Dallas Fort Worth 5.0 Mustang Club - View Single Post - Vorshlag 2011 Mustang 5.0 GT

Fair · 12-29-2013, 04:33 PM

continued from above

We started on 255mm tires and quickly moved to 265mm, 275mm and finally 295mm wide street tires. And when it came to R-compounds we tried 275, 285, 295, 305, and 315mm widths ranging from Kumho to Hoosier.

We tested briefly in 2012 with the 345/35/18 rear Hoosier A6, and it had ferocious forward bite on these nearly 14" wide tires (13.9" section width/13.2" tread. The 315/30/18 is only 11.8" of tread/12.5" of section width, fully 1.4" narrower), but they rubbed the inside body structure and fenders badly under cornering (before the Watts Link). The rubbing caused other handling issues, and a huge smoke screen, so we shelved that size for a while. When we cut and flared the front fenders (to clear the new 18x12" wheels) I had every intention of doing the same to the rear fenders, then upgrading the front to 335mm and the rear to the 345mm tire again. I met with considerable resistance from Amy about "cutting on her car", but I'm wearing her down.

The 345mm rear Hoosier was wider than the stock rear fenders could accommodate and made lots of tire smoke from rubbing

As we noted many times in our Time Trial events this past year (with 15 separate NASA events in 2013) my fastest laps were almost always my first or second lap, barring traffic problems. On one or two rare occasions I ended up making my best lap on hot lap 3, but that was always due to a driving mistake or traffic on previous laps. The Hoosier A6 is a temperamental tire and works best in ambient temps from 50-60°F, and more often than not the lap times fell off a full second per lap after the first. We were also only getting 20-30 hot laps per set of tires before they are GONE.

Tires that only work for 1 or 2 laps, coupled with slower cars in front = TT traffic frustration!

My theory is that with another 20mm up front and another 30mm on the rear that our "golden lap zone" of ideal conditions could be expanded from 1 or 2 hot laps to maybe 3-4 hot laps. That is a big improvement for Time Trial that could have allowed for faster lap records at a few events in 2013 where I had serious traffic issues in the first couple of laps (more times than I can count). Not to mention a potential increase in mechanical grip from the additional two or three inches of tire on the ground at each axle. And possibly an increase in total tire life? That +20/+30mm change is not a small increase in tire width.

Another area we dabbled with late in the 2013 season was adding downforce, which I think still has more room for improvement on this car. While Vorshlag is first and foremost a suspension shop we have been seeing more and more aero development creep into club level road racing and time attack/time trial competition, and we were finding lap time improvements using aero changes very late into the season. The 10" long front splitter we added right before Miller, that many told us was "too long to be effective", coupled with our front grill block-off and ducted hood made more front downforce than the APR GTC-300 rear wing could match. That meant that at high speeds the car had an aero imbalance, and it was prone to oversteer. I cannot emphasize enough how loose this car was at Miller with that long front splitter, and we ran out of AoA on the rear wing to stabilize the car in high speed corners. Nothing like going 150+ sideways, wee!

To "fix" this we lopped 4 inches off the front of the 10" long splitter (well, actually a spare we had), right after returning from Nationals. Magically the car was balanced once again at the 150+ mph corner entry speeds we saw at TWS in late September, and was faster than ever at ECR in November. But it always nagged me... if we only had more rear downforce wouldn't that bigger front splitter be better overall? With some of the latest rear wings on the market having 14" and even 16" long chords and 70"+ widths, there could be a more efficient and more effective wing to test on this car, then we could bring the Big Splitter back (we kept it, just in case).

As I mentioned in my previous posts we would have liked to get into S550 chassis development as soon as possible, and run the 2014 season in NASA TT2 class with the new Mustang (a bump up on power and/or down in weight from TT3, going from 9.5:1 to 8:1 pounds per hp) but my hopes of acquiring one of these in the early spring of 2014 and prepping it to race for most of that year seem to be dashed. At best we might see a car in early August. So recently we began our ST2/TT2 build on an E36 BMW LS1 car, then our paying customer shop work picked up so much (we're building a number of race cars and LS1 swaps for people right now) that this project was delayed. Meaning, if we mothball the 2011 GT we won't have a car to race at all for many months, which pains me. That's half the reason I quit the secure engineering jobs I had in the past - to start a business, create products tailor made to racers, and then using our racing as "testing"!

We have a lot of work left on our ST2 BMW LS1 project before it is ready to race

Long story short, we're going to take our red 2011 Mustang and keep racing and developing with it as long as we need to, until the ST2 car is completed or until the S550 is here and prepped. This might mean an entire extra year competing in the red 2011 GT, known jokingly around the shop as the "pretty pony". And that's one thing I aim to do - make it look less ugly, with a new rear wing, proper metal flares blended into the bodywork, and a more low key graphics theme - say good bye to white strips visible from space!

This is the worst looking pair of flares on any car I've ever owned, and that's saying a lot

Those prototype plastic front fender flares we made look OK at 100 mph, but up close, they ugly. Sure, these were aerodynamically efficient but we have plans to make proper METAL flares welded to the front and rear fenders to cover the much wider Hoosier tires. Amy is still complaining about cutting the rear fenders on "her car" to clear the bigger meats, but I've got the Mustang at the shop all day, there's a fresh blade on the SawsAll, and possession is nine tenths of the saw.... I mean the "law".

continued below

12-29-2013, 04:33 PM	#260
Fair Senior Member Join Date: Nov 2012 Posts: 333	continued from above We started on 255mm tires and quickly moved to 265mm, 275mm and finally 295mm wide street tires. And when it came to R-compounds we tried 275, 285, 295, 305, and 315mm widths ranging from Kumho to Hoosier. We tested briefly in 2012 with the 345/35/18 rear Hoosier A6, and it had ferocious forward bite on these nearly 14" wide tires (13.9" section width/13.2" tread. The 315/30/18 is only 11.8" of tread/12.5" of section width, fully 1.4" narrower), but they rubbed the inside body structure and fenders badly under cornering (before the Watts Link). The rubbing caused other handling issues, and a huge smoke screen, so we shelved that size for a while. When we cut and flared the front fenders (to clear the new 18x12" wheels) I had every intention of doing the same to the rear fenders, then upgrading the front to 335mm and the rear to the 345mm tire again. I met with considerable resistance from Amy about "cutting on her car", but I'm wearing her down. The 345mm rear Hoosier was wider than the stock rear fenders could accommodate and made lots of tire smoke from rubbing As we noted many times in our Time Trial events this past year (with 15 separate NASA events in 2013) my fastest laps were almost always my first or second lap, barring traffic problems. On one or two rare occasions I ended up making my best lap on hot lap 3, but that was always due to a driving mistake or traffic on previous laps. The Hoosier A6 is a temperamental tire and works best in ambient temps from 50-60°F, and more often than not the lap times fell off a full second per lap after the first. We were also only getting 20-30 hot laps per set of tires before they are GONE. Tires that only work for 1 or 2 laps, coupled with slower cars in front = TT traffic frustration! My theory is that with another 20mm up front and another 30mm on the rear that our "golden lap zone" of ideal conditions could be expanded from 1 or 2 hot laps to maybe 3-4 hot laps. That is a big improvement for Time Trial that could have allowed for faster lap records at a few events in 2013 where I had serious traffic issues in the first couple of laps (more times than I can count). Not to mention a potential increase in mechanical grip from the additional two or three inches of tire on the ground at each axle. And possibly an increase in total tire life? That +20/+30mm change is not a small increase in tire width. Another area we dabbled with late in the 2013 season was adding downforce, which I think still has more room for improvement on this car. While Vorshlag is first and foremost a suspension shop we have been seeing more and more aero development creep into club level road racing and time attack/time trial competition, and we were finding lap time improvements using aero changes very late into the season. The 10" long front splitter we added right before Miller, that many told us was "too long to be effective", coupled with our front grill block-off and ducted hood made more front downforce than the APR GTC-300 rear wing could match. That meant that at high speeds the car had an aero imbalance, and it was prone to oversteer. I cannot emphasize enough how loose this car was at Miller with that long front splitter, and we ran out of AoA on the rear wing to stabilize the car in high speed corners. Nothing like going 150+ sideways, wee! To "fix" this we lopped 4 inches off the front of the 10" long splitter (well, actually a spare we had), right after returning from Nationals. Magically the car was balanced once again at the 150+ mph corner entry speeds we saw at TWS in late September, and was faster than ever at ECR in November. But it always nagged me... if we only had more rear downforce wouldn't that bigger front splitter be better overall? With some of the latest rear wings on the market having 14" and even 16" long chords and 70"+ widths, there could be a more efficient and more effective wing to test on this car, then we could bring the Big Splitter back (we kept it, just in case). As I mentioned in my previous posts we would have liked to get into S550 chassis development as soon as possible, and run the 2014 season in NASA TT2 class with the new Mustang (a bump up on power and/or down in weight from TT3, going from 9.5:1 to 8:1 pounds per hp) but my hopes of acquiring one of these in the early spring of 2014 and prepping it to race for most of that year seem to be dashed. At best we might see a car in early August. So recently we began our ST2/TT2 build on an E36 BMW LS1 car, then our paying customer shop work picked up so much (we're building a number of race cars and LS1 swaps for people right now) that this project was delayed. Meaning, if we mothball the 2011 GT we won't have a car to race at all for many months, which pains me. That's half the reason I quit the secure engineering jobs I had in the past - to start a business, create products tailor made to racers, and then using our racing as "testing"! We have a lot of work left on our ST2 BMW LS1 project before it is ready to race Long story short, we're going to take our red 2011 Mustang and keep racing and developing with it as long as we need to, until the ST2 car is completed or until the S550 is here and prepped. This might mean an entire extra year competing in the red 2011 GT, known jokingly around the shop as the "pretty pony". And that's one thing I aim to do - make it look less ugly, with a new rear wing, proper metal flares blended into the bodywork, and a more low key graphics theme - say good bye to white strips visible from space! This is the worst looking pair of flares on any car I've ever owned, and that's saying a lot Those prototype plastic front fender flares we made look OK at 100 mph, but up close, they ugly. Sure, these were aerodynamically efficient but we have plans to make proper METAL flares welded to the front and rear fenders to cover the much wider Hoosier tires. Amy is still complaining about cutting the rear fenders on "her car" to clear the bigger meats, but I've got the Mustang at the shop all day, there's a fresh blade on the SawsAll, and possession is nine tenths of the saw.... I mean the "law". continued below