Project Update for March 5, 2014: After another extremely busy and record breaking month for the business, another 4 weeks has passed without a Mustang build thread post. I haven't had much "internet time", due to a lot of service/race prep work on customers cars. It got so backed up that I had to pitch in back there a few days, which is never a good sign. I hastily wrote this post, finishing it around midnight after a 12 hour work day, because this is the only time I can go more than 30 seconds without being called on by an employee, customer, PM, text or phone call. We've made some key changes to our red 2011 Mustang, the 2013 Mustang finally sold, and we are in the beginning stretch of 6 straight race weekend stint, including 3 days of racing this coming weekend. That means I will be writing at a furious pace with fewer edits - so if I sound a little loopy, and make some grammatical errors, that's due to the late hour and my compressed writing schedule.
2013 Mustang Finally Sold
Hallelujah! After 6 months of trying (or more? I'm afraid to count) the black '13 Mustang GT sold to a buyer out of state. I don't know if it was the latest of many price drops ($25K, ouch!) or the time of year was just right, but a mere 12 days after I lowered the price on January 31st the phones just all of a sudden lit UP. During a 24 hour period I had the car sold over the phone to an out of state buyer, sold and shown to a local buyer (first back-up), and then after we had 3 additional backup buyers lined up on the phone
that same day - and the phones kept blowing up for another 24 hours. We finally just told the rest of the people that kept calling
it was sold, before it was gone. We even had people offering $1000 over the asking price after I had accepted the first verbal offer, but we don't play like that, so I sold it to the first person who gave me confirmation and just waited for him to fly in and pick up the car a few days later.
The buyer loved the car when he arrived, then wanted to upgrade it to the full Bilstein StreetPro struts, shocks and camber plates. We had what he needed in stock, got them installed in a couple of hours, took care of the sale at the bank, and then he drove it 1400+ miles home through an ice storm that hit the east coast, with a smile on his face. Weirdest thing... so many buyers appeared during a 48 hour period, I thought I was being prank called at one point. I guess I won't ever try selling cars in December or January again, that's for sure. Probably the magic of Tax Return Season.
Was sad to see this one go, but with 8 personal cars and projects I needed to reduce the fleet a bit and this one just wasn't being used. Now it can be driven and appreciated by one of our S197 Mustang build thread's long timer readers, and with the new suspension and brake upgrades he should have a lot of fun on track.
Rear Flares Finally Happened!
So if you have been reading this Build Thread for the past 4 years you will know that I've complained about the 315mm tires we have run at all four corners are a bit on the small side and lusted for MOAR TIRE. While the "315s are skinny" statement sounds crazy to many of you, remember: we have been racing at 3770 pounds (with driver) in NASA TT3 class, and the "weight-to-tire" ratio isn't all that great with this many pounds and only a 315mm tire.
Typical TT1 C6 Z06 rear tire is a 345mm Hoosier, and these cars weigh around 3150 pounds stock, not 3550+ like our Mustang
Remember: the typical TT1 classed C6 Z06 Corvette (above) in Time Trial is on 18x12" wheels and 345mm rears under stock fenders, with the same power levels (440 whp) or maybe a tick more. And with a 400 (or more) pound advantage to our car, their "tire-to-weight" ratio is very favorable. We cannot run that light without removing large portions of the chassis, and bumping up classes, but have been making due with 315mm tires on a 3770 race weight, with similar power numbers as a stock Z06.
2012 SCCA ESP and NASA TTS wheel/tire set-up on 315/35/18 Kumho V710
Let's back up and cover the tire and wheel upgrades we've made since ditching the 18x9" then 18x10" wheels and street tires of our first 2 seasons, when we were building around STX/STU autocross classes. After a switch to ESP and TTS classes, we started running the 315mm R-compound DOT tires back in 2012 with a Forgestar 18x11" front and 18x12" rear, both of which just fit under the stock fenders (with some tricks out back to clear the 12's and 3 degrees of negative camber in the front to keep the top of the tire under the fender).
Early 2013 NASA TT3 wheel/tire set-up on 315/30/18 Hoosier A6
We have since perfected the 18x11" wheel fitment at both ends of the S197 and realize that, for most racers, a 295mm-305mm tire works and fits best with that wheel size. Fewer tricks are needed to fit the 18x11" rear wheel and that tire width, compared to the 18x12". But for our "ballasted up" Mustang making 420-430 whp, and with as aggressively as I drive the thing on Hoosier A6 tires, we were overheating the 315s within 2-3 laps. So I bought a pair of the widest DOT radial tires made by Hoosier: the 345/35/18 Hoosier A6. They fit the rear 18x12s "well enough" and looked liked they fit the car without any fender mods (but didn't really).
I did four autocrosses with these big 345 rear tires: a Pro Solo, a National Tour and two local autocross. It looked like it almost fit, until you started cornering and loaded up the read axle, and then they
rubbed like mad and made billowing clouds of tire smoke. It was rubbing so badly on the rear inner fender sheetmetal that the car would bind up on the tires. It would start to load up in a corner, the tires would rub and slow down the car, unload the suspension and free up, lurch back into cornering then rub/slow down/lurch - rinse and repeat. But man, the traction off the line at standing start events was EPIC, and it cornered VERY WELL right up to the point where the rubbing started. Putting the 315s back on the car was a huge let-down, and I was determined to get them on this car again, eventually.
Failed experiment: 345 Hoosiers made tons of smoke from excessive rubbing under stock rear fenders
Back then we were using much softer spring rates (450F/175R) on the AST 4150s and a panhard rod, which of course doesn't control the rear axle location as well as a Watts Link. So why didn't we try the 345 mm tires out back after we went to the Whiteline Watts and upped the spring rates 3 different times on the Motons? Because it still wouldn't have worked on a road course. We noted that as hard as we pushed the car on TRACK with the 18x12" wheel/315/30/18 tire we still had a little whisper of tire rub,
both inboard and outboard. It
may have worked in a parking lot speeds, but no way would it have been safe on high speed road courses with long laterally loaded corners and the added speeds/downforce we see there. There's a big difference in some tire rub at 20-50 mph for 30 seconds at a time and then from 60-150 mph for ten minutes or more on track. We played with spacers and got it to a "pretty dang good" compromise spot with very minimal rubbing on the 12" wheels and 315s, but
any addition of tire or wheel width would go back to the rub/lurch/unload scenario, which was terrible. And at road course speeds that would quickly destroy a tire and potentially cause a catastrophic failure.
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