Comp Clinic Handling Presentation

[DaveW]

I've been getting so many requests for this even though it is somewhat hidden in the FF forum, I thought I should post here, also.

If you want a copy of my handling presentation, it is attached to post #8 below, so you can download it from there.

[Jon Jeffords]

Dave, is there only one version of this document, or did you update or modify it over the years? I know I have a really old version somewhere in my basement, but it must have been one of the early versions as its chiseled into two large stone tablets.

[DaveW]

It's been repeatedly updated - the last update was in early 2015.

[Garey Guzman]

Would you want to upload it as a PDF or would you rather check the requests?

[DaveW]

Would you want to upload it as a PDF or would you rather check the requests?

Hmmmm...

I hadn't thought of that. I didn't think I'd have this many requests. I have had a LOT!

I can't upload it as a PPTX - error message "invalid file". I think my wife's Adobe can convert it to a PDF.

Hopefully I can upload a PDF and it's not too large since it said that is a valid file type.

[Garey Guzman]

Send me a copy, I should have the necessary tools here at work. I assume you still have my email address from the drivers suit thing last year....

Garey

[DaveW]

Send me a copy, I should have the necessary tools here at work. I assume you still have my email address from the drivers suit thing last year....

Garey

OK, will do.

Thanks!

[Garey Guzman]

It works for me! I hope this will save you some time on replies for this excellent document!

Thanks again Dave. Your support to the open wheel community is admired and appreciated!

[DaveW]

Thanks, Garey, I appreciate it. I emailed close to 50 copies already, so this really helps!

[Garey Guzman]

Thanks, Garey, I appreciate it. I emailed close to 50 copies already, so this really helps!

Can't believe you sent out 50 before this! Another example of your great willingness to help! I wonder how fast it will get to 100 downloads?!?!

[DaveW]

Can't believe you sent out 50 before this! Another example of your great willingness to help! I wonder how fast it will get to 100 downloads?!?!

Maybe not quite 50; I stopped counting after 25.

[hdsporty1988]

Can't believe you sent out 50 before this! Another example of your great willingness to help! I wonder how fast it will get to 100 downloads?!?!

An indication of two things. First and foremost as stated Dave's willingness to help and second the great respect people have for his knowledge. Reminds me of the old EF Hutton commercials, when Dave Weitzenhof offers information, people want it!

[CF56]

I've been getting so many requests for this even though it is somewhat hidden in the FF forum, I thought I should post here, also.

If you want a copy of my handling presentation, it is attached to post #8 below, so you can download it from there.

I attended one of Dave's NEOhio clinics many years ago. What a great day!

[EricP]

Can this be “pinned” in Getting Started?

I was one who Dave sent this to via email. Very appreciative. And it’ll save my Carroll Smith books from getting more worn out...

[scott fairchild]

[Garey Guzman]

....it’ll save my Carroll Smith books from getting more worn out...

Speaking of Carroll's books, this one is a MUST GET. Quick summary of how things work which I also use as a driver tool in that it reminds what I need to be conscious of to make good changes:
https://www.pegasusautoracing.com/pr....asp?RecID=163
(FYI, cheaper than Amazon)

I got to help Carroll with this book (in that he asked me to draw something and I drew it).

[racerdad2]

Thx Dave ! Thx Garey ! A great resource !!

[old 59]

Thank you DaveW and Garey.

[Eric Little]

Maybe not quite 50; I stopped counting after 25.

Whatever the number from the present batch, add at least one to that. Dave sent this to me a couple of years ago and it has been a great resource. It has not replaced me hiring an engineer to do set-up work (there are few substitutes for actual experience) but it does help me to better understand what was changed and why it was changed. A very valuable document that provides assistance in many ways. Thanks Dave!

Eric (if I can now just figure out which direction I turn the shock adjusters to stiffen and soften, I will be set) Little

[sathorp]

I attended one of Dave's NEOhio clinics many years ago. What a great day!

I went to a NEOhio Clinic back in 2007 the first year I joined SCCA. They were held at the IX Center during the Autorama, it’s where I meet Jeff Blumenthal. That was a great day, forgot all about that Clinic. I have this presentation somewhere, but I’d have to go dig. Thanks Dave!!!!

[steve zemke]

Thank you Gary and Dave. Not quite as good as the lectures Dave gave at the NEO clinic. I went three times. Each time Dave's presentation was the highlight of the day.

[jhaley]

As a young SCCA a racer many moons ago, I always looked up to Dave and the other Runoffs champions. Thanks for your help Dave!! If you are ever in San Diego, I would love to buy you dinner, a cocktail and talk racing. I got to meet another racer I looked up to (Pratt Cole) while in Napa last weekend.

[DaveW]

Speaking of Carroll's books, this one is a MUST GET. Quick summary of how things work which I also use as a driver tool in that it reminds what I need to be conscious of to make good changes:
https://www.pegasusautoracing.com/pr....asp?RecID=163...

I just bought this from Pegasus so I could look it over and maybe learn something new. I agree that it is helpful in that it states things clearly, but for formula cars it seems especially lacking in one area: the very important effect of proper chassis attitude control.

In particular, a lack of rear ride height control, especially in rebound, is one of the main causes of corner-entry instability. This due to the damper/spring combination being unable to keep the rear ride height and roll center height (RCH) from rising due to weight transfer during hard brake applications entering corners. He does mention RCH, but doesn't discuss in any detail the effects of dynamic RCH changes.

There are other places where I think the advice has to be taken carefully knowing that it doesn't always apply, but in general it is useful. OTOH, one can say the same thing about my advice - sometimes many things can cause similar issues and it's not always obvious which set of changes will solve it.

[Garey Guzman]

I think Carroll was working with the idea that this little helper was to be a general guide for all racers and not necessarily a complete analytical handbook for any specific race car layout. I use this to remind me of things while my brain is still in foggy "driver" mode and get me back to engineer mode.

[DaveW]

I think Carroll was working with the idea that this little helper was to be a general guide for all racers and not necessarily a complete analytical handbook for any specific race car layout. I use this to remind me of things while my brain is still in foggy "driver" mode and get me back to engineer mode.

Of course, you are correct. But since this is a formula car section of ApexSpeed, I thought it would be relevant to point out that it did not always apply to our types of cars. That's not to say it's not useful, only to be aware that for formula cars and similar the advice has to not be always taken as gospel.

[captain_pants]

Dave, can you expand on what you mean by rear ride height control? Are you speaking of increasing stiffness to reduce instantaneous ride height change while braking/accel/bumps? Or damping to control oscillations?

Corey

[DaveW]

Dave, can you expand on what you mean by rear ride height control? Are you speaking of increasing stiffness to reduce instantaneous ride height change while braking/accel/bumps? Or damping to control oscillations?

Corey

Long explanation below, so bear with me:

It's a combination of both wheel rate and damping. With soft bias tires it's not nearly as important/difficult as it is with hard-compound radials.

With soft bias tires, given that their compounds typically have more adhesive grip than the hard radials, partial unloading does not reduce their grip nearly as much as the harder compounds used in spec radials. So you can get away with more rear ride height (RH) change (and other setup issues) in rebound.

For spec radials, and radials in general, one needs more negative camber and a low roll center height (RCH) in order support lateral load in cornering and to put power down. So one wants to have a fairly-low wheel rate so the rear RH and RCH decreases with weight transfer due to acceleration.

During braking, weight transfer away from the rear makes the rear RH and RCH rise, and camber decrease, more with low wheel rates. This makes braking during corner entry (trail-braking) difficult (the car wants to snap oversteer) if this rear RCH rise is not tightly controlled. One would like it not to increase at all, but of course, that means the rear would be too stiff in rebound to allow good grip. So it is a fine balance between RCH control and loss of grip due to being too stiff (over-damping, too much wheel rate, etc.).

[alangbaker]

Long explanation below, so bear with me:

It's a combination of both wheel rate and damping. With soft bias tires it's not nearly as important/difficult as it is with hard-compound radials.

With soft bias tires, given that their compounds typically have more adhesive grip than the hard radials, partial unloading does not reduce their grip nearly as much as the harder compounds used in spec radials. So you can get away with more rear ride height (RH) change (and other setup issues) in rebound.

For spec radials, and radials in general, one needs more negative camber and a low roll center height (RCH) in order support lateral load in cornering and to put power down. So one wants to have a fairly-low wheel rate so the rear RH and RCH decreases with weight transfer due to acceleration.

During braking, weight transfer away from the rear makes the rear RH and RCH rise, and camber decrease, more with low wheel rates. This makes braking during corner entry (trail-braking) difficult (the car wants to snap oversteer) if this rear RCH rise is not tightly controlled. One would like it not to increase at all, but of course, that means the rear would be too stiff in rebound to allow good grip. So it is a fine balance between RCH control and loss of grip due to being too stiff (over-damping, too much wheel rate, etc.).

Very interesting, Dave...

So assuming my car was well set up to run the spec radials, then the chances are that for the American Racers we run as a spec tire here in BC, I probably had too much rebound damping in the setup in addition to spring rates that were too high (particularly too high, because the last place the car was setup to run included the high-banked portion of the Texas Motor Speedway road course), I've probably got dampers that are set up too stiff.

Assuming I got a well set up car, that is...

[DaveW]

Very interesting, Dave...

So assuming my car was well set up to run the spec radials, then the chances are that for the American Racers we run as a spec tire here in BC, I probably had too much rebound damping in the setup in addition to spring rates that were too high (particularly too high, because the last place the car was setup to run included the high-banked portion of the Texas Motor Speedway road course), I've probably got dampers that are set up too stiff.

Assuming I got a well set up car, that is...

In our (Steve L's and mine) experience, going from hard radials back to almost any bias tire seems to be a lot easier than going the other way. I.e., it's a lot easier to set up for bias than radials in terms of necessary damping and wheel rate. The major change to go back to bias is to take out most or all of the negative camber. The radial setup otherwise is likely to work pretty well for bias tires w/o much change.

Of course, fine tuning any setup is likely to improve it, so there would certainly be other changes to optimize even the bias setup.

[alangbaker]

In our (Steve L's and mine) experience, going from hard radials back to almost any bias tire seems to be a lot easier than going the other way. I.e., it's a lot easier to set up for bias than radials in terms of necessary damping and wheel rate. The major change to go back to bias is to take out most or all of the negative camber. The radial setup otherwise is likely to work pretty well for bias tires w/o much change.

Of course, fine tuning any setup is likely to improve it, so there would certainly be other changes to optimize even the bias setup.

Well, I got some good information from David Clubine for a basic setup (reduced spring rates from 440f/900r to 250f/440r, ride heights, droops, toe and cambers of course), and the car was a lot better after that (my first weekend I had only enough time to get the cambers close and make sure the corner weights were alright). In fact, I ran a lap in qualifying faster than last year's lap record. So I figure I'm close.

I think in the off season, I'll have the shocks (Penske triple-adjustable) serviced and then dedicate first dry test day to trying to dialing them in.

[DaveW]

Were the radials your car was running street treaded radials? If so all my comments about going from radials to bias are off. Soft sidewall treaded street radials are a whole different animal.

[alangbaker]

Were the radials your car was running street treaded radials? If so all my comments about going from radials to bias are off. Soft sidewall treaded street radials are a whole different animal.

I bought it off a guy in Texas, and now that I'm thinking of it, it was last run BEFORE the spec tire came in, so strike what I've been saying. :I

[Charles Warner]

Speaking of Carroll's books, this one is a MUST GET. Quick summary of how things work which I also use as a driver tool in that it reminds what I need to be conscious of to make good changes:
https://www.pegasusautoracing.com/pr....asp?RecID=163
(FYI, cheaper than Amazon)

Economically, go to Carroll's website (www.carrollsmith.com/books). To wit:

Amazon Prime (i.e. no shipping) - $21.95
Pegasus - almost $28.00 with shipping (depending on your location)

Carroll's site - $15.95 plus $5.00 shipping.

[DaveW]

Economically, go to Carroll's website (www.carrollsmith.com/books). To wit:

Amazon Prime (i.e. no shipping) - $21.95
Pegasus - almost $28.00 with shipping (depending on your location)

Carroll's site - $15.95 plus $5.00 shipping.

Pegasus shipped mine USPS - $14.99 + $6.80 shipping = $21.79, 84 cents more than Carroll's site's price. Carroll's site's price still is the best I've seen.

[Garey Guzman]

I'm not sure who's running "Carroll's" site. Maybe his son Chris? I guess I should have pointed to that site since the man gave so much to racing and me personally.

[mark elder]

This resource is fantastic, thanks for sharing.

Can someone help me? My FF (RF91) has lovely balanced turn in, is neutral at the apex and we have power induced oversteer. I tune the oversteer with rear ARB changes; 10mm change is very noticable for the exit but the driver does not seem to notice the change for turn in.

Where does rake come in here? In the past I might have altered rear ride height with (say) half a turn on the rear pushrods and this would quickly sort exit oversteer.

I guess my puzzle is both rear ARB and rake alter exit oversteer/understeer but when should I use one tool vs the other. Clearly I want to keep my nice turn in while having a balanced exit.

Thanks

Mark

[mark elder]

thoughts anyone?

[Garey Guzman]

thoughts anyone?

Adding rake (raising the rear) transfers more weight to the front axle. With your exit oversteer, that little extra is giving a little more weight, and a little more grip, in the front during acceleration squat.

[DaveW]

Adding rake (raising the rear) transfers more weight to the front axle. With your exit oversteer, that little extra is giving a little more weight, and a little more grip, in the front during acceleration squat.

Actually, the weight transfer is there, but it's a relatively small part of the balance equation resulting from raising the rear. A much greater effect is raising the rear roll center, and, in effect, adding an additional instant-effect (happens instantly, doesn't need to wait for roll to occur) lateral rear load transfer from inside to outside tire.

Quote from my handling presentation roll center height discussion:
---------------------------------------------------------
Rubber coefficient of friction depends in part on the time rate of load variation –i.e., too fast, and the tread rubber cannot fully conform to and interact with the road surface, and grip will be reduced. Higher-hysteresis compounds are inherently, due to their greater damping coefficient, slower to conform to the road surface, and thus are more affected by friction and RCH.
•Both suspension friction (load increases before motion can occur) and too-high roll center (always-present geometric roll stiffness) will result in almost immediate transfer of load from inside to outside tire as soon as cornering force begins.
•Conversely, load transfer due to spring rates plus swaybar stiffness develops only as the chassis roll angle begins to increase, i.e., more slowly.
--------------------------------------------------------------------------

[billtebbutt]

In our (Steve L's and mine) experience, going from hard radials back to almost any bias tire seems to be a lot easier than going the other way. I.e., it's a lot easier to set up for bias than radials in terms of necessary damping and wheel rate. The major change to go back to bias is to take out most or all of the negative camber. The radial setup otherwise is likely to work pretty well for bias tires w/o much change.

Of course, fine tuning any setup is likely to improve it, so there would certainly be other changes to optimize even the bias setup.

That was exactly my experience at the 50th, Dave. I didn't change a single thing from the Toyo radial setup on the RF90 to go to the treaded Hoosiers, and the car was sooooooooooooo easy - there was a pile of time left on the table at Road America. Just kept getting quicker and quicker every session.

cheers,
bt