To me, 9/10 means that for a given driver in a given car on a given road with whatever weather conditions - there is enough margin left to cover for small errors or minor course corrections to avoid debris, but probably not big mistakes or sudden changes. 10/10 means you have to be spot-on. Really hard driving on the street approaches 7/10 or perhaps a little more.

Numerically, I think it makes more sense to relate this to lateral g's or perhaps with respect to the "friction ellipse" rather than speed or lap times. That's the definition of upper limit here.


Norm

 

Norm

Thanks "Firiction Ellipse", sometimes incorrectly called friction circle, is the phrase I was looking for. Wikipedia calls it the circle of forces

http://en.wikipedia.org/wiki/Circle_of_forces

If you are at 10/10 ths you are on the perimeter of the circle all the time!

 

To continue the digression I agree with you totally about letting the car past and trying to hang with them. On my last track event an M6 was on my bumper for a lap or so and I let him past. The result for me was the best few laps of the day! Sorry about posting another video but here is it is

http://www.youtube.com/watch?v=gcQyOHsSTDk

If do do the let someone past you of course have to be careful to not end up trying to follow a car driver combination that requires you to drive at 11/10 ths!

And you also have to watch out for V8 powered Miatas!

 

Thanks, I love it too! The pictures from Laguna Seca turned out really well. If anybody is already on the "left" coast or thinking of coming out this way, send me a PM. I've run with a few of the track day clubs in the area and can relate my experiences with the clubs and the tracks.

 

.....i'm your Huckleberry. ; )

 

When I had some training at GM, we were doing auto-x stuff in a Tahoe full size SUV. Fun stuff! Anyway, the 8/10ths -9/10ths thing was something the instructor used to get us started. If I remember correctly, our 8/10ths was no acceleration hard enough to kick the trans into first (their autos start in second unless you WOT) and no tire noises. Then we went to '9/10ths', which was hard accel and slight tire tone. At that point someone learning said "There's no way there is 10% beyond this". He was right, basically. It was just a tool for the instructor to set up how hard we were driving the line. With the street tires, they often emit a fairly solid tone when at the limit of grip; if you start squealing you are beyond and sliding more than gripping. 'Course, how long one holds the tone in a turn indicates how well they are staying at the limit of the tires, so there's more...

One can use 9/10ths & 10/10ths in conversation, but really using lesser ratios is kinda pointless. 9/10ths is leaving room for error, 10/10ths isn't, and it is entirely subjective.

 

I was on Summit Point last Monday/Tuesday. My friend and I are both in the advanced run group driving near identical cars. With the exception of two Radicals we were turning some of the fastest lap times of the group (more the cars than the drivers LOL). We stayed right together, I'd take the lead one session then him on the next. I was threshold braking consistently on one corner and making the tires howl (treadwear 100 tires) on several. I thought I was driving pretty hard. On turn 1 and turn 10 I was leaving a decent margin for error but on other safer corners I was clearly at the limit of traction. So I'd say I was running somewhere around 8-9/10ths. So what does my buddy say? "I was at about 7/10ths". Now either he has a lot bigger cajones than I do and is a lot better driver or the way he and I are measuring it is entirely different. I think its the later.

 

This is why I think it has to be data based as otherwise it is too subjective.