THSCC Forums

FYI for folks wondering about the grip at Greenville compared to Laurinburg:

This is from GEEZ data taken in Miles Beam's AS Corvette on Kumho Victoracers on my last runs at both sites so the tires were warm.

Greenville:

Peak left: 1.31 g's
Peak Right: 1.28 g's
Peak Brake: 0.83 g's (Miles trusted his brakes and got 1.02 g's . . . and the class WIN )

Laurinburg:

Peak left 1.35 g's
Peak right: 1.17 g's (probably due to driving rather than car/surface limits)
Peak brake: 0.95


FYI last November in Greenville with very cold (mid 40's?)pavement/air, WIND, and OLD race tires on my formula ford I got the following numbers:

Peak left: 1.62 g's
Peak right: 1.28 g's
Peak brake: 1.24 g's

I think that Greenville pavement when warm and dry has plenty of grip.

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Dick Rasmussen

FS 50 2018 Mustang GT

maybe but i was slipping and sliding all over the place in greenville while for traction then i knew what to do with in laurenburg. Thats what it felt like at least. Lateral G's aren't really a good indicator of traction anyway are they? Where in the coarse did he reach these numbers?

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the dude abides

05 black M3

definitely noticed a difference in grip from morning to afternoon. it was dry and faster in the afternoon. but i am sure i am just stating the obvious here.

Dick,

Thats some REAL good data. I hope you have your GEEZE cube out at the NEXT Greenville event. It should be hotter and dryer, I would love to see the results!

Do you have any data from a Sanford event?

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02 Focus SVT
STF 9

Luke,

I'm not sure what you mean about lateral g's not being representative of traction. Traction in my understanding means the same as "grip" which results in lateral, braking, and forward accelation potential. I only reported the lateral and braking g's since forward acceleration is hard to compare between cars (think power and gearing) and the course design. The start line traction would be hard to compare since there was such a short distance to the first corner at G'ville.

Edit to add in response to another question: The peak g's are generally at transitions (slaloms, lane changes, etc.) but at G'ville they also show up in all three 180's.

All that said, it is possible that if your car had "normal" (not Azenis, etc.) street tires that they might benefit more from the relative "roughness" of L'burg compared to the relative smoothness of G'ville. Conversely the "stickier" tires may not "need" pavement roughness for grip.

Ryan,

As far as data for Sanford, I may have some. What year did we start running there? Event dates will help me find the data on my computer

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Dick Rasmussen

FS 50 2018 Mustang GT

I am no expert, but I would agree. I watched a number of cars on "R" tires (which some people say don't have that much of an advantage on surfaces like Greenville) and I could see that they had much more grip than I was experiencing. I am not running the Azenis, but the tire one step back in their line (Falken 451).

But while I feel I generally am limited by HP most of the time, I felt like it was a lack of grip (particularly at the front) that held me back at Greenville. I also didn't feel like it was "slick". Just less grip than elsewhere. Also by looking at the condition of the tires after each run, you could tell it was not Laurinburg. The roughness of Laurinburg leaves distinct wear marks while the smooth surface at Greenville looked more like aggressive highway mileage.

I have a GEEZ and I didn't use it much last year. I will have to use it this season and try to keep track of some number like Dick is producing.

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Richard Casto
1972 Porsche 914
2013 Honda Fit Sport
2015 Honda Fit EX
http://motorsport.zyyz.com
Money can't buy happiness, but somehow it's more comfortable to cry in a Porsche than a Kia.

Richard,

FYI I have used GEEZ a lot and have found that the most value (for me) comes from comparing various parts of runs after I get home to see where one was faster or slower than another. Especially useful if I "think" some part of a run would have been faster than another run but mistakes elsewhere made the total time slower. It is also useful to figure out why a run I thought would be faster wasn't. With two drivers it is also useful to find out where the differences in style, etc. "help" or "hurt".

Dick (currently trying to figure out how to drive as fast as Miles )

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Dick Rasmussen

FS 50 2018 Mustang GT

I think that Greenville is a good physics lesson.

In general (Teflon excluded) the static coefficient of friction is greater between two objects than the sliding coefficient of friction.

I think that a smooth site (glass smooth) like Greenville can easily generate the same static numbers, but the sliding friction is MUCH lower.

What does that mean? Smooth drivers win!

In Laurinburg you can get the tires sliding and recover pretty quickly (because the sliding grip is still good), in Greenville, once you overdrive the tires they are done and you have to get good and slow to get them back.

Scott

Ditto to what Scott said, speaking from experience.

Dick, you crack me up!

What Dick didn't mention is that I drove second, on warmer tires, both heats. So, I had some advantages that he didn't. He succeeded in his mission to help me get a little quicker. I'm just trying to be a good student. Maybe someday, I'll be half as good as he is. He's helping me to realize how silly some of my thoughts are about how to drive and attack a course. Slowly, little by little, some of my foolish thinking is leaving me.
Dick is also having to adjust to a car that is more than twice as heavy as what he's used to. I suspect one of his biggest challenges is to slow everything down enough from what he's used to.

Back to Saturday.. I knew the first time that I walked the course that it would be fun to drive. Patrice and Art did the best job I've seen in a long time of putting a great course on a small lot. I also knew that it would require picking out key cones waaaaay ahead of time and knowing where they were. Even so, I still blew by my braking point about 30 feet on my first run for one of them.

I have to agree with Dick. The grip at Greenville was as good, if not better than any asphalt site we've had. I wonder if it will be even better in the summer. That site really is very temp dependant as to what the grip is like. There was a huge difference from morning to afternoon. The great thing was- it was consistent across the site (except for the morning puddles in the first heat). That meant I didn't have to worry about hitting slick spots, which helped to build confidence in the risky areas.

I was praying for it not to rain and even for there to be a little sun in the afternoon. I was delighted to see the nice weather! A little sun on that shiny black surface goes a long way toward raising surface temps.

We need to make sure next year that any Greenville events are after April and before October!

AS is turning out to be a fun class this year. On any given day, I think there will be three people within .2 tenths in the first three places. That's pretty decent competition for a local club. Of course the third one is Rick, and he's quick enough to give both Dick and I quite a challenge. Now, if Graham would come back and play with us again, there'd be four. We need to get Mitch to come play with us in his Boxster. Mitch, park that BMW and bring the Boxster out! This will be a great year to learn to go faster.

By the way, if any of you are autocrossing this year in a competitive class, enjoy the benefits of that. There is nothing like close competition to make things fun and interesting. I have had years where there was nobody else in the class to compete against, and regardless of how well or how badly I drove, those events just weren't quite as much fun.

Thanks again to the fine crew that made the last event so much fun. Excellent course and a very, very well run event.

Miles

I couldn't agree more. During my first course walk, I was stunned by how much bigger the site seemed than last November, it literally felt like twice the space. Part of it was probably due to the lack of cars parked along the inside of the back fence, which I'm sure forced significantly more runoff room last November, but I think a big part of it also was due to the course design. The course Patrice and Art (and others?) put together on Saturday was truly outstanding. They somehow figured out a way to make a relatively small lot feel much larger. Great job, guys!

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Keith Q.
2008 Top Gun
http://www.youtube.com/watch?v=KmX8XuZ_DCo&NR=1

I agree, I think the site owner now understands what we NEED. There was only one vehicle on the site when we started setting up and that was gone by the end of the day.

I will throw this out, now that we have a FULL autox under out belts. What is the viability of pitting outside the fence (where the car show was) and using the front parking and the back lot for the course?

I know T&S will not be able to see the whole course, and probably a multitiude of other problems. But could it be done?

On another note, we currently do not have event chairs for the August event in Greenville, we desparately need 2 kind souls to step up to chair this event. It is currently a Saturday event with 24 hour/late night possiblities. If you have ever wanted your chance to design your own course, here it is!

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02 Focus SVT
STF 9

I can't say if that would work or not, but I can say the grid was short of space. So it could use some loving. There was piles of cars and it was unclear as to what you was supposed to do (where was A and B, etc.). There was some type of announcement during the drivers meeting about how Grid was supposed to work, but I was unable to hear it. Regardless, the grid seemed to work OK and I personally didn't have any problems as we had a two driver car and it really didn't matter if we was in A or B as we needed to be in both for each set of runs.

So maybe grid up front (where pit was on Sat) and course in back might work better. You could maybe even move the start back toward where the grid was on Saturday.

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Richard Casto
1972 Porsche 914
2013 Honda Fit Sport
2015 Honda Fit EX
http://motorsport.zyyz.com
Money can't buy happiness, but somehow it's more comfortable to cry in a Porsche than a Kia.

I would vote for keeping it the way it was this time. I'd rather have my stuff on the pavement, inside the fence than have an extra few turns added to the course. Of course, I didn't really notice if we were using all of the available space for pitting, so if we could stay inside but use some of the space on the left, I'd say go for it.

The timing people and safety experts might have a different opinion, though.

i vote for pitting inside the monitored gate access for sure.