SCCA Street Class Changes in '15 just released

Andrew Jonell · **Joined:** Mon Mar 23, 2009 6:43 pm **Posts:** 1350

All of them have been gutted for some sick SR20 swaps into their 240SXs.

michaelsmiller · **Posted:** Tue Sep 30, 2014 10:07 pm

My high school car was a Datsun 510 which I hopped up in auto shop. Rolled it 5 times, once end over end, street racing. Not one of my best moments. High school auto shop was really a free speed shop. The cars that we worked on were, 911, 914, Charger RT(440, 4 spd), Z28's,67 427 Vette, MG's, 302 Pinto, VW trike, Road Runner, 64 impala SS, 455 X 442, Mustangs, and a lot of crap. The Pinto and the trike were great wheel standing vehicles.

Arthur McDonald · **Joined:** Fri Aug 29, 2003 1:54 am **Posts:** 2052

DickRasmussen wrote:

Cash Davidson wrote:

Arthur McDonald wrote:

Ouch! Boss 302s in FS? I didn't think the Shelby GT belonged in FS way back when. I'll have to pedal a lot faster next year.

Seriously?! From AS to FS? Holy cow!

One or more SAC members has commented that the regular Boss doesn't really have an advantage over many of the other late model FS cars or the Shelby GT. Also I think they suspect that the new Mustang will be at least as fast as the Boss and it "belongs" in FS as a continuation of "Best of the breed" approach with Pony cars with the exception of really special versions. Time will tell.

Looking at the 2015 Mustang option sheet, the GT Performance Pack forces you to a 3.73 final drive, which brings up my favorite "how fast will it go in 2nd gear" question. If you get a GT without the Performance pack, you can choose the base 3.31 or optional 3.55 final drive, but you are stuck with 18x8 wheels.

I think the interesting one will be the Ecoboost Mustang with its Performance pack, which has a 3.55 final drive and 19x9 wheels. I vote that it go in H-stock since it's just a four cylinder.

DickRasmussen · **Posted:** Thu Oct 02, 2014 8:43 am

Arthur McDonald wrote:

Looking at the 2015 Mustang option sheet, the GT Performance Pack forces you to a 3.73 final drive, which brings up my favorite "how fast will it go in 2nd gear" question. If you get a GT without the Performance pack, you can choose the base 3.31 or optional 3.55 final drive, but you are stuck with 18x8 wheels.

I think the interesting one will be the Ecoboost Mustang with its Performance pack, which has a 3.55 final drive and 19x9 wheels. I vote that it go in H-stock since it's just a four cylinder.

Art - Gearing/speed in second with the 3.73's are a concern. 60 mph if the rev limiter hits at 7K. Even slow me was faster than that on the East course this year at Nationals.

Regarding wheels. Thanks to the new +/- 1 inch rule there are lots of ways to get to 8.5 or 9 inch wheels with 18, 19, 20, or even 21 inch :lol:

diameter since there are many optional 8.5 and 9 inch wheels. However, only the PP allows 9 F, 9.5 R starting with 19 diameter so 18 or 20 are allowed if they will clear the big front brakes. I'm pretty sure the rules allow different diameters F/R as long as the starting point of +/- 1 is an optional "package".

I'm more interested in the "tuning" and "handling" aspects of the PP versus the standard GT. Plus the hoped for advantages of a Torsen versus the clutch type diff.

Or you could keep your car and I'll sell you my Kazera 18x8.5's at a really good price if I get a 2015.

Arthur McDonald · **Joined:** Fri Aug 29, 2003 1:54 am **Posts:** 2052

DickRasmussen wrote:

Arthur McDonald wrote:

Looking at the 2015 Mustang option sheet, the GT Performance Pack forces you to a 3.73 final drive, which brings up my favorite "how fast will it go in 2nd gear" question. If you get a GT without the Performance pack, you can choose the base 3.31 or optional 3.55 final drive, but you are stuck with 18x8 wheels.

I think the interesting one will be the Ecoboost Mustang with its Performance pack, which has a 3.55 final drive and 19x9 wheels. I vote that it go in H-stock since it's just a four cylinder.

Art - Gearing/speed in second with the 3.73's are a concern. 60 mph if the rev limiter hits at 7K. Even slow me was faster than that on the East course this year at Nationals.

Regarding wheels. Thanks to the new +/- 1 inch rule there are lots of ways to get to 8.5 or 9 inch wheels with 18, 19, 20, or even 21 inch :lol:

diameter since there are many optional 8.5 and 9 inch wheels. However, only the PP allows 9 F, 9.5 R starting with 19 diameter so 18 or 20 are allowed if they will clear the big front brakes. I'm pretty sure the rules allow different diameters F/R as long as the starting point of +/- 1 is an optional "package".

I'm more interested in the "tuning" and "handling" aspects of the PP versus the standard GT. Plus the hoped for advantages of a Torsen versus the clutch type diff.

Or you could keep your car and I'll sell you my Kazera 18x8.5's at a really good price if I get a 2015.

I have a friend who has a '15 Performance Pack on order. A listing of observed mph in gear and the transmission ratios with an OEM wheel/tire package would help with choosing the right aftermarket wheels and competition tires. Car and Driver used to include that in road tests, but they've gotten sloppy.

Cash Davidson · **Posted:** Fri Oct 03, 2014 10:24 am

Arthur McDonald wrote:

I think the interesting one will be the Ecoboost Mustang with its Performance pack, which has a 3.55 final drive and 19x9 wheels. I vote that it go in H-stock since it's just a four cylinder.

I agree! I have to admit, I'm intrigued. Must ... resist ... too many projects ... two kids in college next year ...

DickRasmussen · **Posted:** Fri Oct 03, 2014 5:28 pm

Arthur McDonald wrote:

I have a friend who has a '15 Performance Pack on order. A listing of observed mph in gear and the transmission ratios with an OEM wheel/tire package would help with choosing the right aftermarket wheels and competition tires. Car and Driver used to include that in road tests, but they've gotten sloppy.

There are some spread sheets around but "math" and "ford specs" and "Tirerack" tire revs per mile (about 753) work also.

Using one of the spreadsheets here are some rough numbers.

Assume 7000 rpm rev limiter until we have more info. Careful using tire diameter and "math" to determine revs per mile since the calculated value typically is fewer revs/mile than Tire Rack specs indicate. Of course, all the autocross capable tires are lower profile so lower speed in each gear. Frequently, including for the oem Pirelli's on the new Mustang the revs per mile for the Ford spec tire are not shown in the TR table . . . but one or more versions of the same size tire is . . . 753 in this case.

1 3.66 40.9
2 2.43 61.5
3 1.69 88.5
4 1.32 113.3
5 1 149.5
6 0.65 230.1

Yes, I'm an engineer.

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SCCA Street Class Changes in '15 just released

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