What Wheels/Tire set up on your GT body race car? Options

[jmz]

What's everyone running for wheels and tire size on their race cars?

Do you go with a staggered setup or square?

What size wheel?

What size tire?

What do you run for rains?

So far I've tried

15x8&9 with 245x40x15 DOT comp tires on all four corners Maxxis Victra RC-1

16x10 with slicks on all four corners. Dunlop 265x60x16 slicks


I'm most likely going to run 16x8&9 next weekend with 245x45x16 on all four corners with RA-1s.

I've got some 15x9&11 that I may try down the road with my local club

and when I run COTA with SVRA later this year I'll have to go to 15x8 on all 4.

I'm new to this car and am still learning it and learning to race.

[Cracker]

Regarding the spoilers, splitters, spoiler and wings....

My on-track experience leads me to believe:
1) The duckbill spoiler is of no tangible performance value but it does greatly help the aesthetics of the rear on a 914. That air is dead as dead as can be...
2) The spoiler is a decent place to mount brake cooling ducts but not much else..it increases drag vs a stock valance. The increased stability is probably a function of the car being slowed down due to the increased vertical surface area. I run this air-dam too...
3) A wing needs to be way the hell up there to grab clean air - the bottom of my wing is 1" (and should be higher) above the highest point of the roof line.
4) An actual splitter must be able to support at least 250 pounds of direct vertical force to remain stable at speed. My first effort fractured at 160 mph (mid-corner T9 RA) and I thought I had lost a wheel!!! IF you install one - bring it back all the way to the front suspension cross-member - there is more to aero than just the leading edge reveal.

Not meant to offend and step on toes - just sharing what I have learned...

T

[brant]

Regarding the spoilers, splitters, spoiler and wings....

My on-track experience leads me to believe:
1) The duckbill spoiler is of no tangible performance value but it does greatly help the aesthetics of the rear on a 914. That air is dead as dead as can be...
2) The spoiler is a decent place to mount brake cooling ducts but not much else..it increases drag vs a stock valance. The increased stability is probably a function of the car being slowed down due to the increased vertical surface area. I run this air-dam too...
3) A wing needs to be way the hell up there to grab clean air - the bottom of my wing is 1" (and should be higher) above the highest point of the roof line.
4) An actual splitter must be able to support at least 250 pounds of direct vertical force to remain stable at speed. My first effort fractured at 160 mph (mid-corner T9 RA) and I thought I had lost a wheel!!! IF you install one - bring it back all the way to the front suspension cross-member - there is more to aero than just the leading edge reveal.

Not meant to offend and step on toes - just sharing what I have learned...

T

I'm no aero expert
but Tony is!!!!

I think the car designers only had rudimentary aero in mind when they designed the car and the dead space is hard to over come with the roof line.

most classes will not allow the change
but the old PCA classes did....
this is how the aero was improved by a local 914 race shop (AJRS) on many of the PCA club race cars 15 years ago....

they changed the roof line to improve the high speed aero
they used clear lexan to build a square duct to get air into the electric fan shrouds for engine cooling....

notice the windshield is layed back... and the base of the windshield covers the cowl vents as it is moved forward all the way to the edge of the front trunk.

[Charles Freeborn]

Regarding the spoilers, splitters, spoiler and wings....

My on-track experience leads me to believe:
1) The duckbill spoiler is of no tangible performance value but it does greatly help the aesthetics of the rear on a 914. That air is dead as dead as can be...
2) The spoiler is a decent place to mount brake cooling ducts but not much else..it increases drag vs a stock valance. The increased stability is probably a function of the car being slowed down due to the increased vertical surface area. I run this air-dam too...
3) A wing needs to be way the hell up there to grab clean air - the bottom of my wing is 1" (and should be higher) above the highest point of the roof line.
4) An actual splitter must be able to support at least 250 pounds of direct vertical force to remain stable at speed. My first effort fractured at 160 mph (mid-corner T9 RA) and I thought I had lost a wheel!!! IF you install one - bring it back all the way to the front suspension cross-member - there is more to aero than just the leading edge reveal.

Not meant to offend and step on toes - just sharing what I have learned...

T

I'm no aero expert
but Tony is!!!!

I think the car designers only had rudimentary aero in mind when they designed the car and the dead space is hard to over come with the roof line.

most classes will not allow the change
but the old PCA classes did....
this is how the aero was improved by a local 914 race shop (AJRS) on many of the PCA club race cars 15 years ago....

they changed the roof line to improve the high speed aero
they used clear lexan to build a square duct to get air into the electric fan shrouds for engine cooling....

notice the windshield is layed back... and the base of the windshield covers the cowl vents as it is moved forward all the way to the edge of the front trunk.

I have the little brother to this car. Same builder, same roof mods. Haven't had it out enough to comment on it' performance, but according to the logbooks it took a couple of podiums in the day. Ran GT5S class.