / FS students do not know how lucky they are. Today FSAE / FS teams can have access to tire data of several tires brand, sizes, compound for 500$. That is because of Doug Milliken and the TTC guys. If you want a race or a passenger tire decent data it could cost you any where between 10 K$ and 25 K$. For one given tire! Think that if you have different front and rear tires (as it is often on most race cars) the cost will simply be multiplied by 2.

If you are a TTC member, TTC asks you to put a Calspan sticker on your FSAE / FS car. Only a fraction of the team do respect their contract. Guys; just be realistic and just be fair.

[Edward M. Kasprzak]

Thanks for the kind words, Claude. We (the TTC) will be contacting all members in the next few weeks regarding their display of the Calspan decal. We will also be uploading a better set of Calspan logos to the TTC private forum. Calspan has been an exceptional TTC partner from the start, conducting the tests with their usual high standards at a substantially reduced price. We feel Calspan's contribution has been somewhat overlooked lately. Stay tuned.

[Dunk Mckay]

Originally posted by Edward M. Kasprzak:
Thanks for the kind words, Claude. We (the TTC) will be contacting all members in the next few weeks regarding their display of the Calspan decal. We will also be uploading a better set of Calspan logos to the TTC private forum.
Good to hear, I need to make sure we can log in to the forum (a lot of account data has been lost over the past few years) so we can grab that logo.

[DougMilliken]

Originally posted by Dunk Mckay:
Good to hear, I need to make sure we can log in to the forum ...
Anyone from a university/school that has joined the TTC can register to access our secure forum.

Also -- thanks again to Claude for the kind words. With all the new teams forming around the world, TTC membership continues to grow at a healthy rate.