You know what we do when we distribute our roll resistance between front and rear. And how we redistribute dynamic cornerweights with our driver inputs. Everything we do as driver and engineer with respect to chassis setup and controls operator comes down to the vertical and planar loads on the contact patches.

And by now you know that the typical front wheel drive car is, by virtue(?) of it's front weight bias, and regardless of external appearances, a three wheeled vehicle.

You've seen me refer to tire force variation in some of my writing. What it refers to generally is the response to surface irregularity in the vertical force on the tire contact patch. What it means is driveability and grip.

I think of tire force variation as the micro form of dynamic weight transfer. The big picture is set by springs, bars, and driver inputs. The fine picture is set by damper settings.

One thing we do when we change spring rates is to change the effect of a surface irregularity on dynamic cornerweight change. Double the wheel rate and the effect of a bump is nearly doubled. We balance this cost off against the benefits of a lower cg and quicker response.

But lets restrict our thinking to a fwd car - the outside rear in particular. What's the effect of super stiff rear rates on a three wheeled vehicle on tire force variation? Not much. No effect on diagonal cross weights - there being only one, and nothing you do at the rear affects it. We need only not overwhelm the tire. And, there comes a point when each subsequent increment of spring rate is so deep into dimishing returns it's pointless. I still don't quite grasp the 3000 lb springs on the rear of RSX's - dynamic rear steer or not. Must have been a hell of a gain curve.

It's more complicated at the front - the end we need to work on. Surface irregularities Will affect the L/R front split.

Some basics - "the springs hold the car up - the bars control roll". Rubbish. Means nothing. Makes the ignorant go away scratching their heads.

It's a true statement of fact in the sense that the sprung mass - the chassis - is supported by the springs. And this heavy body, with plenty of rotational inertia about it's various axies, moves relatively slowly. This is the range of velocity we refer to as low speed in damper-speak.

As to bars - "too much bar and you've converted your IRS to Solid Axle". Rubbish. Solid axles have two things against them relevant to this criticism in our context - high unsprung weight, and offside camber effects (lift or drop one end and it affects the camber at the other end). Bar doesn't really add much unsprung weight, and IRS isn't completely immune from offside camber reaction either. Find some other reason to dislike big bars.

For a given single wheel rate the change in dynamic cross weight is the same. This much spring and that much bar, or a little less spring and a little more bar - the same. The tire don't know. And if the tire is happy enough at that single wheel rate, it's gonna be happy at the reduced rate when the both wheels are going the same direction.

Oh? Bumps on the inside wheel? Spring minus bar.

Bumps on the outside wheel? Spring plus bar.

Dips on the inside wheel? Spring minus bar

Dips on the outside wheel? Spring plus bar.

The more bar, the bigger the difference between inside and outside wheel rates - inner softer and outer stiffer. But the stiffer the bar and the softer the springs, the quicker the convergence to the bar zero point and it's reversal. (I think it's in this range of operation that some people are trying to use tender springs on race cars.)

Is this a good thing? For crashing curbs the softer springs and bigger bar may look better. (Pretend that I've next written a bunch of qualifications and disclaimers here - and don't forget to think about the effects of bumps and curbs and such as horizontal inputs/moments about the cg).

Unsprung weight - all that stuff that a bump pushes upward against the spring - "it can't be low enough". Troo Dat! You want to get hit in the chest by a dodgeball or a cannonball?

Hit a bump with one front wheel. Say you got no compression damping - you're going to use X shaft travel. Add compression damping - you use a little less travel, and it still works ok. Add some more - even better. Add some more - uh-oh, too much - harsher and less driveable. At each step too you increase the dynamic weight transfer onto that diagonal. Compression damping is additive to spring rate.

Drop a wheel into a dip. Say you got no rebound damping - the spring pushes the wheel down into the dip with a force that varies strictly as to position and cornerweight. Add some rebound damping - the force on the tire is reduced. Add some more - it's reduced some more. Too much? You goin' slower yet? At each step you increase the dynamic weight transfer off of that diagonal. Rebound damping subtracts from spring rate.

Spring force is position sensitive. Shock force is velocity sensitive. The instantaneous summation of their forces is what we're pushing down on the tires with. In the same way we use the steering wheel and pedals - gently but decisively - so to do we want to treat our tires.

These dynamic weight transfer functions of the dampers must be balanced against the general drivability of the vehicle. Ever drive a boneheads street drag racer with the front dampers drilled and drained? Ever drive a car with no dampers installed? Ever drive a car with ridiculously high damping forces? I have. Terrifyingly great fun. Hell of a way to gain some basic insight.

You know what's great about this stuff? First: there's alot of speed in chassis setup. Second: when was the last time you heard a racer describe his dampers as grenades like you might a hot motor? Suspension is reliable speed. It's relatively low maintenance. It's relatively low cost.

Scott, who's probably just trying to rationalize his neglect of the horses...



Modified by RR98ITR at 9:29 AM 8/10/2004

 

I made some peppered deer jerky this weekend.
It actually came out pretty good.

 

Scott,

You know...it's this kind of mentality that can stunt a racers development.

I hate to say it - but the way you're headin' you may never grow up to be anything more than an ITC driver.

Such a shame. All that potential. Brother Hominid.

But I guess if you're happy....But, I mean: "Damn it Man! You only got One Cam!"

Scott, who only wishes he'd been dreaming that he couldn't get to sleep last night...

 

All this suspension talk nonsense and balh, blah, blah. Wasn't it Mr. Bentley who said something like "everyone knows races are won in the straights"

Claude who warns you to mind your anti's, as in antihp.

 

Claude,

"Yeah, antihp....I think I got too much of it."

Scott, who really just uses this stuff to get to sleep at night...I plop my head down and think a few thoughts about Kaa's, and BAM! I'm usually out...You don't think it has any ill side effects do you?".... I like Mark - he both shares and can be bought.

 

Well I just ordered my copy of the second edition of "An Introduction to Race Car Engineering" which hopefully has all the little errors corrected. As I just changed my driver's side axle, whose inner-joint metallurgical failure I attribute to too much newly-found hp (or perhaps just dumping the clutch too hard), and am thinking of new cams to not feel so thwarted as the GT3 rockets away from me off the corner, I will return my attention to antisprings. But first I have to go through Ch. 15 (Mathematical Analysis) of my first edition and get a better handle on the dynamics of the situation. This will surely help me sleep at night. So many matrices, and so many thoughts on how antisprings could help keep the tire on the tarmac! Oh yes and I also have to figure out how those monstrous 225/45/15's Hoosiers are going to fit in my little wheel wells. And you have time to worry about rebound! Must be a Motonic kind of thing.

 

I'm in a state. Not Catatonic...let's call it Motonic.

So, what, everythings an anti-something now?

Did you get Hands-On Race Car Engineer yet? Comments?

Scott, who is almost ready to race this weekend...but not yet on the Motons..."Don't say anything!"

 

I will try to get off my anti thing. It is just that I was reading about anti-forces in that Ch.15 I was referring to and it must have gotten lodged in my brain. As for Hands-On Race Car Engineer, when I saw the following 2-star review on amazon, I decided to keep my money.

"I did not. I expected to see a book with information on race engineering and how to adjust a car (or bike) to go faster. It seems that the word "engineer" here is rather loosely applied as is all too common these days. The chapter on setup was actually very good, if short and that's why I rated it as I did. The chapter on how to choose a transporter, I could really do without.

It does seem to me that if you like Carroll Smith's books, then this might have something for you. It may fit the bill of something in between. Still, I think it incomplete. It seems to be a collection of nice things a technician would want to know. There isn't the first mention of damper selection of spring setup except that someone should do it.

I quote from the book in one section on testing - it goes over a testing plan (which is quite nice and does point to how things work. Part of the plan states "adjust dampers as necessary" Well, duh - now how and why? In the review of this plan the author states:

"If the engineer was satisfied with the tire temperatures and heat spread ... he would move on to adjust the balance of the car. In this case, the engineer decided to correct the aerodynamic balance first, as opposed to the mechanical."

Nowhere does the author talk in detail about heat spread or how camber affects it, etc. There is mention of data acquisition, describing each of the sensors a bit, but no where is there any example of the data or what it might mean. I expected some analysis, but found none. I can only guess that the engineer in question is someone other than the author. I want the book by that person.

I can't bring myself to recommend any book on car setup, engineering or racing that does not discuss how to choose and adjust dampers, springs and tires. I found nothing beyond basic setup - nothing.
"

Imagine a book that does not tell you what springs to use or how to choose and adjust your dampers. Might as well buy a book on Macrame. What in the world was the author thinking? I wonder what books the reviewer has that make him think this one is deficient in the spring selection chapter?

 

catch22 when was the last time you raced your car?


rr98itr when was the last time you raced your car?

yes....scott rr98itr....you are thinking too much again!!!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RR98ITR &raquo;</TD></TR><TR><TD CLASS="quote">

there's alot of speed in chassis setup. </TD></TR></TABLE>

So it goes...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by chad &raquo;</TD></TR><TR><TD CLASS="quote">catch22 when was the last time you raced your car?
</TD></TR></TABLE>

Actually I missed the last race because Renee busted the budget for that one when she decided to test the flexibility of the armco at Barber last month (note: the armco at Barber isn't very flexible).
But I'll be back in action in 3 weeks, with new tires too!!!
Can't beat $92 Hoosiers.

Scott, who will defend Scott R's right to spend stupid amounts of money to make the white shelf in his garage handle wonderfully, will defend his right to ramble aimlessly about stuff that will likely never gain him as much time as consistent seat time, but also reserves the right to make fun of him for it.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by chad &raquo;</TD></TR><TR><TD CLASS="quote">...rr98itr when was the last time you raced your car?

yes....scott rr98itr....you are thinking too much again!!!</TD></TR></TABLE>


I've raced the last 3 Regionals this year (ok - one was a double) - last one about a month ago. And I'll be racing this weekend.

Thinking too much eh? I'll have to think about that. I'd ask my friend Scott Giles about it, but I think I already know what he thinks, although I don't think he's thought it out properly.

Scott, who wonders if someday I'll be sought out as a guy who still remembers how to think..."We all made fun of him back in the day"...

 

See, now you're confusing the *ability* to think with the *need* to apply such thought.

The mere mention of engineering principles gives my math dyslexic noggin a throbber of a headache. But I bet my car handles just as well, actually probably better, than yours. I haven't even taken the little white Koni **** out of my tool box all year (no, seriously, I haven't).

I think I'll go chew on some deer jerky and do some more wet sanding on my now heartily bondoed left front fender.

Scott, who says this stuff is already complicated, don't make it worse.

 

chad who is just happy to race....be on track...anything!!!

chad who thinks the car is almost ready for road atlanta this weekend....only need new rotors installed and brakes flushed oil changed....and lower the rear a "red" one.....hehehe...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Catch 22 &raquo;</TD></TR><TR><TD CLASS="quote">See, now you're confusing the *ability* to think with the *need* to apply such thought.

The mere mention of engineering principles gives my math dyslexic noggin a throbber of a headache. But I bet my car handles just as well, actually probably better, than yours. I haven't even taken the little white Koni **** out of my tool box all year (no, seriously, I haven't).

I think I'll go chew on some deer jerky and do some more wet sanding on my now heartily bondoed left front fender.

Scott, who says this stuff is already complicated, don't make it worse.</TD></TR></TABLE>

Oh no I'm not. And don't say "need". There's no "need" for any of this. This is all "want".

Sorry bout yur haid throbbin' - maybe you should get it looked at. Maybe drill a hole to relieve the pressure?

Now your car may handle better than mine - whatever that means - but it's probably got more to do with how many fewer pounds you're asking your 225's to push around than with your virginal adjusters.

While yous' a chewin' on your dear jerky cognitate on this: You don't know how much better your car might work with more development (that's thought put into operation).

You've said you're in sight of the fast guys and you've got some time to find. What if your progress stops, and no visiting shoe demonstrates that it's still to be looked for in the driver? Now where are you?

It's awfully easy to say of another driver that he's got some work to do. Who's going to deny that they could always do better. But come a point in a reasonably able and active driver and the remainder is denominated in 10th's at most.

Road Racing automobiles is not like Motocross. The equipment plays a far more significant role in the laptime. You can't give away very much in a competitive class and expect that your brilliance is going to carry you. James Stewart by comparison could win a national on a stocker off the showroom.

Now a guy like Chad doesn't seem to have any problem with the horsepower component of the equation, and that's were alot of people focus their attention. Horsepower fiends outnumber chassis tuners greatly. But $5000 for a set of Motons that will live for years is a bargain compared to a few professionally built race motors that periodically explode.

If what I talk about is wrong - demonstrate my errors. If what I talk about doesn't interest you - ignore it. But to suggest that I shouldn't write on technical topics is very perplexing.

Scott, who's gotta go work on his car...I'm going racing.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Catch 22 &raquo;</TD></TR><TR><TD CLASS="quote">
Can't beat $92 Hoosiers.
</TD></TR></TABLE>

So it was YOU!!

 

with all the thought you put into stuff some big race team needs to hire you.

i don't race yet but i do love doing HPDEs and honestly i wouldn't be content with driving a slow car. reason why i just droped alot on a motor. i had the suspension thing going good, now i think that i got the motor thing kinda sorted out im going to be stuck on the suspension thing for along time.

sometimes i wish there weren't things such as aerodynamic's and all this physics in cornering, just going out there and driving the **** out of your car. ehhh but then that lead to other problems oo well

 

I have this to add.

The entire racing concept is not about the most power, or best suspension setup or brakes.........it is who can use 100% of the tire 100% of the time........everytime around the track.............in the end result of a race is always the person with the highest average lap time..........

So if you are not using 100% of your tires down the straight, or in braking......then who cares if do use 100% of the tires on 30 % of the track...... corners.........what about all the rest? And we all know how important pit stops are. Sticker tires have more rolling resistance always.........it's like carring evrat weight if your car does not have enought power.......

Corners are just there to join the straights together and make the entire act of dancing with the curbs a talent to holding the momentum of the previous turn and not loosing time........but they are the most complicated part of the dynamic event of racing, beacuse it is all a comprimise.

But Motons are good.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RR98ITR &raquo;</TD></TR><TR><TD CLASS="quote">

You've said you're in sight of the fast guys and you've got some time to find. What if your progress stops, and no visiting shoe demonstrates that it's still to be looked for in the driver? Now where are you?

</TD></TR></TABLE>

And theres the rub. Right now I have a car that handles very well. You don't need data acquisition to prove it either, all you need is to take a quick look at the in-car video tape and/or do some segment times. The car outcorners and outbrakes the opposition almost 100% of the time that the driver doesn't make a mistake. Where I get beat is in making those mistakes (I know its hard to believe, but a couple of my regular opponents just don't seem to EVER make a mistake) and in traffic management (mostly mid pack Spec Miatas, which are a massive PITA for an ITC driver). The car also almost unfailingly does whatever I ask it to do and it does it very very well. Its not really tight and its not really loose. It just kind of does what I need it to do.

So... What use would I possibly have in worrying over improving the handling or saving up for a set of motons?
Now, IF (and thats a HUGE "if") I reach the point where the driver is spot on, virtually mistake free, and eating mid-pack Miatas for lunch... And I can't manage to catch the leaders in my class. Well then I'll pull that little white **** out of me tool box and do some test days. Maybe even consider plunking down some money on some pimpy suspension bits.

But, and I ask this in all seriousness (for a change), if the car is handling well, wearing tires well, and fully capable of bagging trophies... Then why, unless you are confident the driver is at his limit of skill and ability, would you spend 5ish race weekends of your budget to improve the ability of an already competent suspension system? This is where the Rinde Forest gets thick for me and I lose the trail.

In other words, if you are confident that you are more competent than your current dampers it makes perfect sense to buy better ones. If you aren't, then focus that effort on having your *** in the seat.

I know, I just "don't get it" because I'm not a person that is driven by the constant need to fiddle with **** that isn't broken. But what the hell, Its a free country.

Scott, who only gives Scott hell because he just can't grasp spending THAT much time, effort, and money on an amatuer race car thats already quite competent, maybe even very good.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Catch 22 &raquo;</TD></TR><TR><TD CLASS="quote">...The car also almost unfailingly does whatever I ask it to do and it does it very very well. Its not really tight and its not really loose. It just kind of does what I need it to do.
</TD></TR></TABLE>

I cannot argue with that. Nope. I really can't.

I have to say that there might be even more to be had, but if I could have said the same for my car, I'd have been much less likely to spend that last wad.

Scott, who's ITR isn't just a car....and not just a racecar....it's a laboratory....and I'm Mad...MAD I tell you!

 

Scott, I enjoy all of your posts.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Dr Pooface &raquo;</TD></TR><TR><TD CLASS="quote">Scott, I enjoy all of your posts.</TD></TR></TABLE>

And Rindes' aren't that bad either...

Good read. But as a monosyllabic reader and thinker, I just like to drive - while chewing on venison jerky. That's as far as my analysis can go.

Greg ~ who really doesn't get the thing about... never mind.

 

uncle scott, what if there was an adjustment you could make to the suspension of the car that would make your mistakes less costly? what if the adjustment made it less likely to make a mistake?

nate

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Catch 22 &raquo;</TD></TR><TR><TD CLASS="quote">...My car currently handles so well that I'm afraid to make any adjustments for fear of messing it up.
</TD></TR></TABLE>

Have Definitely heard that one before. Whether thru buying right, or dumb luck, that's not a bad place to be when your number one priority is pedaling faster.

Scott, who writes in the 3rd person to honor, emulate and perpetuate the inspirational core of the H-T community (they know who they are)...and to create the opportunity to have that much more fun...Mock me all you want Scott Giles! My narcissism shields me from your puny blows!

PS - this is a technical thread. Anybody. Really. Feel free to put it back on topic.



Modified by RR98ITR at 10:43 AM 8/11/2004

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by bulldog_RS20 &raquo;</TD></TR><TR><TD CLASS="quote">

Greg ~ who really doesn't get the thing about... never mind.


</TD></TR></TABLE>

Hmmm.....what could you have been wondering about......Hmmmmmm.

Could it be....TOSSED SALAD!!!!!!

Scott, who must refer you to others for that....Hey, did you race last weekend?