Tyre Information

[ben]

Hi All,

Following the post on the Garrett presentation due at FSAE-West I've got my boss to agree to try and do something similar on tyres at either the UK event or one of the seminars they do over the winter.

I've come up with a rough agenda and again I'd like some feedback on what you guys want to hear and any specific questions we could (try!) and answer.

FORCES AND MOMENTS
Linear, transition, saturation regions
Construction effects
Cornering stiffness
Self aligning torque
Compound and surface effects
Grip level
Temperature generation
Is softer always better?

EXAMPLES OF USING TYRE DATA
Matching tyre widths and weight distribution
Spring rates - Load transfer calculations
Cornering stiffness - Basic stability calcs
Self-aligning torque - Steering feedback
Rolling radius – traction control setup and data logging speed correction

TEMPERATURE AND PRESSURE
Rubber is a poor thermal conductor
Surface temperatures can vary quickly
Probe the tread base not the surface
Try to measure the temperature every time the car runs
Three positions
Probe tyres in same order
Outside front first
Aim for 10-15 degrees maximum spread
Record ambient and track temperature
Pressure important for correct contact patch shape
Will vary in service
Hot pressure related to tyre temperature
When do you want the tyre to come in?
Vehicle balance

WEAR AND HEAT CYCLES
A tyre can be past it's best despite having tread remaining
Record heat cycles and track performance
Graining
Self-perpetuating once initiated
Generally initiated by using too much negative camber
Also initiated by too soft a compound
Event specific camber settings?

TYRE MODELS
Curve fitting
Pacejka
MRA Non-dimensional
Physical models
Hallum Tyre Model (HTM)
Trevorrow Tread Model (TTM)

TYRE TESTING CONSORTIUM
$500 for all data – raw and model fits
This is effectively free information due to the actual cost of the testing
A tyre company will not usually force/moment test the tyres you use due to cost. Don't ask – buy the TTM data
Contacts
Edward Kasprzak – MRA
Denny Trimble – University of Washington
www.fsae.com (http://www.fsae.com)

SUMMARY
Use basic linear tyre data to develop initial designs
Study interactions using tyre models in vehicle simulations (ADAMS, etc)
Understand the limitations of tyre models – they are not a full picture of the tyre
Test and race on the same tyres and the same surface if you can this is the only way to truly assess grip level
Try different settings for different events
Don't use front negative camber as a crutch!

Anything else?

Ben

[Big Bird]

Cheers Ben, that looks like it would be really helpful. Bloody shame it is on the other side of the world, but if I hadn't blown all my money on flights to the US then I'd seriously consider it. About time RMIT did another trip to FStudent....

If ever you want to do it in Oz, (if you are ever over here testing at Phillip Island or the like) let us know and we'll arrange whatever is needed. And thanks for thinking of us - it is damn nice to see alumni still looking out to help.

Cheers squire,

[Ché]

Having looked at the tire testing data slip angle seems to be very important. A discussion on how to design for a known slip angle curve (F and R) would be helpful. Unfortunetly I most likely won't be able to make it to the UK though.

Ché

[ben]

This is the question I was expecting and the reason I put try! in brackets.

That's not something we do a lot of. The only specific (and confidential) example used ADAMS modelling and was in a scenario where coupling with aerodynamic behaviour tended to dominate.

Having said that, my feeling is that the MRA Moment Method is probably the best approach for this sort of thing. The RCVD workbook (the second edition) did a really simple example using a linear cornering stiffness with a saturation value to represent the onset of sliding. The linear range in the MM indicates the sub limit balance and the saturation value will tell you what the limit balance is likely to do.

I'll ask around though...

Ben

[Ché]

Ben, I just sent you a PM

[RacingManiac]

At what time would this seminar/presentation be taking place?

[ben]

At this stage it's not gone further than the idea having been mentioned to me by the I Mech E and me getting clearance from my boss. I'd like to do it at the UK event, but nothing is concrete at this stage.

Ben

[PatClarke]

Hi Ben,
I'll be in the UK then and would like to attend if poss.
Regards
Pat

[Kirk Feldkamp]

Originally posted by Suddenlee:
The Wombat. Eats roots, shoots and leaves

That has got to be one of the greatest signatures I've ever read. Well done.

[PatClarke]

See!!! Design judges can have a sense of humour ;-)
Pat

[murpia]

Originally posted by ben:
I've got my boss to agree to try and do something similar on tyres at either the UK event or one of the seminars they do over the winter.


Superb idea Ben. I would suggest trying to do the presentation at one of the winter seminars, as you know there's a lot going on at the FStudent event itself and it would be a shame for teams to miss it because they're too busy.
Regards, Ian

[RiNaZ]

any plans on having the event taped so that guys from US can watch it too?

[ben]

Originally posted by RiNaZ:
any plans on having the event taped so that guys from US can watch it too?

I am a bit camera-phobic. I got roped into doing a bit on the Turkish national MotoGP coverage last week. I have no interest whatsoever in seeing it :-)

I'll try and put together a pack of stuff that could be posted somewhere.

Ben

[Lukin]

The TTC has helped by getting data, but for a lot of series around the world there is no tyre data.

I think a look at how (even if it's qualitive) a better understanding on tyres can be achieved through the basic measurements (ambiemt/track/tyre temperatures, pressures, wear, heat cycles) in comparison to settings (camber/castor/toe and dampers/RC/springs/bars) would be helpful to a lot of people.

Haney is a good start, but in series where data and testing is limited, getting a better understanding of how the tyre works with limited information can be a very big gain I would think.

I guess that is a bit of a dumb down compared to what most people want (especially those involved in FSAE) but sometimes, you can get tripped up by the most basic things, no matter how professional you are. All the data in the world doesn't help when your half way through practice on a track that has been slightly re-surfaced with higher ambients and your car is a total dog.

Just a thought.

[ben]

I've been asked to do this for the "Learn to Win" event that the Formula Student organisers will be running in October.

With that in mind, if there are any more thoughts or specific questions I could endevour to answer in time please post.

Regards,

Ben

[kwancho]

Tapppeeee itttttt.....

[ed_pratt]

I know this is a massive thread dredge up but did anything happen with this?

The subjects to be covered in the presentation would be incredibly helpful to us new teams trying to make a start on the tyre data.

Were there any notes/powerpoint created?

Ed

[ben]

I think I sent some notes to the I Mech E following the event.

Frankly my knowledge base has subsequently improved vastly having done a year with LMPs in 2008 and two years with BMW in testing/ALMS.

Probably need to do an update - bloody busy though. I'll see what I can do.

Ben

[ed_pratt]

Ah, I'll try and get in touch with them.

An updated version would be fantastic but I appreciate the difficulty!

Cheers

Ed

[Jersey Tom]

Originally posted by ben:
Aim for 10-15 degrees maximum spread

Don't use front negative camber as a crutch

There's one audience I wish would take this into consideration.

[ben]

Scary example from the day job of why adding tyre compliance into roll angle calcs is important...

http://www.caranddriver.com/var/ezflow_site/storage/images/reviews/car/10q2/bmw_m3_gt_race_car-feature_test/gallery/bmw_m3_gt_race_car_photo_4/3669769-1-eng-US/bmw_m3_gt_race_car_12_cd_gallery.jpg

Ben