SCCA F-Street Setup. What's Everyone Done so Far?

[Norm Peterson]

A couple mph of speedometer error isn't something I'd ever worry about.

Fixed.

What's slightly humorous is that the MPH function in my A-pillar mounted Aeroforce Interceptor gauge is in better agreement with those "Your Speed Is xx" signs than the factory speedometer . . .


Norm

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[kz]

For me the speedometer should be dead on with the 265/40R19, with the stock 275/40R19 it actually reads slow. I thought the would work well on both the 9" front and 9.5" rear. The 265/40R19 is 2lbs lighter and $48 cheaper than the 275/35R19. Wouldn't the 275/35R19 only be a tiny gain in traction over the 265/40R19 given the same tire and tread compound?

As others said - why do you even care ?? You are posting in autocross thread, people are universally fitting 285s on 9 inch wheels. If there's any gain in traction, why don't you want it especially for car that heavy ?
And the cost here isn't something I'd be even remotely worried about - you're going to throw this +$1000 set of tires away after a season anyway, this whole sport is just literally burning money away for plastic trophies ;-)

 

[Brazos609]

So how about
265/35R19 RE-71R on a 22lb 19"x9"
285/35R19 RE-71R on a 22lb 19"x9.5"
with correct offsets to stay inside the Stock rules? Both rim widths are at the minimum for their given tire by Bridgestone's site. Each front wheel should be 12lbs lighter and each rear 13lbs lighter than the stock PP rims and 255/275 P Zeros.

 

[DickR]

So how about
265/35R19 RE-71R on a 22lb 19"x9"
285/35R19 RE-71R on a 22lb 19"x9.5"
with correct offsets to stay inside the Stock rules? Both rim widths are at the minimum for their given tire by Bridgestone's site. Each front wheel should be 12lbs lighter and each rear 13lbs lighter than the stock PP rims and 255/275 P Zeros.

Try and report.

Seriously in over 3 years of attending major SCCA events starting in 2015 and monitoring tire size discussions involving top FS autocrossers I haven't seen or heard of anyone using smaller than 275/35x19 RE-71R's on a top performing S550 or the 6th gen Camaro SS (8.5 inch fronts). The only real question is whether to run 275 or 285 square or 275/285. Plus the last I heard the dominant DS Camaro turbo 4 is running 275's square on 8.5 inch wheels and it is MUCH lighter than even an EB Mustang, let alone a GT.

 

[jdub.csu]

So how about
265/35R19 RE-71R on a 22lb 19"x9"
285/35R19 RE-71R on a 22lb 19"x9.5"
with correct offsets to stay inside the Stock rules? Both rim widths are at the minimum for their given tire by Bridgestone's site. Each front wheel should be 12lbs lighter and each rear 13lbs lighter than the stock PP rims and 255/275 P Zeros.

Why give up front grip and cause understeer by going with a smaller size up front. The rear grip will overdrive the front. 285's fit up front and are better if your doing a 2 driver car due to they take longer to get hot otherwise stick with 275's imho as the 285's feel a bit numb compared to the 275s

 

[Brazos609]

I want everyone to know I do appreciate the input. I'm asking because I want the advise but I also don't want to run spacers or rub the struts with the tire up front because the front rims are stock offset.
275/35R19 RE-71R on a 22lb 19"x9"
285/35R19 RE-71R on a 22lb 19"x9.5"
I know I won't be winning anything but I hope to have a good time and learn some things.

 

[destoups]

A heads up for '18 owners: We got serious fuel starve at Crow's with nearly an eighth of a tank still showing. My '15 used to be good down to 0 miles and even beyond.

 

[qtrracer]

So how about
265/35R19 RE-71R on a 22lb 19"x9"
285/35R19 RE-71R on a 22lb 19"x9.5"
with correct offsets to stay inside the Stock rules? Both rim widths are at the minimum for their given tire by Bridgestone's site. Each front wheel should be 12lbs lighter and each rear 13lbs lighter than the stock PP rims and 255/275 P Zeros.

Not the RE-71Rs, but MPSS in your sizes running on the stock PP wheels with a .25" spacer up front which keeps me under the 7mm.

Does it work? Yes. But I have to run no more than 29F; 27R hot. Do I have clearance issues? No. Could it be better? Yes.

As far as weight, I'm not sure this is an issue. I've read many tests with both light and stock weight wheels on the same car with the same tires, on the same day (time of day differences of course) - no statistically significant difference in time on a typical long A/X course taking the three fastest times and averaging them.

I suppose if one is at the pointy end of competition then perhaps the weight would matter. But not where I'm at. For me, cost is a big factor to consider and I'd rather spend the money on a little less wheel and tire/more wear. These things are already in the $300+ range each.

 

[NightmareMoon]

A heads up for '18 owners: We got serious fuel starve at Crow's with nearly an eighth of a tank still showing. My '15 used to be good down to 0 miles and even beyond.

No surprises there, the S550 is known to do that when below ~1/4 tank.. Some people report that their cars can fuel starve with as little as 3/4! tank. That's for 15+ cars, not just the 18s. Its usually going to starve first in long left hand sweepers.

Keep in mind the fuel needle doesn't really keep up when drinking fuel as fast as the car does on track. 1/8th may read 0 if you park it for 5 minutes, and the miles remaining display is entirely B.S (its based on average fuel consumption from the last hundreds of miles).

 

[DickR]

A heads up for '18 owners: We got serious fuel starve at Crow's with nearly an eighth of a tank still showing. My '15 used to be good down to 0 miles and even beyond.

THANKS!!!!

FYI the gauge on my 18 is "more optimistic" than the gauge on my 15 was. That is there is less fuel in the tank at 1/8 tank with the 18. I have no idea whether this is a design difference vs production tolerance difference between my cars.

 

[Whiskey11]

Why give up front grip and cause understeer by going with a smaller size up front. The rear grip will overdrive the front. 285's fit up front and are better if your doing a 2 driver car due to they take longer to get hot otherwise stick with 275's imho as the 285's feel a bit numb compared to the 275s

Honestly, the difference in width when a 285 is crammed on a 9" wheel vs a 275, is pretty minimal. That 10mm extra width might only see the contact patch grow by a mm or so due to the pinching. Ideally, the 285 would be on a 10" wheel for flattest contact patch, but we don't run 275's on my car for a reason: Heat Tolerance.

The S550 is a fat heavy car. I'm no small guy at 6'5" and 300lbs, so the car + driver is just over 4k pounds on course... with a co-driver adding to this, it is not uncommon for us to be spraying tires after both of us finish our first runs with 285's due to the heat buildup... the 275's would overheat before the end of my first run (I'm first driver out). Mostly the "damage" is to the front tires and they see the most spraying.

 

[DocWalt]

Does anyone know if the '18+ swaybars have changed from the '15-'17 cars?
[MENTION=12865]DickR[/MENTION] asked me over the weekend about a front bar for his Mustang and I was curious what the bar dimensions were so I could whip up a comparison to see where the '18+ cars stand and where to go from stock.

I'm thinking the BMR front bar is likely still the way to go then adjust bar setting as needed. I know the MR shock wiring makes things difficult in regards to end links up front.

 

[svtsnake]

Does anyone know if the '18+ swaybars have changed from the '15-'17 cars?
[MENTION=12865]DickR[/MENTION] asked me over the weekend about a front bar for his Mustang and I was curious what the bar dimensions were so I could whip up a comparison to see where the '18+ cars stand and where to go from stock.

I'm thinking the BMR front bar is likely still the way to go then adjust bar setting as needed. I know the MR shock wiring makes things difficult in regards to end links up front.

I am not sure on the diameter, but my front is sitting on the garage floor. I changed out the front to a 1-3/8" steeda. Make sure you do the end links, my stock ones were bent with the stock PP bar. I am putting on the BMR ones this week. The car tended to oversteer a lot with the stock bar. With the front bar change (hole 2 of 4), it feels very balanced. I have 2.4°/2.6° front camber, and run 1/16" toe in on the street, then give it a 1/4 turn of toe out for autocross, and it seems to work well.

 

[DickR]

Does anyone know if the '18+ swaybars have changed from the '15-'17 cars?
[MENTION=12865]DickR[/MENTION] asked me over the weekend about a front bar for his Mustang and I was curious what the bar dimensions were so I could whip up a comparison to see where the '18+ cars stand and where to go from stock.

I'm thinking the BMR front bar is likely still the way to go then adjust bar setting as needed. I know the MR shock wiring makes things difficult in regards to end links up front.

Thanks for asking and good meeting you in person at the NJ Pro Solo!

The vendor info (Eibach and Whiteline for sure) shows the same bar for 2015 - 2018. I purchased a Whiteline 35 mm and their endlinks yesterday at about 6 PM from Sam Strano. Using UPS ground from the distributor Sam uses in PA the parts are already in Raleigh with delivery tomorrow.

FYI doing the comparison keep in mind bushing "bind" with the stock bar. According to expert sources many Ford (and other) oem bar bushings are so tight that bushings need to twist for the bar to deflect/twist using its full length.

FYI the oem 18 GT PP front bar is 32.0 mm per the tag on the bar. Same as the 15's.

 

[DocWalt]

Likely exactly the same bar then.

I'd personally start on medium front bar, but everyone is really fond of the stiff front bar. I just noticed that it pushed more in big sweepers and didn't help much else. Maybe the MR shocks are the difference from everyone running normal shocks on the 15-17 GTs.

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