Shocking Truth about Racing

[RaceProEngineer]

Noel and all,

Reading your post about street tires brings up one other very important point. Stating the obvious - street tires, regardless of their speed rating, are not designed for racing. But their "UNsuitability" is not readily apparent.

When asked to provide extreme traction, street tires not only vary widely in their ability to grip, but are quite inconsistant within themselves from moment to moment. On the track, these characteristics can translate into very "tricky" handling. For example, if your rears have a substantially higher friction coeffecient that your fronts, you are going to have "your hands full" under threshold braking. Similarly, if during the last 4 laps the driver has been able to "plant his foot" before the apex of Turn 7, but THIS time doing so produces severe understeer . . . . . well, you get the point.

Race tires, in general, provide much higher levels of traction than tires made for the street. But equally important, the best of the racing rubber offers supreme consistancy, which in turn inspires confidence, which in turn translates into lower lap times, etc.

None of this becomes apparent until one starts driving the car at, or near, its limits!

Ed

[Noel]

Ed,

I agree with your comments to a point. I used to use R compound tires about 9-10 years ago when I autocrossed a lot. I also used them 7 years ago for my first year of track driving. It was only when I switched back to street tires (Z rated, etc) that I was able to really learn how much the sticky rubber was hiding my mistakes and making me feel faster than I actually was. After continuing to use streets for the last 6 seasons, I can say that I would not be as good a driver without doing this. I'm still faster than a fair number of guys that use race tires with faster cars. And I truly love when it rains, as I am pretty comfortable with slipping and sliding around the track.

IMO, there should be a minimum number of track days of experience required (Say 40 or so) before a driver is allowed to use anything other than streets. Or they must reach a certain group first, lets say White or Black.


However, all that said, I'm switching to Toyo RA1s this season, but will still use my streets too, mainly because I really can't keep up with the other high HP, sticky rubber laden, ABS and PSM equipped 996s, GT3s and 997s with my 172 horsepower and skinny street tire relic and I need all the help I can get.

[Rory Mckenna]

When is the last time you were at Putnam or Mid Ohio Noel?
What are your fastest times there at those tracks with steet rubber?

[gestalt1]

i kind of disagree with noel, getting good on street tires does not mean you will be better able to go faster on race tires. race tires can be pushed to 95% and feel comfortable, street tires start feeling inconsistant at about 80% of there max. i had a older corvette that i raced on street tires and switched to race tires with no other changes. the race tires were much faster obviously but i was also able to drive much closer to the max grip of the tires and feel confident. that was the big difference to me, not the added grip. driving ability counts far more than tire grip. i think carrol smith suggested it is wise to learn on a properly set up race car with low horsepower such as a formula ford. the reasoning is that you can focus on driving rather than adapting to the uniquness of a particular car. the skill you learn in getting a fwd production car on street tires does not translate to a well prepped race car. the skills learned on a race car will always translate to a street car and you will know what needs to change on the street car to make it faster on the track. i have been racing production based cars for the past 10 years all in different states of prep, going to skip barber's school and driving there formula cars (admittedly on street tires) was an eye opener and something i should have done years ago.
-matt

[Noel]

Originally Posted by Rory Mckenna

When is the last time you were at Putnam or Mid Ohio Noel?
What are your fastest times there at those tracks with steet rubber?

at Mid-Ohio last May with the Potomac region and Drove Jay North's SC with a 3.6L on streets and I remember a 1:48.????, but I need to check with Jay on that, as he and I were comparing times. That was actually the first time I have ever really timed myself so I really couldn't tell you any other times.

BTW, is that Eric McKenna??? If so, I hope to see you at Mid-Ohio this May, as I plan to tow out there from Boston.

[Rory Mckenna]

Originally Posted by Noel

at Mid-Ohio last May with the Potomac region and Drove Jay North's SC with a 3.6L on streets and I remember a 1:48.????, but I need to check with Jay on that, as he and I were comparing times. That was actually the first time I have ever really timed myself so I really couldn't tell you any other times.

BTW, is that Eric McKenna??? If so, I hope to see you at Mid-Ohio this May, as I plan to tow out there from Boston.

You betcha I'll be out there.... Yes, it's me Noel.. Rory is my daughters name..
She turns One in a week.

[Noel]

Wow, what a cutie. She definitely has your eyes.

I'll send you info on the Potomac Region event when they release their calendar for the year.

Looking forward to seeing you.

BTW, what times were you running at Mid-Ohio???

[rfn026]

Here's some really hard core tech stuff on stiffness. The paper is over ten years old but the information is still valid.

http://www.ces.clemson.edu/%7Elonny/pubs/journal/sae983053.pdf


Richard Newton
Autocross Performance Handbook

[RaceProEngineer]

Richard,

Thanks for the great addition. While the topic of that paper certainly applies to effectiveness of suspension in general, and to many of the details we have discussed in this thead, I believe it is too valuable an article to remain "buried" here, on the 3rd page of a shock absorber thread.

I suggest you open a brand new thread, with the title something like "Building a Cage? Look here First!", and show the link, along with appropriate cautions, such as:
[1] Results were obtained without a mounted motor or trans, which would already strengthen the front clip.
[2] Most 911 chassis would flex "backwards" from the NASCAR roller, ie. need more triangulation in the "rear clip".
[3] A unibody is NOT a ladder frame.

[n] many others . . .

This was a great find, and deserves its own topic, especially for those who are welding up their own cages over the winter!

Ed LoPresti

[jluetjen]

That's a great paper, but I'd caution readers about cutting and pasting any of their solutions into a 911. They are two completely different animals for the reasons that you listed. But that doesn't mean that the paper is worthless. Most readers on this board could learn a lot from the way that the authors approached the problem.

- Design a base frame in CAD. If possible compare to reality
- Define the key criteria for "success". Torsional twist? Suspension mounting point displacement? Weight?
- Add or subtract tubes while measuring the affect on the key torsional criteria

It was really an excellent example of an optimization project.

[DG624]

Ed I am looking for a better solution...I have the Koni Yellow Sport version but they are difficult to adjust for best benefit. It is hard to know if I am overpowering my springs by too much shock or not getting the proper front to rear ratio.

I was thinking of getting them revalved (over 15 years old) and want to know how best to measure the existing motion ration of the car (shocks to wheel ratio) and the bar rate. I wanted to get something that fits the current suspension and corner weight. What factors should I consider?

[The Watson]

Subscribed

[burgermeister]

It's been a while since that discussion died down ... ;-)

[BRO]

Really helped my understanding. Thanks!
I started door to door racing this year and knew set up was going to be a big challenge for a rookie racer. Looking forward to sway your bar discussion.
Interestingly I had a sway bar mishap that cost me a podium position in my official first race. I had worked my way up to third with two laps to go and then spun in an unusual place. It turned out that my newly installed rear drop links were too long and the bolt at the bottom hung up on my left rear control arm causing a sudden and negative change in handling in a low speed (luckily) right hander.

[Dave at Pelican Parts]

Since the post is from 13 years ago, you may have to do some searching through the archives to see if the sway bar discussion ever happened. I don't remember if it did or not.

--DD

[winders]

Originally Posted by Dave at Pelican Parts

Since the post is from 13 years ago, you may have to do some searching through the archives to see if the sway bar discussion ever happened. I don't remember if it did or not.

--DD

Look at post #32 of this thread.......