Are you an S197 racer that likes to autocross with the SCCA? Well this thread might be worth reading. This subject (STX vs STU vs ESP) keeps popping up in various thread, including my build S197 built thread (see link in my sig) and Chilema's STX/ESP build thread located here. If a moderator wants to tow some of the replies on this subject (most of which I have quoted below) to this thread, it might make more sense.
S197 Mustang in SCCA Solo: STX vs STU vs ESP?
If you have followed my trials and tribulations trying to compete with a heavy, powerful 2011 Mustang GT trying to autocross in three different SCCA Solo classes, you might know a little something about this subject already. And plenty of you on this forum have jumped into STX, ESP and even some ran in STU, briefly.
The silver 2006 GT above was a Vorshlag tester we started working with back in 2008 who started in STU class and eventually moved to ESP. We bought the red 2011 GT above in August 2010 and built it around SCCA's "STX" class from August 2010 until about November 2011 (and even raced it in STX up until March 2012). We raced it briefly in STU class in late 2011, then switched to ESP class in Spring 2012, where we stayed through the SCCA Solo Nationals and up until December 2012. Then the SCCA made some part we had on the car illegal (I won't get into that again), so we left the class. We raced this car dozens and dozens of times with the SCCA, from regional Solo events, to National Tours, Pro Solos and even the Solo Nationals. We did "OK" in the car... once we got enough tire under it (STU then ESP).
Alphabet Soup!
So what do all these three letter class designations mean? The three classes in the subject line are the three most common places people have raced their S197 Mustangs. Well, that and "Stock" class (F Stock is a whole other animal, and looks to be changing drastically in 2014-15 to "Street" class - but that's another subject that needs it's own thread entirely) Let me back up and explain the basic rules for these 4 classes, where the S197 falls (or fell).
F Stock (FS): This is where you race your bone stock Mustang. HAHAHA! I kid, I kid. No, this is an odd class where you can do some crazy things but not the most basic of suspension mods, which these cars need to handle well. FStock is not a class we raced our car in personally, but we have worked with many FStock customers. It also happens to be my least favorite category of classes in all of the SCCA Solo (but it is getting a major reboot next year). In "Stock" you can use giant gumball Hoosier A6 tires but you cannot adjust camber (except thru some shady TSB that applies so some cars). The diff must be bone stock (again, other than some TSB for some models). Stock wheel sizes are used but they can be lightweight/custom 3-piece/aftermarket sizes. You can use high dollar custom doubler adjustable monotubes with remotes (but some people still win there on Konis - still doesn't mean that better shocks won't help you go faster still). You can change one swaybar but not both. Cat-back exhaust is free, as is the air cleaner element in the stock housing, but that's about it.
See these Moton 2-way Shocks with remote reservoirs, custom spring hats to use the OEM springs? That's "Stock" class legal...
Personally I think the S197 is a big hot mess in F Stock. The tires are the only thing you can do to make big changes, as the lack of camber, spring rate or ride height adjustment really hurt the performance. I've driven competitive F Stock cars and it ... just isn't fun to me. But without camber adjustment, stiffer spring rates and some other basic suspension mods the super stick race tires have an atrociously short lifespan.
Street Touring Xtreme (STX): This is one of two Street Touring classes where this chassis was classed initially. The tires have to be 140 treadwear or higher and 2WD cars can only used up to a 265mm width. Wheel width is limited to 9", diameter is open. You can use aftermarket brakes (either "big brake kits", or lighter ones as large in diameter as stock). Exhaust is open (headers, cat back) but you have to run a catalyst within 6" of the exit of the stock location. Cold air kits are allowed but the throttle body and intake cannot be modified. Internal engine mods are verboten but you can tweak the ECU tuning to your heart's delight. Suspension is pretty wide open - Watts Links (well, 2 choices are legal), swaybars, coilovers with as many adjustments as you want, non-metal aftermarket bushings, camber plates, and the rear upper control arms are wide open on these cars. You can also use race seats but aero devices must be chosen from OEM parts used on the 2005-2013 cars only.
Street Touring Unlimited (STU): This was legal to run in the S197 up until December 2011, then there were changes that made "class hopping" no longer allowed. It was necessary to keep the lightest cars from jumping up a class and winning easily (ST Hondas that continually won in STX) , but it left a few cars in the wrong class, such as the S197. The STU rules were the same as STX except 2WD cars could use up to a 285mm wide 140 treadwear tire, and wheel width was UNLIMITED.
E Street Prepared (ESP): This class allows everything allowed in STX/STU + you can swap intake manifolds, ditch ALL emissions equipment, wheel width was unlimited and you could cut and flare fenders. "DOT Legal" R compound tires are allowed with no width limitations. Aero devices could be chosen from OEM bits or you could use a 10" tall, flat rear spoiler (circa 1960) and a very limited splitter (but the OEM Leguna Seca part was bigger, and legal).
What Works, What Doesn't?
So if you go back and read our build thread you will see how much we tested, developed, raced, and struggled trying to make these big, heavy cars work on a 265mm street tire. The rear tire was a huge limitation - we were making 430 whp in STX legal trim but trying to put it to the ground in 1st and 2nd gear through a super skinny, low grip street tire. We couldn't make it halfway through a run with any sort of acceleration without overheating the rear tires. The car was always sideways and not at all fun to drive.
A lot of people warned us that STX would suck in a high hp/high weight/solid axle RWD car, since the maximum tire width is the same for all of the car in class - from the lightest to the heaviest (Mustang). But I am stubborn and tried it anyway (since nobody else had tried it in a 5.0L S197). After 18 months of getting sand kicked in my face by the big STX bullies on the beach (200 hp 328 BMWs - ha!) we threw in the towel and tried STU. STX was a total disaster for this car. Maybe it would work better with LESS horsepower, so the 3V 4.6L S197s still could give it a go here. But I publicly discouraged anyone with a 2011+ 5.0L S197 to try this class. It is a recipe for disappointment.
We went to STU briefly by slapping on some 18x10" wheels and 275/40/18 Bridgestone RE-11 tires. Wow, what an improvement! The car put down power so much better (+10mm tire and +1" of wheel width), with a huge boost in PAX placing, and who knows how it would have done on a 285/35/18 on an 18x11?? But we moved to STU too late - when we were there we noticed BIG gains in performance and the car was MUCH easier to drive.
Will an S197 ever dominate STU? Not likely, not without some rules help. These cars are still handicapped in the weight department when compared to the 2900-3100 pound AWD rally cars that dominate the class (well, except for one win by an E36 M3 at Nats!). We raced in STU from 2005-09 in various cars and an AWD turbo car is still the best bet in this class. But... the STU class is still the better home for the S197 Mustang. The car is night and day better on a 285 than a 265 street tire. And maybe with a little extra tire (295? 315?) the car could be even a tick more competitive against the "AWD BOOST BUGGIES!"
I wrote in a proposal to the SEB (look for the note in my build thread) and they are supposedly addressing it in the very next FasTrack publication.
Of course when we moved to ESP the car was that much faster, and now matched up with cars more similar than in the previous two ST classes. With 315mm A6 rubber the car was infinitely easier to drive than on the skinny street tires we were handicapped with in STX. It could still use more tire, as there's still hp to overpower the rears, but it was a lot better. We changed nothing from our STX set-up moving to ESP other than the rear spoiler and the wheels/tires. We kept developing the car beyond where it was in STX/STU, but the changes we made in ESP were all still STX legal (Watts Link, swaybars, spring rates).
Ultimately we only placed 4th in ESP at Nationals but spring rate changes we made right after the Solo Nationals (stiffer!) improved our PAX placings and results locally to the best we had seen in the car. With some more development and some weight saving measures (A/C, radio, Nav removed, rear seats replaced with Leguna Seca seat delete, etc) we think the S197 5.0 is THE car to race with in ESP. Well, other than the hybrid, uber-light, 15 year developed 3rd gen Firebird that keeps winning at Nationals.
OK, there are a lot of quotes I wanted to add but I will do that in a reply, below...
S197 Mustang in SCCA Solo: STX vs STU vs ESP?
If you have followed my trials and tribulations trying to compete with a heavy, powerful 2011 Mustang GT trying to autocross in three different SCCA Solo classes, you might know a little something about this subject already. And plenty of you on this forum have jumped into STX, ESP and even some ran in STU, briefly.
The silver 2006 GT above was a Vorshlag tester we started working with back in 2008 who started in STU class and eventually moved to ESP. We bought the red 2011 GT above in August 2010 and built it around SCCA's "STX" class from August 2010 until about November 2011 (and even raced it in STX up until March 2012). We raced it briefly in STU class in late 2011, then switched to ESP class in Spring 2012, where we stayed through the SCCA Solo Nationals and up until December 2012. Then the SCCA made some part we had on the car illegal (I won't get into that again), so we left the class. We raced this car dozens and dozens of times with the SCCA, from regional Solo events, to National Tours, Pro Solos and even the Solo Nationals. We did "OK" in the car... once we got enough tire under it (STU then ESP).
Alphabet Soup!
So what do all these three letter class designations mean? The three classes in the subject line are the three most common places people have raced their S197 Mustangs. Well, that and "Stock" class (F Stock is a whole other animal, and looks to be changing drastically in 2014-15 to "Street" class - but that's another subject that needs it's own thread entirely) Let me back up and explain the basic rules for these 4 classes, where the S197 falls (or fell).
F Stock (FS): This is where you race your bone stock Mustang. HAHAHA! I kid, I kid. No, this is an odd class where you can do some crazy things but not the most basic of suspension mods, which these cars need to handle well. FStock is not a class we raced our car in personally, but we have worked with many FStock customers. It also happens to be my least favorite category of classes in all of the SCCA Solo (but it is getting a major reboot next year). In "Stock" you can use giant gumball Hoosier A6 tires but you cannot adjust camber (except thru some shady TSB that applies so some cars). The diff must be bone stock (again, other than some TSB for some models). Stock wheel sizes are used but they can be lightweight/custom 3-piece/aftermarket sizes. You can use high dollar custom doubler adjustable monotubes with remotes (but some people still win there on Konis - still doesn't mean that better shocks won't help you go faster still). You can change one swaybar but not both. Cat-back exhaust is free, as is the air cleaner element in the stock housing, but that's about it.
See these Moton 2-way Shocks with remote reservoirs, custom spring hats to use the OEM springs? That's "Stock" class legal...
Personally I think the S197 is a big hot mess in F Stock. The tires are the only thing you can do to make big changes, as the lack of camber, spring rate or ride height adjustment really hurt the performance. I've driven competitive F Stock cars and it ... just isn't fun to me. But without camber adjustment, stiffer spring rates and some other basic suspension mods the super stick race tires have an atrociously short lifespan.
Street Touring Xtreme (STX): This is one of two Street Touring classes where this chassis was classed initially. The tires have to be 140 treadwear or higher and 2WD cars can only used up to a 265mm width. Wheel width is limited to 9", diameter is open. You can use aftermarket brakes (either "big brake kits", or lighter ones as large in diameter as stock). Exhaust is open (headers, cat back) but you have to run a catalyst within 6" of the exit of the stock location. Cold air kits are allowed but the throttle body and intake cannot be modified. Internal engine mods are verboten but you can tweak the ECU tuning to your heart's delight. Suspension is pretty wide open - Watts Links (well, 2 choices are legal), swaybars, coilovers with as many adjustments as you want, non-metal aftermarket bushings, camber plates, and the rear upper control arms are wide open on these cars. You can also use race seats but aero devices must be chosen from OEM parts used on the 2005-2013 cars only.
Street Touring Unlimited (STU): This was legal to run in the S197 up until December 2011, then there were changes that made "class hopping" no longer allowed. It was necessary to keep the lightest cars from jumping up a class and winning easily (ST Hondas that continually won in STX) , but it left a few cars in the wrong class, such as the S197. The STU rules were the same as STX except 2WD cars could use up to a 285mm wide 140 treadwear tire, and wheel width was UNLIMITED.
E Street Prepared (ESP): This class allows everything allowed in STX/STU + you can swap intake manifolds, ditch ALL emissions equipment, wheel width was unlimited and you could cut and flare fenders. "DOT Legal" R compound tires are allowed with no width limitations. Aero devices could be chosen from OEM bits or you could use a 10" tall, flat rear spoiler (circa 1960) and a very limited splitter (but the OEM Leguna Seca part was bigger, and legal).
What Works, What Doesn't?
So if you go back and read our build thread you will see how much we tested, developed, raced, and struggled trying to make these big, heavy cars work on a 265mm street tire. The rear tire was a huge limitation - we were making 430 whp in STX legal trim but trying to put it to the ground in 1st and 2nd gear through a super skinny, low grip street tire. We couldn't make it halfway through a run with any sort of acceleration without overheating the rear tires. The car was always sideways and not at all fun to drive.
A lot of people warned us that STX would suck in a high hp/high weight/solid axle RWD car, since the maximum tire width is the same for all of the car in class - from the lightest to the heaviest (Mustang). But I am stubborn and tried it anyway (since nobody else had tried it in a 5.0L S197). After 18 months of getting sand kicked in my face by the big STX bullies on the beach (200 hp 328 BMWs - ha!) we threw in the towel and tried STU. STX was a total disaster for this car. Maybe it would work better with LESS horsepower, so the 3V 4.6L S197s still could give it a go here. But I publicly discouraged anyone with a 2011+ 5.0L S197 to try this class. It is a recipe for disappointment.
We went to STU briefly by slapping on some 18x10" wheels and 275/40/18 Bridgestone RE-11 tires. Wow, what an improvement! The car put down power so much better (+10mm tire and +1" of wheel width), with a huge boost in PAX placing, and who knows how it would have done on a 285/35/18 on an 18x11?? But we moved to STU too late - when we were there we noticed BIG gains in performance and the car was MUCH easier to drive.
Will an S197 ever dominate STU? Not likely, not without some rules help. These cars are still handicapped in the weight department when compared to the 2900-3100 pound AWD rally cars that dominate the class (well, except for one win by an E36 M3 at Nats!). We raced in STU from 2005-09 in various cars and an AWD turbo car is still the best bet in this class. But... the STU class is still the better home for the S197 Mustang. The car is night and day better on a 285 than a 265 street tire. And maybe with a little extra tire (295? 315?) the car could be even a tick more competitive against the "AWD BOOST BUGGIES!"
I wrote in a proposal to the SEB (look for the note in my build thread) and they are supposedly addressing it in the very next FasTrack publication.
Of course when we moved to ESP the car was that much faster, and now matched up with cars more similar than in the previous two ST classes. With 315mm A6 rubber the car was infinitely easier to drive than on the skinny street tires we were handicapped with in STX. It could still use more tire, as there's still hp to overpower the rears, but it was a lot better. We changed nothing from our STX set-up moving to ESP other than the rear spoiler and the wheels/tires. We kept developing the car beyond where it was in STX/STU, but the changes we made in ESP were all still STX legal (Watts Link, swaybars, spring rates).
Ultimately we only placed 4th in ESP at Nationals but spring rate changes we made right after the Solo Nationals (stiffer!) improved our PAX placings and results locally to the best we had seen in the car. With some more development and some weight saving measures (A/C, radio, Nav removed, rear seats replaced with Leguna Seca seat delete, etc) we think the S197 5.0 is THE car to race with in ESP. Well, other than the hybrid, uber-light, 15 year developed 3rd gen Firebird that keeps winning at Nationals.
OK, there are a lot of quotes I wanted to add but I will do that in a reply, below...
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