Sam

I'd say 1.2 G is pretty d**n good!

My car can pull up to 1 G with the KDWs so is the .2 difference in ultimate Gs pretty much all in the tires? I'm not comparing myself to you in terms of driving as I don't get to 1 G very often but am trying to determine the real effect of the tires at the instantaneous limit.

 

I run 285/30/18 and I find they really limit my 2nd gear top speed because of the increase in effective gear ratio. Do you notice the same thing? That tire size is basically 2" shorter than stock.

 

There are times you'll see spikes higher. That last video was on good concrete, but all the right hand turns are way off camber, with the left turns being some sort and varying degrees of on camber (it's an old B52 alert pad sloped for drainage). If you look back at other videos you can find even higher numbers on other surfaces.

And yes, tires matter that much. The suspension has to handle it, and yours certainly would have no issue with that Colin. I tell folks all the time, the tires are what touch the ground, and Michael Jordan--great as he was (is probably still) could not have done the things he did if you made him play in dress shoes or even normal cross-trainers, right?

 

The 295 is somewhat taller which is one reason I run them and not 285's anymore (but not the only reason). Also the Rev-limiter in a Shelby GT is different than that of a Mustang GT, and so even when I get to it, things don't just shut down like on a Mustang GT. There is a soft touch limiter that you have to pull through first (and you can, but it's rare). In 2007 @ the Milwaukee Tour I had to short shift to 3rd because I would have run out of 2nd while making big fast offsets. In fact someone did, the car shut down and they went for a HUGE ride.

 

I've never had a problem with the car shutting off, but I'm running a Bama tune with an extended redline to 6498 rpm. When I hit it, which is every course now, the engine just mantains the top allowable revs. I've only once gone into 3rd and that was at the end of a course when I knew I would not have to downshift.

I won't be running this size again. 275/40/17 seems like the best option.

 

Took my GT to Washington DC yesterday and ran against proven competition in Shelby GT's----and won FS outright. Note, I don't think the GT is a better car, but I wanted to see what I could do on that lot and see if I could prove that a GT is a competitive car. I did. FWIW, 4 of the 8 trophy winners @ Nationals were there (and always run there).

I also Paxed 4th out of 245 cars, including multiple other National level winning cars and drivers.

 

To each his own. I wouldn't touch a 275/40-17 over 18". All else being equal the CG is way higher, and if I can't get it down without messing up geometry (and tire size does that), I want it.

I backed to backed taller and shorter tires in 2007, and was MARKEDLY quicker on the shorter tires--repeatably so.

 

Yes the CG is worth mentioning for sure. For me the change is due to practical reasons including expense, ground clearance in rough parking lots and the fact the previous owner ruined the car for auto x by adding 4.10 gears. Now shifting into 3rd is required on every course with these short wheels, while I just want to concentrate on driving.

 

Forgot you had 4.10's, that sucks.

 

Track Report - just spent 2 days (days 9 and 10 for this year) on Summit Point main course. Absolutely beatutiful weather - 80s with low humidity. Summit is known to be a bumpy track. Turn 1 at the end of the long front straight was, in the past, particularly bad. So...they put concrete down. We were the 2nd group to drive on it. Tons of grip in the dry but it would be kind of dicy in the rain. Turn in is pavement, then you hit concrete and then track out back on pavement.

Some nice cars: two Radicals - those things are wicked fast. There was a Mercury Marauder (sp?) vintage stock car - 500+ cubic inches of rolling thunder, very cool. Honda NSX. Usual assortment of BMWs, STIs and EVOs. One of the instructors had an old MG, he was of course slow but having a great time. A 400 HP turbo'd Civic blew up and sprayed his texas tea all over the track in the intermediate group. In the advanced group we had a red flag - fellow put his STI into the gravel trap on turn 10 (entrance to the main straight) and rather than staying off course, tried to get back on and ended up head on into the tire wall on the opposite side of the track, 1/3 of the way down the straight. He was ok, thank goodness, but the car was a mess.

I ran Nitto NT01 in the front and 555RIIs in the rear (with used rubber you take what you can get). Tires worked great. Excellent grip, good slip angle (can easily hang the rear end out), very predictable. Carbotech XP10/XP8.

Between myself and a friend (running identical cars) we cracked three stock rotors over the two days. We were occasionally hitting 140 on the front straight with a very hard brake for turn 1. Turn 4 is also a very hard brake and Turn 10 a good medium hard. This is what happens when you subject lousy Chinese metallurgy to high stress. I ran out of rotors and couldn't run the final session! You sure can feel it through the pedal - bad vibration. Had to drive home like this.

I'm really starting to feel the limitations of a stock brake system. The brakes on my Vette are almost identical to those on the GT. PBR two piston, floating caliper. Same size rotor. In the past I have wax'd on about how this system is suitable for most drivers with the simple pad, fluid, ducts and SS line upgrade - and indeed they have served me well. However, as I've progressed in run groups and the accompaning increase in speeds I've grown less confident in their ability. Time to start looking into that BBK.