Questions about TTC & tire data

[whitenoise]

Hello,

I found my way to this website after looking at MRA's TTC page. Its my understanding that non-FSAE people are also allowed to be part of the TTC.

I am in the process of designing an A-mod car that will conform to FSAE rules for SCCA national competition, and would prefer to use real tire data to drive the suspension design of my car.

I'd appreciate it if someone can answer these questions:

1) I'm interested mainly in the 10" hoosier tires - since these are the only 10" available here in the US to privateers outside of FSAE.

In Rounds 1, 2 and 3 it appears only one type of 10" tire (Hoosier 18x6 R25A) has been tested. Is the round 4 set of tests scheduled to investigate more 10" tires?


2) The MRA page does not specify which pacejka fits are included - is it 96, 02 or 06?

[whitenoise]

Hello,

I found my way to this website after looking at MRA's TTC page. Its my understanding that non-FSAE people are also allowed to be part of the TTC.

I am in the process of designing an A-mod car that will conform to FSAE rules for SCCA national competition, and would prefer to use real tire data to drive the suspension design of my car.

I'd appreciate it if someone can answer these questions:

1) I'm interested mainly in the 10" hoosier tires - since these are the only 10" available here in the US to privateers outside of FSAE.

In Rounds 1, 2 and 3 it appears only one type of 10" tire (Hoosier 18x6 R25A) has been tested. Is the round 4 set of tests scheduled to investigate more 10" tires?


2) The MRA page does not specify which pacejka fits are included - is it 96, 02 or 06?

[exFSAE]

Why are you already set on 10" ?

[whitenoise]

Many reasons - i am trying to keep weight to an absolute minimum - FSAE cars dont have minimum weight in A-mod, and cheaper tires being two of the main ones.

[exFSAE]

I'd be pretty wary of limiting yourself to 10" tires.

There have been plenty of times when relatively heavy cars on 13's have smoked much lighter ones on 10's.

It's entirely possible that you'll find 13's that have so much more grip than a 10.. that it'd more than make up for the weight penalty.

Plus, packaging and kinematics are definitely more challenging on a 10" wheel package.

Not to mention there isn't much selection for 10" wheels to begin with.. and you'll throw away heaps of grip and response with a shitty wheel.

Not saying 13 is hands down better than 10. But automatically discarding the 13 option seems silly IMO.

[RyMan]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> There have been plenty of times when relatively heavy cars on 13's have smoked much lighter ones on 10's.
</div></BLOCKQUOTE>

See University of Stuttgart.

How do you plan on using and working with the data? Being proficient in MATLAB goes a long way in being able to digest the data visually in terms of graphs and such. Otherwise you just have raw data that is a bit difficult to sort through. MATLAB probably isn't the only software you can use to analyze the data, it is just what we used. What do other teams out there use?

Do you know what information is most important in the tire data, and what data you want to compare? I merely overheard a few conversations about tire data between our MATLAB guru and another team member who attended Optimum G, so I cannot claim to be omniscient but they are just some things to consider. If you haven't done so already I would do some reading up on race tires.

Also, there is a strong correlation between the top finishers in skidpad and running 13" tires. This is just a correlation, but it warrants taking a closer look. In my opinion, the skidpad results give a better indication of the car's cornering performance and not the driver's ability to consistently push the tires to their limits as is the case in auto X and endurance. Keeping weight down is never a bad thing, but keep in mind that maximizing the potential of your tires is very important as well.

Long story short, you can make a reacecar that will blow the doors off the competition with 13" wheels. A lot of the top teams do it every year.

[bob.paasch]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by whitenoise:

In Rounds 1, 2 and 3 it appears only one type of 10" tire (Hoosier 18x6 R25A) has been tested. Is the round 4 set of tests scheduled to investigate more 10" tires?

</div></BLOCKQUOTE>

I know we're hoping that Round 4 includes the Hoosier 18x6 LC0. Most top FSAE teams running 10's (TU Delft, RMIT, ETS, Michigan, OSU) are using this compound. These cars range from 145-185 kg.

[whitenoise]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by rp:

I know we're hoping that Round 4 includes the Hoosier 18x6 LC0. Most top FSAE teams running 10's (TU Delft, RMIT, ETS, Michigan, OSU) are using this compound. These cars range from 145-185 kg. </div></BLOCKQUOTE>

Thanks, Bob. I was hoping they would test the 18x7.5 10 incher as well but I guess no one uses that in FSAE?

While the 13" may well be superior to the 10", a set of 13s also costs roughly $200 more. Not to mention wheel cost. I expect to be going through at least 3 or 4 sets a season doing competitive auto-x and time trials, and also HPDEs. I'm not discarding the idea of 13s completely, but 10s dont look that silly when you're paying the bills.

Ryan, I do vehicle dynamics simulation professionally so software tools for data analysis are not an issue. I intend using the PAC 02 coefficients directly in ADAMS for sensitivity studies and optimizing the kinematics.

[bob.paasch]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by RyMan:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> There have been plenty of times when relatively heavy cars on 13's have smoked much lighter ones on 10's.
</div></BLOCKQUOTE>

See University of Stuttgart.

</div></BLOCKQUOTE>

Autocross, FSG09:

http://www.odeki.de/fsg09/galerie2/pages/P1017738.html

Bit of a stretch to attribute Rennteam's 0.119 second advantage entirely to the their use of 13" tires....

[MalcolmG]

So do you think the life of a 10" tyre is going to be the same as a 13" tyre? I'm going to put it out there (if you don't like it, send it right back), that 13's may work out cheaper because you end up using one less set (or pair if you wear faster at one end) than the 10's anyway.

[whitenoise]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by MalcolmG:
So do you think the life of a 10" tyre is going to be the same as a 13" tyre? I'm going to put it out there (if you don't like it, send it right back), that 13's may work out cheaper because you end up using one less set (or pair if you wear faster at one end) than the 10's anyway. </div></BLOCKQUOTE>

I dont know about autocross, but from what I've seen in road racing, the 10" are not that different in terms of wear. Its entirely possible that this is because the car running 10" was significantly lighter, but this is all conjecture.

All I want to know is whether 10" tires are scheduled for Round 4, and I've been told that that's not the case. Personally I think that's a shame, but everyone has an opinion I guess.

[flavorPacket]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by RyMan:
Also, there is a strong correlation between the top finishers in skidpad and running 13" tires. This is just a correlation, but it warrants taking a closer look. In my opinion, the skidpad results give a better indication of the car's cornering performance and not the driver's ability to consistently push the tires to their limits as is the case in auto X and endurance. </div></BLOCKQUOTE>

Well, Ryan, then it's a good thing that the original poster is not building a car for a skidpad competition, but for actual racing! And in that case, 10's are easier to drive, cheaper, and get hot quicker.

In addition, I find your statement to be spurious at best. Look at the skidpad results from FSG 2009: there were 3 10" wheel teams in the top 11, and less than 27% of teams use 10" wheels.

As an alumnus of a team with privately obtained data for the 18x6 LC0, I can tell you that what we figured out in 2 years of development without tire data matched up reasonably well with what we saw on the flat trac. You don't need tire data to make a fast car.

[RyMan]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">I do vehicle dynamics simulation professionally so software tools for data analysis are not an issue </div></BLOCKQUOTE>
Very nice. I hope I'm in a situation where I have access to such software after graduation. Those packages aren't very cheap to non-students.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Bit of a stretch to attribute Rennteam's 0.119 second advantage entirely to the their use of 13" tires </div></BLOCKQUOTE>

I agree, but I didn't attribute fast auto X times to tire size. I attributed skidpad to tire size. As I said earlier, I feel that auto X times are more of a benchmark for driver skill. You do have to have a good car to finish high in auto X, but having a great driver goes a long way. So I look to skidpad to determine which car should theoretically be driven the fastest around a track. It is up to the driver to reach the potential of the tires, but the car must allow him/her to do so.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">
Well, Ryan, then it's a good thing that the original poster is not building a car for a skidpad competition, but for actual racing! </div></BLOCKQUOTE>
True, skidpad is not the only thing that matters when it comes to being fast, but it tells you which cars can get the most out of their tires.

In my original post I was merely suggesting that 13" tires shouldn't be thrown out the window. I agree that using 10" tires helps out in a lot of areas. Our team doesn't run hasn't run them so I don't know what they are, but I believe their benefits have been touched on already. I (as well as my team)completely identify with reducing costs, especially since you are an individual presumably using your own money. Since cost is the determining factor in most cases, 10's will more than likely be your best bet.

[exFSAE]

Ryan.. there's still a fair amount of driver skill required to post a high skidpad time, believe it or not.

[Thrainer]

If I remember correctly, Delft and ETS can wear down a set of tires in a good day of testing or two. This can come to a point where testing time is money-limited. I would guestimate that 13" tires are considerably cheaper over the entire season.

[Zac]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Well, Ryan, then it's a good thing that the original poster is not building a car for a skidpad competition, but for actual racing! And in that case, 10's are easier to drive, cheaper, and get hot quicker. </div></BLOCKQUOTE>

How is the tire wear on the hoosier 10's?

[exFSAE]

Additionally..

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">10's are easier to drive, cheaper, and get hot quicker. </div></BLOCKQUOTE>

That's pretty debatable.. certainly the drivability and heat-up points.. and even the cost point depending on tire wear (though I don't know much about that).

[whitenoise]

Here's another question for you guys: Has anyone successfully used the TTC data for vehicle dynamics simulation? If not, what do the teams do with it?

[RyMan]

Optimum T allows you to use the TTC data in conjunction with the kinematics software package Optimum K. Not sure on the specifics of how it is done though, as Optimum T is in beta testing right now. Would any beta testers care to share their experiences thus far?

[scott_rfr]

You can role out simple models relatively quick using the tire data and add complexity and you go along. I would recommend doing some sort of MMM or Steady-State. Just remember steady state does not have to be Yaw Moment=0.

Using the supplied tire model and my MMM simulator we have seen trimmed and non tried Ay that match up from sim to data. Just need some slip angle sensors and see if those match up too. Tried doing some observer based estimation stuff over the summer curious to see how that matches up to what slip sensors would say.

Supplied is the 96' coefficients. Curious to see the difference between 96' and 06' with all the additions that were put in the latter.

Scott
Rutgers Formula Racing

[STRETCH]

Whitenoise,

I can only speak for our team, but we are constantly developing a lapsim using TTC data. However, TTC do not provide combined loading coefficients for the Pacejka model, so this work tends to be limited to non-transient modelling. Personally, I have used the tyre data to predict mechanical balance and use this to influence suspension design.

As for wheel size, the only reason that 10" tyres are competitive in FSAE, is that they can obtain temperature on the low mass vehicles i.e: the 140 - 180kg single cylinder cars, and the fact the 3 of the dynamic events are very short. So in many ways it depends on the mass of the vehicle you're building. All the quick 600cc cars use 13" tyres, giving the lateral and braking power they need for the &gt;200kg mass, plus traction for 90bhp.

Furhermore @ RyMan, the fastest skidpad car is not necessarily the fastest theoretically around a track at all. Skidpad is purely a test of steady state performance, encompassing grip, balance and weight. The quickest cars on a track cope with braking, traction, direction change, stability etc... (and a good driver). We finished 2nd and 3rd in Skidpad at FSUK and FSG this year and were SECONDS off the quickest cars around the endurance.

[MalcolmG]

I'm not convinced that the only reason 10" tyres are competitive is temperature related - I'd think the effects of the smaller wheels and tyres on mass, reduced overturning moment at the spindle, lower unsprung CoG height, yaw inertia etc all contribute.

[exFSAE]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by STRETCH:
However, TTC do not provide combined loading coefficients for the Pacejka model </div></BLOCKQUOTE>

You may want to check again. Combined coefficients are there.

[whitenoise]

Thanks to all who replied.

I read a little deeper into the MRA TTC page and also read the SAE paper posted there. It appears that the 10" tires were never subjected to braking and driving torques due to the flat trac motion head being too large to accomodate the tire. Therefore its impossible that the combined coefficients are there for those tires, at least beyond a certain slip ratio range.

I doubt I could do any kind of serious modeling work without combined coefficients. But then again, there's a lot to be gained from a kinematics-targets perspective by just knowing what the load and IA sensitivities are.

[toomuchtodo]

Speaking of coefficents...does anyone have a Pacejka model(Lat & Long) made in excel? I've got coefficients for other tires (non-FSAE) and I would like mess around with them in excel a bit.

[exFSAE]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by whitenoise:
I doubt I could do any kind of serious modeling work without combined coefficients. </div></BLOCKQUOTE>

Disagree, strongly.

There's a tremendous amount that can be done, and learned, with good free-rolling data. Few really even nail that type of simulation down, using all the tire data available (more than just Fy and Mz).. getting into tire compliances, suspension compliances, force-based centers, etc.

I've seen no team at the FSAE level really pull it off, so there's still tremendous room for competitive advantage.

And that's before even getting into combined slip...

[scott_rfr]

I agree with exFSAE a lot can be done without combined data and make use of it.

Part of the problem I think is most students dont know where to start. Or where to go once they have a base. University typically don't have a vehicle dynamics department, and those in industry are very tight lipped about what they do/know.

Scott
Rutgers University